CN116892171A

CN116892171A - Construction method for downward-supporting type basket steel box tied arch bridge deck structure

Info

Publication number: CN116892171A
Application number: CN202310614544.6A
Authority: CN
Inventors: 周艇; 于长彬; 彭勇军; 张延辉; 顾颖; 赵静波; 李惠民; 赵梦春; 高昌建; 王�琦; 张�杰; 田波; 陈利; 周祥鑫; 高清炎; 古松; 王天阳; 扈晓立; 费元佑; 王祥臣
Original assignee: Southwest University of Science and Technology; China Railway 18th Bureau Group Co Ltd; Second Engineering Co Ltd of China Railway 18th Bureau Group Co Ltd; China Railway Jiujiang Bridge Engineering Co Ltd
Current assignee: Southwest University of Science and Technology; China Railway 18th Bureau Group Co Ltd; Second Engineering Co Ltd of China Railway 18th Bureau Group Co Ltd; China Railway Jiujiang Bridge Engineering Co Ltd
Priority date: 2023-05-26
Filing date: 2023-05-26
Publication date: 2023-10-17

Abstract

The invention provides a construction method for a lower-bearing type basket steel box tied arch bridge deck structure, which comprises the construction steps of gantry crane installation, girder assembly support and pushing support construction, girder assembly, girder support erection, girder hoisting, bridge deck pavement, removal of a girder support and the like. And dragging the dismantled beam bracket to the next section for the installation of the beam of the next section. According to the construction method, stress changes in the assembling process of the structure, and the designed structure force transmission path is adopted, so that compared with a conventional girder erection method of the full-span bracket, the bracket erection cost for assembling the arch bridge deck structure is greatly saved, and meanwhile, the construction period is shortened.

Description

Construction method for downward-supporting type basket steel box tied arch bridge deck structure

Technical Field

The invention belongs to the technical field of construction of a bridge deck structure of a downward-supporting type basket steel box tied arch bridge, and particularly relates to a construction method for a bridge deck structure of a downward-supporting type basket steel box tied arch bridge.

Background

The bridge deck structure of the lower-bearing type basket steel box tied arch bridge is generally composed of three parts, namely a cross beam, a longitudinal beam (side girder/girder) and a bridge deck, wherein the bridge deck is supported on the cross beam, and the cross beam is supported on the side girder.

Aiming at the bridge deck structure of the downward-supporting type basket steel box tied arch bridge, a bracket method is generally adopted at present for assembly, a bracket is firstly erected, then a cross beam and a longitudinal beam are assembled on the bracket, and finally a bridge deck is installed on the cross beam. The traditional construction process has the problems that a large number of brackets are required to be erected in the width and length ranges of the bridge deck so as to assemble the cross beams, the brackets are required to be erected at the lower parts of the side main beams to assemble the longitudinal beams, the number of the brackets is large, the foundation pouring amount is large, the brackets are complex to erect and disassemble, and the like. Secondly, because the crossbeam supports on the limit girder, before crossbeam and decking welding, the crossbeam need bear the dead weight and the weight of upper portion decking, nevertheless the special form of falling T cross-section of crossbeam has decided its very easily appearance lateral instability's problem, and to this usual processing method be add the support in the crossbeam lower part, let the crossbeam be in the state of multiple spot support to reduce the lateral instability risk, this quantity that has further increased the support again. In addition, the main beam section of the basket arch bridge is generally an inclined section which is inclined inward, and has a tendency to rotate inward. In addition, the inward inclined main beam bears the torque exerted by the cross beam, so that the main beam is further twisted inwards, the space positioning of the main beam is difficult, particularly, the space posture of the main beam can directly influence the inward inclination angle of the arch rib, and the positioning is very difficult.

In conclusion, the lower-bearing type basket steel box tied arch bridge deck structure has three problems of large number of brackets, easy instability of the cross beam and difficult space positioning of the main beam in the assembling process.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a construction method for a bridge deck structure of a downward-supporting type basket steel box tied arch bridge, which solves the problems of a large number of brackets, easy instability of a cross beam and difficult space positioning of the main beam existing in the process of splicing the bridge deck structure of the downward-supporting type basket steel box tied arch bridge by adopting a bracket method in the prior art.

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

the construction method for the bridge deck structure of the downward-supporting type basket steel box tied arch bridge comprises a plurality of sections of mutually spliced sections, each section of section comprises two main beams arranged at intervals, a plurality of cross beams are arranged between the two main beams, and a plurality of bridge panels are arranged on the cross beams; the bottoms of the main beam assembly brackets and the pushing brackets are fixedly connected with the ground; the cross section of each beam is of an inverted T-shaped structure;

the construction method of the deck structure of the downward-supporting basket steel box tied arch bridge comprises the following steps:

step 1, installing a portal crane, namely installing two vertical supports of the portal crane on two sides of the length direction of a downward-supporting type basket steel box tied arch bridge; the horizontal bracket of the gantry crane is positioned at the top of the downward-bearing basket steel box tied arch bridge, and a winch is arranged on the horizontal bracket of the gantry crane in a sliding manner;

step 2, constructing a main girder assembling bracket and a pushing bracket, wherein a plurality of main girder assembling brackets and pushing brackets are arranged on two sides of the lower-bearing type basket steel box tied arch bridge in the length direction;

step 3, assembling main beams, namely respectively hanging two main beams in the current section on main beam assembling brackets and pushing brackets on two sides of the lower-bearing basket steel box tied arch bridge in the length direction through a winch on a gantry crane;

step 4, erecting a beam bracket, namely erecting the beam bracket between two main beams in the current section, wherein a first jack is arranged at the top of the beam bracket;

step 5, hoisting the cross beams, namely hoisting the cross beams to the two main beams and the cross beam bracket through the gantry crane, after the cross beams are positioned, fixedly connecting the two ends of the cross beams with webs of the two main beams respectively, and enabling the first jack to extend upwards and apply a lifting force to the middle part of a cross beam bottom plate;

step 6, paving bridge decks, hoisting a plurality of bridge decks to the top of the cross beam through a gantry crane, and welding and fixing the bridge decks and the top of the cross beam after confirming the positions of the bridge decks on the cross beam; completing the assembly work of the current segment;

step 7, removing the beam support, wherein after the construction of the current section is completed, the bridge deck, the beam and the girder in the current section form a whole which can be stressed, removing the beam support, and dragging the beam support to the beam hoisting position of the next section by using a winch for hoisting the beam of the next section;

and 8, continuously splicing the next section, repeating the steps 2-7, completing the splicing work of the next section, and fixedly connecting the completed current section with the next section until the splicing construction of the whole downward-supporting type basket steel box tied arch bridge deck structure is completed.

Further, in the step 2, the tops of the main beam assembling bracket and the pushing bracket are respectively provided with a support.

Further, in step 3, the two main beams are steel box beams with parallelogram cross sections, and a pre-deflection angle is arranged between the bottoms of the two main beams and the support.

Further, in the step 3, a pre-deflection angle is required to be set when the main beam is hoisted, so that after the bracket is removed, the torsional deformation of the main beam caused by the dead weights of the cross beam and the bridge deck and the set pre-deflection angle are mutually offset, thereby avoiding the support on the outer side of the main beam from being separated and preventing the inner side of the main beam bottom plate from being concentrated;

the bridge deck is provided with a bidirectional transverse slope, the cross beam is of a variable cross section, the geometric properties of the cross sections of the bridge deck and the cross beam at different positions are slightly different, and the equivalent treatment can be carried out on the integral rigidity of the bridge deck and the cross beam for the convenience of calculation; the self weight of the beam and the bridge deck is simplified into rectangular uniform load, as the two ends of the girder are directly placed on the supports of the girder assembling support, the counter forces of the two supports are respectively represented by fa and fb, a mechanical simplified model is obtained, and two mechanical balance types are listed according to the principle of two-force balance:

two formulas in the combined type 3.1 calculate out that the magnitude of the supporting reaction force of the cross beam and the bridge deck is fa=fb=1/2 ql;

according to moment balance of any section, bending internal force of any section of the whole beam and the bridge deck is calculated, and a calculation formula is as follows:

wherein q is the unit dead weight of the cross beam and the bridge deck, and the unit is N; l is the distance between the inner side webs of the two main beams, and the unit is m; x is the distance from any section to the left end point, and the unit is m;

the pre-deflection angle of the main beam has an inverse relation with the bending moment, so the equation 3.2 is integrated and multiplied by the inverse of the rigidity to obtain a pre-deflection angle calculation formula:

wherein θ is the pre-deflection angle of the main beam; EI is the equivalent stiffness of the deck and cross member.

Further, in step 3, when the main beam is hoisted, two second jacks are placed on the inner side of the main beam, the main beam is deflected by the lifting of the second jacks, the elevation of the lower edge of the web plate of the main beam is monitored at the moment by using the total station synchronously, and a pre-deflection angle theta is converted by using a geometric relation formula, wherein the conversion formula of the pre-deflection angle theta is as follows:

wherein h1 is the elevation of the lower edge of the main beam, which is close to the side web plate in the middle of the beam; h2 is the elevation of the lower edge of the main beam away from the middle side of the beam; and b is the distance between two webs of the main beam.

Further, in step 4, the bottom of the beam bracket is provided with a ground connection beam.

Further, in step 5, the calculation method of the lift force is:

step 5.1, establishing a main beam and cross beam finite element model in ANSYS, and applying position constraint to the main beam and cross beam finite element model;

step 5.2, applying different vertical loads to the midspan of the bottom plate of the beam model, simulating a jacking force, and simultaneously obtaining the upper edge stress of the web span of the beam under the different vertical loads through ANSYS;

and 5.3, fitting different vertical load data and different cross beam web span upper edge stress data, wherein the fitted functions are as follows:

y＝10.82-1.03F

wherein y represents the upper edge stress across the beam web and F represents the jacking force of the first jack.

Further, in step 5, a construction ramp is provided between the two beams, the construction ramp including a ramp plate provided on the two beam wing plates.

The beneficial effects of the invention are as follows: 1. according to the construction method for the bridge deck structure of the downward-supporting type basket steel box tied arch bridge, after the current section is built, a structural system with bearing capacity is formed by the main beam, the cross beam and the bridge deck in the current section, the dead weights of the cross beam and the bridge deck are not needed to be borne by a cross beam bracket, the cross beam and the bridge deck are transmitted to the main beams on two sides and are finally borne by the supports on the lower parts of the main beams, and therefore, when the bridge deck structure of one section is assembled, the cross beam bracket can be removed. At this point, the removed beam bracket may be towed to the next section for installation of the next section beam. According to the construction method, stress changes in the assembling process of the structure, and the designed structure force transmission path is adopted, so that compared with a conventional girder erection method of the full-span bracket, the bracket erection cost for assembling the arch bridge deck structure is greatly saved, and meanwhile, the construction period is shortened.

2. According to the construction method for the bridge deck structure of the downward-supporting type basket steel box tied arch bridge, when the main beam is hoisted, the pre-deflection angle is arranged on the main beam to resist the inward deflection of the main beam, so that the torsional deformation of the main beam caused by the dead weights of the cross beam and the bridge deck plate and the pre-deflection angle are mutually offset after the cross beam support is removed, the support on the outer side of the main beam is prevented from being emptied, and the stress concentration on the inner side of a bottom plate of the main beam is prevented.

3. According to the construction method for the bridge deck structure of the downward-bearing type basket steel box tied arch bridge, the first jack is arranged on the beam support, when the beam is hoisted, the extending end of the first jack is controlled to extend, so that the vertical upward jacking force is applied to the middle position of the beam, under the action of the jacking force, the middle bending moment of the beam is greatly reduced, the middle upper edge of the beam web is changed from being pressed into being pulled, the problem of the pressed buckling of the beam web is fundamentally solved, and the construction is ensured to be carried out smoothly.

4. According to the construction method for the bridge deck structure of the downward-supporting type basket steel box tied arch bridge, the floor connecting cross beam is arranged at the bottom of the cross beam support, and is welded with the stand columns in the cross beam support into a whole to serve as an expanding foundation of the cross beam support, so that the cross beam support does not need to pour the foundation of the support, and the upper bearing requirement can be met only by leveling a site.

Drawings

Fig. 1 is a process flow diagram of a construction method for a deck structure of a downward-bearing basket steel box tied-arch bridge.

Fig. 2 is a schematic cross-sectional structural view of a deck structure of a downward-bearing basket steel box tied arch bridge.

Fig. 3 is a schematic structural view of the bottom-up basket steel box tied arch bridge deck in the length direction.

Fig. 4 is a schematic view of deflection of the main beam on the support.

Fig. 5 is a schematic diagram of a simplified mechanical model with a main beam mounted on a support.

Fig. 6 is a schematic view of conversion of the pre-deflection angle of the main beam by the total station.

Fig. 7 is a schematic structural view of the cross beam bracket.

1, a main beam; 2. a cross beam; 3. a bridge deck; 4. the main beam is assembled with the bracket; 5. pushing the support; 6. a cross beam bracket; 7. a first jack; 8. a support; 9. and the ground is connected with the cross beam.

Detailed Description

The following description of the embodiments of the present invention is provided to facilitate understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and all the inventions which make use of the inventive concept are protected by the spirit and scope of the present invention as defined and defined in the appended claims to those skilled in the art.

As shown in fig. 1 to 3, the invention provides a construction method for a bridge deck structure of a downward-supporting type basket steel box tied arch bridge, wherein the downward-supporting type basket steel box tied arch bridge deck comprises a plurality of sections which are mutually spliced, each section comprises two main beams 1 which are arranged at intervals, a plurality of cross beams 2 are arranged between the two main beams 1, and a plurality of bridge panels 3 are arranged on the plurality of cross beams 2; a main beam assembling bracket 4 and a pushing bracket 5 are arranged below the two main beams 1, and the bottoms of the main beam assembling bracket 4 and the pushing bracket 5 are fixedly connected with the ground; the cross section of each beam 2 is of an inverted T-shaped structure.

step 1, installing a portal crane, namely installing two vertical supports of the portal crane on two sides of the length direction of a downward-supporting type basket steel box tied arch bridge; the horizontal bracket of the gantry crane is positioned at the top of the downward-bearing basket steel box tied arch bridge, and a winch is arranged on the horizontal bracket of the gantry crane in a sliding manner.

Specifically, portal crane installation includes steps such as track laying, landing leg assembly and standing and dolly installation, and track laying steps are: and (3) leveling the fields on two sides of the length direction of the lower-bearing type basket steel box tied arch bridge, then arranging a strip foundation on the flat field according to the requirements of a design drawing, wherein the strip foundation is of a reinforced concrete structure, installing a rail pressing device on the strip foundation and paving a rail at the same time after the strip foundation reaches the design strength, wherein the elevation deviation of the top surface of the rail is not more than +/-5 mm, and the flatness is not more than 5mm in every two meters. On the rail, a setting slit was provided every 12 m.

The supporting leg assembling and erecting steps are as follows: firstly, the rigid and flexible supporting legs are flatly placed on the ground, the bottoms of the rigid and flexible supporting legs are flatly padded by sleeper, then the flanges of the top cross beam and the bottom cross beam are in butt joint with the flanges of the supporting legs, bolts are arranged, spring gaskets and nuts are arranged, and the bolts are corrected and screwed. And then horizontally placing the bottom trolley on two sides of the bottom cross beam according to requirements, correcting and driving the pin shafts, and installing the safety clamping plates. Before the landing leg is erected, a steel wire rope with the diameter of 24mm is buckled at a proper position on the landing leg, then the landing leg is hung by an 80t automobile crane, a large car running wheel is dropped on a track, the position of the running wheel is adjusted, and the rim of the outer side of the running wheel needs to be abutted against the outer side of the track. And then the chain block is buckled on the steel wire rope and the ground anchor, one chain block is respectively arranged at each side, the verticality of the supporting leg is tensioned and adjusted, and after the adjustment is finished, the main girder 1 is hung.

The trolley is installed by the following steps: four hanging rings are welded on two sides of the trolley, a steel wire rope is wound before the hoisting, and the trolley is hoisted by an 80t automobile crane. And then the steel wire rope in the winch is reeled out, and reeled around the fixed pulley in the upper crane trolley after reeving around the lower movable pulley, and reeled around to the last pulley group after being reeved through the first pulley group, the rope head is locked on the force transducer at the side edge of the fixed pulley of the crane, the power supply is connected, and the whole crane is debugged in an idle load manner. It should be noted that the mechanism and the installation method of the arch bridge gantry crane apparatus belong to the prior art, and the principle thereof will not be repeated here.

Step 2, constructing a main beam assembling bracket 4 and a pushing bracket 5, wherein a plurality of main beam assembling brackets 4 and pushing brackets 5 are arranged along the two sides of the length direction of the downward-bearing type basket steel box tied arch bridge; specifically, the tops of the girder assembling bracket 4 and the pushing bracket 5 are respectively provided with a support 8, and the supports 8 are used for bearing the two girders 1. In the embodiment, the pushing support 5 is also used as the main beam assembly support 4, so that the cost is saved and the construction period is shortened.

And 3, splicing the girders 1, namely respectively hanging two girders 1 in the current section on a girder splicing bracket 4 and a pushing bracket 5 on two sides of the lower-bearing basket steel box tied arch bridge in the length direction through a winch on a gantry crane.

Specifically, the girder 1 arranged in a segmented manner is arranged on the girder assembling bracket 4 and the pushing bracket 5 through a gantry crane, and before hoisting, the influence of the girder arrangement position on the construction sequence is fully considered. In the hoisting process, the special personnel command and the total station is used for synchronously checking the accuracy of the position of the steel beam.

Preferably, in this embodiment, the girders 1 in each section are steel box girders with parallelogram cross sections, and a pre-deflection angle is arranged between the bottoms of the two girders 1 and the support 8.

The main beam 1 is provided with a pre-deflection angle because: as shown in fig. 4, after the current segment is assembled and welded, the force transmission path becomes: bridge deck 3- & gt cross beam 2- & gt main beam 1. The girder 1, the cross beam 2 and the bridge deck 3 form a whole which can be stressed, at the moment, the cross beam bracket 6 can be removed, but the deformation caused by the dead weight of the cross beam 2 and the bridge deck 3 can generate torque on the girder 1, and the torque can lead the side girder 1 to twist inwards and cause the support 8 on the outer side of the girder 1 to be loosened, thereby further causing the stress concentration of the bottom plate on the inner side of the girder 1.

And through setting up the pretilt angle with girder 1, make the support withdraw the back, girder 1 torsional deformation that crossbeam 2 and deck slab 3 dead weight arouse offset each other with the pretilt angle that sets up to avoid girder 1 outside support 8 to take off, prevent that girder 1 bottom plate inboard from appearing stress concentration.

Specifically, the bridge deck 3 is provided with a bidirectional transverse slope, the cross beam 2 is of a variable cross section, the geometric properties of the cross sections of the bridge deck 3 and the cross beam 2 at different positions are slightly different, and for the convenience of calculation, the whole rigidity of the bridge deck 3 and the cross beam 2 can be equivalently processed; the dead weights of the cross beam 2 and the bridge deck 3 are simplified into rectangular uniform load, as shown in fig. 5, as the two ends of the main beam 1 are directly placed on the supports 8 of the main beam assembly support 4, the counterforces of the two supports 8 are respectively represented by fa and fb, a mechanical simplified model is obtained, and two mechanical balance types are listed according to a two-force balance principle:

the magnitude of the supporting reaction force of the cross beam 2 and the bridge deck 3 is calculated by two formulas in the combined type 3.1, wherein fa=fb=1/2 ql;

according to moment balance of any section, bending internal force of any section of the whole beam 2 and the bridge deck 3 is calculated, and a calculation formula is as follows:

wherein q is the unit dead weight of the cross beam 2 and the bridge deck 3, and the unit is N; l is the distance between the inner side webs of the two main beams 1, and the unit is m; x is the distance from any section to the left end point, and the unit is m;

the pre-deflection angle of the main beam 1 has an inverse relation with the bending moment, so the equation 3.2 is integrated and multiplied by the inverse of the rigidity to obtain a pre-deflection angle calculation formula:

wherein θ is the pre-deflection angle of the main beam 1; EI is the equivalent stiffness of the deck slab 3 and the cross beam 2.

As shown in fig. 6, when the main beam 1 is hoisted, two second jacks are placed at the inner side of the main beam 1, the main beam 1 is deflected by lifting the second jacks, the elevation of the lower edge of a web plate of the main beam 1 is monitored at the moment by using a total station synchronously, and a pre-deflection angle theta is converted by using a geometric relation, wherein a conversion formula of the pre-deflection angle theta is as follows:

wherein h1 is the elevation of the lower edge of the main beam 1, which is close to the side web plate in the middle of the cross beam 2; h2 is the elevation of the lower edge of the main beam 1 far away from the middle side of the cross beam 2; b is the distance between the two webs of the main beam 1.

Because the pre-deflection angle of the girder 1 is inconvenient to directly measure and obtain in a specific construction process, through the construction control of controlling the elevation of the lower edge of the web plate of the girder 1, the corner formula of the transverse beam 2 can be calculated based on a mechanical basis, the corner of the girder 1 can be further calculated, the angle is difficult to control in the construction process, and the accurate control of the pre-deflection angle can be realized through the elevation monitoring of the lower edge of the web plate of the girder 1 and the geometric relation.

Step 4, erecting a beam bracket 6, wherein as shown in fig. 1 and 7, the beam bracket 6 is built between two main beams 1 in the current section, and a first jack 7 is arranged at the top of the beam bracket 6; preferably, the bottom of the beam bracket 6 is provided with the ground connecting beam 9, the ground connecting beam 9 and the upright posts in the beam bracket 6 are welded into a whole and serve as an expanding foundation of the beam bracket 6, so that the beam bracket 6 can meet the requirement of upper bearing without pouring the foundation of the bracket, and compared with the traditional construction method in which the bottom of the beam bracket 6 is provided with a pouring concrete foundation, the construction method not only saves the number of the beam brackets 6 when the beam 2 is assembled with a bridge deck, but also saves 100% of pouring quantity of the bracket foundation, and has obvious advantages.

And 5, hoisting the cross beams 2 to the two main beams 1 and the cross beam bracket 6 through a gantry crane, after the cross beams 2 are positioned, respectively fixedly connecting the two ends of the cross beams 2 with webs of the two main beams 1, and applying a lifting force to the middle part of the bottom plate of the cross beam 2 by a first jack 7.

Preferably, the cross beam 2 is lifted by two lifting points, the lifting points being located at a distance of 0.207l from the end points of the cross beam 2, l being the length of the cross beam 2. After the beam 2 is hung to a preset position, checking whether a first jack 7 at the top of a beam bracket 6 is centered with the center of a bottom plate of the beam 2 by using a total station, if not, fine adjustment of the bracket position is needed, and after the adjustment is finished, the beam 2 is reliably connected with a web plate of the main beam 1 by using a high-strength bolt; after the cross beams 2 are connected, a construction ramp is arranged between the two cross beams 2 and comprises a ramp plate arranged on wing plates of the two cross beams 2, and the construction ramp is convenient for workers to construct.

Specifically, in this embodiment, the calculation method of the lift force is:

step 5.1, establishing a main beam 1 and a cross beam 2 finite element model in ANSYS, and applying position constraint to the main beam 1 and the cross beam 2 finite element model; in actual construction, the main beams 1 are directly supported on the assembling bracket without anchoring, so that in the finite element models of the main beams 1 and the cross beams 2, the bottom plates of the two main beams 1 are restrained from translating in three directions, and the transverse bridge is released to rotate in the directions; under the action of the dead weight of the cross beam 2 and the bridge deck 3, the stability coefficient of the cross beam 2 is 0.99, which is expressed as buckling outside the cross web surface. After being hoisted in place, the cross beam 2 is connected with the web plate of the main beam 1 through high-strength bolts. Because the cross beam 2 is of an inverted T-shaped section, and the upper edge of the web plate is not supported by a small longitudinal beam, the web plate of the cross beam 2 is bent outside the pressed surface under the action of dead weight.

On the basis, a beam bracket 6 is additionally arranged below the beam 2 to improve the stability of the beam 2. To verify if the solution is effective, in a finite element model, vertical constraints are applied to the mid-span position of the floor of the beam 2 to simulate the beam support 6. The stability coefficient of the beam 2 is calculated to be 3.75 through ANSYS software, and the stability is obviously improved as compared with the case that no bracket is arranged, the upper edges of webs at two ends of the beam 2 are buckled. The standard requirement is that the linear buckling characteristic value coefficient of the bridge structure is larger than 4.0 in the construction process, and the requirement of construction is not met even though the stability of the beam 2 can be improved by additionally arranging the beam bracket 6.

And 5.2, applying different vertical loads to the midspan of the bottom plate of the beam 2 model, simulating a jacking force, and simultaneously obtaining the upper edge stress of the web span of the beam 2 under the different vertical loads through ANSYS.

In order to prevent the beam 2 from buckling after being installed and ensure construction safety, the beam 2 is further provided with an upward jacking force by a jack at the top of the beam bracket 6, so that the midspan bending moment of the beam 2 is reduced, and the stability of the beam 2 is further improved. The critical value of the jacking force is that the stress of the upper edge of the web plate of the cross beam 2 is 0, namely, the web plate is not pressed.

In order to determine reasonable jacking force values, in the finite element models of the main beam 1 and the cross beam 2, vertical loads are applied to the bottom plate span of the cross beam 2 to simulate the jacking force, wherein the loading values are 1KN, 2KN, 3KN, 4KN, 5KN and 6KN respectively. The calculation target is the upper edge stress of the web span of the beam 2, and the calculation result of the upper edge stress of the web span of the beam 2 is shown in the following table:

step 5.3, fitting different vertical load data and different cross beam 2 web span upper edge stress data, wherein the fitted functions are as follows:

y＝10.82-1.03F

where y represents the upper edge stress across the web of the beam 2 and F represents the lifting force of the first jack 7. Let y=0 (stress at the upper edge of the web of the beam 2 is 0), the calculation shows that the lifting force of the first jack 7 is 10.50KN, so that the designed lifting force of the first jack 7 is 1.05t when the beam 2 is hoisted.

Step 6, paving the bridge deck boards 3, hoisting a plurality of bridge deck boards 3 to the top of the cross beam 2 through a gantry crane, and welding and fixing the bridge deck boards 3 and the top of the cross beam 2 after confirming the position of the bridge deck boards 3 on the cross beam 2; and finishing the assembly work of the current section.

Specifically, the welding position of the bridge deck plate 3 is required to be provided with a 45-degree groove, the groove is polished, rust and burrs are avoided, the bridge deck plate 3 is lifted by a gantry crane, the bridge deck plate 3 is positioned by a code plate after the position of the bridge deck plate 3 is confirmed to be correct, and then the first welding is carried out. And after the welding is finished, the code plate is cut off by a gas cutting gun, the code plate and the welding line are polished, and then the second welding is carried out. The welding mode is submerged arc welding, and the welding flux is baked for 1-2 hours at the temperature of 250 ℃. The track position of the welding machine is fixed after confirming that the track position is correct, so that the deviation of the welding machine in the moving process is prevented. The moving speed of the welding machine is controlled to be 20-40 cm/min, the welding current is 520A, and the voltage is 34v.

And 7, removing the beam support 6, after the construction of the current section is completed, forming a stressed whole by the bridge deck 3, the beam 2 and the main beam 1 in the current section, removing the beam support 6, and dragging the beam support 6 to the hoisting position of the beam 2 of the next section by using a winch for hoisting the beam 2 of the next section.

In summary, according to the construction method for the downward-supporting type basket steel box tied arch bridge deck structure, the pushing support 5 is also used as the main beam assembly support 4, so that the cost is saved, and the construction period is shortened; the main beam 1 is provided with a pre-deflection angle, and the pre-deflection torsion and the reverse deformation are quasi-preset, so that the problem of space positioning caused by the torsion of the inward-inclined main beam 1 is solved; the movable beam support 6 is used for assembling the beams 2 in the sections, and the beam support 6 is provided with a foundation, so that the repeated utilization is realized, and the materials and the labor cost are saved; the lifting force is applied to the midspan of the cross beam 2 through the first jack 7, the stress of the cross beam 2 is actively changed, and the problem of instability of the cross beam 2 outside the plane is thoroughly solved by pressure change and pulling. The construction method for the deck structure of the downward-supporting type basket steel box tied arch bridge can be applied to construction of roads, railways and municipal bridges of the same type, and has wide application prospect and high economic value.

Claims

1. The construction method for the bridge deck structure of the downward-supporting type basket steel box tied-arch bridge is characterized in that the bridge deck of the downward-supporting type basket steel box tied-arch bridge comprises a plurality of sections which are spliced with each other, each section comprises two main beams which are arranged at intervals, a plurality of cross beams are arranged between the two main beams, and a plurality of bridge panels are arranged on the cross beams; a main beam assembling bracket and a pushing bracket are arranged below the two main beams, and the bottoms of the main beam assembling bracket and the pushing bracket are fixedly connected with the ground; the cross section of each beam is of an inverted T-shaped structure;

2. The construction method for the downward-supporting type basket steel box tied arch bridge deck structure according to claim 1, wherein in the step 2, the tops of the main beam assembling bracket and the pushing bracket are respectively provided with a support.

3. The construction method for the floor structure of the downward-supporting basket steel box tied arch bridge according to claim 2, wherein in the step 3, the two main beams are steel box beams with parallelogram cross sections, and a pre-deflection angle is arranged between the bottoms of the two main beams and the support.

4. The construction method for the downward-supporting type basket steel box tied arch bridge deck structure according to claim 3, wherein in the step 3, a pre-deflection angle is required to be set when the main beam is hoisted, so that after the support is removed, the torsion deformation of the main beam caused by the dead weight of the cross beam and the bridge deck plate and the set pre-deflection angle are mutually offset, thereby avoiding the support on the outer side of the main beam from being emptied and preventing the stress concentration on the inner side of the main beam bottom plate;

5. The construction method for the downward-supporting type basket steel box tied arch bridge deck structure according to claim 4, wherein in the step 3, when the main beam is hoisted, two second jacks are placed on the inner side of the main beam, the main beam is deflected by the second jacks, the elevation of the lower edge of a web plate of the main beam is monitored synchronously by using a total station at the moment, a pre-deflection angle theta is converted by using a geometric relation, and a conversion formula of the pre-deflection angle theta is as follows:

6. A construction method for a bottom-mounted basket steel box tied arch bridge deck structure according to claim 1, wherein in step 4, the bottom of the beam bracket is provided with a ground connection beam.

7. The construction method for the deck structure of the downward-bearing type basket steel box tied arch bridge according to claim 1, wherein in the step 5, the calculation method of the jacking force is as follows:

y＝10.82-1.03F

8. The construction method for the floor structure of the downward-bearing type basket steel box tied arch bridge according to claim 7, wherein in the step 5, a construction ramp is arranged between two beams, and the construction ramp comprises ramp plates arranged on wing plates of the two beams.