An eccentric pseudo-static loading device and testing method for the stiffness of existing brick masonry structures

Abstract

The present invention discloses an eccentric pseudo-static loading device and a testing method for the stiffness of an existing brick masonry structure, and relates to the technical field of quasi-static loading tests for brick masonry. The device comprises a loading pedestal, a loading assembly is provided above the loading pedestal, a load distribution assembly is provided above the loading assembly, reaction walls are provided at both ends of the load distribution assembly and the loading assembly, and the loading assembly is connected to the reaction wall on one side, a portal is provided between the reaction walls on both sides, and the portal is connected to the load distribution assembly. The present invention adopts the above-mentioned eccentric pseudo-static loading device and a testing method for the stiffness of an existing brick masonry structure, ensures the authenticity of the load conditions of the simulated wall pseudo-static test process in the test, adjusts and refines the vertical load loading position, optimizes the load application method, adjusts the loading device, reduces the influence of the vertical load on the horizontal dynamic load, and improves the overall accuracy of the test.

Description

Technical Field

[0001] The invention relates to the technical field of brick masonry quasi-static loading test, in particular to an eccentric quasi-static loading device and a test method for the stiffness of an existing brick masonry structure. Background Art

[0002] Due to their age, masonry structures lacked appropriate seismic protection measures during their construction. During moderate or strong earthquakes, masonry structures often suffer severe damage due to their poor seismic performance. Under seismic loads, masonry walls may be subject to in-plane loads (bending or shear), out-of-plane loads (bending), and a combination of these. Quasi-static tests on masonry walls can effectively assess the seismic performance of masonry structures, observe the failure process, and analyze failure characteristics.

[0003] In response to the needs of pseudo-static test loading, during normal testing, the commonly used loading method is usually to simply stack the distribution beam and the loading beam and directly apply the vertical load on the distribution beam. This loading method can only simulate the arrangement of vertical uniformly distributed loads. In actual practical application, masonry walls at different positions are subjected to different vertical loads, and the vertical loads of masonry walls in different areas are not evenly distributed at the centroid of the masonry wall. Existing loading devices are difficult to accurately evaluate the performance of masonry walls under non-uniformly distributed loads. In addition, in existing loading devices, the vertical load applied by the jack is directly transmitted to the loading beam through hard contact. When the horizontal actuator applies the horizontal load, the friction between the loading beams under the action of the vertical load is large, which has a great impact on the application of the horizontal actuating force of the test, thereby affecting the overall accuracy of the test.

[0004] Existing specimen-fixing bottom beams often simply secure the specimen within the beam through the simple blocking effect of concrete protrusions on the left and right sides, making it difficult to truly simulate the embedded mutual restraint between the masonry wall and the foundation. During the application of horizontal forces, the pseudo-static masonry specimen is prone to bottom slippage due to the weak restraint between the bottom and the pedestal, affecting the test results and causing the specimen to suffer horizontal shear failure along the weak area at the base of the reinforced wall. This makes it difficult to truly simulate the "X"-shaped shear failure of the wall under earthquake action. Summary of the Invention

[0005] The purpose of the present invention is to provide an eccentric pseudo-static loading device and a testing method for the stiffness of an existing brick masonry structure, so as to solve the problems raised in the above-mentioned background technology. By strengthening the bottom constraint of the specimen, adjusting the application method of the vertical load, and designing the inter-layer rolling shaft method, the accuracy and operation effect of the specimen can be effectively improved. During the actual loading process, the vertical loads at different positions can be reasonably adjusted according to the needs of the test simulation, while avoiding the influence of the horizontal friction force generated by the large vertical load on the horizontal load, thereby improving the operability of the test.

[0006] To achieve the above-mentioned purpose, the present invention provides an eccentric pseudo-static loading device for the stiffness of an existing brick masonry structure, comprising a loading pedestal, a loading assembly is arranged above the loading pedestal, a load distribution assembly is arranged above the loading assembly, reaction walls are arranged at both ends of the load distribution assembly and the loading assembly, and the loading assembly is connected to the reaction wall on one side, a portal is arranged between the reaction walls on both sides, and the portal is connected to the load distribution assembly.

[0007] Preferably, the load distribution assembly includes a jack arranged below the gantry, a load distribution beam is arranged below the jack, a toothed pad is arranged below the load distribution beam, and a plurality of latch teeth are arranged on the toothed pad;

[0008] A single-column latch is fixedly provided at the bottom of the load distribution beam. The single-column latch engages with the latches. By making the single-column latch engage with the latches at different positions, the out-of-plane loading position of the vertical load applied by the jack on the masonry wall specimen is adjusted to achieve eccentric pseudo-static loading.

[0009] Preferably, the jack and the load distribution beam are slidably connected by a slide rail and a slider. The slider is set at the bottom of the jack, and the slide rail is set at the top of the load distribution beam. By adjusting the position of the slider on the slide rail, the in-plane loading position of the vertical load applied by the jack on the masonry wall specimen is adjusted to achieve eccentric quasi-static loading.

[0010] Preferably, the jack and the gantry are connected via a plurality of rolling shafts and a steel support plate. The steel support plate is arranged on the top of the jack, and the plurality of rolling shafts are arranged between the steel support plate and the gantry.

[0011] Preferably, the loading assembly includes a loading beam disposed below the toothed pad, a masonry wall specimen is disposed below the loading beam, and a lower portion of the masonry wall specimen is disposed in a groove of the bottom beam;

[0012] One end of the loading beam is connected to a horizontal actuator, and the horizontal actuator is connected to a reaction wall on one side.

[0013] Preferably, lifting rings are symmetrically provided on both sides of the bottom beam, and the bottom beam is fixed to the loading platform by fixing bolts.

[0014] Preferably, a first displacement meter is provided on the masonry wall specimen, a second displacement meter is provided on the bottom beam, and a third displacement meter is provided on each loading beam.

[0015] A method for testing the stiffness of an existing brick masonry structure using an eccentric pseudo-static loading device comprises the following steps:

[0016] Step S1, casting the test piece: During use, first design and manufacture a bottom beam with a groove. After the concrete material of the bottom beam reaches the design strength, build a masonry wall test piece in the groove of the bottom beam using masonry bricks. The casting height of the masonry wall test piece is set to 800-1400 mm, and the width is set to 1000-1500 mm. During the masonry process, the wall surface of the masonry wall test piece is made flat and the top plane is horizontal. The wall width of the masonry wall test piece is set between 200-300 mm.

[0017] Step S2, fixing the test piece: After the concrete material of the masonry wall specimen reaches its designed strength, the masonry wall specimen is moved to the loading position via the lifting ring, and the bottom beam is fixed to the loading platform via fixing bolts. The rolling shaft and steel support plate are then pre-tied to the door frame via steel wire ropes;

[0018] Step S3, arranging the loading device: hoist and fix the loading beam and the horizontal actuator, place a toothed pad on the loading beam, determine the corresponding tooth position on the toothed pad according to the designed loading point position, place the load distribution beam so that the single column tooth and the corresponding tooth are engaged, determine the in-plane loading position of the jack according to the in-plane eccentric loading design requirements and arrange it between the steel support pad and the load distribution beam, fix the jack and the steel support pad with bolts, and remove the wire rope between the steel support pad and the fixed portal frame;

[0019] Step S4: Perform pseudo-static test loading according to design requirements.

[0020] Therefore, the present invention adopts the above-mentioned eccentric pseudo-static loading device and testing method for the stiffness of existing brick masonry structures, which has the following beneficial effects:

[0021] (1) This device uses a load distribution beam with a slide rail at the vertical load position to provide a non-uniform load, simulating the vertical load conditions of the masonry wall during actual use. At the same time, the dimensions of the various structural components of the load distribution beam are optimized. During use, it is ensured that the load distribution beam has sufficient rigidity and will not cause bending deformation.

[0022] (2) This device arranges a toothed pad on the lower side of the load distribution beam, and fixes the vertical loading point by using the column teeth to interlock during the loading process.

[0023] (3) This device uses an improved bottom beam with a groove as the lower fixed node to ensure the fixed constraint effect of the masonry wall specimen during loading and prevent the bottom of the masonry wall specimen from shifting and causing damage during loading.

[0024] (4) This device uses a rolling shaft as a vertical load transfer device, which effectively avoids the friction caused by the vertical load affecting the data monitoring of the horizontal force loading device. The rolling shaft contacts the jack through the steel support plate and is in direct contact with the steel gantry. The rolling shafts are arranged in parallel, and no torsional collision occurs during the horizontal rolling process.

[0025] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of an embodiment of an eccentric pseudo-static loading device and a testing method for the stiffness of an existing brick masonry structure according to the present invention;

[0027] Figure 2 It is a layout diagram of the load distribution component and the loading component of an existing brick masonry structure stiffness eccentric pseudo-static loading device and testing method of the present invention;

[0028] Figure 3 A top view of a bottom beam of an existing brick masonry structure stiffness eccentric pseudo-static loading device and testing method according to the present invention;

[0029] Figure 4 It is a structural schematic diagram of a load distribution assembly of an existing brick masonry structure stiffness eccentric pseudo-static loading device and testing method of the present invention;

[0030] Figure 5 A side view of a load distribution assembly of an existing brickwork structure stiffness eccentric pseudo-static loading device and testing method according to the present invention;

[0031] Figure 6 It is a schematic diagram of the loading end arrangement of an existing brick masonry structure stiffness eccentric pseudo-static loading device and testing method of the present invention;

[0032] Figure numerals: 1. Loading pedestal; 2. Loading assembly; 21. Loading beam; 22. Masonry wall specimen; 23. Bottom beam; 231. Lifting ring; 232. Fixing bolt; 24. Groove; 25. Horizontal actuator; 3. Load distribution assembly; 31. Jack; 32. Load distribution beam; 33. Toothed pad; 34. Rolling shaft; 35. Steel support pad; 36. Slide rail; 37. Slider; 38. Single column tooth; 4. Reaction wall; 5. Door frame; 6. First displacement meter; 7. Second displacement meter; 8. Third displacement meter. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0034] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0035] Example

[0036] See also Figure 1-6 The present invention provides an eccentric pseudo-static loading device for the stiffness of an existing brick masonry structure, comprising a loading pedestal 1, a loading assembly 2 being arranged above the loading pedestal 1, a load distribution assembly 3 being arranged above the loading assembly 2, reaction walls 4 being arranged at both ends of the load distribution assembly 3 and the loading assembly 2, and the loading assembly 2 being connected to the reaction wall 4 on one side, a portal 5 being arranged between the reaction walls 4 on both sides, and the portal 5 being connected to the load distribution assembly 3.

[0037] The load distribution assembly 3 includes a jack 31 positioned below the gantry. A load distribution beam 32 is positioned below the jack 31, and a toothed pad 33 is positioned below the load distribution beam 32. The teeth of the toothed pad 33 have a diameter of 50 to 120 mm and a spacing of 25 to 80 mm. The teeth are welded to the toothed pad 33, which is made of steel plate with a thickness of 15 to 40 mm, a width of 300 to 500 mm, and a length of 1000 to 2000 mm. By installing the toothed pad 33, the loading point can be adjusted according to design requirements before loading in a pseudo-static test, simulating the actual vertical load distribution of the masonry wall specimen 22. This provides an important test method for simulating the stress-bearing process of an actual masonry wall.

[0038] The jack 31 and the gantry 5 are connected via several rolling shafts 34 and steel support plates 35. The steel support plates 35 should be 10 to 50 mm thick, 200 to 500 mm wide, and 800 to 1500 mm long. The steel support plates 35 are mounted on top of the jack 31, with several rolling shafts 34 positioned between them and the gantry 5. The rolling shafts 34 are in direct contact with the gantry 5 and should have a smooth surface free of grooves and protrusions. The steel rollers should be arranged in parallel to prevent torsional collisions during horizontal rolling. The spacing between the rolling shafts 34 should be 100 to 200 mm, and the diameter of the rolling shafts 34 should be 10 to 50 mm, with a length that matches the width of the steel support plates 35. By providing a rolling shaft 34 at the support of the jack 31, effective support can be provided for the vertical load, and the influence of the vertical friction of the load distribution component 3 on the horizontal force can be reduced, thereby improving the authenticity and reliability of the pseudo-static test.

[0039] The jack 31 and the load distribution beam 32 are slidably connected by a slide rail 36 and a slider 37. The slider 37 is set at the bottom of the jack 31, and the slide rail 36 is set at the top of the load distribution beam 32. By adjusting the position of the slider 37 on the slide rail 36, the in-plane loading position of the vertical load applied by the jack 31 on the masonry wall specimen 22 is adjusted to achieve eccentric pseudo-static loading. The width of the slide rail 36 is controlled to be 40-200 mm, and the height is 20-60 mm. The length of the load distribution beam 32 should be 800-2500 mm, and the steel plate thickness of the load distribution beam 32 should be 20-50 mm. Each meter of the load distribution beam 32 should have at least six beam ribs, with a rib spacing of 200-500 mm. The height of the load distribution beam 32 should be 200-600 mm. A single-column latch 38 with a semicircular cross-section is arranged on the underside. Each load distribution beam is welded with a single-column latch 38. The diameter of the single-column latch 38 is controlled to be 40-120 mm and runs the entire length of the load distribution beam 32. During use, the load distribution beam 32 is guaranteed to have sufficient rigidity and will not bend or deform.

[0040] A single-column latch 38 is fixedly mounted on the bottom of the load distribution beam 32. This latch 38 engages with the teeth of the toothed pad 33. By engaging the single-column latch 38 with teeth at different positions, the out-of-plane loading position of the vertical load applied by the jack 31 on the masonry wall specimen 22 is adjusted, achieving eccentric pseudo-static loading. The toothed pad 33 and the single-column latch 38 are used to adjust the out-of-plane eccentric loading position of the vertical load on the masonry wall specimen 22. By controlling the out-of-plane eccentric position, the effects of different loading methods, such as centroidal axial load and stiffness center axial load, are compared. The arrangement of the single-column latch 38 also effectively prevents the loading point from shifting due to overall specimen deformation at the end of the vertical load during loading.

[0041] This device adopts the connection method of the slide rail 36 and the slider 37, and the connection method of the single column tooth 38 and the toothed pad 33. Before the pseudo-static test loading, the horizontal and front-back positions of the jack 31 in the test can be adjusted according to the test design requirements to simulate the uneven distribution of the vertical load on the masonry wall specimen 22 in the plane, reflect the unevenness of the vertical load on the masonry wall specimen 22 under real conditions, simulate the eccentric loading effect of the vertical load on the masonry wall specimen 22 in the plane during actual use, and ensure the adjustability of the application position of the vertical load during the test.

[0042] Loading assembly 2 includes a loading beam 21 positioned beneath a toothed pad 33. One end of loading beam 21 is connected to a horizontal actuator 25, which is in turn connected to a side reaction wall 4. A masonry wall specimen 22 is positioned beneath loading beam 21, its lower portion positioned within a recess 24 in bottom beam 23. Recess 24 has a wall thickness of 30 to 100 mm and is reinforced with ribbed steel bars to ensure the overall strength and rigidity of bottom beam 23. In order to ensure the fixing effect between the masonry wall specimen 22, the bottom beam 23 and the foundation, and to ensure the stability of the masonry wall specimen 22 during the loading test, a rectangular groove 24 is opened at the center of the bottom beam 23 on the basis of the connection between the masonry wall specimen 22 and the bottom beam 23. During the casting process of the masonry wall specimen 22, the first layer of masonry is cast in the groove 24 in advance, and then the masonry wall specimen 22 is gradually cast upward. In this process, the peripheral part of the masonry wall specimen 22 in the groove 24 is cast and fixed with concrete to ensure the stability of the connection between the masonry wall specimen 22 and the loading platform 1, and effectively ensure the simulation effect of the destruction process of the real masonry wall specimen 22 during the test.

[0043] Lifting rings 231 are symmetrically provided on both sides of the bottom beam 23, and the bottom beam 23 is fixed to the loading platform 1 via fixing bolts 232. The minimum distance between the position of the lifting ring 231 and the outer side of the masonry wall specimen 22 should be controlled at 50 to 200 mm to prevent the lifting rope from colliding with the masonry wall specimen 22 during the lifting process. During the fixed installation of the bottom beam 23, the diameter of the fixing bolts 232 and the corresponding holes is 50 to 150 mm to provide sufficient connection capacity. The fixing bolts 232 should be positioned tightly enough and equipped with rigid gaskets to prevent the bottom beam 23 from tilting and sliding during loading. The top surface of the bottom beam 23 coincides with the plane between the brick layers of the masonry wall specimen 22.

[0044] A first displacement meter 6 is provided on the masonry wall specimen 22 , a second displacement meter 7 is provided on the bottom beam 23 , and a third displacement meter 8 is provided on each of the loading beams 21 .

[0045] The above-mentioned testing method of the existing brick masonry structure stiffness eccentric pseudo-static loading device comprises the following steps:

[0046] Step S1, casting the test piece: during use, first design and manufacture a bottom beam 23 with a groove 24. After the concrete material of the bottom beam 23 reaches the design strength, build a masonry wall specimen 22 in the groove 24 of the bottom beam 23 using masonry bricks. The casting height of the masonry wall specimen 22 is set to 800-1400 mm, and the width is set to 1000-1500 mm. During the masonry process, the wall surface of the masonry wall specimen 22 is made flat, the top plane is horizontal, and the wall width of the masonry wall specimen 22 is set between 200 and 300 mm.

[0047] Step S2, fixing the test piece: After the concrete material of the masonry wall specimen 22 reaches its design strength, move the masonry wall specimen 22 to the loading position through the lifting ring 231, and fix the bottom beam 23 on the loading platform 1 through the fixing bolts 232, and then pre-tie the rolling shaft 34 and the steel support plate 35 to the door frame 5 through steel wire ropes.

[0048] Step S3, arrange the loading device: hoist and fix the loading beam 21 and the horizontal actuator 25, place the toothed pad 33 on the loading beam 21, determine the corresponding tooth position on the toothed pad 33 according to the designed loading point position, place the load distribution beam 32 so that the single column tooth 38 and the corresponding tooth are engaged, determine the loading position of the jack 31 in the plane according to the in-plane eccentric loading design requirements and arrange it between the steel support pad 35 and the load distribution beam 32, fix the position of the jack 31 and the steel support pad 35 with bolts, and remove the wire rope between the steel support pad 35 and the fixed portal frame 5.

[0049] Step S4: Perform pseudo-static test loading according to design requirements.

[0050] Therefore, the present invention adopts the above-mentioned eccentric pseudo-static loading device and testing method for the stiffness of existing brick masonry structures to ensure the authenticity of the load conditions in the simulated pseudo-static test process of the wall in the test, adjusts and refines the vertical load loading position, optimizes the load application method, adjusts the loading device, reduces the influence of the vertical load on the horizontal dynamic load, and improves the overall accuracy of the test.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An eccentric pseudo-static loading device for stiffness of existing brick masonry structures, characterized by: It includes a loading pedestal, a loading assembly is provided above the loading pedestal, a load distribution assembly is provided above the loading assembly, reaction walls are provided at both ends of the load distribution assembly and the loading assembly, and the loading assembly is connected to one side of the reaction wall, a gantry is provided between the two sides of the reaction walls, and the gantry is connected to the load distribution assembly; The load distribution assembly includes a jack disposed below the gantry, a load distribution beam disposed below the jack, a toothed pad disposed below the load distribution beam, and a plurality of latches disposed on the toothed pad; a single-column latch is fixedly disposed at the bottom of the load distribution beam, the single-column latch engages with the latches, and by engaging the single-column latch with the latches at different positions, the out-of-plane loading position of the vertical load applied by the jack on the masonry wall specimen is adjusted to achieve eccentric quasi-static loading; The jack and the load distribution beam are connected by a sliding rail and a slider. The slider is set at the bottom of the jack and the slide rail is set at the top of the load distribution beam. By adjusting the position of the slider on the slide rail, the in-plane loading position of the vertical load applied by the jack on the masonry wall specimen is adjusted to achieve eccentric pseudo-static loading. The jack and the mast are connected through a plurality of rolling shafts and a steel support pad. The steel support pad is arranged on the top of the jack, and the plurality of rolling shafts are arranged between the steel support pad and the mast. The loading assembly includes a loading beam arranged below the toothed pad, a masonry wall specimen is arranged below the loading beam, and the lower part of the masonry wall specimen is arranged in the groove of the bottom beam; one end of the loading beam is connected to a horizontal actuator, and the horizontal actuator is connected to a reaction wall on one side.

2. The eccentric pseudo-static loading device for stiffness of an existing brickwork structure according to claim 1, characterized in that: Lifting rings are symmetrically arranged on both sides of the bottom beam, and the bottom beam is fixed to the loading pedestal by fixing bolts.

3. The eccentric pseudo-static loading device for stiffness of an existing brickwork structure according to claim 2, characterized in that: A first displacement meter is provided on the masonry wall specimen, a second displacement meter is provided on the bottom beam, and a third displacement meter is provided on each loading beam.

4. A method for testing the stiffness of an existing brickwork structure using the eccentric pseudo-static loading device described in claim 3, characterized in that: The following steps are involved: Step S1, casting the test piece: During use, first design and manufacture a bottom beam with a groove. After the concrete material of the bottom beam reaches the design strength, build a masonry wall test piece in the groove of the bottom beam using masonry bricks. The casting height of the masonry wall test piece is set to 800-1400 mm, and the width is set to 1000-1500 mm. During the masonry process, the wall surface of the masonry wall test piece is made flat and the top plane is horizontal. The wall width of the masonry wall test piece is set between 200-300 mm. Step S2, fixing the test piece: After the concrete material of the masonry wall specimen reaches its designed strength, the masonry wall specimen is moved to the loading position via the lifting ring, and the bottom beam is fixed to the loading platform via fixing bolts. The rolling shaft and steel support plate are then pre-tied to the door frame via steel wire ropes; Step S3, arranging the loading device: hoist and fix the loading beam and the horizontal actuator, place a toothed pad on the loading beam, determine the corresponding tooth position on the toothed pad according to the designed loading point position, place the load distribution beam so that the single column tooth and the corresponding tooth are engaged, determine the in-plane loading position of the jack according to the in-plane eccentric loading design requirements and arrange it between the steel support pad and the load distribution beam, fix the jack and the steel support pad with bolts, and remove the wire rope between the steel support pad and the fixed portal frame; Step S4: Perform pseudo-static test loading according to design requirements.

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