Weak Stiffness Beam-Column Joints for Shaking Table Tests of Scale Structural Models

Abstract

A weak-stiffness beam-column joint for shaking table tests of scaled structural models. As a whole, this joint can achieve the purpose of widely regulating the overall dynamic characteristics of the model by only adjusting the state of the joint itself without changing other components in the scaled model. That is, by adjusting the stiffness of the beam-column joint, the model stiffness can be reduced so that the scaled model and the prototype structure can meet the similarity requirements derived from the similarity theory. The purpose is to be able to adjust the stiffness of the beam-column joint of the structural scaled model to solve the problem that the geometric dimensions, material parameters similarity and dynamic characteristics similarity conditions of the scaled model in structural dynamic tests cannot be satisfied simultaneously, improve the accuracy of test results, and expand the applicable range of the scaled model.

Description

Technical Field

[0001] The present invention belongs to the field of dynamic test research on engineering structures, and particularly relates to a weak stiffness beam-column joint for shaking table test of a scaled structure model. Background Art

[0002] Earthquakes are characterized by strong destructiveness and difficulty in prediction. Therefore, it is necessary to deeply study the actual responses of building structures under earthquake actions, so as to propose correct structural seismic design methods.

[0003] The actions of earthquakes on structures are multiple reciprocating horizontal and vertical dynamic loads, which are irregular and change rapidly. At the same time, buildings in practical applications are often structures with multiple floors, multiple spans, and unequal span distances. Due to the complexity of earthquake loads and building structure systems, it is generally difficult for people to obtain the accurate responses of building structures under earthquake actions by pure theoretical methods. Through earthquake simulation shaking table tests, the accurate dynamic characteristics and dynamic responses of structures can be obtained, which is very necessary for the research on seismic design of building structures. In addition, with the emergence and application of various new materials and new technologies, the demand for dynamic tests on various new forms of structures is also increasing significantly.

[0004] In earthquake simulation shaking table tests, due to site conditions and equipment capabilities, except for some small-scale local components that can be tested with full-scale models, most of the others use scaled models for testing. In order to apply the data results obtained from scaled model tests to prototype structures, the scaled model and the prototype must satisfy certain similarity relationships in terms of geometric relationships, material parameters, loading methods, boundary conditions, dynamic characteristics, etc., and it is necessary to follow similarity theory for model design, generally using dimensional analysis. The analysis results show that considering that the model and the prototype are subjected to the same gravitational acceleration, that is, the similarity ratio of gravitational acceleration is 1, the similarity ratios of elastic modulus, material density, and geometric dimensions must satisfy certain mutual relationships and cannot be arbitrarily selected independently. Since the reduction ratio of the geometric dimensions of the scaled model is generally large, it results in that the required density of the model material is much larger than that of the prototype material, or the stiffness of the model material is much smaller than that of the prototype material. And the existing materials are difficult to meet such requirements, and completely similar models cannot be obtained, and errors will occur when the test results are applied to the prototype structure.

[0005] To solve this problem, additional mass is often stacked on the test model, which is called the artificial mass model. Although the artificial mass model can meet the similarity conditions of the horizontal inertial force, due to the load-bearing capacity of the shaking table and the limited space of the model, it is often difficult to fully realize the setting of its artificial mass. Or a centrifuge is used to simulate the supergravity phenomenon of the model. However, limited by the space and equipment capacity of the centrifuge, this method is difficult to be widely applied and is generally expensive. In addition, an invention has proposed a shaking table expansion device to overcome the gravity distortion effect, but the device is relatively complex and occupies a large space. Some scholars have also proposed to correct it by using different scale ratios in three-dimensional directions, but different scale ratios will lead to different damage evolutions of the model structure and the prototype structure. These methods all attempt to solve the problem of non-satisfaction of similarity conditions from the perspective of changing the model density or mass, rather than from the perspective of reducing the model stiffness. Summary of the Invention

[0006] The object of the present invention is to be able to adjust the stiffness of the beam-column joints of the scaled structural model, so as to solve the problem that the geometric dimensions, material parameters similarity and dynamic characteristics similarity conditions of the scaled model in the structural dynamic test cannot be satisfied simultaneously, improve the accuracy of the test results, and expand the applicable range of the scaled model.

[0007] To achieve the above object, the present invention is implemented by the following scheme:

[0008] A weak-stiffness beam-column joint for a shaking table test of a scaled structural model, characterized in that the whole joint can achieve the purpose of widely regulating the overall dynamic characteristics of the model without changing other components in the scaled model, only by adjusting the state of the joint itself. That is, by adjusting the stiffness of the beam-column joint, the model stiffness can be reduced, so that the scaled model and the prototype structure can meet the similarity requirements derived from the similarity theory.

[0009] The structural features of the present invention are characterized in that: the joint includes a column head (1), a universal hinge (2), a first positioning hook (3), a sliding tooth plate (4), a biting slider (5), a second positioning hook (6), and an adjusting spring (7); the column head (1) is a short steel column with a box-shaped cross-section, one end is welded with a column head end plate (11), and can be connected to the column end plate of the model through a bolt one (12), and the other end is welded to the bottom plate (21) of the universal hinge (2); the universal hinge (2) can make the column rotate around its two cross-section main axes at the same time, but restricts the column from twisting around the vertical axis; the top plate (22) of the universal hinge (2) is connected to the beam bottom plate through a bolt two (26), and several first positioning hooks (3) are welded on the lower surface of the top plate (22), and one end of the first positioning hook (3) is connected to one end of the adjusting spring (7); the back surface of the sliding tooth plate (4) is welded to each side surface of the column head (1), and a first locking tooth (41) is provided on the front surface of the sliding tooth plate (4); a second locking tooth (51) is provided on the inner side surface of the biting slider (5), and the biting slider (5) is placed on the sliding tooth plate (4), and a second positioning hook (6) is welded on the outer side surface of the biting slider (5), and the other end of the second positioning hook (6) is connected to the adjusting spring (7); the adjusting spring (7) can adjust the inclination angle by changing the positions of the connected first positioning hook (3) and second positioning hook (6); the overall stiffness of the joint is provided by the tensile stiffness of the adjusting spring (7), and the dual requirements of weak stiffness and variable stiffness can be realized.

[0010] Further, to ensure that the tension of the adjusting spring (7) only provides rotational stiffness and does not produce a torsional effect on the column, the sliding tooth plate (4) is centered and aligned with the lower surface of the beam bottom plate facing it; the first positioning hook (3) is arranged along the center line of the lower surface of the beam bottom plate; the second positioning hook (6) is welded to the center point of the outer side surface of the biting slider (5).

[0011] Further, to enable the position of the second positioning hook (6) connected to the adjusting spring (7) to be movable or fixed, the setting direction of the first locking tooth (41) is opposite to the setting direction of the second locking tooth (51); there is a fastening screw (52) on the biting slider (5), when the fastening screw (52) is tightened, the first locking tooth (41) meshes with the second locking tooth (52), so that the biting slider (5) is fixed; when the fastening screw (52) is loosened, the biting slider (5) can move up and down along the sliding tooth plate (4).

[0012] Further, to prevent both ends of the adjusting spring (7) from falling off the first positioning hook (3) and the second positioning hook (6) under the action of dynamic loads, the opening directions of the first positioning hook (3) and the second positioning hook (6) both face away from the universal hinge (2).

[0013] Further, the application method of the weak stiffness beam-column joint for the shaking table test of the scaled structural model includes the following steps:

[0014] (1) Weld column end plates at the ends of each column of the structural scaled model, and drill holes at the corresponding positions of the column end plates and the beam bottom plates. Connect the column, the joint, and the beam together through bolt one (12) and bolt two (26);

[0015] (2) Calculate the target lateral stiffness of the scaled model, calculate the rotational stiffness of each joint, select a regulating spring (7) with appropriate stiffness, calculate the angle of the regulating spring (7) and determine the positions of the first positioning hook (3) and the second positioning hook (6), move the engaging slider (5) and fix it, and tension the regulating spring (7);

[0016] (3) Calculate the similarity ratio of the natural vibration frequencies between the model and the prototype according to the similarity theory, measure the natural vibration frequency of the model using a seismic simulation shaking table, and adjust the position of the second positioning hook (6) based on the measured natural vibration frequency until the true natural vibration frequency of the model meets the accuracy requirements compared with the calculated result;

[0017] (4) Conduct a dynamic loading test.

[0018] The joint of the present invention has the advantages of simple structure, convenient installation and disassembly, can effectively solve the problem that the physical similarity and dynamic similarity conditions cannot be satisfied simultaneously during the dynamic test of the scaled structure model, coordinate the contradiction between the low demand for lateral (flexural) stiffness and the high demand for axial bearing capacity of the scaled beam-column model, and expand the applicable range of the scaled model. Description of the Drawings

[0019] Figure 1 is the front view schematic diagram of the embodiment of the present invention;

[0020] Figure 2 is the universal hinge schematic diagram of the embodiment of the present invention;

[0021] Figure 3 is the sliding tooth plate schematic diagram of the embodiment of the present invention;

[0022] Figure 4 is the positioning slider schematic diagram of the embodiment of the present invention;

[0023] Figure 5 is the meshing state schematic diagram of the sliding tooth plate and the positioning slider of the embodiment of the present invention;

[0024] Figure 6 is the structural scaled model schematic diagram of the embodiment of the present invention;

[0025] Figure 7 is the 3D effect diagram of the embodiment of the present invention. Detailed Embodiments

[0026] The technical solution of the present invention will be further introduced below in conjunction with embodiments and the accompanying drawings. It should be particularly noted that the key technology of the present invention lies in the introduction of the node rotation stiffness adjustment device, and any changes made to the column head shape and universal hinge should be within the protection scope of the present invention.

[0027] In this embodiment, as Figure 1 shown, a weak stiffness beam-column joint for a shaking table test of a scaled structural model includes a column head 1, a universal hinge 2, a first positioning hook 3, a sliding tooth plate 4, a biting slider 5, a second positioning hook 6, and an adjusting spring 7; the column head 1 is a short steel column with a box-shaped cross-section, one end is welded with a column head end plate 11, and can be connected to the column end plate of the model through a bolt 12, and the other end is welded to the bottom plate 21 of the universal hinge 2; the universal hinge 2 enables the column to rotate simultaneously around its two cross-section main axes, but restricts the column from twisting around the vertical axis; the top plate 22 of the universal hinge 2 is connected to the beam bottom plate through a bolt 26, and several first positioning hooks 3 are welded on the lower surface of the top plate 22, and one end of the first positioning hook 3 is connected to one end of the adjusting spring 7; the sliding tooth plate 4 is welded to each side surface of the column head 1, and a first locking tooth 41 is provided on the front surface of the sliding tooth plate 4; a second locking tooth 51 is provided on the inner side surface of the biting slider 5, and the biting slider 5 is placed on the sliding tooth plate 4, and a second positioning hook 6 is welded on the outer side surface of the biting slider 5, and the other end of the second positioning hook 6 is connected to the other end of the adjusting spring 7; the adjusting spring 7 can adjust the inclination angle by changing the positions of the connected first positioning hook 3 and second positioning hook 6; the overall stiffness of the joint is provided by the tensile stiffness of the adjusting spring 7, and the dual requirements of weak stiffness and variable stiffness can be achieved.

[0028] In this embodiment, the column head 1 is a short steel column with a box-shaped cross-section, and in actual application, it can be replaced with an H-section column, a rectangular column, a circular-section column, etc. according to needs, as long as the back surface of the sliding tooth plate 4 can be reliably connected to the side surface of the column; similarly, in this embodiment, there is no regulation on the forms of the beam and column, as long as the top plate 22 and the column head end plate 11 can be reliably connected to the beam and column.

[0029] In this embodiment, as Figure 2 shown, the universal hinge 2 is composed of a bottom plate 21, a top plate 22, a lower support 23, an upper support 24, a sphere 25, a bolt 26, and a screw 27; the bottom plate 21 is welded to the column head 1, the lower support 23 and the upper support 24 are respectively welded to the bottom plate 21 and the top plate 22, the sphere 25 is connected to the lower support 23 and the upper support 24 through a screw 27, and the bolt 26 connects the top plate 22 to the beam bottom plate; it should be noted that the form of the universal hinge given in the present invention is not a limiting requirement, that is, other existing forms on the market can also be used, as long as it meets the requirement of enabling the column to rotate simultaneously around its two cross-section main axes but restricting the column from twisting around the vertical axis.

[0030] In this embodiment, to ensure that the tensile force of the adjusting spring 7 only provides rotational stiffness and does not produce a torsional effect on the column, one sliding tooth plate 4 is distributed on the side surface of the column head 1 under each beam, and the sliding tooth plate 4 is centered and aligned with the lower surface of the beam bottom plate facing it; the first positioning hook 3 is arranged along the center line of the lower surface of the beam bottom plate; the second positioning hook 6 is welded to the center point of the outer side surface of the engaging slider 5.

[0031] In this embodiment, to enable the position of the second positioning hook 6 connected to the adjusting spring 7 to be movable or fixed, as Figure 3 shown, the opening of the first locking tooth 41 faces downward, and the sliding tooth plate 4 has a flank 42 as the moving track of the engaging slider 5; as Figure 4 shown, the opening of the second locking tooth 51 faces upward, and both sides of the engaging slider 5 have sliding grooves formed by cold bending of steel plates, and internal threaded holes are opened on the sliding groove walls and are equipped with fastening screws 52. The setting direction of the first locking tooth 41 is opposite to the setting direction of the second locking tooth 51. When the fastening screw 52 is tightened, as Figure 5 shown, the first locking tooth 41 and the second locking tooth 51 are engaged to fix the engaging slider 5, and the position of the second positioning hook 6 will not move under the tensile force of the adjusting spring 7; when the fastening screw 52 is loosened, the engaging slider 5 can move up and down along the sliding tooth plate 4, so that the angle of the adjusting spring 7 can be continuously adjusted to accurately adjust the rotational stiffness of the joint.

[0032] In this embodiment, to prevent both ends of the adjusting spring 7 from falling off the first positioning hook 3 and the second positioning hook 6 under the action of dynamic loads, the opening directions of the first positioning hook 3 and the second positioning hook 6 both face away from the universal hinge 2.

[0033] In this embodiment, the application method of the weak-stiffness beam-column joint for the shaking table test of the scaled structural model includes the following steps:

[0034] (1) As Figure 6 , Figure 1 shown, weld column end plates at the ends of each column of the structural scaled model, and open holes at the corresponding positions of the column end plates and the beam bottom plates, and connect the column, the joint, and the beam by bolts 12 and bolts 26;

[0035] (2) Calculate the target lateral stiffness of the scaled model, calculate the rotational stiffness of each joint, select an adjusting spring 7 with a suitable stiffness, calculate the angle of the adjusting spring 7 and determine the positions of the first positioning hook 3 and the second positioning hook 6, move the engaging slider 5 and fix it, and tension the adjusting spring 7;

[0036] (3) Calculate the similarity ratio of the natural vibration frequencies between the model and the prototype according to the similarity theory, measure the natural vibration frequency of the model using the seismic simulation shaking table, and adjust the position of the second positioning hook 6 until the measured natural vibration frequency of the model meets the accuracy requirements compared with the calculated result;

[0037] (4) Conduct a dynamic loading test using the adjusted model.

[0038] The specific preferred embodiments of the present invention have been described above. It should be understood that the above-described embodiments are not intended to limit the present invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A weak-stiffness beam-column joint for shaking table tests of scaled structural models, characterized in that: Without changing other components in the scaled model, the overall dynamics of the model can be widely adjusted by only changing the state of the node itself. The column head (1) is a short steel column with a box-shaped cross-section. One end is welded with a column head end plate (11) and connected to the column end plate of the model through bolt one (12). The other end is welded to the bottom plate (21) of the universal hinge (2). The universal hinge (2) enables the column to rotate around two cross-section principal axes simultaneously, but restricts the column from twisting around the vertical axis. The top plate (22) of the universal hinge (2) is connected to the beam bottom plate through bolt two (26). A number of first positioning hooks (3) are welded to the lower surface of the top plate (22), and one end of the adjustment spring (7) is connected to the first positioning hook (3). The back of the sliding tooth plate (4) is welded to each side of the column head (1), and a first locking tooth (41) is provided on the front of the sliding tooth plate (4). A second locking tooth (51) is provided on the inner side of the engaging slider (5). The engaging slider (5) is placed on the sliding tooth plate (4). A second positioning hook (6) is welded to the outer side of the engaging slider (5), and the other end of the adjustment spring (7) is connected to the second positioning hook (6). The adjustment spring (7) adjusts the inclination angle by changing the positions of the connected first positioning hook (3) and second positioning hook (6). The overall stiffness of the node is provided by the tensile stiffness of the adjustment spring (7), meeting the dual requirements of weak stiffness and variable stiffness.

2. The weak-stiffness beam-column joint for shaking table tests of scaled structural models according to claim 1, characterized in that: By adjusting the stiffness of the beam-column node, the stiffness of the model is reduced, enabling the scaled model to meet the similarity requirements derived from the similarity theory with the prototype structure.

3. The weak-stiffness beam-column joint for shaking table tests of scaled structural models according to claim 1, characterized in that: The universal hinge (2) consists of a bottom plate (21), a top plate (22), a lower support (23), an upper support (24), a sphere (25), bolt two (26), and a screw (27). The bottom plate (21) is welded to the column head (1). The lower support (23) and the upper support (24) are respectively welded to the bottom plate (21) and the top plate (22). The sphere (25) is connected to the lower support (23) and the upper support (24) through the screw (27), and bolt two (26) connects the universal hinge (2) to the beam.

4. The weak-stiffness beam-column joint for shaking table tests of scaled structural models according to claim 1, characterized in that: To ensure that the tension of the adjustment spring (7) only provides rotational stiffness and does not produce a torsional effect on the column, the sliding tooth plate (4) is centered and aligned with the lower surface of the beam bottom plate it faces. The first positioning hook (3) is arranged along the center line of the lower surface of the beam bottom plate. The second positioning hook (6) is welded to the center point of the outer side of the engaging slider (5).

5. The weak-stiffness beam-column joint for shaking table tests of scaled structural models according to claim 1, characterized in that: To enable the position of the second positioning hook (6) connected to the adjustment spring (7) to be movable or fixed, the setting direction of the first locking tooth (41) is opposite to that of the second locking tooth (51). There is a fastening screw (52) on the engaging slider (5). When the fastening screw (52) is tightened, the first locking tooth (41) meshes with the second locking tooth (51) to fix the engaging slider (5). When the fastening screw (52) is loosened, the engaging slider (5) can move up and down along the sliding tooth plate (4).

6. The weak-stiffness beam-column joint for shaking table tests of scaled structural models according to claim 1, characterized in that: To prevent both ends of the adjustment spring (7) from falling off the first positioning hook (3) and the second positioning hook (6) under the action of dynamic loads, the opening directions of the first positioning hook (3) and the second positioning hook (6) both face away from the universal hinge (2).

7. The weak-stiffness beam-column joint for shaking table tests of scaled structural models according to claim 1, characterized in that: The application method includes the following steps: (1) Weld column end plates at the ends of each column of the structural scale model, and drill holes at corresponding positions on the column end plates and beam bottom plates, and connect the column, joint and beam together through bolt one (12) and bolt two (26); (2) Calculate the target lateral stiffness of the scale model, calculate the rotational stiffness of each joint, select a regulating spring (7) with appropriate stiffness, calculate the angle of the regulating spring (7) and determine the positions of the first positioning hook (3) and the second positioning hook (6), move the engaging slider (5) and fix it, and tension the regulating spring (7); (3) Calculate the similarity ratio of the natural vibration frequencies between the model and the prototype according to the similarity theory, measure the natural vibration frequency of the model using a shaking table for seismic simulation, and adjust the position of the second positioning hook (6) according to the measured natural vibration frequency until the true natural vibration frequency of the model meets the accuracy requirements compared with the calculated result; (4) Conduct a dynamic loading test.

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