Experimental device for testing shear hysteresis effect of concrete box girder

Abstract

The utility model relates to an experimental device for testing the shear hysteresis effect of a concrete box girder, which is characterized by comprising an organic glass box girder model, an inhaul cable, a reaction frame, a loading system, a testing system and a computer, the reaction frame comprises a vertical rod, a top cross beam, a top longitudinal beam, a bottom cross beam, a bottom longitudinal beam, a special screw rod and a suspension beam, the loading system comprises a stacking frame, a force transmission column and a balancing weight, the test system comprises a force measurement module and a strain measurement module, the organic glass box girder model is arranged right above a suspension beam, and a strain test element is sequentially connected with a strain acquisition instrument and a computer through a data transmission line. The box girder shear hysteresis effect test device is novel and reasonable in design, simple in loading mode, accurate and reliable in test result, high in simulation degree, good in practicability and easy to popularize and apply in the field of box girder shear hysteresis effect analysis and test, and measured data can truly reflect the shear hysteresis effect of the box girder under the action of cable force.

Description

Technical Field

[0001] The utility model relates to a vertical force loading device, in particular to an experimental device for testing shear lag effect of a concrete box beam. Background Art

[0002] As a cable system, the cable-stayed bridge has a greater spanning capacity than the beam bridge and is the most important bridge type among long-span bridges. Due to the advantages of large cross-sectional bending and torsional rigidity, small shrinkage deformation, strong integrity, and high industrial construction efficiency, the box girder can adapt to different forms of cable arrangement, which is very beneficial to cantilever construction. In addition, it can be partially prefabricated and partially cast in place, providing a variety of options for construction plans. Therefore, it has become a commonly used main beam form in cable-stayed bridges. The cable-stayed concrete box girder bridge is a bridge in which the concrete box girder is directly anchored to the bridge tower with many cables (high-strength steel strands). It is a structural system composed of a pressure-bearing bridge tower, tension cables, and a bending main beam. During the service of the bridge, the tension cables cause the concrete box girder to be subjected to horizontal pressure and upward elastic support reaction force, thereby improving the bridge's bearing capacity and spanning capacity. Therefore, the cable-stayed concrete box girder bridge is often the preferred bridge type for long-span bridges in my country. Compared with solid cross-section beams, box girders are hollow thin-walled structures composed of top plates, web plates, and bottom plates. Under use loads such as moving live loads and dead loads, they exhibit a shear lag effect of longitudinal bending, which causes the longitudinal positive stress of the flange to be unevenly distributed in the transverse direction, thus causing structural safety hazards. With the development of new materials and new technologies, concrete box girders are gradually developing in the direction of long cantilever plates, large web spacing, and thin walls and lightweight, which will lead to more significant uneven stress distribution in box girders. Therefore, it is increasingly important to analyze and study the shear lag effect of box girders.

[0003] According to the research on the shear lag effect of box girders by foreign scholars, for typical cross-section beams, scholars from various countries have used a combination of theoretical models, numerical simulations and model tests to study the shear lag effect of box girders under different working conditions and different main beam cross-section forms. Theoretical analysis methods such as energy variation method and analog rod method and numerical analysis methods such as finite element method and finite beam segment method have been established, but the application is mainly concentrated in conventional bridges such as simply supported beams, cantilever beams and continuous beams with box beams as the main beam cross-section. The research on the shear lag effect of cable-stayed bridge box girders is relatively limited, especially in the existing reports on the research on the shear lag effect model test of cable-stayed bridge box girders. As one of the most effective means to understand the real force behavior and force transmission mechanism of the structure, bridge structure model test has become an important means to study and develop bridge structure theory at home and abroad. Organic glass has been widely used in bridge structure models due to its good homogeneity and convenient processing and production. Using indoor organic glass scale model experiments, the shear lag effect of cable-stayed box girder bridges under the action of cables can be experimentally studied. Due to the small size of the plexiglass model, it is impossible to obtain the shear lag effect of the plexiglass box girder model under the action of cables by tensioning high-strength steel strands as in actual engineering. Therefore, it is urgent to develop an experimental device for the shear lag effect of box beams that can effectively simulate the action of cables. Summary of the invention

[0004] In order to solve the above technical problems, the technical solution adopted by the utility model is: an experimental device for testing the shear lag effect of a concrete box girder, comprising an organic glass box girder model, a cable, a reaction frame, a loading system, a testing system, and a computer, characterized in that the reaction frame comprises a vertical pole, a top cross beam, a top longitudinal beam, a bottom cross beam, a bottom longitudinal beam, a special screw and a suspension beam, the loading system comprises a stacking frame, a transmission column and a counterweight, the testing system comprises a force measuring module and a strain measuring module, the strain measuring module comprises a strain testing element and a strain collector, the strain testing element is connected to the strain collector and the computer in sequence through a data transmission line, the organic glass box girder model is placed directly above the suspension beam, and an organic glass pad for fixing the cable is arranged on the surface at the intersection of the top plate and the web of the organic glass box girder model, the organic glass pad is connected to the cable through the cooperation between a T-shaped bolt, a baffle and a cotter pin, the stacking frame is connected to the upper surface of the organic glass box girder model through a force transmission column, and the counterweight is placed directly above the stacking frame.

[0005] Preferably, in order to facilitate the application of vertical cable force to the plexiglass box girder model, a circular hole for a T-shaped bolt is provided on the side of the plexiglass pad, and a circular hole for a cotter pin to pass through is provided at the tail of the T-shaped bolt. The end of the cable passes through the bolts between the plexiglass pads and is fixed by a cable fastener that slides through the cable. The cable should be made of high-strength steel wire, and the cable diameter is determined by the number of counterweights.

[0006] Preferably, the force measuring module includes a distribution beam, a hook hanger, a tension sensor, a hanger, and a data converter. The bottom of the tension sensor is connected to the plexiglass box girder model through the hook hanger, the distribution beam and the cable, and the top of the tension sensor is connected to the top crossbeam of the reaction frame through the hanger. The data transmission interface of the tension sensor is connected to the data converter and the computer in sequence through a data transmission line, thereby realizing the test of the cable force of the plexiglass box girder model.

[0007] Preferably, the strain testing element is arranged on the surface of the top plate and the bottom plate of the organic glass box girder model by gluing, so as to measure the shear lag effect at different positions of the organic glass box girder.

[0008] Preferably, the suspension beam is composed of two, namely the first suspension beam and the second suspension beam from left to right. Circular holes are provided on both sides of the suspension beam for the special screw to slide through, and are clamped on the end of the special screw through two sets of nuts. At the same time, it is suitable for plexiglass box beam models of different heights. The middle and lower parts of the special screw are provided with threads that match the nuts.

[0009] Preferably, in order to realize the loading of concrete box girders of different widths and different positions, the top cross beam of the reaction frame can be moved along the direction of the top longitudinal beam, and the inner and outer surfaces of the top longitudinal beam of the reaction frame are provided with rulers, so that the position of the top cross beam of the reaction frame can be calibrated when moving.

[0010] Preferably, the stacking rack is composed of four relatively vertical angle steels with bottom edges supported inwardly and two angle steels along the width direction of the plexiglass box girder model and with bottom edges relatively facing outwardly, and the angle steels are connected into a whole by welding. At the same time, in order to achieve better experimental results and realize the arrangement of longitudinal concentrated loads on the box girder, the force transmission columns are evenly arranged by welding at the bottom of the two outermost angle steels of the stacking rack along the length direction of the plexiglass box girder model, and the counterweight block is a standard lead block.

[0011] Preferably, the distribution beam is composed of a balancing cable and a distribution beam, wherein the balancing cable evenly distributes the tension on the tension sensor to multiple cables fixed on the distribution beam through the lever principle, which can effectively prevent the plexiglass box beam model from overturning during loading.

[0012] Compared with the prior art, the utility model has the following advantages.

[0013] The utility model has scientific and reasonable design, clear ideas, high simulation degree, simple loading method, and can freely and flexibly change the size of the experimental loading cable force by superimposing or reducing standard counterweight blocks.

[0014] The utility model has the advantages of wide application range and strong practicality. By utilizing the special design that the top crossbeam can be freely moved and adjusted along the longitudinal beam direction, the shear lag effect experiment can be conducted on organic glass cable-stayed box girder bridges of different spans by simply changing the relative position between the crossbeams on both sides. In addition, without considering the force measurement module, the utility model can also be used to conduct the shear lag effect experiment on ordinary organic glass box girder bridges.

[0015] During the experimental loading process, the utility model can obtain the shear lag effect of the box girder and the cable force applied to the box girder through the strain measurement module and the force measurement module of the test system, and establish a corresponding mapping relationship through the time-varying curve between the two.

[0016] The utility model has convenient material acquisition, simple structure and low manufacturing cost. Field experiments have shown that the experimental test results of the utility model are accurate and reliable, and can be used for testing the shear lag effect of organic glass cable-stayed box girder bridges. The results can provide a basis for the design and analysis of cable-stayed box girder bridges and have practical engineering significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The utility model is further described in detail below with reference to the accompanying drawings and embodiments.

[0018] Figure 1 It is a schematic diagram of a single-box three-chamber box girder structure.

[0019] Figure 2 It is a schematic diagram of the stacking rack structure.

[0020] Figure 3 It is a schematic diagram of the structure of the utility model.

[0021] Figure 4 It is a schematic diagram of the structural loading of the utility model.

[0022] Figure 5 It is a schematic diagram of the cross-sectional dimensions of a single-box three-chamber box girder.

[0023] Figure 6 It is a schematic diagram of the loading method of a single-box three-chamber box girder.

[0024] Figure 7 It is the comparison result between the experimental value of the top plate stress of 1 / 4 section of single-box three-chamber box girder and the plate and shell value and theoretical value.

[0025] Figure 8 It is the comparison result between the experimental value of the top plate stress of the mid-span section of a single-box three-chamber box girder and the plate and shell value and the theoretical value.

[0026] Fig. 9 It is the comparison result between the experimental value of the bottom plate stress of 1 / 4 section of single-box three-chamber box girder and the plate and shell value and theoretical value.

[0027] Fig.10It is the comparison result between the experimental value of the stress of the bottom plate in the mid-span section of the single-box three-chamber box girder and the plate and shell value and the theoretical value.

[0028] Description of Figure Numbers.

[0029] In the figure: 1—plexiglass box beam model; 2—plexiglass pad; 3—T-shaped bolt; 4—block; 5—split pin; 6—strain test element; 7—data transmission line; 8—vertical pole; 9—top crossbeam; 10—top longitudinal beam; 11—bottom crossbeam; 12—bottom longitudinal beam; 13—suspension beam; 14—cable; 15—cable fastener; 16—balance cable; 17—distribution beam; 18—tension sensor; 19—hook suspension rod; 20—suspender rod; 21—special screw; 22—nut; 23—strain collector; 24—computer; 25—ruler; 26—stacking rack; 27—force transmission column; 28—counterweight; 29—data converter. DETAILED DESCRIPTION

[0030] like Figure 1~Figure 4 As shown, the utility model includes an organic glass box beam model 1, a cable 14, a reaction frame, a loading system, a test system, and a computer 24, characterized in that the reaction frame includes a vertical rod 8, a top cross beam 9, a top longitudinal beam 10, a bottom cross beam 11, a bottom longitudinal beam 12, a special screw 21 and a suspension beam 13, the loading system includes a stacking frame 26, a force transmission column 27 and a counterweight block 28, the test system includes a force measurement module and a strain measurement module, the strain measurement module includes a strain test element 6 and a strain collector 23, the strain test The element 6 is connected to the strain collector 23 and the computer 24 in sequence through the data transmission line 7. The plexiglass box girder model 1 is placed directly above the suspension beam 13. A plexiglass pad 2 for fixing the cable 14 is provided on the surface where the top plate and the web of the plexiglass box girder model 1 meet. The plexiglass pad 2 is connected to the cable 14 through the cooperation between the T-shaped bolt 3, the baffle 4 and the cotter pin 5. The stacking rack 26 is connected to the upper surface of the plexiglass box girder model 1 through the force transmission column 27, and the counterweight block 28 is placed directly above the stacking rack 26.

[0031] like Figure 1~Figure 4 As shown, in this embodiment, the side of the plexiglass pad 2 is provided with a circular hole for a T-shaped bolt 3, and the tail of the T-shaped bolt 3 is provided with a circular hole for a cotter pin 5 to pass through. The end of the cable 14 passes through the bolt 3 between the plexiglass pads 2 and is fixed by a cable fastener 15 that slides through the cable 14. The cable 14 should be made of high-strength steel wire, and the diameter of the cable 14 is determined by the number of counterweights 28.

[0032] The force measuring module in this embodiment includes a distribution beam, a hook hanger 19, a tension sensor 18, a hanger 20, and a data converter 29. The bottom of the tension sensor 18 is connected to the organic glass box beam model 1 through the hook hanger 19, the distribution beam and the cable 14. The top of the tension sensor 18 is connected to the top cross beam 9 of the reaction frame through the hanger 20. The data transmission interface of the tension sensor 18 is connected to the data converter 29 and the computer 24 in sequence through the data transmission line 7.

[0033] In this embodiment, the strain testing element 6 is arranged on the top plate and bottom plate surfaces of the organic glass box beam model 1 by gluing.

[0034] In this embodiment, the suspension beam 13 is composed of two, which are the first suspension beam and the second suspension beam from left to right. Circular holes for the special screw 21 to slide through are respectively provided on both sides of the suspension beam 13, and are clamped on the end of the special screw 21 through two sets of nuts 22. In order to be suitable for organic glass box beam models 1 of different heights, the middle and lower parts of the special screw 21 are provided with threads matching the nuts 22.

[0035] In this embodiment, the top cross beam 9 of the reaction frame can move along the direction of the top longitudinal beam 10, and the inner and outer surfaces of the top longitudinal beam 10 of the reaction frame are provided with scales 25 to calibrate the position of the top cross beam 9 of the reaction frame.

[0036] In this embodiment, the stacking rack 26 is composed of four relatively vertical angle steels with bottom edges supported inwardly and two angle steels along the width direction of the plexiglass box girder model 1 and with bottom edges relatively facing outwardly, and the angle steels are connected into a whole by welding. The force transmission columns 27 are evenly arranged at the bottom of the two outermost angle steels of the stacking rack along the length direction of the plexiglass box girder model 1 by welding, and the counterweight block 28 is a standard lead block.

[0037] In this embodiment, the distribution beam is composed of a balancing cable 16 and a distribution beam 17, wherein the balancing cable 16 distributes the tension on the tension sensor 18 evenly to multiple cables 14 fixed on the distribution beam 17 through the lever principle, and the connection between the end of the balancing cable 16 and the distribution beam 17 can be fixed by welding or bolts.

[0038] When in use, firstly, the strain test element 6 is pasted on the surface of the base plate of the plexiglass box girder model 1, and the plexiglass pad 2 is pasted on the corresponding position of the top plate surface of the plexiglass box girder model 1. Then, according to the ruler 25 pasted on the inner and outer surfaces of the top longitudinal beam 10 of the reaction frame, the position of the top cross beam 9 is adjusted according to the longitudinal size of the plexiglass box girder model 1, and the position of the suspension beam 13 is determined according to the vertical size of the plexiglass box girder model 1, and it is fastened with a set of nuts 22. Then, the plexiglass box girder model 1 pasted with the strain test element 6 and the plexiglass pad 2 is placed directly above the suspension beam 13, and the plexiglass pad 2 is connected to the cable 14 through the cooperation between the T-shaped bolt 3, the baffle 4 and the split pin 5. Then, one end of the cable 14 is connected to the distribution beam 17, and the other end is formed into a circular ring through the cable fastener 15. After the T-shaped bolt 3 passes through the cable 14, the plexiglass pad 2 and the baffle 4 in sequence, the cotter pin 5 is inserted into the hole at the tail of the bolt, and the tail of the cotter pin 5 is opened to prevent the baffle 4 and the T-shaped bolt 3 from falling off.

[0039] Then, the tension sensor 18 is arranged, the bottom hook suspension rod 19 of the tension sensor 18 is connected to the balance cable 16 and the distribution beam 17 in sequence, the top of the tension sensor 18 is connected to the top beam 9 of the reaction frame through the suspension rod 20, the data transmission interface of the tension sensor 18 and the strain test element 6 are connected to the data converter 29 and the strain collector 23 respectively through the data transmission line 7, and the data converter 29 and the strain collector 23 are connected to the computer 24 through the data transmission line 7. After the above steps are completed, vertical loading can be performed by stacking counterweights 28 on the stacking rack 26. When the number of stacked counterweights 28 reaches the experimental requirements, the loading is stopped, and the cable force and strain data are collected using the computer 24.

[0040] Example Analysis

[0041] In order to investigate the experimental effect of the utility model, a single-box three-chamber plexiglass box girder model is taken as an example. The test model has a span of L = 1000mm and a simple supported box girder. The cross-sectional dimensions of the single-box three-chamber box girder are shown in Figure 5 . Elastic modulus of plexiglass E =2600×10 5 MPa, Poisson's ratio is 0.385. A vertical cable force of 0.25 kN is applied at the intersection of the web and top plate of the single-box three-chamber box girder. The loading method is shown in Figure 6 In order to verify the accuracy and reliability of the experimental results of the utility model, the finite element numerical model of the box girder was established using the ANSYS finite element software shell63 unit. At the same time, the analog rod theoretical analysis method was used to compare and analyze the test values, finite element values ​​and theoretical values ​​of the model test of the utility model. The comparison results are as follows: Figure 7~Figure 10 shown.

[0042] from Figure 7~Figure 10 It can be seen that under the action of vertical cable force, the top and bottom plates of the box girder mid-span and 1 / 4 span sections show obvious shear lag effect, and the shear lag effect is the largest at the intersection of the top and bottom plates of the box girder and the web. Figure 7~Figure 10 From the comparison results, it can be seen that the experimental values ​​of the stress of the top and bottom plates of the box girder mid-span and 1 / 4 span sections obtained according to the utility model are very consistent with the finite element values ​​and the theoretical values, and the maximum deviation between the experimental values ​​and the finite element values ​​and the theoretical values ​​does not exceed and, indicating that the utility model can be used for the analysis of the shear lag effect of the plexiglass cable-stayed box girder model bridge, and the loading accuracy is high, and the experimental results are consistent with the expected goals.

[0043] The above is only a preferred embodiment of the utility model, and does not limit the utility model in any way. Any simple modification, change and equivalent change made to the above embodiment according to the essence of the utility model technology still falls within the protection scope of the technical solution of the utility model.

Claims

1. An experimental device for testing the shear lag effect of a concrete box girder, comprising a plexiglass box girder model (1), a cable (14), a reaction frame, a loading system, a testing system, and a computer (24), characterized in that: The reaction frame comprises a vertical rod (8), a top cross beam (9), a top longitudinal beam (10), a bottom cross beam (11), a bottom longitudinal beam (12), a special screw rod (21) and a suspension beam (13); the loading system comprises a stacking frame (26), a force transmission column (27) and a counterweight (28); the test system comprises a force measurement module and a strain measurement module; the strain measurement module comprises a strain measurement element (6) and a strain acquisition instrument (23); the strain measurement element (6) is connected to the strain acquisition instrument (23) and a computer (23) in sequence via a data transmission line (7). 4), the plexiglass box girder model (1) is placed directly above the suspension beam (13), a plexiglass pad (2) for fixing the cable (14) is provided on the surface of the junction between the top plate and the web of the plexiglass box girder model (1), the plexiglass pad (2) being connected to the cable (14) through the cooperation between the T-shaped bolt (3), the baffle (4) and the cotter pin (5), the stacking frame (26) is connected to the upper surface of the plexiglass box girder model (1) through the force transmission column (27), and the counterweight block (28) is placed directly above the stacking frame (26).

2. The experimental device for testing the shear lag effect of concrete box beams according to claim 1, characterized in that: The side of the organic glass pad (2) is provided with a circular hole for a T-shaped bolt (3), and the tail of the T-shaped bolt (3) is provided with a circular hole for a split pin (5) to pass through. The end of the cable (14) passes through the bolt (3) between the organic glass pads (2) and is fixed by a cable fastener (15) that slides through the cable (14). The cable (14) should be made of high-strength steel wire, and the diameter of the cable (14) is determined by the number of counterweights (28).

3. The experimental device for testing the shear lag effect of concrete box beam according to claim 1, characterized in that: The force measurement module comprises a distribution beam, a hook suspension rod (19), a tension sensor (18), a suspension rod (20), and a data converter (29); the bottom of the tension sensor (18) is connected to the organic glass box beam model (1) through the hook suspension rod (19), the distribution beam, and the cable (14); the top of the tension sensor (18) is connected to the top crossbeam (9) of the reaction frame through the suspension rod (20); and the data transmission interface of the tension sensor (18) is connected to the data converter (29) and the computer (24) in sequence through a data transmission line (7).

4. The experimental device for testing the shear lag effect of concrete box beam according to claim 1, characterized in that The strain testing element (6) is arranged on the top plate and bottom plate surfaces of the organic glass box beam model (1) by gluing.

5. The experimental device for testing the shear lag effect of concrete box beam according to claim 1, characterized in that: The suspension beam (13) is composed of two parts, namely, a first suspension beam and a second suspension beam from left to right. Circular holes are respectively provided on both sides of the suspension beam (13) for the special screw rod (21) to slide through, and are clamped on the ends of the special screw rod (21) through two sets of nuts (22). The special screw rod (21) is suitable for organic glass box beam models (1) of different heights. The middle and lower parts of the special screw rod (21) are provided with threads matching with the nuts (22).

6. The experimental device for testing the shear lag effect of concrete box beam according to claim 1, characterized in that: The top cross beam (9) of the reaction frame can move along the direction of the top longitudinal beam (10), and scales (25) are provided on the inner and outer surfaces of the top longitudinal beam (10) of the reaction frame to calibrate the position of the top cross beam (9) of the reaction frame.

7. The experimental device for testing the shear lag effect of concrete box beams according to claim 1, characterized in that: The stacking frame (26) is composed of four relatively vertical angle steels with bottom edges supported inwardly and two angle steels along the width direction of the organic glass box beam model (1) and with bottom edges facing outwardly, and the angle steels are connected into a whole by welding. The force transmission columns (27) are evenly arranged at the bottom of the two outermost angle steels of the stacking frame along the length direction of the organic glass box beam model (1) by welding. The counterweight block (28) is a standard lead block.

8. The experimental device for testing the shear lag effect of concrete box beams according to claim 3, characterized in that: The distribution beam is composed of a balancing cable (16) and a distribution beam (17), wherein the balancing cable (16) evenly distributes the tension on the tension sensor (18) to a plurality of cables (14) fixed on the distribution beam (17) through the principle of a lever.

Images