CN113897870A

CN113897870A - Assembled longitudinal beam, assembled buttress-free support, assembled buttress-free system and design method of assembled longitudinal beam and assembled buttress-free support

Info

Publication number: CN113897870A
Application number: CN202111205750.9A
Authority: CN
Inventors: 魏华; 韩玉; 叶志权; 梁厚燃; 解威威; 董宏源; 梁铭; 王振琦
Original assignee: Guangxi Road and Bridge Engineering Group Co Ltd
Current assignee: Guangxi Road and Bridge Engineering Group Co Ltd
Priority date: 2021-10-15
Filing date: 2021-10-15
Publication date: 2022-01-07
Anticipated expiration: 2041-10-15
Also published as: CN113897870B

Abstract

The invention relates to the technical field of cast-in-place bridge construction, in particular to an assembled longitudinal beam, an assembled pier-free support, a system and a design method. The application a fabricated longitudinal beam, can adjust the adjustable section cooperation through fixed standard truss section of length and length, standard truss section and both ends vertical total length scope after the adjustable section cooperation can satisfy two at least span lengths between first threshold value to the second threshold value to realize fabricated longitudinal beam and realize assemblization, modulization and standardized design, production and use in the scope between first threshold value to the second threshold value.

Description

Assembled longitudinal beam, assembled buttress-free support, assembled buttress-free system and design method of assembled longitudinal beam and assembled buttress-free support

Technical Field

The invention relates to the technical field of cast-in-place bridge construction, in particular to an assembled longitudinal beam, an assembled buttress-free support system and a design method thereof.

Background

High mound, curve, geology are complicated to be the problem that often meets in the cast-in-place bridge construction, adopt the support form that falls to the ground this moment, no matter be traditional bowl mouth full hall support, dish buckle full hall support, still the support such as steel pipe stand + bailey roof beam + support set up the form, finally all need transmit the load to the ground basis on, it is poor to the topography adaptability, high to the ground bearing capacity requirement, the construction is complicated, the risk is high.

For solving above-mentioned problem, no buttress support scheme appears in the field, and support no buttress support both ends on the buttress of bridge, make it need not directly transmit the load to the ground basis on, it can strengthen greatly to topography adaptability, but still domestic still mostly carries out the support equipment with bailey piece at present, its whole rigidity of structure is poor, stability is not good enough, and can not full play steel's atress performance, the whole waste of material is serious, the efficiency of construction still is waited to promote.

The large truss type buttress-free support developed in Spain, Japan and other countries can avoid the problems caused by the assembly of the traditional Bailey sheets, but the span of the buttress of the construction bridge is often not uniform, so that the universality of the conventional buttress-free support is poor, and the problems of complex design, material waste, poor applicability and the like are further caused.

Disclosure of Invention

The invention aims to: aiming at the problems that the existing buttress-free support is poor in universality and further faces to the problems of complex design, material waste, poor applicability and the like, the assembled longitudinal beam, the assembled buttress-free support system and the design method are provided, and the assembly, the modulus and the standardized design, the production and the use of the buttress-free support in a certain span range are realized.

In order to achieve the purpose, the invention adopts the technical scheme that:

the utility model provides an assembled longeron, includes standard truss section, the both ends of standard truss section can be dismantled and be connected with the adjustable section, the length of adjustable section can be adjusted, standard truss section and both ends vertical total length scope after the adjustable section cooperation can satisfy two at least span lengths between first threshold value to the second threshold value.

The application a fabricated longitudinal beam, can adjust the adjustable section cooperation through fixed standard truss section of length and length, standard truss section and both ends vertical total length scope after the adjustable section cooperation can satisfy two at least span lengths between first threshold value to the second threshold value to realize fabricated longitudinal beam and realize assemblization, modulization and standardized design, production and use in the scope between first threshold value to the second threshold value.

Preferably, the first threshold is 20m and the second threshold is 30 m.

In the experiment, it was found that: the span exceeds 30m, the stability of the truss cannot be guaranteed, the span is less than 20m, and the advantage of the truss is not obvious compared with that of a Bailey beam.

Preferably, the standard truss section comprises at least two standard truss section units which are detachably connected, and each standard truss section unit is provided with a connecting part which is detachably connected with the adjustable section,

and the detachable connection configuration of the standard truss section and the adjustable section is as follows: the longitudinal total length range of one to a plurality of standard truss section units matched with the two adjustable sections can meet at least two span lengths between the first threshold value and the second threshold value.

The space truss of the technical scheme mainly bears the load transmitted by the transverse distribution beam and the stressed members above the transverse distribution beam, the lower chord in the pier-free support in the prior art is generally inclined from two ends to the middle to form a large-angle sharp angle, and when the trapezoidal steel structure support bears the upper load to generate deformation, stress concentration is easily formed at the position to cause the lower chord to be damaged by tension.

Preferably, the standard truss section comprises three different lengths of the standard truss section units, respectively defined as a third standard truss section unit, a second standard truss section unit and a first standard truss section unit, wherein,

the third standard truss section unit length < the second standard truss section unit length < the first standard truss section unit;

the longitudinal length of the first standard truss section unit is X1, and X1 is more than or equal to 8m and less than or equal to 10 m; the longitudinal length of the second standard truss section unit is X2, and X2 is more than or equal to 6m and less than or equal to 8 m; the longitudinal length of the third standard truss section unit is X3, and X3 is more than or equal to 4m and less than or equal to 6 m.

Through the mutual matching of the standard truss section units with different lengths, the longitudinal total length range of the standard truss section and the adjustable sections at two ends after matching can better meet at least two span lengths between a first threshold value and a second threshold value, so that the assembled longitudinal beam can realize assembling, modulization and standardized design, production and use in the range between the first threshold value and the second threshold value.

Preferably, the total longitudinal length range of one or more standard truss section units matched with two adjustable sections can satisfy all the integral meters between the first threshold value and the second threshold value.

Preferably, the third standard truss section unit length, the second standard truss section unit length and the first standard truss section unit are arranged in an arithmetic progression.

Preferably, the first standard truss section unit has a longitudinal length of 9 m; the longitudinal length of the second standard truss section unit is 7 m; the third standard truss section unit has a longitudinal length of 5 m.

Preferably, the longitudinal length L1 of the adjustable segment is 3.5 m-5 m.

More preferably, the longitudinal length L1 of the adjustable segment is 4 m-4.5 m.

Preferably, the adjustable section comprises a connecting truss and an adjustable support, one end of the adjustable support is telescopically connected with the upper part of the connecting truss, and the end part of the adjustable support, far away from the connecting truss, is connected with the lower part of the connecting truss through an expansion link.

The adjustable section telescopic rod, the upper chord and the straight web member form an approximate structure right-angled triangle, a local truss structure is formed, and the stability of the adjustable section is greatly improved. If the telescopic rod is not arranged, the cantilever section similar to a suspended heavy object is formed, and the risk of instability and rollover is further improved.

Preferably, the connecting truss is provided with first connecting holes at intervals along the longitudinal direction of the connecting truss, the adjustable support is correspondingly provided with at least two second connecting holes, the first connecting holes and the second connecting holes are correspondingly arranged, the first connecting holes and the second connecting holes are connected through first connecting pieces, and the number of the first connecting pieces is at least two.

Preferably, connect the truss including vertical interval setting and interconnect's lateral plate, the lateral plate includes upper chord and lower chord, be connected with piece frame subassembly and down tube between upper chord and the lower chord, the down tube is located the piece frame subassembly is kept away from one side of standard truss section, first connecting hole is located on the upper chord.

Be connected with piece frame subassembly and down tube between chord member and the lower chord member, the down tube is located the piece frame subassembly is kept away from one side of standard truss section for the side sheet shape of adjustable section is like right trapezoid, and right trapezoid's hypotenuse has sufficient space and position ann to tear open anchor system at the tip of adjustable section, is convenient for on-the-spot segmentation block assembly hoist and mount and workman construction operation.

Preferably, the axis of the first connecting hole closest to the adjustable support intersects with the axis of the inclined rod, and the axis is subjected to the smallest bending moment and is subjected to better force.

Preferably, the adjustable support comprises an adjustable portion and a supporting portion which are perpendicular to each other, the second connecting hole is located in the adjustable portion, the supporting portion serves as a support of the assembled longitudinal beam, the telescopic rod is hinged to the supporting portion, and the supporting portion is adopted at the end portion of the space truss in the technical scheme to resist shearing deformation damage.

Preferably, connect the truss including vertical interval setting and interconnect's lateral plate, the lateral plate includes upper chord and lower chord, is connected with straight web member and X type diagonal web member between upper chord and the lower chord.

Preferably, the number of the straight web members is two, and the X-shaped inclined web member is located between the two straight web members.

At present, for a truss girder, the stress conditions of a single diagonal web member and an X-shaped diagonal web member are not different, and the single diagonal web member is easier to install, so that the single diagonal web member is common.

And in this application, the adjustable section is including connecting truss and adjustable brace, the one end of adjustable brace with the upper portion telescopically of connecting the truss is connected, adjustable brace is kept away from the tip of connecting the truss with the lower part of connecting the truss is connected through the telescopic link, based on above-mentioned design, under the unanimous condition of model boundary condition and load operating mode, only changes the form of adjustable section web member, and the adjustable section web member of this technical scheme adopts the form of two straight web members + X shape web member, and the biggest combination stress only adopts the form two-thirds of straight web member + single oblique web member for the adjustable section web member, therefore the adjustable section web member form of this technical scheme adopts the combination stress that X type diagonal web member can greatly reduced connect the truss, makes its structural rigidity and intensity more excellent.

The application also discloses an assembly type buttress-free support, which comprises the assembly type longitudinal beam, wherein a transverse distribution beam assembly is supported above the assembly type longitudinal beam, a longitudinal distribution beam assembly is supported on the transverse distribution beam assembly and is used for supporting a pouring template, wherein,

the transverse distribution beam assembly comprises at least two transverse distribution beams, the adjacent transverse distribution beams are arranged at intervals, and all the transverse distribution beams are arranged transversely along the assembled longitudinal beam;

the longitudinal distribution beam assembly comprises at least two longitudinal distribution beams, the adjacent longitudinal distribution beams are arranged at intervals, and all the longitudinal distribution beams are arranged transversely along the transverse distribution beam.

An assembled buttress-free support, support through assembled longeron top and be provided with horizontal distribution roof beam subassembly, support on the horizontal distribution roof beam subassembly and be provided with vertical distribution roof beam subassembly, vertical distribution roof beam subassembly is used for supporting pouring the template for an assembled buttress-free support overall structure atress is clear and definite, and structural security controls is simpler, and the adjustable section cooperation that can adjust through fixed standard truss section of length and length moreover, standard truss section and both ends vertical total length scope after the adjustable section cooperation can satisfy two at least span lengths between first threshold value to the second threshold value to realize assembled longeron at the within range realization assembly, modulization and standardized design, production and use between first threshold value to the second threshold value.

Preferably, the number of the fabricated stringers is at least two, and all the fabricated stringers are arranged at intervals in the transverse direction of the bridge.

An assembled buttress mounting system that does not have, include like this application assembled buttress support, the adjustable section below is provided with the buttress staple bolt, the buttress staple bolt is through supporting the adjustable section supports assembled buttress support that does not have, the buttress staple bolt is used for the staple bolt cover to establish and connects in the buttress outside.

An assembled buttress-free support system, through the buttress staple bolt with the tip fixed value bridge buttress of assembled buttress-free support on, and then effectively reduce the requirement of assembled buttress-free support to bridge below basis, make its adaptability to the topography strengthen greatly.

Preferably, the top of the buttress anchor ear is in supporting connection with at least two main cross beams, all the fabricated longitudinal beams are arranged at intervals along the transverse direction of the bridge, and the main cross beams are in supporting connection with the same side ends of all the fabricated longitudinal beams.

The application also discloses a design method for the assembly type buttress-free support, which comprises the following steps:

s1, counting the construction size data parameters of the cast-in-place box beam and the buttress-free support for the existing bridge, establishing a cast-in-place box beam-buttress-free support database, and determining the load transmission path from the cast-in-place box beam to the fabricated longitudinal beam and the load limit value applied to the buttress-free support by the cast-in-place box beam based on the cast-in-place box beam-buttress-free support database;

s2, obtaining a load distribution rule and a design value range of the internal force of the fabricated longitudinal beam based on a load limit value applied to the buttress-free support by the cast-in-place box beam and a load transmission path from the cast-in-place box beam to the fabricated longitudinal beam;

s3, determining the length of a standard truss section and the length range of the adjustable section in the fabricated longitudinal beam based on site construction requirements, the load distribution rule of the fabricated longitudinal beam and the internal force design value range of the fabricated longitudinal beam, calculating to obtain the internal force design value range of each rod piece of the standard truss section and the internal force design value range of each rod piece of the adjustable section, and determining the arrangement of each rod piece of the standard truss section and the arrangement of each rod piece of the adjustable section;

and S4, designing the assembled longitudinal beams, the transverse distribution beams and the longitudinal distribution beams, and rechecking the strength, the rigidity and the stability.

The design method for the fabricated buttress-free support provided by the invention is characterized in that the construction condition of a cast-in-place box beam is summarized and counted based on a large amount of data, the construction condition of the cast-in-place box beam is counted by counting the structural size data parameters of the cast-in-place box beam and the buttress-free support for the existing bridge and establishing a cast-in-place box beam-buttress-free support database, the load transmission path from the cast-in-place box beam to the fabricated longitudinal beam and the load limit value applied to the buttress-free support by the cast-in-place box beam are obtained based on the cast-in-place box beam-buttress-free support database, the load distribution rule of the fabricated longitudinal beam and the internal force design value range of the fabricated longitudinal beam are obtained, the length of a standard truss section in the fabricated longitudinal beam and the length range of the adjustable section are determined, and the fabricated buttress-free support structure is optimized, so that the economy, reasonableness and the technology are feasible; by the design method, the designed assembled pier-free support can meet at least two span lengths between a first threshold value and a second threshold value due to the fact that the longitudinal total length range of the standard truss section and the adjustable sections at two ends after being matched, so that the assembled longitudinal beam can be assembled, modularized and designed, produced and used in a standardized mode in the range between the first threshold value and the second threshold value.

Preferably, step S3 specifically includes the following steps,

s31, selecting the length size of one standard truss section based on transportation and manufacturing conditions, and defining the length size as a first standard truss section unit;

s32, based on the length size of the first standard truss section unit, drawing up the length sizes of the other two standard truss sections, and defining the length sizes as a second standard truss section unit and a third standard truss section unit respectively, so that the length of the third standard truss section unit is less than that of the second standard truss section unit and less than that of the first standard truss section unit, and the length adjusting range of the adjustable section is drawn up based on the length size of the first standard truss section unit, the length size of the second standard truss section unit and the length size of the third standard truss section unit;

s33, determining whether the length range of the assembled longitudinal beam covers the length of all integers in the range of 20m-30m or not based on the length and the number of the first standard truss section units and the length adjusting range of the adjustable sections;

s34, if the length range of the fabricated longitudinal beam in the step S33 cannot cover all the lengths of the integer meters in the range of 20m-30m, determining whether the length range of the fabricated longitudinal beam covers all the lengths of the integer meters in the range of 20m-30m or not based on the length and the number of the first standard truss section units, the length and the number of the second standard truss section units and the length adjusting range of the adjustable sections;

s35, if the length range of the fabricated longitudinal beam in the step S34 cannot cover all the lengths of the integer meters in the range of 20m-30m, determining whether the length range of the fabricated longitudinal beam covers all the lengths of the integer meters in the range of 20m-30m or not based on the length and the number of the first standard truss section units, the length and the number of the second standard truss section units, the length and the number of the third standard truss section units and the length adjusting range of the adjustable sections;

s36, if the length range of the fabricated longitudinal beam in the step S35 can not cover all the length of the whole integer meter in the range of 20m-30m,

adjusting the length of the second standard truss section unit, and repeating the steps S34-S35 until the length range of the assembled longitudinal beam covers all the integral meter lengths within the range of 20m-30 m;

and/or the presence of a gas in the gas,

adjusting the length of the third standard truss section unit, and repeating the step S35 until the length range of the assembled longitudinal beam covers all the integral meter lengths in the range of 20m-30 m;

and S37, in the step, when the length range of the assembled longitudinal beam covers all the integral meter lengths in the range of 20m-30m, stopping, taking the length and the number of the first standard truss section units, the length and the number of the second standard truss section units and the length and the number of the third standard truss section units under the condition as final values, and determining the final value of the length adjusting range of the adjustable section according to the final values.

The application discloses a design method for assembled buttress-free support, from the aspect of structural style, space steel truss (assembled longeron) is as the main atress structure of buttress-free support, its section is assembled and is followed the principle of "few specification, multiunit combination", satisfies under the prerequisite of science and economic theory promptly, reduces section specification type, reduces the manufacturing cost of steel, can realize accomplishing quick assembly hoist and mount requirement at the job site. In addition, the section specification of the space steel truss can meet basic conditions of highway transportation, and is also suitable for the transportation conditions in mountainous areas.

Preferably, step S1 is specifically:

step S11: the method comprises the steps of counting the structural size data parameters of a cast-in-place box beam and a buttress-free bracket for the existing bridge, establishing a cast-in-place box beam-buttress-free bracket database, obtaining the structural size limit value of the cast-in-place box beam with the span of 20-30 m based on the cast-in-place box beam-buttress-free bracket database, and determining the arrangement form of the buttress-free bracket;

step S12: determining a load transfer path from the cast-in-place box girder to the fabricated longitudinal girder based on the arrangement form of the buttress-free supports;

step S13: and calculating the load limit value of the cast-in-place box beam applied to the buttress-free support based on the load transmission path from the cast-in-place box beam to the fabricated longitudinal beam and the structural size limit value of the cast-in-place box beam.

Preferably, step S13 is specifically:

SS131, calculating a fluid load limit value applied to the longitudinal distribution beam assembly by the cast-in-place box beam based on a load transmission path from the cast-in-place box beam to the fabricated longitudinal beam and a structural size limit value of the cast-in-place box beam;

s132, calculating a concentrated load limit value applied to the transverse distribution beam assembly by the longitudinal distribution beam assembly based on a load limit value applied to the longitudinal distribution beam assembly by the cast-in-place box beam;

and S133, calculating the limit value of the concentrated load applied to the assembled longitudinal beam by the transverse distribution beam assembly based on the limit value of the concentrated load applied to the transverse distribution beam assembly by the longitudinal distribution beam assembly.

Preferably, in step S1, the parameters of the construction size data of the cast-in-place box girder for the bridge include a girder height, a bottom width, a flange overhanging length and a web thickness of the cast-in-place box girder.

Preferably, the cast-in-place box girder includes a solid section, a transition section and a general section, and step S2 is specifically:

s21, obtaining a longitudinal distribution beam load distribution rule, a transverse distribution beam load distribution rule and an assembly type longitudinal beam load distribution rule corresponding to a solid section, a transition section and a general section based on a load limit value applied to the buttress-free support by the cast-in-place box beam and a load transmission path from the cast-in-place box beam to the assembly type longitudinal beam;

and S22, analyzing and obtaining the design value range of the internal force of the longitudinal distribution beam, the design value range of the internal force of the transverse distribution beam and the design value range of the internal force of the assembled longitudinal beam corresponding to the solid section, the transition section and the general section based on the load distribution rule of the longitudinal distribution beam, the load distribution rule of the transverse distribution beam and the load distribution rule of the assembled longitudinal beam.

The application also discloses a design method for the assembled buttress-free support system, which comprises the following steps:

a1, completing the design of the fabricated longitudinal beam based on the design method for the fabricated buttress-free support frame, and obtaining the support reaction force data parameters of the fabricated longitudinal beam;

a2, counting the size data parameters of the buttresses for the existing bridge, establishing a buttresses database, obtaining the most common data parameter values of the size of the buttresses with the span within the range of 20m-30m based on the buttresses database, and drawing the structure size of the anchor ear of the buttresses according to the most common data parameter values;

a3, introducing a main cross beam based on the structure size of the fabricated longitudinal beam structure and the buttress anchor ear, and determining a load transmission path from the fabricated longitudinal beam to the buttress anchor ear;

a4, obtaining the maximum bending moment and the maximum shearing force of the cross section of the main cross beam based on the support reaction force data parameters of the fabricated longitudinal beams, performing cross section shape selection on the main cross beam according to the maximum bending moment and the maximum shearing force, and then calculating to obtain the load applied to the anchor ear of the buttress by the main cross beam;

and A5, checking the strength, rigidity and stability of the structure size of the simulated buttress anchor ear based on the load applied to the buttress anchor ear by the main cross beam.

The application discloses a design method for assembled buttress-free support system, based on pier size data parameter assembled longeron for current roof beam and founding the pier database, obtain the most common data parameter value of pier size, and confirm the structure size of pier staple bolt based on this to and introduce the main beam, and confirm the load transmission route of assembled longeron to pier staple bolt, further the parameter foundation that provides for the design of pier staple bolt, improved the efficiency of pier staple bolt design.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. the application a fabricated longitudinal beam, can adjust the adjustable section cooperation through fixed standard truss section of length and length, standard truss section and both ends vertical total length scope after the adjustable section cooperation can satisfy two at least span lengths between first threshold value to the second threshold value to realize fabricated longitudinal beam and realize assemblization, modulization and standardized design, production and use in the scope between first threshold value to the second threshold value.

2. The application a fabricated longitudinal beam, through mutually supporting of different length standard truss section units, can make better standard truss section and both ends vertical total length scope after the adjustable section cooperation can satisfy two at least span lengths between first threshold value to the second threshold value to realize fabricated longitudinal beam and realize that assemblization, modulization and standardized design, production and use are within range between first threshold value to the second threshold value.

3. An assembled longeron, adjustable section is including connecting truss and adjustable support, the one end of adjustable support with the upper portion telescopically of connecting the truss is connected, adjustable support is kept away from the tip of connecting the truss with the lower part of connecting the truss is connected through the telescopic link, based on above-mentioned design, under the unanimous condition of model boundary condition and load operating mode, only change the form of adjustable section web member, the adjustable section web member of this technical scheme adopts the form of two straight web members + X shape web member, the biggest combined stress only adopts the form two-thirds of straight web member + single diagonal web member for the adjustable section web member, consequently the adjustable section web member form of this technical scheme adopts the combined stress that X type diagonal web member can greatly reduced connect the truss, makes its structural rigidity and intensity more excellent.

4. According to the assembly type buttress-free support, the combination mode with small number of the sections is selected as much as possible, so that the sections in the technical scheme are few, and the number of connecting devices among the sections is small. Because the connecting devices at the nodes are easier to damage relative to the segments and are more influenced by shearing force, the truss is less prone to fatigue damage and has longer service life due to fewer nodes and connecting devices. This is also a large starting point for the combination.

5. An assembled buttress-free support, support through assembled longeron top and be provided with horizontal distribution roof beam subassembly, support on the horizontal distribution roof beam subassembly and be provided with vertical distribution roof beam subassembly, vertical distribution roof beam subassembly is used for supporting pouring the template for an assembled buttress-free support overall structure atress is clear and definite, and structural security controls is simpler, and the adjustable section cooperation that can adjust through fixed standard truss section of length and length moreover, standard truss section and both ends vertical total length scope after the adjustable section cooperation can satisfy two at least span lengths between first threshold value to the second threshold value to realize assembled longeron at the within range realization assembly, modulization and standardized design, production and use between first threshold value to the second threshold value.

6. An assembled buttress-free support system, through the buttress staple bolt with the tip fixed value bridge buttress of assembled buttress-free support on, and then effectively reduce the requirement of assembled buttress-free support to bridge below basis, make its adaptability to the topography strengthen greatly.

7. The design method for the fabricated buttress-free support provided by the invention is characterized in that the construction condition of a cast-in-place box beam is summarized and counted based on a large amount of data, the construction condition of the cast-in-place box beam is counted by counting the structural size data parameters of the cast-in-place box beam and the buttress-free support for the existing bridge and establishing a cast-in-place box beam-buttress-free support database, the load transmission path from the cast-in-place box beam to the fabricated longitudinal beam and the load limit value applied to the buttress-free support by the cast-in-place box beam are obtained based on the cast-in-place box beam-buttress-free support database, the load distribution rule of the fabricated longitudinal beam is obtained, the length of a standard truss section in the fabricated longitudinal beam and the length range of the adjustable section are determined, and the fabricated buttress-free support structure is optimized, so that the economy, reasonability and feasibility of technology are achieved; by the design method, the designed assembled pier-free support can meet at least two span lengths between a first threshold value and a second threshold value due to the fact that the longitudinal total length range of the standard truss section and the adjustable sections at two ends after being matched, so that the assembled longitudinal beam can be assembled, modularized and designed, produced and used in a standardized mode in the range between the first threshold value and the second threshold value.

8. The application discloses a design method for assembled buttress-free support, from the aspect of structural style, space steel truss (assembled longeron) is as the main atress structure of buttress-free support, its section is assembled and is followed the principle of "few specification, multiunit combination", satisfies under the prerequisite of science and economic theory promptly, reduces section specification type, reduces the manufacturing cost of steel, can realize accomplishing quick assembly hoist and mount requirement at the job site. In addition, the section specification of the space steel truss can meet basic conditions of highway transportation, and is also suitable for the transportation conditions in mountainous areas.

9. The application discloses a design method for assembled buttress-free support system, based on pier size data parameter assembled longeron for current roof beam and founding the pier database, obtain the most common data parameter value of pier size, and confirm the structure size of pier staple bolt based on this to and introduce the main beam, and confirm the load transmission route of assembled longeron to pier staple bolt, further the parameter foundation that provides for the design of pier staple bolt, improved the efficiency of pier staple bolt design.

Drawings

FIG. 1 is a schematic (front view) of one form of the fabricated buttress-free mounting system of the present invention.

FIG. 2 is an enlarged view of portion A of FIG. 1 according to the present invention.

FIG. 3 is a schematic structural view (with the pouring deck removed from above) of one form of the fabricated buttress-free scaffolding system of the present invention.

FIG. 4 is a schematic cross-sectional view of another form of the fabricated buttress-free brace system of the present invention.

Fig. 5 is a schematic structural view of a fabricated stringer of the present invention.

Fig. 6 is a schematic structural view (front view) of the adjustable segment of the present invention.

Fig. 7 is a schematic structural view (top view) of the adjustable segment of the present invention.

Fig. 8 is a schematic structural view (front view) of the adjustable support of the present invention.

Fig. 9 is a schematic structural view (top view) of the adjustable support of the present invention.

Fig. 10 is a schematic structural view of the connection truss of the present invention.

Fig. 11 is a front view of a structure of a prior cast-in-place box girder.

FIG. 12 is a cross-sectional view taken along line I-I of FIG. 11 in accordance with the present invention.

FIG. 13 is a sectional view taken along line II-II of FIG. 11 in accordance with the present invention.

FIG. 14 is a sectional view taken along line III-III of FIG. 11 in accordance with the present invention.

Fig. 15 is a general flow chart of the design for the fabricated bracket structure in embodiment 7.

Figure 16 is a load transfer path diagram for a cast-in-place box beam to fabricated side rails of the present invention.

Figure 17 is a schematic view of the general section/transition section-transverse distribution beam loading of a cast-in-place box beam in example 7 of the present invention.

Fig. 18 is a solid section-lateral distribution beam load diagram of a cast-in-place box beam in example 7 of the present invention.

Fig. 19 is a load diagram of a fabricated side member of a cast-in-place box girder in example 7 of the present invention.

Fig. 20 is a schematic view of the load of the transverse distribution beam and an internal force diagram in example 7 of the present invention.

Fig. 21 is a load diagram and an internal force diagram of a fabricated stringer in example 7 of the present invention.

Fig. 22 is a schematic view of a longitudinal distribution beam model in example 7 of the present invention.

Fig. 23 is a schematic view of a transverse distribution beam model in example 7 of the present invention.

Fig. 24 is a model schematic view of a fabricated stringer according to example 7 of the present invention.

Fig. 25 is a schematic diagram of a panel strength and stiffness calculation for a web segment in example 7 of the present invention.

Fig. 26 is a schematic diagram of the strength and stiffness verification of a general segment, web-longitudinal distributor beam in example 7 of the present invention.

Fig. 27 is a schematic diagram of the checking calculation of the strength and rigidity of the transverse distribution beam, which is a general segment in example 7 of the present invention.

FIG. 28 is a schematic diagram of the verification of the stiffness of the displacement contour of the buttress-free stent in example 7 of the present invention.

Fig. 29 is a force-receiving schematic view of a connecting pin in embodiment 7 of the present invention.

Fig. 30 is a schematic view of a mating connection of a male and female head of one form of embodiment 7 of the present invention.

FIG. 31 is a schematic diagram of finite element analysis software extraction support reaction force in example 7 of the present invention.

Fig. 32 is a combined stress plot for the adjustable section of the present invention (straight web + X-web, maximum indicated by the line frame).

Fig. 33 is a composite stress plot for the adjustable section of the present invention (straight web + single diagonal web, maximum indicated by the line frame).

FIG. 34 is a schematic front view of the inventive buttress in combination with a buttress anchor ear.

FIG. 35 is a schematic top view of the configuration of the buttress of the present invention in cooperation with a buttress anchor ear.

FIG. 36 is a schematic view of a main beam force analysis of the present invention.

Icon: 1-standard truss section; 2-adjustable section; 3-a third standard truss section unit; 4-a second standard truss section unit; 5-a first standard truss section unit; 6, connecting a truss; 7-adjustable support; 8, a telescopic rod; 9-a first connection hole; 10-a second connection hole; 11-a first connection member; 12-side panels; 13-a transverse frame; 14-upper chord; 15-lower chord; 16-a rack assembly; 17-a diagonal rod; 18-straight web member; 19-X type diagonal web members; 20-an adjustable part; 21-a support part; 22-transverse distribution beam assembly; 23-longitudinal distribution beam assembly; 24-pouring a template; 25-transverse distribution beams; 26-longitudinal distribution beams; 27-fabricated stringers; 28-anchor ear of buttress; 29-a main beam; 30-casting box girder in situ; 31-buttress; 32-vulva; 33-male head; 34-a second connector; 35-a connecting part; 36-rib plate.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

As shown in fig. 1 to 10, the fabricated longitudinal beam according to this embodiment includes a standard truss section 1, two ends of the standard truss section 1 are detachably connected with adjustable sections 2, the length of each adjustable section 2 can be adjusted, and a longitudinal total length range of the standard truss section 1 and the adjustable sections 2 at two ends after being matched can satisfy at least two span lengths between a first threshold and a second threshold.

Here, it is to be noted that: the longitudinal direction of the total longitudinal length of the standard truss section 1 and the adjustable sections 2 at two ends after matching is the longitudinal direction of the assembled longitudinal beam 27 as shown in fig. 24.

The standard truss section 1 has the following specific structure:

the standard truss section 1 comprises at least two standard truss section units which are detachably connected through a second connecting piece 34, each standard truss section unit is provided with a connecting part 35 which is detachably connected with the adjustable section 2,

and the detachable connection configuration of the standard truss section 1 and the adjustable section 2 is as follows: the longitudinal total length range of one or more standard truss section units matched with the two adjustable sections 2 can meet at least two span lengths between the first threshold value and the second threshold value.

At least two span lengths between the first threshold to the second threshold: refers to a set of at least two length points between a first threshold value and a second threshold value, the length and the number of the length points are different according to the types, the lengths and the number of the standard truss section units in the standard truss section 1, and the length of the adjustable section 2 can be adjusted, so that the assembled longitudinal beams 27 can present different total length values after being combined, namely, a plurality of point values in a section range can be formed.

For example: the first threshold value is 20m, and the second threshold value is 30 m. Two span lengths between 20m and 30m, 20m and 30m respectively; by selecting the types, such as two types, of the standard truss section units with different lengths or according to the different number of the standard truss section units, the longitudinal total length of the assembled longitudinal beam after final combination can reach 20m in a combination mode, the types or the number of the standard truss section units are changed, and the longitudinal total length of the assembled longitudinal beam after combination can reach 30m

For another example, the first threshold is 20m, and the second threshold is 30 m. Three span lengths between 20m and 30 need to be met: 22.5m, 25.5m and 27.5m, the longitudinal total length of the assembled longitudinal beam after final combination can reach 22.5m in a combination mode by selecting the types, such as two or three types, of the standard truss section units with different lengths or according to the different number of the standard truss section units, the types or the number of the standard truss section units are changed, and the longitudinal total length of the assembled longitudinal beam after combination can reach 25.5 m; and the longitudinal total length of the assembled longitudinal beam can reach 27.5m after the assembled longitudinal beam is combined by changing the type or the number of the standard truss section units or adjusting the length of the adjustable section 2 and matching the standard truss section units and the adjustable section units.

Specifically, the second connector 34 is typically a pin or bolt.

Specifically, the standard truss section 1 includes three different lengths of the standard truss section units, which are respectively defined as a third standard truss section unit 3, a second standard truss section unit 4 and a first standard truss section unit 5, wherein,

length of the third standard truss section unit 3 < length of the second standard truss section unit 4 < length of the first standard truss section unit 5;

the longitudinal length of the first standard truss section unit 5 is X1, and X1 is more than or equal to 8m and less than or equal to 10 m;

the longitudinal length of the second standard truss section unit 4 is X2, and X2 is more than or equal to 6m and less than or equal to 8 m;

the longitudinal length of the third standard truss section unit 3 is X3, and X3 is more than or equal to 4m and less than or equal to 6 m.

The longitudinal length L1 of the adjustable segment 2 is 3.5 m-5 m, and preferably the longitudinal length L1 of the adjustable segment 2 is 4 m-4.5 m.

Specifically, the longitudinal total length range of the standard truss section 1 and the adjustable sections 2 at two ends after being matched can meet all integral meters between a first threshold value and a second threshold value.

The specific structure of the adjustable section 2 is as follows:

as shown in fig. 5 and 6, the adjustable segment 2 includes a connecting truss 6 and an adjustable support 7, one end of the adjustable support 7 is telescopically connected with an upper portion of the connecting truss 6, and an end of the adjustable support 7 away from the connecting truss 6 is connected with a lower portion of the connecting truss 6 through an expansion link 8.

As shown in fig. 7 to 9, first connection holes 9 are formed in the connection truss 6 at intervals along a longitudinal direction thereof, at least two second connection holes 10 are correspondingly formed in the adjustable support 7, the first connection holes 9 and the second connection holes 10 are correspondingly formed, the first connection holes 9 and the second connection holes 10 are connected through first connection members 11, the number of the first connection members 11 is at least two, and the first connection members 11 may specifically be pins or bolts.

Connecting truss 6 includes lateral plate 12 that vertical interval set up, two be connected through crossbearer 13 between the lateral plate 12, lateral plate 12 includes upper chord 14 and lower chord 15, be connected with a piece frame subassembly 16 and down tube 17 between upper chord 14 and the lower chord 15, down tube 17 is located piece frame subassembly 16 keeps away from one side of standard truss section 1, first connecting hole 9 is located on the upper chord 14.

Because one end of the adjustable support 7 is telescopically connected with the upper part of the connecting truss 6, and the contraction rod 8 is mainly pulled, the contraction rod 8 is taken as an adaptive structure when the adjustable support 7 and the connecting truss 6 are relatively stretched, and meanwhile, the telescopic rod 8 of the adjustable section 2, the upper chord 14 and the straight web member 18 form an approximate structure right triangle, so that a local truss type structure is formed, and the stability of the adjustable section 2 is greatly improved. If the telescopic rod 8 is not arranged, the cantilever section similar to a suspended heavy object is formed, and the risk of instability and rollover is further improved.

Be connected with piece frame subassembly 16 and down link 17 between upper chord member 14 and the lower chord member 15, down link 17 is located piece frame subassembly 16 is kept away from one side of standard truss section 1 for lateral plate 12 of adjustable section 2 is like right trapezoid, and right trapezoid's hypotenuse has sufficient space and position to ann and tear down anchor system at the tip of adjustable section 2, is convenient for on-the-spot segmentation spelling hoist and mount and workman construction operation.

The adjustable support 7 comprises an adjustable part 20 and a supporting part 21 which are perpendicular to each other, the second connecting hole 10 is located at the adjustable part 20, the supporting part 21 serves as a support of the assembled longitudinal beam 27, the telescopic rod 8 is hinged to the supporting part 21, and the end part of the space truss of the technical scheme adopts the supporting part 21 to resist shearing deformation damage.

When in manufacturing, the axis of the first connecting hole 9 closest to the adjustable support 7 is intersected with the axis of the inclined rod 17, the bending moment is minimum, and the stress is better.

An assembled longeron 27, cooperate through the adjustable section 2 that length fixed standard truss section 1 and length can be adjusted, standard truss section 1 and both ends vertical total length scope after the adjustable section 2 cooperation can satisfy two at least span lengths between first threshold value to the second threshold value to realize assembled longeron 27 at the within range realization of first threshold value between to the second threshold value that the modularization is gone up, production and use.

Example 2

As shown in fig. 10, the fabricated side member according to the present embodiment is different from embodiment 1 in that: based on blanking, transportation, manufacturing or well distinguishing different types of standard truss section units, and meanwhile, combination consideration is facilitated, and the longitudinal total length range of one to more standard truss section units matched with the two adjustable sections 2 can meet all integer meters between the first threshold value and the second threshold value.

Specifically, the length of the third standard truss section unit (3), the length of the second standard truss section unit (4) and the first standard truss section unit (5) are arranged in an arithmetic progression.

More specifically, the first standard truss section unit 5 has a longitudinal length of 9 m; the longitudinal length of the second standard truss section unit 4 is 7 m; the third standard truss section unit 3 has a longitudinal length of 5 m.

More specifically, the total longitudinal length range of one or more standard truss section units coupled with two adjustable sections 2 can satisfy all the integral meters between the first threshold value and the second threshold value.

Specifically, the first threshold value is 20m, and the second threshold value is 30 m. Namely, the longitudinal total length range of the standard truss section 1 and the adjustable sections 2 at two ends after being matched can meet all integral meters between 20m and 30m, namely 20m, 21m, 22m, 23m, 24m, 25m, 26m, 27m, 28m, 29m and 30m, and the specific combination is shown in the following table:

TABLE 1 Standard truss section combination mode table

As can be seen from the above table: the standard truss section units with different lengths are matched with each other, so that the longitudinal total length range of the matched standard truss section 1 and the adjustable section 2 at two ends can better meet at least two span lengths between a first threshold value and a second threshold value, and the assembled longitudinal beam 27 can be assembled, modularized and designed, produced and used in a standardized manner in the range between the first threshold value and the second threshold value.

Because the span of the buttresses of the bridge is often not uniform and has zero and integrity, at the moment, the longitudinal total length of the matched fabricated longitudinal beam can cover a decimal range of the span of the buttresses which is close to the integer meters even if the length of the longitudinal total length is the integer meters through the design of the connecting structure between the lower part of the fabricated longitudinal beam and the buttresses.

Example 3

As shown in fig. 10, the fabricated side member according to the present embodiment is different from

embodiment

1 or 2 in that: the connecting truss 6 comprises side pieces 12 which are vertically arranged at intervals and are connected with each other, the side pieces 12 comprise two straight web members 18 which are arranged at intervals, an X-shaped inclined web member 19 is arranged between the two straight web members 18, wherein,

one end of the straight web member 18 is connected with the upper chord 14, and the other end of the straight web member 18 is connected with the lower chord 15;

one end of the X-shaped diagonal web member 19 is connected with the upper chord 14, and the other end of the X-shaped diagonal web member 19 is connected with the lower chord 15.

As shown in fig. 8, 32 and 33, in the test, under the condition that the model boundary condition and the load condition are consistent, only the form of the adjustable segment 2 web member is changed, the adjustable segment 2 web member of the present technical solution adopts the form of two straight web members + X-shaped web members, and the maximum combined stress is 116MPa, while if the adjustable segment 2 web member adopts the form of a straight web member + a single inclined web member, the maximum combined stress is 172MPa, so the adjustable segment 2 web member of the present technical solution has a better form.

The beneficial effects of this embodiment: at present, for a truss girder, the stress conditions of a single diagonal web member and the stress conditions of the X-shaped diagonal web member 19 are not much different, and the single diagonal web member is easier to install, so that the single diagonal web member is generally used. In the embodiment, the adjustable section 2 comprises a connecting truss 6 and an adjustable support 7, one end of the adjustable support 7 is telescopically connected with the upper part of the connecting truss 6, the end of the adjustable support 7 far away from the connecting truss 6 is connected with the lower part of the connecting truss 6 through a telescopic rod 8, the telescopic rod 8 is mainly pulled, based on the design, under the condition that the boundary conditions of the model are consistent with the load working conditions, only the form of the adjustable section 2 web members is changed, the adjustable section 2 web members of the technical scheme adopt the form of two straight web members and an X-shaped web member, the maximum combined stress is only two thirds of the form of the adjustable section 2 web members adopting the straight web members and a single inclined web member, therefore, the adjustable section 2 web member form of the technical scheme adopts the X-shaped inclined web member 19, so that the combined stress of the connecting truss 6 can be greatly reduced, and the structural rigidity and the strength are better.

Example 4

As shown in fig. 2-3, the present application further discloses a fabricated pier-free support, which includes a fabricated longitudinal beam 27 as described in

embodiment

1 or 2 or 3, a transverse distribution beam assembly 22 is supported above the fabricated longitudinal beam 27, a longitudinal distribution beam assembly 23 is supported on the transverse distribution beam assembly 22, the longitudinal distribution beam assembly 23 is used for supporting a casting formwork 24, and the casting formwork 24 is used for casting a cast-in-place box beam 30, wherein the transverse distribution beam assembly 22 includes at least two transverse distribution beams 25, the transverse distribution beams 25 are spaced apart from each other, and all the transverse distribution beams 25 are disposed transversely along the fabricated longitudinal beam 27; the longitudinal distribution beam assembly 23 comprises at least two longitudinal distribution beams 26, the adjacent longitudinal distribution beams 26 are arranged at intervals, and all the longitudinal distribution beams 26 are arranged transversely along the transverse distribution beam 25.

Here, it should be noted that: the transverse direction of the fabricated longitudinal beam 27 is the cross-sectional direction of the fabricated longitudinal beam 27, as shown in fig. 24; the transverse distribution beam 25 is transversely the cross-sectional direction of the transverse distribution beam 25, as shown in fig. 23.

Specifically, the number of the fabricated side members 27 is at least two, and all of the fabricated side members 27 are arranged at intervals in the bridge transverse direction.

The beneficial effects of this embodiment: an assembled buttress-free support, support through assembled longeron 27 top and be provided with horizontal distribution beam subassembly 22, support on the horizontal distribution beam subassembly 22 and be provided with vertical distribution beam subassembly 23, vertical distribution beam subassembly 23 is used for supporting pouring template 24 for an assembled buttress-free support overall structure atress is clear and definite, and structural security controls is simpler, and the adjustable section 2 that can adjust through the fixed standard truss section 1 of length and length cooperatees, standard truss section 1 and both ends vertical total length scope after the adjustable section 2 cooperation can satisfy two at least span lengths between first threshold value to the second threshold value to realize assembled longeron 27 and realize assemblization, modulization and standardized design, production and use in the within range between first threshold value to the second threshold value.

Example 5

As shown in fig. 1-3, the assembly-type buttress-free support system of this embodiment includes the assembly-type buttress-free support of embodiment 4, a buttress anchor ear 28 is disposed below the adjustable section 2, the buttress anchor ear 28 supports the assembly-type buttress-free support by supporting the adjustable section 2, and the buttress anchor ear 28 is used for being sleeved and connected to the outer side of a buttress;

specifically, the top of the buttress anchor ear 28 is supported and connected with a main cross beam 29, the number of the fabricated longitudinal beams 27 is at least two, all the fabricated longitudinal beams 27 are arranged along the transverse direction of the bridge at intervals, and the main cross beam 29 is supported and connected with the same side end of all the fabricated longitudinal beams 27.

The beneficial effects of this embodiment: an assembled buttress-free support system of this embodiment, through buttress staple bolt 28 with the tip fixed value bridge buttress of assembled buttress-free support, and then effectively reduce assembled buttress-free support to the requirement of bridge below basis, make its adaptability to the topography strengthen greatly.

Example 6

As shown in fig. 11-15, this embodiment discloses a design method for the fabricated buttress-free support described in embodiment 4, comprising the following steps:

s1, counting the construction size data parameters of the cast-in-place box beam 30 and the support without the buttress for the existing bridge, establishing a cast-in-place box beam-support without the buttress database, and obtaining the load transmission path from the cast-in-place box beam 30 to the fabricated longitudinal beam 27 and the load limit value applied to the support without the buttress by the cast-in-place box beam based on the cast-in-place box beam-support without the buttress database;

s2, obtaining a load distribution rule of the fabricated longitudinal beam 27 and a design value range of internal force of the fabricated longitudinal beam 27 based on a load limit value applied to the buttress-free support by the cast-in-place box beam and a load transmission path from the cast-in-place box beam 30 to the fabricated longitudinal beam 27;

s3, determining the length of the standard truss section 1 and the length range of the adjustable section 2 in the assembled longitudinal beam 27 based on the site construction requirement, the load distribution rule of the assembled longitudinal beam 27 and the internal force design value range of the assembled longitudinal beam 27, calculating to obtain the internal force design value range of each rod piece of the standard truss section 1 and the internal force design value range of each rod piece of the adjustable section 2, and determining the arrangement of each rod piece of the standard truss section 1 and the arrangement of each rod piece of the adjustable section 2;

and S4, designing the fabricated longitudinal beams 27, the transverse distribution beams 25 and the longitudinal distribution beams 26, and rechecking the strength, the rigidity and the stability.

In the above scheme, step S1 specifically includes;

step S11: counting the structural size data parameters of the cast-in-place box beam 30 and the non-buttress support for the existing bridge, establishing a cast-in-place box beam-non-buttress support database, obtaining the structural size limit value of the cast-in-place box beam with the span diameter within the range of 20m-30m based on the cast-in-place box beam-non-buttress support database, determining the arrangement form of the non-buttress support,

step S12: determining a load transmission path from the cast-in-place box girder 30 to the fabricated longitudinal girder 27 based on the arrangement form of the buttress-free supports;

step S13: and calculating the load limit value applied to the non-buttress support by the cast-in-place box girder based on the load transmission path from the cast-in-place box girder 30 to the fabricated longitudinal beam 27 and the structural size limit value of the cast-in-place box girder.

In the above scheme, step S13 specifically includes;

s131, calculating to obtain a fluid load limit value applied to the longitudinal distribution beam assembly 23 by the cast-in-place box beam based on a load transfer path from the cast-in-place box beam 30 to the fabricated longitudinal beam 27 and the structural size limit value of the cast-in-place box beam;

s132, calculating a concentrated load limit value applied to the transverse distribution beam assembly 22 by the longitudinal distribution beam assembly 23 based on a load limit value applied to the longitudinal distribution beam assembly 23 by the cast-in-place box beam;

and S133, calculating the limit value of the concentrated load applied to the assembled longitudinal beam 27 by the transverse distribution beam assembly 22 based on the limit value of the concentrated load applied to the transverse distribution beam assembly 22 by the longitudinal distribution beam assembly 23.

In the above scheme, in step S1, the parameters of the structural dimension data of the cast-in-place box girder 30 for a bridge include the height, the bottom width, the overhanging length of the flange, and the thickness of the web of the cast-in-place box girder 30. The parameters of the data of the construction dimension of the support without the buttress comprise the arrangement form of the support without the buttress in the prior art, and further comprise the arrangement spacing of the transverse distribution beams 25 and the longitudinal distribution beams 26.

Specifically, as shown in fig. 11 to 14, the cast-in-place box girder 30 includes a solid section, a transition section, and a general section, and the step S2 specifically includes:

s21, obtaining a longitudinal distribution beam 26 load distribution rule, a transverse distribution beam 25 load distribution rule and an assembly type longitudinal beam 27 load distribution rule corresponding to a solid section, a transition section and a general section based on a load limit value applied to the buttress-free support by the cast-in-place box beam and a load transmission path from the cast-in-place box beam 30 to the assembly type longitudinal beam 27;

and S22, analyzing and obtaining the design value range of the internal force of the longitudinal distribution beam 26, the design value range of the internal force of the transverse distribution beam 25 and the design value range of the internal force of the assembled longitudinal beam 27 corresponding to the solid section, the transition section and the general section based on the load distribution rule of the longitudinal distribution beam 26, the load distribution rule of the transverse distribution beam 25 and the load distribution rule of the assembled longitudinal beam 27.

The beneficial effects of this embodiment: the design method for the fabricated buttress-free support provided by the invention is characterized in that the construction condition of a cast-in-place box beam is summarized and counted based on a large amount of data, a cast-in-place box beam-buttress-free support database is established by counting the construction size data parameters of the cast-in-place box beam 30 and the buttress-free support for the existing bridge, the load transmission path from the cast-in-place box beam 30 to the fabricated longitudinal beam 27 and the load limit value applied to the buttress-free support by the cast-in-place box beam are obtained based on the cast-in-place box beam-buttress-free support database, the load distribution rule of the fabricated longitudinal beam 27 and the internal force design value range of the fabricated longitudinal beam 27 are obtained, the length of a standard truss section 1 in the fabricated longitudinal beam 27 and the length range of an adjustable section 2 are determined, and the fabricated buttress-free support structure is optimized, so that the economy, reasonableness and the technology are feasible; by the design method, the designed fabricated buttress-free support can meet at least two span lengths between a first threshold and a second threshold due to the longitudinal total length range of the standard truss section 1 and the adjustable sections 2 at two ends after being matched, so that the fabricated longitudinal beam 27 can be fabricated, modularized and standardized in design, production and use within the range between the first threshold and the second threshold.

Example 7

As shown in fig. 11 to 15, this embodiment discloses a design method for the fabricated buttress-free support described in embodiment 4, taking specific tests as examples: the method comprises the following steps:

firstly, carrying out statistics on the structural size data parameters of the cast-in-place box beam 30:

in order to determine the reasonable value range of the load transmission path and the detailed structure size of the small and medium-sized cast-in-place box beam 30, the embodiment takes the cast-in-place box beam 30 with the length of 20-30 m as a research object, collects the existing special construction scheme and related documents, refers to the data of the highway bridge design manual, the special technical scheme of the construction temporary support structure and the like, establishes the cast-in-place box beam-pier-free support database of the structural size of the cast-in-place box beam 30, and counts the upper limit value and the lower limit value of the detailed size of the cast-in-place box beam 30. In addition, the lengths of all sections of the cast-in-place box girder 30 under different spans are counted, and the load contribution of the chamfers of the top plate and the bottom plate is considered.

1. Cast-in-place box girder 30 construction size

As shown in fig. 11 to 14, the 20-30 m span cast-in-place box girder 30 is generally three large areas according to the type of cross section, namely, a solid section, a transition section and a general section, wherein the transition section is different from the general section in the thickness of a top plate, the thickness of a bottom plate and the thickness of a web plate.

The section mainly counts the basic construction size of a 20-30 m span cast-in-place box beam 30, classifies and gathers the construction sizes of the box beams according to different span diameters and different positions, puts the construction sizes of the box beams into a cast-in-place box beam-buttress-free support database, and provides basic basis for subsequent load calculation of design of longitudinal distribution beams, transverse distribution beams and assembled longitudinal beams 27, wherein the specific construction sizes are shown in the following table:

TABLE 2 Box girder dimension statistical table

According to the above table, the limit values of the upper limit and the lower limit of the beam height of the cast-in-place box beam 30 of 20m to 30m are 1.4m to 2.0m based on the statistical table of the construction size of the cast-in-place box beam 30 of 20m to 30 m; the limit value of the overhanging length of the flange is 1.75-2.5 m; the limit value of the bottom width of the box girder is 5-6 m;

in addition, when the surface load concentration of the flange is calculated, the trapezoidal load is simplified into the rectangular load, and the problem of flange thickness dereferencing is involved. Through comparison calculation, when the flange thickness value is the flange root thickness, the bending moment of the flange root is about 1.67 times of the actual bending moment, and when the flange thickness value is the flange average value, the bending moment of the flange root is about 1.17 times of the actual bending moment, so in order to simplify the accuracy of calculation, the flange thickness average value (D3+ D4)/2 is taken as the flange thickness value for calculation.

2. Chamfer size statistics

TABLE 3 cast-in-situ box girder chamfer statistical table

From the above table, the chamfer area is taken into account for simplifying the load calculation of the top and bottom plates. The sizes of upper and lower chamfers of a 20-30 m span cast-in-place box beam 30 are collected and put into a cast-in-place box beam-buttress-free support database, the amplification factor K is further calculated to be A/A2, and the maximum amplification factor K in a table is subsequently recorded into load calculation of a top plate and a bottom plate when the maximum amplification factor K is 1.2.

3. Segment length statistics

Table 420 m-30m statistical table for length of each section of cast-in-situ box girder 30

As can be seen from the above table, based on the length statistical table of each section of the 20m-30m span cast-in-place box girder 30, the length limit value of the general section of the 20m-30m cast-in-place box girder is 6 m-11 m; the limit value of the length of the transition section is 3 m-7 m; the limit value of the width and the length of the bottom of the box girder is 1 m-1.5 m; the lengths of all sections of the cast-in-place box girder 30 are counted, and basic parameters are provided for calculating the internal force value of the control section of the 20-30 m span fabricated longitudinal girder 27.

Second, statistics of structural size data parameters of support without buttress

Based on collected engineering case data, counting the structure type of the support, determining the arrangement form of the support, analyzing the load transmission path after the support is arranged, and summarizing the load distribution rule of the support and determining a reasonable interval according to the load transmission path.

In order to count the construction load of the support without the buttress, the data such as a road and bridge design manual, a special technical scheme for a construction temporary supporting structure and the like are referred, a cast-in-place box girder-support without the buttress database is put into the database, and a design load automatic calculation table is manufactured according to the data, specifically comprises four areas (web and solid sections, top plates and bottom plates of general sections, top plates and bottom plates of transition sections and flanges), a design load table of a longitudinal distribution beam, a design load table of a transverse distribution beam and a design load table of an assembled longitudinal beam 27, and the corresponding internal force value can be obtained by changing basic parameters.

1. The support arrangement form is as follows: after researching a large number of documents and looking up special construction schemes, the traditional 20-30 m span cast-in-place box girder 30 support stress structure mainly comprises 3 layers, and based on the stress structure, the support stress structure is planned to comprise a longitudinal distribution girder (along the forward bridge direction), a transverse distribution girder (along the transverse bridge direction) and an assembled longitudinal girder 27 from top to bottom.

2. A load transmission path: for the statistics of the non-buttress bracket load, firstly, a main load transmission path of a non-buttress bracket stress component is determined, and the transmission path is approximately as follows: the cast-in-place box girder 30 is transmitted to the longitudinal distribution girder by means of fluid load, then is transited to the transverse distribution girder and the fabricated longitudinal girder 27 by means of concentrated force, and finally is transmitted to the buttress and the foundation of the bridge, and the load transmission path is as shown in fig. 16:

3. the load distribution rule of the assembled longitudinal beam 27 is as follows:

TABLE 5 statistical table for arrangement intervals of main stressed members

Arrangement distance and load value of transverse distribution beam 25 and longitudinal distribution beam 26

TABLE 6 static and dynamic load statistical table for construction

The static load of the cast-in-place box girder 30 mainly comprises the load of a template bracket and the volume weight of concrete, and the dead weight of a main stressed member is temporarily not considered because the member selection is not carried out by manual calculation; for the load statistics table of Table 5, (1) consider the self-weight q of the form at the web and the top and bottom plates₂₂(ii) a (2) Consider the bracket and template loads at the wing edges: further, the load of the beam height H of 2m is obtained by a linear interpolation method: q. q.s₂₁＝0.402kN/m²。

And for the construction dynamic load, the construction dynamic load mainly comprises crowd machine tool load and vibration load.

Designing surface load in four areas:

at present, the cast-in-place box girder 30 of 20-30 m is of a hollow structure in other areas except that the adjustable section 2 is a solid body. The hollow structure mainly comprises a web plate, a top plate, a bottom plate and a flange. Because the vertical concrete load is mainly related to the pouring height, the surface load concentration of the web plate and the solid section is consistent, so the web plate and the solid section can be combined into one type, the top plate and the bottom plate are divided into a transition section and a common section, the flange basically keeps unchanged, and the flange can be independently used as one type. So, the case roof beam divide into altogether: the web and solid sections, the general section top and bottom plates, the transition section top and bottom plates and the flanges, and 4 types are used for calculating the design load.

The following web and solid sections are taken as examples: firstly, a load statistical table of the design surface of the web plate and the solid section is made, as shown in table 7, and then the load limit value of the design surface of the web plate and the solid section is calculated: as shown in table 8:

TABLE 7 statistical table of loads of design surfaces of web and solid sections

TABLE 8 statistical table of load limit values of design surfaces of web and solid sections

Obtaining a general section-top plate and bottom plate design surface load limit value, a transition section-top plate and bottom plate design surface load limit value and a flange design surface load limit value statistical summary table in the same way:

TABLE 9 statistical summary of limit values of loads of design surfaces of residual regions

Designing line load of the longitudinal distribution beam:

and simplifying the upper load of the longitudinal distribution beam into a linear load, simplifying the linear load into a multi-span continuous beam, searching by combining a static calculation manual to obtain a shearing force and a bending moment distribution coefficient, and solving to obtain a bending moment and a shearing force internal force value of the control section.

The following takes the general section-web-longitudinal distribution beam as an example: firstly, a general section-web plate-longitudinal distribution beam design line load table is made, as shown in table 10, a general section-web plate-longitudinal distribution beam design line load limit value table is obtained, as shown in table 11, and then a general section-top plate and bottom plate-longitudinal distribution beam design line load limit value, a general section-flange-longitudinal distribution beam design line load value and a general section-flange-longitudinal distribution beam design line load limit value general table are made based on the same principle: as shown in table 12:

TABLE 10 general section-web-longitudinal distribution beam design line load table

TABLE 11 general section-web-longitudinal distribution beam design line load limit table

Obtaining a general section-top plate and bottom plate-longitudinal distribution beam design line load limit value and a general section-flange-longitudinal distribution beam design line load limit value general table in the same way:

table 12 general table of remaining area-longitudinal distribution beam design line load limit value

Design line load of the transverse distribution beam 25: the load diagram of the general section/transition section-transverse distribution beam of the cast-in-place box beam and the load diagram of the solid section-transverse distribution beam of the cast-in-place box beam shown in fig. 17 and 18 are drawn on the basis of simplifying the structural load above the transverse distribution beam into the load of the beam unit line and taking the lower-layer lapped fabricated longitudinal beam 27 as a support.

The following takes the general section-web-longitudinal distribution beam as an example: firstly, a load table of the design line of the transverse distribution beam corresponding to the general section is made, as shown in table 13, a load limit value table of the design line of the transverse distribution beam corresponding to the general section is obtained, as shown in table 14, and then the load limit value of the design line of the longitudinal distribution beam corresponding to the general section-the top plate and the bottom plate, the load value of the design line of the longitudinal distribution beam corresponding to the general section-the flange-and the load limit value total table of the design line of the longitudinal distribution beam corresponding to the general section-the flange are made based on the same principle: as shown in table 15:

table 13 general section corresponding transverse distribution beam design line load table

Table 14 general section corresponding transverse distribution beam design line load limit table

Similarly, a total table of the load limit values of the transverse distribution beam design lines corresponding to the transition section and the solid section is prepared:

table 15 general table of load limit values of corresponding transverse distribution beam design lines in remaining areas

The fabricated stringer 27 design line loads: selecting a cast-in-place box girder 30 of 20-30 m as a research object, simplifying the upper structure load of the fabricated longitudinal girder 27 into a girder element line load, drawing a fabricated longitudinal girder load schematic diagram of the cast-in-place box girder shown as 19, and further carrying out load combination to calculate the design loads of different sections by considering the construction dynamic load.

TABLE 16 Upper structural in-line load statistics for fabricated stringers 27

Thirdly, analyzing the internal force of the component:

1. longitudinal distribution beam internal force analysis

Simplifying the method into a multi-span continuous beam, drawing a load schematic diagram and an internal force diagram, searching by combining a static calculation manual to obtain a shearing force and bending moment distribution coefficient, and further solving to obtain internal force values of control sections of different sections.

TABLE 17 general section-Web-longitudinal distribution Beam design load statistics

And similarly, obtaining a general section-top plate and bottom plate-longitudinal distribution beam design load limit value and a general section-flange longitudinal distribution beam design load limit value summary table.

Table 18 general table of design load limit value of other areas-longitudinal distribution beam

2. Transverse distribution beam internal force analysis

Taking a single transverse distribution beam as a research object, simplifying the upper layer load of the transverse distribution beam into line loads of different areas, drawing a load schematic diagram of a general section, a transition section and an entity section, and calculating the maximum internal force value of the worst section by combining a hand-push formula.

And further drawing an internal force diagram of the structure. The detailed calculation results are shown in fig. 20 and the following table.

TABLE 19 general section-transverse distribution beam design load statistical table

And obtaining a total table of the design load limit values of the transition section-transverse distribution beam and the design load limit values of the entity section-transverse distribution beam in the same way.

Table 20 general table for design load limit of transverse distribution beam in other areas

Through the calculation of fig. 20 and 21, the designed load limit values of the transverse distribution beam corresponding to the respective areas in the tables 19 and 20 are obtained, and the calculation is prepared for the stress calculation of the fabricated longitudinal beam 27.

3. Force analysis in fabricated stringer 27: selecting a cast-in-place box girder 30 of 20-30 m as a research object, simplifying the load of the upper structure of the fabricated longitudinal girder 27 into a girder unit line load, further carrying out load combination to calculate the design loads of different sections by considering the construction dynamic load, and finally obtaining the support counter force and the maximum cross-section internal force of the fabricated longitudinal girder 27, wherein the result is shown in fig. 21 and the following table:

meter 21 assembled longitudinal beam 27 design load statistical meter

Fourthly, selecting the section of the component:

1. internal force distribution rule:

the values of the internal force of the main stress member obtained by the above calculation are summarized as follows:

TABLE 22 general section-distribution beam optimized layout and internal force summary table

Table 23 fabricated longitudinal beam 27 optimizing arrangement and internal force summary table

2. Component internal force analysis

The load transmission path of the fabricated buttress-free support is first defined as shown in fig. 16. And secondly, counting the arrangement conditions of the assembled buttress-free supports, wherein the arrangement conditions comprise the common arrangement intervals of the longitudinal distribution beams 26 and the transverse distribution beams 25 and the arrangement intervals of the assembled longitudinal beams 27, and providing a reference basis for internal force calculation. And analysis is carried out based on a longitudinal distribution beam 26 model, a transverse distribution beam 25 model and an assembly type longitudinal beam 27 model, wherein the assembly type longitudinal beam 27 is mainly formed by splicing a telescopic adjustable section 2 (4-4.5 m) and a standard truss section 1 (the specification is 5m, 7m and 9m), and the cast-in-place box beam 30 support with any span of 20-30 m can be realized. The specific combination pattern is shown in the following table:

design research of support without buttress

Based on support construction load statistics, firstly, determining the distribution condition of internal force of a support structure by adopting a method of combining manual calculation and electric calculation, then searching corresponding industrial specifications to select the section of a rod piece, finally, respectively designing a rod piece connecting system and an anchoring system, verifying the strength, rigidity and stability of the structure, and simultaneously designing the protection level and the design age of the support based on the structural durability, wherein the design comprises the selection of coating, the design of the thickness of the coating and the like.

Sixthly, research on manufacturing technology of support without buttress

According to the structural design drawing, firstly, the standards of the bracket processing and manufacturing are compared and selected, so that the selection of the bracket manufacturing standards is determined, secondly, manufacturers with good use performance and production quality are selected to carry out standardization and modularization manufacturing, and finally, the corresponding transportation mode and the storage scheme are compiled according to the shape, size and stress characteristics of the bracket, so that the bracket is ensured not to deform and loosen in the transportation and storage processes, and the installation quality is ensured. And finally, drawing a stress sketch map and an internal force map of the rod piece according to the actual arrangement condition of the structure, and compiling an Excel automatic calculation table to finish the calculation of the internal force (including bending moment, shearing force, axial force and the like) of the rod piece under different working conditions. And (4) according to the calculated internal force value, disclosing the internal force change rule of the rod piece under different bridge spans and different arrangement conditions, and defining the change range of the rod piece. And finally, providing structure arrangement optimization configuration and internal force design values based on the internal force change rule, wherein the optimization configuration comprises rod piece arrangement intervals, rod piece sections and the like.

Seventhly, selecting the section of the component

As shown in fig. 22 to 24, according to the rod arrangement optimization configuration and the internal force design values, the initial selection of the rod section is performed by a manual calculation method, and then the optimization of the rod section design is calculated by modeling of finite element analysis software.

Pouring a template, selecting the type of the longitudinal and transverse distribution beams and checking calculation: and reversely calculating the inertia moment of the section according to the maximum internal force value and the allowable stress value of the section of the main component, inquiring the type and the size of the selected material of the relevant specification, and checking the strength and the rigidity of the section.

Checking and calculating a pouring template: taking the pouring template 24 as an example, and referring to a simplified panel calculation formula of road and bridge construction handbook, the checking calculation of the strength and rigidity is performed on the bottom membrane panel of the pouring template 24, the specific calculation process is as shown in fig. 25, and the maximum bending moment, the maximum shearing force, the maximum positive stress and the maximum shearing stress in the span in the strength and the maximum deflection in the rigidity are calculated, so as to meet the design requirements of the strength and the rigidity:

checking and calculating a longitudinal distribution beam: taking a longitudinal distribution beam of a general section-web as an example, and referring to a simplified calculation formula of a continuous beam in 'road and bridge construction handbook', the process of checking and calculating the strength and the rigidity of the longitudinal distribution beam is shown in fig. 26, and the maximum bending moment, the maximum shearing force, the maximum positive stress and the maximum shearing stress in the span in the strength of the longitudinal distribution beam and the maximum deflection in the rigidity of the longitudinal distribution beam are calculated to meet the design requirements of the strength and the rigidity.

Checking and calculating a transverse distribution beam: taking a transverse distribution beam of a general section as an example, the strength and rigidity of the transverse distribution beam are checked, and the specific calculation process is as shown in fig. 27, and the maximum bending moment, the maximum shearing force, the maximum normal stress and the maximum shearing stress in the span in the strength of the transverse distribution beam and the maximum deflection in the rigidity of the transverse distribution beam are calculated to meet the design requirements of the strength and the rigidity.

And (3) optimization design of the fabricated longitudinal beam, wherein the optimization design of the fabricated longitudinal beam 27 mainly comprises the design of a structural form and a section form.

The main stressed components of the fabricated stringers 27 include: the upper and lower chord members, the web members, the pull rods and the cross links; specific materials and cross-sectional types are shown in the following table:

table 24 material selection list of main members of the fabricated side member 27

Main component	Upper and lower chord	Web member	Pull rod	Transverse connection
					Type (B)	Double-spliced channel steel	I-shaped steel	Round steel pipe/solid circle	Channel steel

In order to improve the recycling rate and save the construction cost, factors such as assembly, disassembly and transportation are considered, a support combination form without buttresses is adopted, wherein the support combination form meets the requirement that the support combination form spans a cast-in-place box girder 30 by 20-30 m, and the support combination form is adjustable in a telescopic mode and is a standard section (5m-7m-9m), and is specifically shown in figure 1. For the fabricated longitudinal beam 27, the connection of the unit components adopts a double-vertical-rod and double-transverse-connection mode, and the center distance and the clear distance of the double vertical rods are obtained. Taking 30m fabricated stringers 27 as an example, the fabricated stringers 27 are formed by combining 2 4.5m adjustable sections and 37 m standard sections, and the overall section height, the section centroid spacing and the width of the fabricated stringers 27, the section centroid spacing and the spacing of the two groups of fabricated stringers 27 in the transverse bridge direction are calculated.

2. Finite element analysis software integral model verification

The structural size is as follows: as shown in fig. 28, since the non-buttress support of the 30 m-span cast-in-place box girder 30 bears the largest bending moment and shearing force, the 30 m-span cast-in-place box girder 30 is taken as a research object in this chapter, and the basic construction dimensions are shown in the following table:

meter 2530 m span cast-in-place box girder 30 structure size

Type and size of the main stressed member: the atress component of no buttress support has 3 layers, mainly has from top to bottom: longitudinal distribution beams-transverse distribution beams-fabricated longitudinal beams. According to the stress characteristics and the internal force of each layer of component, the corresponding material type (see table 24 in detail) and the cross-sectional dimension are selected

Arrangement spacing: in order to facilitate construction and improve the integral stress performance of the support without the buttress, the longitudinal distribution beam spacing of the general section is adjusted from 350mm to 300mm, and the lengths of the solid section, the transition section and the general section of the half span are respectively 1000mm-7000mm-7000 mm; and the distance between the longitudinal distribution beams, the transverse distribution beams and the upper chord member and the lower chord member of the fabricated longitudinal beam 27 of different sections is calculated to be 100mm to 400 mm.

Boundary conditions: general support, rigid connection and release of beam-end restraint are mainly employed.

Applying a load: and (3) adopting an allowable stress method, considering concrete layered pouring, wherein the loads of the first layer of concrete mainly comprise a bottom plate and a web plate, the loads of the second layer of concrete mainly comprise a top plate and a flange, and applying and calculating the load of the beam unit line by adopting regional segmentation.

For a 30m span cast-in-place box girder 30, the height of the girder is 2m, the first layer is poured to the position of 1.45m, and the second layer is poured with the rest 0.55 m.

Model analysis

And (3) stability analysis: in the former many engineering projects, the checking calculation of the strength and the rigidity of the structure is only concerned, but the stability checking calculation is often neglected, so that most of structures are caused by instability damage, and therefore, the buckling stability analysis is required to be carried out on the temporary structure, and the buckling analysis characteristic value is required to be not less than 4. The characteristic value of the 1 st order stability coefficient of the buckling mode of the model is 19 to be more than 4, so that the overall stability of the 30 m-span cast-in-place box girder buttress-free support meets the requirement. In addition, the buckling mode of the temporary structure can be observed, the parts which are easy to lose stability can be known in advance, the weak rod pieces or the parts are reinforced, and the stability and the safety of the whole structure are improved.

Static analysis

And (3) checking and calculating the strength: the intensity checking calculation mainly comprises the checking calculation of the normal stress and the shearing stress, and the section can compare the calculation results of the manual calculation and the electric calculation stress of the main stressed components of the buttress-free support, continuously optimize a finite element analysis software model and lay a foundation for developing later-stage test research.

Taking the longitudinal distribution beam as an example: hand and computer calculation results

Table 26 longitudinal distribution beam stress summary table

From the above results, the normal stresses of the three regions (entity section, transition section and general section) are all smaller than the allowable normal stress, wherein the maximum normal stress of the general section (manually calculated 6.45Mpa and electrically calculated normal stress 5.76Mpa) is smaller than 11Mpa, the difference between the electrically calculated result and the manually calculated result is relatively close, the primarily analyzed manually calculated result is calculated according to the load of one-time pouring, and the load and boundary conditions of the finite element analysis software model are adjusted according to the actual pouring condition in the later period.

In addition, as for the shearing stress of the longitudinal distribution beam, both the manual calculation result and the electric calculation result are smaller than the allowable shearing stress of 1.7MPa, and the manual calculation result is closer to the electric calculation result, so that the strength meets the specification requirement.

Fabricated side member 27: the stressed member of the fabricated longitudinal beam 27 mainly comprises an upper chord member and a lower chord member on the section of the double-spliced channel steel, a web member on the section of the I-shaped steel, a pull rod on the section of the round pipe and a cross joint on the section of the channel steel. Because the structure of the assembled longitudinal beam 27 is complex, the manual calculation process is complicated, and only the calculation result of the electric calculation is checked and calculated here, the details are shown in the following table:

table 27 fabricated stringer 27 stress summary table

As can be seen from the electric calculation result of the fabricated longitudinal beam 27, the upper chord and the lower chord of the fabricated longitudinal beam 27 basically meet the requirements of end shearing resistance and section bending resistance, the electric calculation normal stress 121MPa is less than the allowable normal stress 210MPa, and the shearing stress 54.1MPa is less than the allowable shearing stress 120MPa, namely the strength design requirement is met; secondly, for the web members, the sectional area is mainly enlarged to resist the shear stress, so that section steel with a larger section is selected as far as possible, the maximum positive stress 135MPa of the assembled longitudinal beam 27 appears at the position, and whether the section of the steel plate is welded at the later stage or not is judged; thirdly, for the pull rod and the transverse connection, the upper chord member and the lower chord member are mainly connected to form a whole to form a stressed frame structure, and the structural size of the pull rod is adjusted in the later period according to the calculation result.

Stiffness verification as shown in fig. 28, the stiffness of the temporary structure represents its ability to resist deformation. For the sake of simple calculation, the 30m span buttress-free brace assembled longitudinal beam 27 can be simplified into a simple beam, the structural deformation of which cannot be ignored, and particularly the mid-span deformation needs to be focused. Considering the self weight of the stressed member and the load of the applied beam unit line, calculating the integral deflection of the support without the buttress, and checking the rigidity, as shown in fig. 28: the integral deflection of the buttress-free support with the span of 30m is 34.9mm and less than the allowable deflection of 75mm, and the requirement on rigidity is met.

Rod connection design

Calculating a connecting pin: as shown in fig. 30, the unit members between the upper and lower chords are connected by using U-shaped male and female heads + connecting pins, so the present embodiment mainly performs design calculation on the connecting pins and the male and female heads. In addition, the connecting pin is taken as a stress research object, the stress sketch of the connecting pin is shown in fig. 29, then the maximum axial force at the chord release beam end constraint unit of the finite element analysis software model is extracted, the maximum axial force at the chord unit is 1265kN, the maximum axial force is taken as the stress performance of the connecting pin, the connecting pin is designed and selected, and meanwhile, the shearing resistance and the bending resistance of the connecting pin are checked.

TABLE 28 bond pin shear calculation

TABLE 29 Link Pin bending calculation

In addition, as can be seen from the above table, the connecting pin with a diameter of 14cm is selected to meet the requirements of shear resistance and bending resistance.

Calculating yin and yang heads: the female head structure and the male head structure are shown in the figure 30, after connecting pins with the diameter of 14cm are selected, structural design and related checking calculation are carried out on the female head and the male head, and the effective sections I, II of the female head and the male head and pin hole contact surfaces meet the stress requirement, so that the structural design is scientific and reasonable.

Example 8

A design method for an assembled buttress-free support described in embodiment 3 is different from that described in

embodiment

6 or 7 in that: step S3 specifically includes the following steps:

s31, selecting the length size of one standard truss section 1 based on transportation and manufacturing conditions, and defining the length size as a first standard truss section unit 5;

s32, based on the length of a first standard truss section unit 5, drawing up the length of another two standard truss sections 1, and defining the lengths as a second standard truss section unit 4 and a third standard truss section unit 3 respectively, so that the length of the third standard truss section unit 3 is less than that of the second standard truss section unit 4 is less than that of the first standard truss section unit 5, and the length adjusting range of the adjustable section 2 is drawn up based on the length of the first standard truss section unit 5, the length of the second standard truss section unit 4 and the length of the third standard truss section unit 3;

s33, determining whether the length range of the assembled longitudinal beam 27 covers all the integral length meters within the range of 20m-30m or not based on the length and the number of the first standard truss section units 5 and the length adjusting range of the adjustable section 2;

s34, if the length range of the fabricated longitudinal beam 27 in the step S33 can not cover all the lengths of the integer meters in the range of 20m-30m, determining whether the length range of the fabricated longitudinal beam 27 covers all the lengths of the integer meters in the range of 20m-30m or not based on the length and the number of the first standard truss section units 5, the length and the number of the second standard truss section units 4 and the length adjusting range of the adjustable section 2;

s35, if the length range of the fabricated longitudinal beam 27 in the step S34 can not cover all the lengths of the integer meters in the range of 20m to 30m, determining whether the length range of the fabricated longitudinal beam 27 covers all the lengths of the integer meters in the range of 20m to 30m or not based on the length and the number of the first standard truss section units 5, the length and the number of the second standard truss section units 4, the length and the number of the third standard truss section units 3 and the length adjusting range of the adjustable section 2;

s36, if the length range of the assembled longitudinal beam 27 in the step S35 cannot cover all the lengths of the integral meters within the range of 20m-30m, adjusting the length of the second standard truss section unit 4, and repeating the steps S34-S35 until the length range of the assembled longitudinal beam 27 covers all the lengths of the integral meters within the range of 20m-30 m; and/or adjusting the length of the third standard truss section unit 3, and repeating the step S35 until the length range of the assembled longitudinal beam 27 covers all the integral length meters within the range of 20m-30 m;

and S37, in the above steps, when the length range of the assembled longitudinal beam 27 covers all the integral length meters within the range of 20m-30m, stopping, and taking the length and the number of the first standard truss section units 5, the length and the number of the second standard truss section units 4 and the length and the number of the third standard truss section units 3 under the condition as final values, so as to determine the final value of the length adjusting range of the adjustable section 2. During calculation, the method specifically comprises the following steps:

the method comprises the following steps: a standard segment combination single specification combination mode: firstly, in the combination process, the size and the number of standard segments are selected according to the principles of structural symmetry and least node, and then the size of the adjustable segment 2 is determined, as shown in formula 4-1:

S＝aLi+2Dj (4-1)

wherein S is span, and S is 20-30 m; a is the number of standard sections and is an odd number; li is the length of a standard segment, and comprises three specifications of 5m, 7m and 9m, and in order to reduce the number of the segments as much as possible, the selection principle is to select the standard segment with the longest segment; dj is the length of the adjustable segment 2, which comprises 4m and 4.5m, and the adjustable segment 2 is determined after the standard segment is selected.

Step two: two standard section combination dual specification combination modes: if the selection rule according to the step one cannot meet the requirement, two standard sections are further selected for combination, and the standard sections selected in the combination process are combined from the two longest specifications, so that the number of the sections is reduced, as shown in a formula 4-2: s ═ aLi + bLj +2Dj (4-2)

Wherein S is span, and S is 20-30 m; a. b is the number of standard sections, and both odd numbers and even numbers can be used; li and Lj are standard segment lengths, including three specifications of 5m, 7m and 9m, and in order to reduce the number of segments as much as possible, the selection principle is to select the standard segment with the longest segment; dj is adjustable segment 2, which comprises 4m and 4.5m, and adjustable segment 2 is determined after the standard segment is selected.

Step three: three specification combination multi-specification combination modes: if the combination can not be carried out according to the step one and the step two, three specifications are adopted for combination, as shown in the formula 4-3: s ═ aLi + bLj + cLk +2Dj (4-3)

Considering from the aspect of structural form, the assembled longitudinal beam 27 is used as a main stress structure of the buttress-free bracket, the segment assembly of the assembled longitudinal beam follows the principle of 'less specification and multiple combination', namely on the premise of meeting scientific and economic concepts, the specification types of the segments are reduced, the processing and manufacturing cost of steel is reduced, and the requirement of quick assembly and hoisting can be met on a construction site. In addition, the section specification of the fabricated side member 27 can satisfy the basic conditions for highway transportation, and is also suitable for the transportation conditions in mountainous areas.

Furthermore, the adjustable segments 2 have 4m and 4.5m, and the standard segments have 5m, 7m and 9m, i.e. there are 5 segment sizes in total. The specification and the size of the segment are selected in the early stage, the basic size of the standard segment is considered, and then the size of the adjustable segment 2 is determined. The transportation condition of the highway and the difference between the lengths of the adjacent standard sections are not less than 2m are mainly considered for the lengths of the sections of the standard sections, and as the shapes and the structural forms of the standard sections are basically consistent, if the adjacent standard sections are relatively close in length difference, field workers can easily mix the sections with different specifications, and the sections with other specifications are mistakenly selected for assembly, so that the field requirements cannot be met, large-area rework occurs, the labor cost and the time cost are increased, and the principle of green circular economy is violated. Therefore, through repeated comparison, 5m, 7m and 9m standard section series are selected, the equal difference series sections with the tolerance of 2m are added with 4m and 4.5m adjustable sections 2, and the space steel truss assembled on site and spanning the cast-in-place box girder 30 at 20-30 m can be met by using 3 specifications including the adjustable sections 2 and the standard sections at most.

The connection mode is as follows: adjustable section 2 and standard section, standard section and adjustable section 2 all adopt negative and positive head + pin to be connected, can accomplish the spelling fast at the scene. When the selection of the male and female heads and the pin is designed, a finite element analysis software model is established, the beam end unit constraint is released at each connection part-beam unit, the axial force of the chord member at the position is extracted to design and calculate the pin as a shearing force, and meanwhile, the pressure bearing of the hole wall of the male and female head and the stress of the pin are checked and calculated.

The spatial steel truss (the fabricated longitudinal beam 27) adopts a fish belly-shaped structural form (the upper chord and the lower chord are parallel and the end pull rod is inclined): mainly considered from the following 3 aspects: structural form aspect: the pull rod of the adjustable section 2, the upper chord member and the web member form an approximate structure right triangle, a local truss structure is formed, and the stability of the adjustable section 2 is greatly improved. If the pull rod is not arranged, the suspension section similar to a suspended heavy object is formed, and the risk of instability and rollover is further improved. In the aspect of site construction: the integral structure of the adjustable section 2 is like a right trapezoid, and the bevel edge of the right trapezoid is arranged at the end part of the adjustable section 2, so that enough space and enough positions are provided for installing and detaching the anchoring system, and the on-site segmental assembling and hoisting and the worker construction operation are facilitated. The stress performance is as follows: the space truss of the technical scheme mainly bears the load transmitted by the transverse distribution beam and the stressed components above the transverse distribution beam, the lower chord in the comparison document 1 inclines from two ends to the middle to form a large-angle sharp angle, and when the trapezoidal steel structure support bears the upper load to generate deformation, stress concentration is easily formed at the position to cause the tensile damage of the lower chord. In addition, the shear keys are adopted at the end parts of the space truss in the technical scheme to resist shear deformation damage.

Example 9

This example provides a design method for the fabricated buttress-free brace system of example 5, comprising the steps of:

a1, completing the design of the fabricated longitudinal beam 27 based on the design method for the fabricated buttress-free support frame as described in the application, and obtaining the support reaction force data parameters of the fabricated longitudinal beam 27;

a2, counting the size data parameters of the buttress 31 for the existing bridge, namely the fabricated longitudinal beam 27, establishing a buttress 31 database, obtaining the most common data parameter values of the buttress 31 size within the span range of 20-30 m based on the buttress 31 database, and accordingly drawing the structure size of the buttress anchor ear 28;

a3, introducing the main cross beam 29 based on the structure of the fabricated longitudinal beam 27 and the structural size of the buttress anchor ear 28, and determining the load transmission path from the fabricated longitudinal beam 27 to the buttress anchor ear 28;

a4, obtaining the maximum bending moment and the maximum shearing force of the section of the main cross beam 29 based on the data parameters of the support reaction force of the fabricated longitudinal beam 27, performing section selection on the main cross beam 29 according to the maximum bending moment and the maximum shearing force, and then calculating to obtain the load applied to the buttress anchor ear 28 by the main cross beam 29;

and A5, verifying the strength, rigidity and stability of the structure size of the proposed buttress anchor ear 28 based on the load applied to the buttress anchor ear 28 by the main cross beam 29.

The beneficial effects of the embodiment are that: the method comprises the steps of assembling the longitudinal beam 27 based on the size data parameters of the existing pier 31 for the beam, establishing a pier 31 database, obtaining the most common data parameter values of the size of the pier 31, determining the structural size of the pier hoop 28 based on the most common data parameter values, introducing the main cross beam 29, determining the load transmission path from the assembled longitudinal beam 27 to the pier hoop 28, and improving the efficiency of the pier hoop 28 design by providing parameter basis for the design of the pier hoop 28 in the whole process.

Example 10

The embodiment provides a design method for the fabricated buttress-free support system in the embodiment 5, and in the practical process, the design method specifically comprises the following operations: a1, completing the design of the fabricated longitudinal beam 27 based on the design method for the fabricated pier-free bracket as described in the

embodiment

5, 6 or 7, and obtaining the data parameters of the support reaction force of the fabricated longitudinal beam 27; as shown in fig. 31 and the following table:

table 30 extracts 27 counter forces of fabricated longitudinal beams and solves the vertical force of the hoop

Fabricated longitudinal beam piece 1

Fabricated longitudinal beam piece 2

Fabricated longitudinal beam piece 3

Fabricated longitudinal beam piece 4

Fabricated longitudinal beam piece 5

Fabricated longitudinal beam sheet 6

Unilateral hoop vertical force

F_{Support 1}

F_{Support 2}

F_{Branch 3}

F_{Branch 4}

F_{Branch 5}

F_{Branch 6}

F_Vertical＝F_{Branch assembly}/2

kN

1060.7

831

833

831

1060.7

2724.7

The maximum support reaction force of the single-piece assembled longitudinal beam 27 is 1060.7kN, and the vertical force of the one-side hoop is 2724.7 kN.

As shown in fig. 34 and 35, the buttress anchor 28 is sleeved and clasped around the outside of the buttress 31, and a plurality of rib plates 36 are arranged on the buttress anchor 28 for reinforcing the structure of the buttress anchor 28.

And A2, counting size data parameters of the buttress 31 for the existing bridge, namely the fabricated longitudinal beam 27, establishing a buttress 31 database, obtaining the most common data parameter values of the buttress 31 with the span within the range of 20-30 m based on the buttress 31 database, drawing up the structural size of the buttress anchor ear 28 according to the most common data parameter values, and selecting the steel anchor ear with the diameter of 1.5m, the height of 1.2m and the thickness of 2 cm.

As shown in fig. 36, step a3, introducing the main cross member 29 based on the structure of the fabricated side member 27 and the structural dimensions of the pier hoops 28, and determining the load transmission path of the fabricated side member 27 to the pier hoops 28;

step A4, obtaining the maximum bending moment and the maximum shearing force of the section of the main cross beam 29 based on the data parameters of the support reaction force of the fabricated longitudinal beam 27, performing section selection on the main cross beam 29 according to the maximum bending moment and the maximum shearing force, and then calculating to obtain the load applied to the buttress anchor ear 28 by the main cross beam 29; specifically, as can be seen from the structural cooperation of the fabricated longitudinal beams 27, the main cross beam 29 and the steel buttress hoops 28, the load transmission paths of the three layers of stressed members are as follows: the assembling type longitudinal beam 27 → the main cross beam 29 → the buttress anchor ear 28 takes the main cross beam 29 as a stress research object, the structure of the stress research object is simplified and calculated, a structural mechanics solver is used for modeling to solve the maximum bending moment and the maximum shearing force of the cross section of the main cross beam 29, the cross section of the main cross beam is subjected to section selection according to the maximum bending moment and the maximum shearing force, and the specific size of the main cross beam is obtained. Calculating to obtain absolute value | M of maximum bending moment of cross section of main beam_maxAbsolute value of | and maximum shearing force | V_maxAnd finally substituting the section bending modulus obtained by inverse calculation into a corresponding calculation formula, and checking and calculating the normal stress and the shear stress to meet the standard calculation requirement.

Step A5, checking the strength, rigidity and stability of the structure size of the proposed buttress anchor ear 28 based on the load applied to the buttress anchor ear 28 by the main beam 29, wherein the checking includes checking the number of high-strength bolts and the checking of shearing resistance and tensile resistance.

Meter 31 hoop structure stress checking calculation summary

A steel hoop with the diameter of 1.5m, the height of 1.2m and the thickness of 2cm is selected. And high-strength bolts M24 and 48 bolts are selected, and meet the basic requirements of the specification through the requirements of tensile resistance and bending resistance.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. The assembled longitudinal beam is characterized by comprising a standard truss section (1), wherein two ends of the standard truss section (1) are detachably connected with adjustable sections (2), the length of each adjustable section (2) can be adjusted, and the longitudinal total length range of the standard truss section (1) and the two ends after the adjustable sections (2) are matched can meet at least two span lengths between a first threshold value and a second threshold value.

2. Fabricated stringer according to claim 1, wherein the standard truss section (1) comprises at least two detachably connected standard truss section units, and each standard truss section unit is provided with a connection portion (35) for detachable connection with the adjustable section (2),

and the detachable connection of the standard truss section (1) and the adjustable section (2) is configured as follows: the longitudinal total length range of one or more standard truss section units matched with the two adjustable sections (2) can meet at least two span lengths between the first threshold value and the second threshold value.

3. Fabricated stringer according to claim 2, wherein said standard truss section (1) comprises three different lengths of said standard truss section units, respectively defined as a third standard truss section unit (3), a second standard truss section unit (4) and a first standard truss section unit (5), wherein,

the length of the third standard truss section unit (3) is less than that of the second standard truss section unit (4) is less than that of the first standard truss section unit (5);

the longitudinal length of the first standard truss section unit (5) is X1, and X1 is more than or equal to 8m and less than or equal to 10 m;

the longitudinal length of the second standard truss section unit (4) is X2, and X2 is more than or equal to 6m and less than or equal to 8 m;

the longitudinal length of the third standard truss section unit (3) is X3, and X3 is more than or equal to 4m and less than or equal to 6 m.

4. A fabricated stringer according to claim 3, wherein the total longitudinal length of one or more standard truss section units in cooperation with two of said adjustable sections (2) is within a range that satisfies all integers of meters between said first threshold value and said second threshold value.

5. Fabricated stringer according to claim 3,

the length of the third standard truss section unit (3), the length of the second standard truss section unit (4) and the first standard truss section unit (5) are arranged in an arithmetic progression;

and/or the presence of a gas in the gas,

the longitudinal length of the first standard truss section unit (5) is 9m, the longitudinal length of the second standard truss section unit (4) is 7m, and the longitudinal length of the third standard truss section unit (3) is 5 m.

6. Fabricated stringer according to claim 3, wherein the longitudinal length L1 of the adjustable section (2) is between 3.5m and 5 m.

7. Fabricated stringer according to claim 6, wherein the longitudinal length L1 of the adjustable section (2) is between 4m and 4.5 m.

8. Fabricated stringer according to any of claims 1 to 7, wherein the adjustable section (2) comprises a connecting truss (6) and an adjustable support (7), one end of the adjustable support (7) being telescopically connected to an upper portion of the connecting truss (6), and an end of the adjustable support (7) remote from the connecting truss (6) being connected to a lower portion of the connecting truss (6) by means of a telescopic rod (8).

9. The fabricated stringer according to claim 8, wherein the connecting truss (6) is provided with at least two first connecting holes (9) at intervals along a longitudinal direction thereof, the adjustable support (7) is provided with at least two second connecting holes (10), the first connecting holes (9) are provided corresponding to the second connecting holes (10), the first connecting holes (9) are connected with the second connecting holes (10) through first connecting members (11), and the number of the first connecting members (11) is at least two.

10. Fabricated stringer according to claim 9, wherein the connecting truss (6) comprises side pieces (12) arranged at a vertical distance and connected with each other, the side pieces (12) comprise an upper chord (14) and a lower chord (15), a truss assembly (16) and an inclined bar (17) are connected between the upper chord (14) and the lower chord (15), the inclined bar (17) is located on one side of the truss assembly (16) far away from the standard truss section (1), and the first connecting hole (9) is located on the upper chord (14).

11. Fabricated stringer according to claim 10, wherein the axis of said first connection hole (9) closest to said adjustable support (7) intersects the axis of said diagonal bar (17).

12. A fabricated stringer according to claim 9, wherein the adjustable support (7) comprises an adjustable portion (20) and a support portion (21) arranged perpendicular to each other, the second connection hole (10) is located at the adjustable portion (20), the support portion (21) serves as a support for the fabricated stringer (27), and the telescopic rod (8) is hinged to the support portion (21).

13. The fabricated longitudinal beam of claim 8, wherein the connecting truss (6) comprises side pieces (12) which are vertically spaced and connected with each other, the side pieces (12) comprise an upper chord (14) and a lower chord (15), a straight web member (18) and an X-shaped diagonal web member (19) are connected between the upper chord (14) and the lower chord (15), the number of the straight web members (18) is at least two, and the straight web members (18) are arranged on two sides of the X-shaped diagonal web member (19).

14. Fabricated stringer according to any of claims 1 to 13, wherein said first threshold value is 20m and said second threshold value is 30 m.

15. Fabricated pier-free support, comprising a fabricated stringer (27) according to any of claims 1 to 14, supported above the fabricated stringer (27) with a transverse distribution beam assembly (22), supported on the transverse distribution beam assembly (22) with a longitudinal distribution beam assembly (23), supported on the transverse distribution beam assembly (22), the longitudinal distribution beam assembly (23) being intended to support a casting form (24), wherein,

the transverse distribution beam assembly (22) comprises at least two transverse distribution beams (25), the adjacent transverse distribution beams (25) are arranged at intervals, and all the transverse distribution beams (25) are arranged transversely along the assembled longitudinal beams (27);

the longitudinal distribution beam assembly (23) comprises at least two longitudinal distribution beams (26), the adjacent longitudinal distribution beams (26) are arranged at intervals, and all the longitudinal distribution beams (26) are arranged transversely along the transverse distribution beam (25).

16. A fabricated buttress-free support according to claim 15, wherein there are at least two fabricated stringers (27), all fabricated stringers (27) being spaced apart in the transverse direction of the bridge.

17. A prefabricated buttress-free support system, comprising a prefabricated buttress-free support according to claim 15 or 16, wherein a buttress anchor ear (28) is arranged below the adjustable section (2), wherein the buttress anchor ear (28) supports the prefabricated buttress-free support by supporting the adjustable section (2).

18. A fabricated buttress-free brace system according to claim 17, wherein the buttress hoops (28) are top-supported and connected with main beams (29), the fabricated stringers (27) are at least two, all the fabricated stringers (27) are transversely spaced along the bridge, and the main beams (29) are supported and connected with the same side ends of all the fabricated stringers (27).

19. A design method for an assembled pier-less support according to claim 15 or 16, comprising the steps of:

s1, counting the construction size data parameters of the existing cast-in-place box beam (30) for the bridge and the construction size data parameters of the buttress-free support, establishing a cast-in-place box beam-buttress-free support database, and determining the load transmission path from the cast-in-place box beam (30) to the assembled longitudinal beam (27) and the load limit value applied to the buttress-free support by the cast-in-place box beam based on the cast-in-place box beam-buttress-free support database;

s2, obtaining a load distribution rule of the fabricated longitudinal beam (27) and a design value range of internal force of the fabricated longitudinal beam (27) based on a load limit value applied to the buttress-free support by the cast-in-place box beam and a load transmission path from the cast-in-place box beam (30) to the fabricated longitudinal beam (27);

s3, determining the length of a standard truss section (1) and the length range of an adjustable section (2) in the assembled longitudinal beam (27) based on the site construction requirement, the load distribution rule of the assembled longitudinal beam (27) and the internal force design value range of the assembled longitudinal beam (27), calculating to obtain the internal force design value range of each rod piece of the standard truss section (1) and the internal force design value range of each rod piece of the adjustable section (2), and determining the arrangement of each rod piece of the standard truss section (1) and the arrangement of each rod piece of the adjustable section (2);

s4, designing the fabricated longitudinal beams (27), the transverse distribution beams (25) and the longitudinal distribution beams (26), and rechecking the strength, the rigidity and the stability.

20. The design method for an assembled buttress-free brace according to claim 19, wherein the step S3 comprises the following steps,

s31, selecting the length size of one standard truss section (1) based on transportation and manufacturing conditions, and defining the length size as a first standard truss section unit (5);

s32, drawing up the length dimensions of the other two standard truss sections (1) based on the length dimension of the first standard truss section unit (5), respectively defining the length dimensions as a second standard truss section unit (4) and a third standard truss section unit (3), enabling the length of the third standard truss section unit (3) to be smaller than the length of the second standard truss section unit (4) to be smaller than the length of the first standard truss section unit (5), and drawing up the length adjusting range of the adjustable section (2) based on the length dimension of the first standard truss section unit (5), the length dimension of the second standard truss section unit (4) and the length dimension of the third standard truss section unit (3);

s33, determining whether the length range of the assembled longitudinal beam (27) covers all integral meter lengths in the range of 20m-30m or not based on the length and the number of the first standard truss section units (5) and the length adjusting range of the adjustable section (2);

s34, if the length range of the fabricated longitudinal beam (27) in the step S33 cannot cover all the integral meter lengths in the range of 20m-30m, determining whether the length range of the fabricated longitudinal beam (27) covers all the integral meter lengths in the range of 20m-30m or not based on the length and the number of the first standard truss section units (5), the length and the number of the second standard truss section units (4) and the length adjusting range of the adjustable section (2);

s35, if the length range of the fabricated longitudinal beam (27) cannot cover all the integral meter lengths in the range of 20m-30m in the step S34, determining whether the length range of the fabricated longitudinal beam (27) covers all the integral meter lengths in the range of 20m-30m or not based on the length and the number of the first standard truss section units (5), the length and the number of the second standard truss section units (4), the length and the number of the third standard truss section units (3) and the length adjusting range of the adjustable section (2);

s36, if the length range of the assembled longitudinal beam (27) in the step S35 can not cover all the length of the whole number meter in the range of 20m-30m,

adjusting the length of the second standard truss section unit (4), and repeating the steps S34-S35 until the length range of the assembled longitudinal beam (27) covers all integral meter lengths in the range of 20m-30 m;

and/or the presence of a gas in the gas,

adjusting the length of the third standard truss section unit (3), and repeating the step S35 until the length range of the assembled longitudinal beam (27) covers all the integral length meters within the range of 20m-30 m;

s37, in the step, when the length range of the assembled longitudinal beam (27) covers all the integral length of the length range from 20m to 30m, stopping, taking the length and the number of the first standard truss section units (5), the length and the number of the second standard truss section units (4) and the length and the number of the third standard truss section units (3) under the condition as final values, and determining the final value of the length adjusting range of the adjustable section (2) according to the final values.

21. The design method for the fabricated buttress-free support according to claim 19, wherein the step S1 is specifically as follows:

step S11: the method comprises the steps of counting the structural size data parameters of a cast-in-place box beam (30) and a buttress-free bracket for the existing bridge, establishing a cast-in-place box beam-buttress-free bracket database, obtaining the structural size limit value of the cast-in-place box beam with the span diameter within the range of 20m-30m based on the cast-in-place box beam-buttress-free bracket database, and determining the arrangement form of the buttress-free bracket;

step S12: determining a load transfer path from the cast-in-place box girder (30) to the fabricated longitudinal girder (27) based on the arrangement form of the buttress-free supports;

step S13: and calculating the load limit value applied to the support without the buttress by the cast-in-place box beam based on the load transmission path from the cast-in-place box beam (30) to the fabricated longitudinal beam (27) and the structural size limit value of the cast-in-place box beam.

22. The design method for the fabricated buttress-free support according to claim 21, wherein the step S13 is specifically as follows:

s131, calculating a fluid load limit value applied to the longitudinal distribution beam assembly (23) by the cast-in-place box beam based on a load transmission path from the cast-in-place box beam (30) to the fabricated longitudinal beam (27) and a structural size limit value of the cast-in-place box beam;

s132, calculating a concentrated load limit value applied to the transverse distribution beam assembly (22) by the longitudinal distribution beam assembly (23) based on a load limit value applied to the longitudinal distribution beam assembly (23) by the cast-in-place box beam;

s133, calculating the limit value of the concentrated load applied to the assembled longitudinal beam (27) by the transverse distribution beam assembly (22) based on the limit value of the concentrated load applied to the transverse distribution beam assembly (22) by the longitudinal distribution beam assembly (23).

23. The design method for the fabricated buttless support according to claim 20, wherein the data parameters of the construction size of the cast-in-place box girder (30) for the bridge in the step S1 include the height, the bottom width, the overhanging length of the flange and the web thickness of the cast-in-place box girder (30).

24. A design method for an assembly type buttress-free brace according to claim 19, wherein the cast-in-place box girder (30) comprises a solid section, a transition section and a general section, and the step S2 is specifically as follows:

s21, obtaining a load distribution rule of a longitudinal distribution beam (26), a load distribution rule of a transverse distribution beam (25) and a load distribution rule of an assembly longitudinal beam (27) corresponding to a solid section, a transition section and a general section based on a load limit value applied to a buttress-free support by a cast-in-place box beam and a load transmission path from the cast-in-place box beam (30) to the assembly longitudinal beam (27);

s22, analyzing and obtaining the design value range of the internal force of the longitudinal distribution beam (26), the design value range of the internal force of the transverse distribution beam (25) and the design value range of the internal force of the assembly type longitudinal beam (27) corresponding to the solid section, the transition section and the general section based on the load distribution rule of the longitudinal distribution beam (26), the load distribution rule of the transverse distribution beam (25) and the load distribution rule of the assembly type longitudinal beam (27).

25. A design method for an assembled buttress-free brace system of claim 17 or 18, comprising the steps of:

a1, completing the design of a fabricated longitudinal beam (27) based on the design method for the fabricated pier-free bracket as claimed in any one of claims 19-22, and obtaining the support reaction force data parameters of the fabricated longitudinal beam (27);

a2, counting size data parameters of the existing buttress (31) for the bridge, establishing a buttress (31) database, obtaining the most common data parameter value of the size of the buttress (31) with the span within the range of 20m-30m based on the buttress (31) database, and drawing the structure size of the buttress anchor ear (28) according to the most common data parameter value;

a3, introducing the main cross beam (29) based on the structure of the fabricated longitudinal beam (27) and the structure size of the buttress anchor ear (28), and determining the load transmission path from the fabricated longitudinal beam (27) to the buttress anchor ear (28);

a4, obtaining the maximum bending moment and the maximum shearing force of the section of the main cross beam (29) based on the support reaction data parameters of the fabricated longitudinal beam (27), performing section selection on the main cross beam (29) according to the maximum bending moment and the maximum shearing force, and then calculating to obtain the load applied to the buttress anchor ear (28) by the main cross beam (29);

a5, checking the strength, rigidity and stability of the structure size of the proposed buttress anchor ear (28) based on the load applied to the buttress anchor ear (28) by the main cross beam (29).