A double-top L-beam loading compression shear test system

Abstract

The present invention belongs to a test device for the seismic resistance of shear wall specimens, and discloses a double-top L-beam loading compression shear test system. The system includes a test bench, a fixing device, a supporting device, an L-shaped loading beam, a loading device and a guiding device; the guiding device includes a four-linkage for beam rotation constraint and a vertical guiding mechanism, and the vertical guiding mechanism includes a guiding base, a horizontal guide rail, a vertical guide rail, a guiding beam and a sliding block. The guiding base is installed on the test bench, the horizontal guide rail is installed on the guiding base, the guiding beam is connected to the horizontal guide rail, the vertical guide rail is installed on the guiding beam, and the sliding block is installed inside the lower end of the vertical beam of the L-shaped loading beam and is slidably connected to the vertical guide rail. The system can ensure that the L-shaped loading beam can remain horizontal and simulate earthquake loads well.

Description

Technical Field

[0001] The invention relates to a test device for the seismic resistance of a shear wall specimen, and in particular to a double-top L-beam loading compression shear test system. Background Art

[0002] When the traditional loading frame conducts seismic shear test and beam-column node hysteresis test of shear wall specimens, the horizontal loading actuator is generally directly connected to the upper part of the specimen for loading. The disadvantage of this loading method is that the maximum bending moment appears at the bottom of the specimen, and the bottom of the specimen is prone to bending failure, resulting in failure to obtain the ideal shear test effect. For example, Chinese patent CN104198300A discloses a civil engineering array loading test system, the system includes a reaction frame, a vertical actuation unit, at least one horizontal actuation unit and a loading beam, the vertical actuation unit is arranged above the loading beam, and includes at least two vertical actuators arranged vertically and parallelly, the reaction frame, the vertical actuator and the loading beam constitute a plane linkage mechanism or a spatial connection mechanism, the horizontal actuation unit is arranged on the side of the loading beam, each group of horizontal actuation units includes at least one horizontally arranged horizontal actuator, and the two ends of the vertical actuator and the horizontal actuator are respectively hingedly connected to the reaction frame and the loading beam. The test loading is carried out through a loading beam, and the actuator provides the loading force of the loading beam. Different test loadings are carried out through different deformations of the connecting rod mechanism. The test system can not only meet the requirements of civil compression and shear tests well, but also does not require a special follow-up device and is not affected by friction. At the same time, the system does not require modification and can directly complete more types of structural test loadings.

[0003] It can be seen that although the above technical solution can optimize the stress state of the specimen and reduce the bending moment at the bottom of the specimen, it will occupy a large experimental space due to the long vertical actuator, and the offset angle of the vertical actuator needs to be considered after the specimen undergoes horizontal displacement, resulting in a relatively complex control method. The most important thing is the lack of a guide device. During the experiment, the loading beam is prone to a series of problems such as tilting and instability. In view of this, it is of great significance to develop a new compression shear test device to ensure that the L-shaped loading beam can remain horizontal and simulate earthquake loads well. Summary of the invention

[0004] In order to solve the technical problems in the prior art that the test device occupies a large space and the loading beam is prone to a series of tilting and instability, the present invention provides a double-top L-beam loading compression and shear test system.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A double-top L-beam loading compression and shear test system comprises an experimental bench seat, a fixing device, a supporting device, an L-shaped loading beam, a loading device and a guiding device, wherein the fixing device fixes a shear wall specimen on the experimental bench seat, the L-shaped loading beam comprises an L-shaped loading beam cross beam and an L-shaped loading beam vertical beam, the L-shaped loading beam cross beam is fixedly connected to the upper end of the shear wall specimen, the loading device is connected to the L-shaped loading beam and applies horizontal load and vertical load to the shear wall specimen; the supporting device comprises two mutually parallel columns installed on the experimental bench seat and a main cross beam connected to the columns, the guiding device comprises a cross beam rotation constraint four-link and a vertical guiding mechanism, the vertical guiding mechanism comprises a guiding base frame, a horizontal guide rail, a vertical guide rail, a guiding beam and a sliding block, the guiding base frame is installed on the experimental bench seat, the horizontal guide rail is installed on the guiding base frame, the guide beam is connected to the horizontal guide rail, the vertical guide rail is installed on the guide beam, and the sliding block is installed inside the lower end of the L-shaped loading beam vertical beam and is slidably connected to the vertical guide rail.

[0007] The guide device includes a four-link guide mechanism between the main frame and the L-shaped loading beam crossbeam, and a vertical guide mechanism is provided inside the lower end of the L-shaped loading beam vertical beam to limit its rotation. In this improved scheme, in order to ensure the test accuracy, the guide mechanism can limit the rotation of the loading beam, ensure that the L-shaped loading beam crossbeam always remains horizontal during the experiment, and prevent the loading beam from being out of plane instability. At the same time, the bending moment at the bottom of the specimen is reduced to half of the top loading method.

[0008] Preferably, the bottom of the column of the present invention is fixedly connected to the experimental pedestal through a pedestal pull rod, the top of the column is connected to the main crossbeam of the column through a secondary crossbeam, and the two ends of the beam rotation constraint four-link are respectively connected to the L-shaped loading beam crossbeam and the main crossbeam.

[0009] The loading device includes a vertical loading system and a lateral loading system; the vertical loading system includes a small follower platform fixed to the crossbeam of the L-shaped loading beam, two hydraulic loading cylinders installed on the small follower platform, and a closed-loop control system for controlling the vertical double-top synchronous loading of the vertical loading system. The loading cylinder only occupies a small experimental space, and a test piece of a larger height can be tested under the premise of limited loading frame space. The vertical loading system adopts a vertical double-top synchronous loading control system for closed-loop control, which ensures that the displacement of the two vertical loading cylinders is the same and the resultant force remains unchanged during the experiment, ensuring that the crossbeam of the L-shaped loading beam remains horizontal, and simulating earthquake loads well.

[0010] The lateral loading system includes a horizontal actuator connected to the vertical beam of the L-shaped loading beam, and a horizontal reaction frame connected to the horizontal actuator and installed on the experimental bench seat. The horizontal actuator is installed on the vertical beam of the L-shaped loading beam, and the height of the horizontal loading system can be adjusted arbitrarily. As a preferred embodiment, the horizontal actuator can also be installed at 1 / 2 of the height of the vertical beam of the L-shaped loading beam. By changing the height of the loading point, the inflection point is moved to the position of half the height of the specimen. The lateral loading system is installed at 1 / 2 of the height of the specimen, which can make the L-shaped loading beam more stable.

[0011] The fixing device fixes the shear wall specimen on the experimental bench seat. Preferably, the fixing device includes a lower compression beam and a lower anchor rod installed at the lower part of the shear wall specimen, and an upper compression beam and an upper anchor rod installed at the upper part of the shear wall specimen. The compression beam and the anchor rod are used to press the specimen and transfer the bending moment.

[0012] The present invention provides a double-top L-beam loading compression-shear test system. Compared with the prior art, the test device adopts multiple means to ensure that the L-shaped loading beam is in a horizontal state, and can limit the rotation of the loading beam, so that the middle position of the shear wall specimen is close to a pure shear section, and ensure that the crossbeam of the L-shaped loading beam always maintains a horizontal state during the experiment, which can prevent the loading beam from being out-of-plane instability; the loading system only occupies a small experimental space, and can test specimens of greater height under the premise of limited loading frame space. During the experiment, the displacements of two vertical loading cylinders are guaranteed to be the same, the resultant force is unchanged, and the crossbeam of the L-shaped loading beam is guaranteed to remain horizontal, so as to simulate earthquake loads well. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the structure of the double-top L-beam loading compression and shear test system provided by the present invention;

[0014] Figure 2 This is a schematic structural diagram of the vertical guiding mechanism provided by the present invention. DETAILED DESCRIPTION

[0015] The present invention aims to provide a double-top L-beam loading compression shear test system to solve the technical problems in the prior art such as the large space occupied by the test device and the easy occurrence of a series of tilting and instability of the loading beam.

[0016] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with specific implementation methods and drawings.

[0017] Figure 1-Figure 2As a preferred embodiment of the present invention, as shown in the figure, a double-top L-beam loading compression and shear test system includes an experimental bench 14, a fixing device, a supporting device, an L-shaped loading beam, a loading device and a guiding device, wherein the supporting device includes two mutually parallel columns 1 installed on the experimental bench 14 and a main crossbeam 2 connected to the column 13, the bottom of the column 1 is fixedly connected to the experimental bench 14 through a bench pull rod 4, the top of the column 1 is connected to the main crossbeam 3 through a secondary crossbeam 2, the L-shaped loading beam includes an L-shaped loading beam crossbeam 6 and an L-shaped loading beam vertical beam 7, the L-shaped loading beam crossbeam 6 is fixedly connected to the upper end of the shear wall specimen H, the loading device is connected to the L-shaped loading beam and applies horizontal and vertical loads to the shear wall specimen; the guiding device includes a four-bar linkage with a crossbeam rotation constraint. 11 and a vertical guide mechanism, the two ends of the crossbeam rotation constraint four-link 11 are respectively connected to the L-shaped loading beam crossbeam 6 and the main crossbeam 7, the vertical guide mechanism includes a guide base 20, a horizontal guide rail 19, a vertical guide rail 18, a guide beam 17 and a slider 21, the guide base 20 is fixedly mounted on the experimental bench seat 14, the horizontal guide rail 19 is mounted on the guide base 20, the guide beam 17 is connected to the horizontal guide rail 19, the vertical guide rail 19 is mounted on the guide beam 17, the slider 21 is mounted inside the lower end of the L-shaped loading beam vertical beam 7, and is slidably connected to the vertical guide rail 19, the guide beam 17 can realize horizontal and vertical reciprocating motion under the drive of the L-shaped loading beam vertical beam 7, and at the same time can constrain the L-shaped loading beam vertical beam 7 from rotating in the plane and losing stability out of the plane.

[0018] The loading device includes a vertical loading system and a lateral loading system; the vertical loading system includes a small follower platform 8 fixed to the L-shaped loading beam 6, two hydraulic loading cylinders 9 installed on the small follower platform 8, and a closed-loop control system (not shown) for controlling the vertical double-top synchronous loading of the vertical loading system. The lateral loading system includes a horizontal actuator 10 connected to the vertical beam 7 of the L-shaped loading beam, and a horizontal reaction frame 5 connected to the horizontal actuator 10 and installed on the experimental bench seat. The horizontal actuator 10 is installed at a 1 / 2 height position of the vertical beam 7 of the L-shaped loading beam.

[0019] The fixing device fixes the shear wall specimen H on the experimental platform 14. In a preferred embodiment, the fixing device includes a lower compression beam and a lower anchor rod 13 installed at the lower part of the shear wall specimen, and an upper compression beam and an upper anchor rod 15 installed at the upper part of the shear wall specimen.

[0020] The specific test method of the test device provided by the present invention is as follows:

[0021] After the shear wall specimen H is installed in place, the vertical load is applied through the two hydraulic loading cylinders of the vertical loading system. During the loading process, the displacements of the two cylinders are always controlled to be equal. When the sum of the loads of the two cylinders reaches the required load, the load is maintained.

[0022] The lateral loading system adopts a low-cycle repeated loading mode. First, load graded cyclic loading is carried out. When obvious cracks are found in the specimen, the load corresponding to the first crack of the specimen is taken as the cracking load. A load sensor (not shown) is set at the front end of the horizontal actuator to measure the vertical load. Then, displacement graded loading is carried out until the specimen reaches the limit displacement and loading is stopped. The failure load is 85% of the peak load. During the horizontal loading process, the displacement values ​​of the two hydraulic loading cylinders of the two vertical loading systems are always kept equal, and the sum of the cylinder loads is customized. The difference between the two cylinder loads is used to balance the additional bending moment generated during the loading process. A magnetostrictive displacement sensor can be placed in the cylinder to measure the vertical displacement. According to the above collected data, the corresponding hysteresis curve and other related curves that can reflect the seismic resistance of the shear wall specimen can be produced.

[0023] The above is a detailed introduction to a double-top L-beam loading compression and shear test system provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and central idea of ​​the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A double-top L-beam loading compression shear test system, characterized in that: It includes an experimental bench seat, a fixing device, a supporting device, an L-shaped loading beam, a loading device and a guiding device, wherein the fixing device fixes the shear wall specimen on the experimental bench seat, the supporting device includes two mutually parallel columns installed on the experimental bench seat and a main crossbeam connected to the columns, the L-shaped loading beam includes an L-shaped loading beam crossbeam and an L-shaped loading beam vertical beam, the L-shaped loading beam crossbeam is fixedly connected to the upper end of the shear wall specimen, the loading device is connected to the L-shaped loading beam and applies horizontal load and vertical load to the shear wall specimen; the guiding device includes a four-link with a crossbeam rotation constraint and a vertical guiding mechanism, the vertical guiding mechanism includes a guiding base frame, a horizontal guide rail, a vertical guide rail, a guiding beam and a sliding block, the guiding base frame is installed on the experimental bench seat, the horizontal guide rail is installed on the guiding base frame, the guide beam is connected to the horizontal guide rail, the vertical guide rail is installed on the guide beam, and the sliding block is installed inside the lower end of the L-shaped loading beam vertical beam and is slidably connected to the vertical guide rail.

2. The double-top L-beam loading compression shear test system according to claim 1, characterized in that: The loading device includes a vertical loading system and a lateral loading system; the vertical loading system includes a small follower platform fixed on the crossbeam of the L-shaped loading beam, two hydraulic loading cylinders installed on the small follower platform, and a closed-loop control system for controlling the vertical double-top synchronous loading of the vertical loading system.

3. The double-top L-beam loading compression shear test system according to claim 2, characterized in that: The lateral loading system comprises a horizontal actuator connected to the vertical beam of the L-shaped loading beam, and a horizontal reaction frame connected to the horizontal actuator and installed on the experimental bench seat.

4. The double-top L-beam loading compression shear test system according to claim 3, characterized in that: The horizontal actuator is mounted on the vertical beam of the L-shaped loading beam.

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