CN116148074A - Device and method for loading and testing closure section model of large-span beam-arch combined rigid frame bridge - Google Patents

Abstract

The invention belongs to the technical field of large-span beam-arch combined rigid frame bridge closure section model test, and discloses a large-span beam-arch combined rigid frame bridge closure section model loading test device and method, wherein the device comprises a support module, a loading module and a measuring module; the support module comprises a base, a vertical wall, a door-shaped frame and a three-level distribution beam arranged at the top of the test member; the loading module comprises a third hydraulic jack arranged on the upper side of the portal frame, a loading actuator at the top of the test member, a first hydraulic jack at the corner coupling of the closure section, a second hydraulic jack and a fourth hydraulic jack for stretching the prestressed steel beam along the bridge direction of the member; the measuring module comprises a strain measuring point, a plurality of electromechanical dial indicators and two pressure sensors. The invention has simple structure and convenient operation, can carry out full-circle loading of the closure section of the large-span beam-arch combined rigid frame bridge, is used for simulating the three-dimensional model of the closure section of the large-span beam-arch combined rigid frame bridge, and has high force transmission accuracy and wide application range.

Description

Device and method for loading and testing closure section model of large-span beam-arch combined rigid frame bridge

Technical Field

The invention belongs to the technical field of large-span beam-arch combined rigid frame bridge closure section model test, and particularly relates to a large-span beam-arch combined rigid frame bridge closure section model loading test device and method.

Background

Along with the continuous development of technology, the bridge type structure of the beam-arch combined rigid frame bridge is widely applied in engineering. However, through related investigation and research, the structure of the large-span beam-arch combined rigid frame bridge is relatively complex in bearing and force transmission, particularly the corner nodes of the closure section are particularly complex in stress, the complex stress distribution rule of the joint under a specific load combination is difficult to reveal by adopting conventional bridge structure calculation and analysis, deflection after cracking, crack behaviors and the like cannot be reasonably and correctly guided for the construction and construction of the bridge. It is very important to design a new test method to correctly and reasonably study the corner nodes of the arched girder junction.

The large-span beam arch combined rigid frame bridge closure section structure is very complex, stress distribution at the corner coupling node is complex, and the load bearing is inconvenient to directly calculate. Therefore, the stress characteristics of closure segments of the large-span beam-arch combined rigid frame bridge and the overall stress situation of the structure are explored, and a common test method is an in-situ test or an indoor model test. The former is more realistic and reliable, but the experiment is greatly influenced by external influence factors such as topography, structure and the like, the direct experiment difficulty is very large, and the difficulty is far greater than the latter. The model test has the advantages of small difficulty, strong operability, small influence from the outside and wide application range, and is the most applicable means in the experiment of exploring the closure stress performance and the structural characteristics of the large-span beam-arch combined rigid frame bridge.

For the model experiment of the closure section of the large-span beam-arch combined rigid frame bridge, because the structure of the structure is inconvenient to directly serve as a test object, a reduced scale model is often adopted for the test piece. The reduced scale model experiment obtains relevant data and checks design defects by performing corresponding experiments on a scaled down or equal ratio model. And (3) applying proportional load on a test structure (or a component) which is made of a proper proportion and similar materials and is similar to the prototype, so that the model is stressed and then the structural test of the actual work of the prototype structure is performed. The test object is a test proxy which imitates a prototype (actual structure) and is reproduced to a scale, and which has all or part of the characteristics of the actual structure, the model size being generally smaller than the prototype structure. According to the model similarity theory, the operation of the actual structure can be calculated from the test result of the model. The stringent requirements must be simulated under geometric, physical and material similarities. The model can be divided into a similar model and a reduced scale model according to the similar conditions, and can be divided into an elastic model and an intensity model according to the test purposes.

Through the above analysis, the problems and defects existing in the prior art are as follows: in the prior art, the limitation of the stress characteristics and the structural characteristics of the closure section of the large-span beam-arch combined rigid frame bridge is explored due to the fact that the original components are overlarge in size and no experimental conditions exist, and meanwhile, the limitation of size effects and boundary effects is avoided, and the model simulation test which cannot be performed due to the fact that the original structure is overlarge in size cannot be performed.

Disclosure of Invention

Aiming at the problems existing in the prior art, the invention provides a loading test device and a loading test method for a closure section model of a large-span beam-arch combined rigid frame bridge.

The invention is realized in such a way that a loading testing device for a closure section model of a large-span beam-arch combined rigid frame bridge comprises: the device comprises a supporting module, a loading module and a measuring module;

the support module comprises a base, a vertical wall, a door-shaped frame and a three-level distribution beam arranged at the top of the test member;

the loading module comprises a third hydraulic jack arranged on the upper side of the portal frame, a loading actuator at the top of the test member, a first hydraulic jack at the corner coupling of the closure section, a second hydraulic jack and a fourth hydraulic jack for stretching the prestressed steel beam along the bridge direction of the member;

the measuring module comprises a strain measuring point, a plurality of electromechanical dial indicators and two pressure sensors, wherein the resistance strain gauge is arranged on the concrete surface and the internal steel bars of the closure section of the large-span beam-arch combined rigid frame bridge, the electromechanical dial indicators are arranged on the test component of the closure section of the large-span beam-arch combined rigid frame bridge, and the two pressure sensors are respectively arranged on the first hydraulic jack and the third hydraulic jack.

Further, the portal frame is arranged at the lower part of the upper chord end head to serve as a loading platform of the third hydraulic jack.

Further, the length and the width of the closure section of the combined rigid frame bridge of the base and the large-span beam arch are kept consistent, and the base is connected into a whole through a screw rod and a floor.

Further, the vertical wall is connected with the test member, and the test member and the vertical wall are connected into a whole through bolts.

Further, the loading module is also provided with a hydraulic pump set, the hydraulic pump set comprises at least 4 hydraulic pumps, and each hydraulic pump is matched with a corresponding hydraulic jack for use.

Further, the tertiary distribution beam at test component top axial leads to long setting, and tertiary distribution beam's length equals the length of test component, transversely places in test component upside center, closely laminates the setting with test component top.

Further, 126 strain measuring points are arranged in total, 82 strain gauges are arranged on the top base concrete, and 44 strain gauges are arranged on the side direction.

Further, strain gages are arranged on the top surface and the bottom surface of the main beam section of the test member, and 45-degree strain gages are arranged on the outer side surfaces of the two webs of the section of the test member.

Further, 5 deflection measuring sections are selected for the test component, each deflection measuring section comprises 4 upper chord beam sections and 1 lower chord beam section, and a total of 10 linear displacement meters are respectively arranged at the left side and the right side of each test section.

The invention further aims to provide a loading test method for the closure section model of the large-span beam-arch combined rigid frame bridge, which comprises the following steps:

step one, manufacturing a portal frame foundation and manufacturing a three-level distribution beam at the top of a test member;

step two, preparing a large-span beam-arch combined rigid frame bridge closure section test member: pouring and curing a closure section model of the large-span beam-arch combined rigid frame bridge;

step three, installing a measuring module: placing a large-span beam arch combined rigid frame bridge closure section model on a test area, and connecting a base, a vertical wall and a test ground into a whole by using a high-strength screw; after adjusting and positioning, sticking a resistance strain gauge, installing an electromechanical dial indicator and installing a pressure sensor above the hydraulic jack;

step four, setting a loading module: a loading module is arranged above a top plate of a closure section test component of the large-span beam-arch combined rigid frame bridge; a hydraulic jack is arranged between an upper chord beam and a lower chord beam of a closure section test piece of the large-span beam-arch combined rigid frame bridge, and a hydraulic jack is arranged between a door-type frame and the upper chord jack; installing a prestress tensioning hydraulic jack at a reserved prestress steel strand, starting a loading module, propping against a closure section model of a large-span beam-arch combined rigid frame bridge, and zeroing a pressure sensor and a displacement meter;

step five, carrying out a loading test: adjusting the power of the loading module, and carrying out graded loading on the bridge closure section model of the span beam-arch combined rigid frame bridge according to different working condition requirements; recording data of each measuring instrument in the measuring system;

step six, destroying the model: and continuously and graded loading is carried out on the large-span beam-arch combined rigid frame bridge closure section model until the large-span beam-arch combined rigid frame bridge closure section model is integrally unstable and damaged, loading is stopped, and the loading module is reset for comprehensive analysis.

In combination with the above technical solution and the technical problems to be solved, please analyze the following aspects to provide the following advantages and positive effects:

first, aiming at the technical problems in the prior art and the difficulty in solving the problems, the technical problems solved by the technical proposal of the invention are analyzed in detail and deeply by tightly combining the technical proposal to be protected, the results and data in the research and development process, and the like, and some technical effects brought after the problems are solved have creative technical effects. The specific description is as follows:

according to the invention, an innovative framework is adopted, the closure section of the large-span beam-arch combined rigid frame bridge is scaled down and converted into a scaled model experiment of the original component, the limitation that the original component is too large in size and has no experimental condition for exploring the stress characteristics and the structural characteristics of the closure section of the large-span beam-arch combined rigid frame bridge is eliminated, the experimental foundation of the closure section of the large-span beam-arch combined rigid frame bridge is perfected, the experimental basis is provided for researching the stress characteristics and the structural characteristics of the closure section of the large-span beam-arch combined rigid frame bridge, and the reference basis is provided for subsequent construction and research of the closure section of the large-span beam-arch combined rigid frame bridge; meanwhile, the method is not limited by size effect and boundary effect, is suitable for model simulation tests which cannot be performed due to the fact that the original structure is too large in size, and is wide in application range; the local objectivity of the large scale model is stronger, and the effect is better, clearer and more visual; the measurement data is convenient to acquire and study, and the test accuracy is higher.

According to the stress characteristics and structural characteristics of the closure section of the large-span beam-arch combined rigid frame bridge, the large-span beam-arch combined rigid frame bridge closure section model can achieve the stress effect of the original structure by adopting a plurality of independent hydraulic jacks, prestress tensioning jacks and loading actuators and arranging according to the stress characteristics of the original structure of the model component; each jack adopts a hydraulic pump matched with the hydraulic pump and independently acts, and the jacks are controlled respectively, so that each jack can be loaded independently, and further, the stress effect of the original component can be achieved at each loading point of the large-span beam arch combined rigid frame bridge closure section model.

According to the invention, the loading test device is entirely built on the base, all counterforces in the experimental loading process are acted on the base at the bottommost layer, and the whole base is connected with the ground listening screw rod of a laboratory to form a whole, so that the requirements and the influence of the simulation test on the external environment are reduced to the greatest extent; the door-shaped frame is fixed on the base, so that the door-shaped frame is convenient to detach and move, and has high turnover flexibility.

According to the invention, the output power of each hydraulic pump is independently controlled, so that different loads are applied to jacks at different positions and different loads are applied to actuators at the top, so that the bridge deck pavement, secondary and pre-stress and the stress effect at each boundary of a member are respectively simulated, the simulation situation is more fit with the actual situation, the operability of a test is improved, and the authenticity and the comprehensiveness of a simulation experiment are improved.

According to the invention, the load value applied by each jack and the actuator is fed back at any time through the pressure sensor arranged on each jack and the hydraulic value of the hydraulic pump of the jack, so that the pressure applied by the jack is accurately controlled, and the accuracy and the operability of the simulated loading test are greatly improved.

According to the invention, the change condition of each measuring point in the loading test process is accurately recorded through the strain gauges and the electromechanical dial indicators arranged on different observation points, so that the observation is more comprehensive and visual.

Secondly, the technical scheme is regarded as a whole or from the perspective of products, and the technical scheme to be protected has the following technical effects and advantages:

the invention has simple structure and convenient operation, can carry out full-circle loading of the closure section of the large-span beam-arch combined rigid frame bridge, is used for simulating the three-dimensional model of the closure section of the large-span beam-arch combined rigid frame bridge, and has high force transmission accuracy and wide application range.

Thirdly, as inventive supplementary evidence of the claims of the present invention, the following important aspects are also presented:

(1) The technical scheme of the invention fills the technical blank in the domestic and foreign industries:

by combining theoretical analysis and the test loading test research, the structural characteristics and stress conditions of the arched girder combined rigid frame bridge arched girder combined part are effectively disclosed, the stress characteristics of the whole process of the part are analyzed and simulated in detail, and the arched girder combined part bearing capacity calculation method of a plurality of construction parameters under applicable conditions is provided, so that the domestic arched girder combined part research test method is well filled.

(2) The technical scheme of the invention solves the technical problems that people are always desirous of solving but are not successful all the time:

compared with the prior art, the test loading test technology of the invention changes the closure section of the large-span beam arch combined rigid frame bridge into the scaled-down model test of the original component by combining reasonable theoretical calculation, eliminates the defect that the field test is inconvenient to test due to the oversized test component, provides a reference test case for the large-scale test of the same type, and provides guidance for the subsequent construction of the large-span beam arch combined rigid frame bridge; meanwhile, the novel test loading device test method is not limited by size effect and boundary effect, is suitable for model simulation tests which cannot be performed due to overlarge volume of the original structure, has stronger local objectivity compared with the traditional field test, and has better and clear effect, intuitionistic performance and higher test accuracy.

The mechanism of the bridge test piece testing device is improved and optimized, the problem of difficult loading test of the complex structure of the beam-arch combined angle coupling part is solved, the state of the test piece and the born pressure are convenient to grasp and record timely through the measuring method of the novel test loading device, the experiment of the test piece by a worker is greatly facilitated, the whole process of the test process is grasped, accurate experimental results are obtained, and theoretical support is provided for the construction of a later bridge.

Drawings

FIG. 1 is a schematic structural diagram of a loading test device for a closure segment model of a large-span beam-arch combined rigid frame bridge, which is provided by the embodiment of the invention;

FIG. 2 is a schematic diagram of the installation and distribution of an electromechanical dial indicator provided by an embodiment of the present invention;

FIG. 3 is a first principal stress cloud of a corner node according to an embodiment of the present invention;

FIG. 4 is a finite element model deflection cloud image provided by an embodiment of the present invention;

FIG. 5 is a schematic diagram of deflection calculation results provided by an embodiment of the present invention;

FIG. 6 is a graph of the stress distribution of roof concrete provided by an embodiment of the present invention; (a) section 3; (b) section 4; (c) section 5; (d) 6 cross section;

FIG. 7 is a graph of the stress distribution of roof concrete provided by an embodiment of the present invention; (a) section 3; (b) section 4; (c) section 5; (d) 6 cross section; (e) section 7; (f) section 8;

FIG. 8 is a top panel concrete deflection profile provided by an embodiment of the present invention;

FIG. 9 is a calculation model of the failure mode provided by an embodiment of the present invention;

FIG. 10 is a model deflection cloud provided by an embodiment of the present invention;

FIG. 11 is a graph comparing deflection values provided by embodiments of the present invention;

in the figure: 1. a test member; 2. a vertical wall and a base; 3. a first hydraulic jack; 4. a first pressure sensor; 5. a second hydraulic jack; 6. a door-type frame; 7. a third hydraulic jack; 8. a second pressure sensor; 9. a fourth hydraulic jack; 10. a three-stage distribution beam; 11. loading an actuator; 12. a fourth hydraulic jack; 13. a third pressure sensor; 14. a first electromechanical dial gauge; 15. a second electromechanical dial gauge; 16. a third electromechanical dial indicator; 17. a fourth electromechanical dial indicator; 18. resistance strain gage.

Detailed Description

The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

1. The embodiments are explained. In order to fully understand how the invention may be embodied by those skilled in the art, this section is an illustrative embodiment in which the claims are presented for purposes of illustration.

Fig. 1 to fig. 2 are schematic views of a loading test device for a closure section model of a large-span beam-arch combined rigid frame bridge, which is provided by an embodiment of the invention, and comprises a reaction frame foundation, a loading system and a measuring system.

The reaction frame foundation comprises a base and a vertical wall 2, a portal frame 6 arranged on the ground and a three-stage distribution beam 10 arranged on top of the test member 1. The base and the vertical wall 2 are reinforced concrete with the thickness not less than 40cm, and are connected into a whole through a high-strength screw rod and the ground; the number of the gate-shaped frames 6 is 1, the lower part of the upper chord end of the test member is used as a supporting foundation of the third hydraulic jack 7, and the distance between the top of the gate-shaped frames 6 and the lower surface of the upper chord end is required to be larger than the sum of the heights of the third hydraulic jack 7 and the second pressure sensor 8; the tertiary distribution beam 10 is arranged on top of the test member 1 with the longitudinal length being consistent with the test member longitudinal length and in the width direction directly above the box web of the test member 1.

The loading system comprises a first hydraulic jack 3 arranged on the upper side of the base, and a third hydraulic jack 7 above the portal frame 6; a hydraulic jack 12 at the corner coupling point of the test member 1; the second hydraulic jack 5 and the fourth hydraulic jack 9 along the upper chord end direction and the lower chord end direction are arranged on a loading actuator 11 at the top of the three-stage distributing beam 10.

The hydraulic jacks are divided into two groups according to different working conditions, and four hydraulic jacks of the first hydraulic jack 3, the second hydraulic jack, the third hydraulic jack 7 and the fourth hydraulic jack 9 are used for the working condition of the maximum bending moment; four hydraulic jacks 5, 7, 9 and 12 are used for the damage working conditions.

The measuring system comprises a first pressure sensor 4, a second pressure sensor 8, electromechanical dialmeters 12, 13, 14, 15 and a resistance strain gauge 16. As shown in fig. 1, the first pressure sensor 4 is disposed above the first hydraulic jack 3, and the second pressure sensor 8 is disposed above the third hydraulic jack 7; as shown in fig. 2, the electromechanical dial indicators are disposed on the side wall of the test member 1, the first electromechanical dial indicator 12 is mounted directly under the upper chord end of the test member 1, the second electromechanical dial indicator 13 is disposed directly under the lower chord end of the test member 1, the third electromechanical dial indicator 14 is disposed directly under the corner coupling node of the test member 1, the fourth electromechanical dial indicator 15 is disposed on the lower chord side wall of the test member 1, and all the electromechanical dial indicator pointers are mounted vertically downward. The resistive strain gage 16 is arranged as shown in fig. 2 to observe the stress conditions of the test member 1 during pressure loading.

The loading test method for the closure section model of the large-span beam-arch combined rigid frame bridge provided by the embodiment of the invention specifically comprises the following steps:

step one, manufacturing a portal frame foundation 6 and manufacturing a three-level distribution beam 10 at the top of a test member 1;

step two, preparing a large-span beam-arch combined rigid frame bridge closure section test member 1: pouring and curing a closure section model of the large-span beam-arch combined rigid frame bridge;

step three, installing a measuring system: placing a large-span beam arch combined rigid frame bridge closure section model on a test area, and connecting a base, a vertical wall foundation 2 and a test ground into a whole by using a high-strength screw; after the adjustment and positioning, a resistance strain gauge 18 is stuck, electromechanical dial indicators 14, 15, 16 and 17 are installed, and a first pressure sensor 4 and a second pressure sensor 8 are installed above the hydraulic jacks 3 and 7;

step four, setting a loading system: a loading device (loading actuator 11) is arranged above a top plate of a closure section test piece 1 of the large-span beam-arch combined rigid frame bridge; a hydraulic jack 12 is arranged between an upper chord beam and a lower chord beam of a closure section test piece of the large-span beam-arch combined rigid frame bridge; a hydraulic jack 7 is arranged between the door-shaped frame and the upper chord jack; a second hydraulic jack 5 and a fourth hydraulic jack 9 of prestress tensioning are arranged at the reserved prestress steel strand, a loading device is started, a jack is supported on a closure section model of the large-span beam-arch combined rigid frame bridge, and a pressure sensor and a displacement meter are zeroed;

step five, carrying out a loading test: adjusting the power of the loading device, and carrying out graded loading on the bridge closure section model of the span beam-arch combined rigid frame bridge according to different working condition requirements; recording data of each measuring instrument in the measuring system;

step six, destroying the model: and continuously and graded loading is carried out on the large-span beam-arch combined rigid frame bridge closure section model until the large-span beam-arch combined rigid frame bridge closure section model is integrally unstable and damaged, loading is stopped, and the loading device is reset for comprehensive analysis.

2. Application example.

1. Design of test element

Researching the influence of a beam-arch combined continuous rigid frame bridge corner node structural form on the stress performance of the corner node, manufacturing a model test piece, carrying out a load test, strictly carrying out 1/8 scale according to an actual bridge structure, reflecting the stress state of the corner node in the actual bridge by applying proper boundary conditions and external load, and comparing with the rest model; the total length of the test piece is 4.275m, the section height of the end part of the upper chord cantilever is 62.5cm, and the section width is 223.125cm; the section of the end part of the lower chord cantilever is 60cm, and the section width is 112.5cm. The specific dimensions are shown in the following figures.

2. Measurement module design

The total model is provided with 62 concrete strain measuring points, 15 concrete strain gages on the top and bottom plates and 47 web measuring points. Strain gages are arranged on the top and bottom surfaces of the main beam section at the test site, and 45-degree strain gages are arranged on the 4, 5 and 6 section (namely corner node section) measuring points on the outer side surface of the web.

3. Load condition design

1) Maximum bending moment working condition:

and (3) calculating through the integral finite element model, and determining the internal force value of the corner node section of the worst working condition of the test model under the short-term combined action of the normal use limit state.

The test mainly considers that the maximum positive and negative bending moment working condition occurs at the corner node position under the normal use limit state. And the reduction ratio of the test piece is 1:8, and the internal control force of the test piece node section is obtained according to the internal force conversion of the original structure section. In order to ensure that the stress state of the corner joint is consistent with that of the solid bridge, an L-shaped pedestal is designed outside the main body part of the test piece, an anchor hole is formed in the pedestal, and the anchor rod is firmly connected with the ground and the counter-force wall, so that the boundary condition of one side fixation is simulated; in the test process, the axial force and the section bending moment are applied by tensioning the external prestressed tendons of the eccentric body through the penetrating jack, and the vertical shearing force and the bending moment are applied by utilizing the hydraulic jack, so that loading is realized. The control internal force of the corner node section, namely the upper chord connection section and the lower chord connection section of the test piece, is obtained by converting the internal force of the real bridge section under the working condition of the maximum bending moment according to the reduction ratio, and the specific numerical values are shown in the table below.

TABLE 1 control of internal force at corner node section

In order to make the load diagram of the model test coincide with the actual load of the prototype as much as possible, the load of the model such as a first-stage constant load balance weight, a second-stage constant load, a live load and the like is applied in the following form in the test;

1) Beam end concentration force

And the uniformly distributed load is equivalent to the concentrated force load applied to the end part of the model by controlling the principle that the forces in the equivalent section are equal. The concentrated force at the end of the model is simulated by using a mode of loading a prestressed tendon and a jack outside the tensioning body.

2) Constant load compensation counterweight

The constant load counterweight aims to simulate the dead weight of the main girder, so that the dead weight load meets the requirement of the similar ratio. By applying uniform load on the test beam.

3) Equivalent vehicle load

The lane load concentration force effect in the actual structure is simulated, and the lane load concentration force effect is realized by applying uniform load on the test beam. And (5) calculating loading forces of the upper and lower chord beams of the test model according to the internal force control of the corner node section.

Table 2 test model loading values

The stress conditions of the joint model test are ensured to be consistent with the actual engineering through the integral rod system model calculation of the real bridge and the joint entity finite element calculation, and the positions of the loading end and the fixed end pedestal are different from the stress conditions of the real bridge, but the joint area which is seriously inspected by the test is not influenced.

In order to accurately collect strain and deflection data, the change trend of the strain and deflection data along with the increase of load is inspected, and meanwhile, in order to ensure the safety of loading, the model test piece is subjected to graded loading. The loading force corresponding to the least adverse working condition is divided into 10 stages for loading, and the specific loading stages are shown in the table.

TABLE 3 external bundle tension value table (kN)

Table 4 vertical jack loading value table (kN)

TABLE 5 weight values Table (kN)

2. Damage condition

And removing the upper limit jack and the lower limit jack, and arranging the jacks between the upper chord and the lower chord for loading until the structure is damaged.

In order to prove the inventive and technical value of the technical solution of the present invention, this section is an application example on specific products or related technologies of the claim technical solution.

The loading test device for the closure section three-dimensional model of the large-span beam-arch combined rigid frame bridge provided by the embodiment of the invention can be used for researching the stress behavior of the closure section node part of the large-span beam-arch combined rigid frame bridge, researching the rationality of the design of the large-span beam-arch combined rigid frame bridge and providing technical reference for the same type of bridge.

3. Evidence of the effect of the examples. The embodiment of the invention has a great advantage in the research and development or use process, and has the following description in combination with data, charts and the like of the test process.

According to the loading testing device and method, a large-span beam-arch combined rigid frame bridge closure section corner node test is carried out, and obtained test data and a theoretical model are compared and analyzed, wherein the results are shown as follows:

1. stress calculation and analysis

As can be seen from fig. 3 and 4, the corner node model appears at maximum at the web bundle anchoring location. The corner node is stressed at the upper chord joint part and the lower chord joint part under the action of prestressing force to be mainly stressed; considering that the actual test piece has local tensile stress in the actual situation because the thickness of the test piece is thinner in the small range of the anchoring area of the web plate bundle and the top plate bundle and the structure under the anchor is more complex, and the value of the tensile stress is smaller.

2. Deflection calculation and analysis

As shown in FIG. 5, the deflection of the end of the cantilever under the maximum working condition of the upper chord Liang Wanju of the corner node is 12.37mm, and the deflection is gradually decreased along the length direction of the test piece as known by the finite element model.

And comparing the test result with the finite element model calculation result, and comparing stress values and deflection of each measuring point under the maximum bending moment working condition.

Table 6 top plate measurement point numerical comparison (MPa)

As can be seen from Table 6, the test values agree well with the finite element calculated values, except that the individual measurement point errors are large, and the overall average error is about 3.0%. The roof concrete stress distribution curve is shown in fig. 6.

The web is mainly pressed along the bridge direction due to the action of the prestress steel beam. From the principal stress values, it is seen that there is a greater stress concentration near the site of web bundle anchoring, and that the principal stress of the web drops rapidly after leaving this region.

Table 7 Web measurement point numerical comparison (MPa)

As can be seen from Table 7, the test values are substantially identical to the finite element calculated values except that the stress levels at the individual stations are significantly different from the theoretical calculated values. Because of the effect of the prestress steel bundles, the top plate is mainly pressed along the bridge direction, the anchoring section position of the top plate is similar to the anchoring section position of the web plate bundles, on the prestress steel bundle anchoring section, the main stress of the top plate is larger, and the main stress of the top plate is rapidly reduced after leaving the area. The roof concrete stress distribution curve is shown in fig. 7. The roof concrete deflection profile is shown in figure 8.

Table 8 deflection measuring point numerical comparison (mm)

Analysis shows that the test value is relatively close to the finite element calculated value, and the deflection of the model is expressed as a rule of decreasing from the cantilever end to the fixed end.

2. Damage condition

Modifying the boundary condition and the load condition of the model on the basis of the finite element calculation model of the bending moment maximum condition so as to simulate the experimental breaking condition: and removing the lifting force of the upper and lower chords of the model, adding a pair of vertical couples between the upper and lower chords of the model to activate the vertical constraint boundary condition of the bottom plate of the model under the lifting action of the jack at the position of the model.

The model calculation results are shown in fig. 9 and 10.

As shown in FIG. 11, the test value is better matched with the finite element calculated value by comparing the deflection value of the test piece under the failure working condition.

According to the comparison analysis of the test and the finite element model result, the phenomenon of local stress concentration exists at the intersection section of the upper chord and the lower chord of the corner node under the maximum bending moment working condition, so that the stress is gradually reduced towards two sides of the section; obvious stress concentration phenomenon exists at the anchoring position of the prestressed steel strand; in the loading process of the damage working condition, the primary crack of the test piece is generated from the intersection of the upper chord member and the lower chord member, and the crack gradually develops along with the increase of the load; when the upper chord web plate is provided with oblique cracks, the structure gradually yields; when the bottom plate steel bar of the upper chord member yields and the top plate concrete reaches the compression strength, the structure reaches the ultimate bearing capacity, and the stress characteristics of the corner joint of the closure section of the large-span beam-arch combined rigid frame bridge are met. The loading testing device and the loading testing method can play a positive role in the research of the complex test piece.

In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front," "rear," "head," "tail," and the like are used as an orientation or positional relationship based on that shown in the drawings, merely to facilitate description of the invention and to simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

The foregoing is merely illustrative of specific embodiments of the present invention, and the scope of the invention is not limited thereto, but any modifications, equivalents, improvements and alternatives falling within the spirit and principles of the present invention will be apparent to those skilled in the art within the scope of the present invention.

Claims (10)

1. The loading testing device for the closure section model of the large-span beam-arch combined rigid frame bridge is characterized by comprising the following components: the device comprises a supporting module, a loading module and a measuring module;

the support module comprises a base, a vertical wall, a door-shaped frame and a three-level distribution beam arranged at the top of the test member;

the loading module comprises a third hydraulic jack arranged on the upper side of the portal frame, a loading actuator at the top of the test member, a first hydraulic jack at the corner coupling of the closure section, a second hydraulic jack and a fourth hydraulic jack for stretching the prestressed steel beam along the bridge direction of the member;

the measuring module comprises a strain measuring point, a plurality of electromechanical dial indicators and two pressure sensors, wherein the resistance strain gauge is arranged on the concrete surface and the internal steel bars of the closure section of the large-span beam-arch combined rigid frame bridge, the electromechanical dial indicators are arranged on the test component of the closure section of the large-span beam-arch combined rigid frame bridge, and the two pressure sensors are respectively arranged on the first hydraulic jack and the third hydraulic jack.

2. The loading testing device for the closure section model of the large-span beam-arch combined rigid frame bridge, as set forth in claim 1, wherein the portal frame is arranged at the lower part of the upper chord end and is used as a loading platform of the third hydraulic jack.

3. The loading testing device for the closure section model of the large-span beam-arch combined rigid frame bridge according to claim 1, wherein the base and the large-span beam-arch combined rigid frame bridge closure section keep the same length and width, and the base is connected into a whole through a screw rod and a floor.

4. The loading testing device for the closure section model of the large-span beam-arch combined rigid frame bridge according to claim 1, wherein the upright wall is connected with the test member, and the test member and the upright wall are connected into a whole through bolts.

5. The loading testing device for the closure section model of the large-span beam arch combined rigid frame bridge according to claim 1, wherein the loading module is further provided with a hydraulic pump set, the hydraulic pump set comprises at least 4 hydraulic pumps, and each hydraulic pump is matched with a corresponding hydraulic jack.

6. The loading testing device for the closure section model of the large-span beam-arch combined rigid frame bridge according to claim 1, wherein the three-stage distribution beam at the top of the test member is axially arranged in a through length mode, the length of the three-stage distribution beam is equal to that of the test member, and the three-stage distribution beam is transversely placed in the center of the upper side of the test member and is tightly attached to the top of the test member.

7. The loading testing device for the closure section model of the large-span beam-arch combined rigid frame bridge according to claim 1, wherein 126 strain measuring points are arranged in total, 82 strain gauges are arranged on the top base concrete, and 44 strain gauges are arranged on the side direction.

8. The loading testing device for the closure section model of the large-span beam-arch combined rigid frame bridge according to claim 7, wherein strain gages are arranged on the top surface and the bottom surface of the main beam section of the test member, and 45-degree strain relief is arranged on the outer side surfaces of two webs of the section of the test member.

9. The loading testing device for the closure section model of the large-span beam-arch combined rigid frame bridge according to claim 1, wherein 5 deflection measuring sections are selected by the testing component, the deflection measuring sections comprise 4 upper chord beam sections and 1 lower chord beam section, and one linear displacement meter is respectively arranged at the left side and the right side of each testing section, and the total number of the linear displacement meters is 10.

10. A method for implementing the loading test device for the closure section model of the large-span beam-arch combined rigid frame bridge according to any one of claims 1 to 9, characterized in that the loading test method for the closure section model of the large-span beam-arch combined rigid frame bridge comprises the following steps:

step one, manufacturing a portal frame foundation and manufacturing a three-level distribution beam at the top of a test member;

step two, preparing a large-span beam-arch combined rigid frame bridge closure section test member: pouring and curing a closure section model of the large-span beam-arch combined rigid frame bridge;

step three, installing a measuring module: placing a large-span beam arch combined rigid frame bridge closure section model on a test area, and connecting a base, a vertical wall and a test ground into a whole by using a high-strength screw; after adjusting and positioning, sticking a resistance strain gauge, installing an electromechanical dial indicator and installing a pressure sensor above the hydraulic jack;

step four, setting a loading module: a loading module is arranged above a top plate of a closure section test component of the large-span beam-arch combined rigid frame bridge; a hydraulic jack is arranged between an upper chord beam and a lower chord beam of a closure section test piece of the large-span beam-arch combined rigid frame bridge, and a hydraulic jack is arranged between a door-type frame and the upper chord jack; installing a prestress tensioning hydraulic jack at a reserved prestress steel strand, starting a loading module, propping against a closure section model of a large-span beam-arch combined rigid frame bridge, and zeroing a pressure sensor and a displacement meter;

step five, carrying out a loading test: adjusting the power of the loading module, and carrying out graded loading on the bridge closure section model of the span beam-arch combined rigid frame bridge according to different working condition requirements; recording data of each measuring instrument in the measuring system;

step six, destroying the model: and continuously and graded loading is carried out on the large-span beam-arch combined rigid frame bridge closure section model until the large-span beam-arch combined rigid frame bridge closure section model is integrally unstable and damaged, loading is stopped, and the loading module is reset for comprehensive analysis.

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