A method for testing the pull-shear fatigue performance of a weld stud connector

Abstract

The present application relates to a kind of pull-shear fatigue performance test methods of weld stud connector, make weld stud (13) welded in the pure steel test piece (1) of steel beam, when fatigue loading, the weld stud (13) of pure steel test piece (1) is fixed in steel clamp (2), the support and embedded solidification effect of steel clamp (2) to weld stud (13) are simulated;Vertical pressure is applied to the steel beam welded with weld stud (13), simulates the stress of steel member in composite structure;By changing the distance D of slider (21) in steel clamp (2) to the root of weld stud (13), the constraint stiffness of weld stud (13) is controlled, by changing the inclination angle θ between weld stud (13) and horizontal plane, the pull-shear load ratio is determined.Compared with prior art, the present application has the advantages of low test piece manufacturing difficulty, low cost, low pull-shear fatigue load application difficulty, high testing precision and efficiency etc..

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel and concrete composite structure, and particularly relates to a tensile-shear fatigue performance test method of a welded stud connector. BACKGROUND

[0002] In the steel and concrete composite structure, the connector between the steel member and the concrete member is a key component for fully exerting the composite effect, and transmits the pulling force and the shear force between the steel and concrete members. Therefore, the connector must have sufficient bearing capacity and stiffness under the combined action of the pulling force and the shear force (tensile-shear). In particular, the fatigue performance of the connector under the tensile-shear cyclic load is crucial to the safety and durability of the steel and concrete composite structure subjected to fatigue load.

[0003] The welded stud connector is the most widely used connector with excellent mechanical properties. At present, in order to test the fatigue performance of the welded stud connector such as fatigue life, fatigue strength and fatigue damage law, whether it is the traditional push-out test for testing the pure shear fatigue performance or the steel and concrete composite beam fatigue test for testing the tensile-shear fatigue performance, destructive fatigue tests are carried out on the steel and concrete composite members. These composite members for testing embed the welded stud in the concrete slab, aiming to simulate the constraint of the concrete member on the welded stud connector in the actual composite structure. However, the current fatigue performance test methods have the following shortcomings:

[0004] 1) The test specimen for testing needs to cast the welded stud in a large-size concrete slab with a thickness greater than the height of the welded stud, and the specimen manufacturing cycle is long, difficult and costly;

[0005] 2) The traditional test method cannot accurately apply the tensile-shear fatigue load, wherein the traditional push-out test can only test the pure shear fatigue performance, and the composite beam fatigue test needs to apply the tensile-shear fatigue load to multiple rows of welded stud connectors. During the loading process, the redistribution of the pulling force or shear force load between the multiple rows of connectors is inevitable, and it is difficult to accurately determine the tensile-shear load on each connector;

[0006] 3) Since the welded stud is embedded in the concrete slab, and the mechanical properties of the concrete are highly dispersed at the microscopic scale, it is difficult to control the real constraint condition of the welded stud and to measure and observe the fatigue failure process of the welded stud connector, so that the quantitative data obtained are limited, and the test precision and efficiency are low.

[0007] Numerous studies have shown that the fatigue failure process of stud joints is essentially the initiation and development of fatigue cracks in the welding details of the studs, with the concrete structure affecting the constraint conditions on the studs. Therefore, based on understanding the essence of the fatigue process of stud joints, new testing methods and supporting devices can be developed to simulate the constraint of concrete structures on the studs, enabling rapid, convenient, and accurate determination of the fatigue performance of stud joints. Summary of the Invention

[0008] The purpose of this invention is to provide a method for testing the tensile and shear fatigue performance of welded stud connectors. The method is easy to prepare specimens, has low cost, is easy to apply tensile and shear fatigue loads, and has high testing accuracy and efficiency.

[0009] The objective of this invention can be achieved through the following technical solution: a method for testing the tensile and shear fatigue performance of welded stud connectors, comprising: fabricating a pure steel specimen with welded studs welded to a steel beam; during fatigue loading, the welded studs of the pure steel specimen are fixed in a steel clamp, which simulates the supporting and embedding effect of concrete on the welded studs; applying vertical pressure to the steel beam welded to the welded studs to simulate the stress on the steel components in the composite structure; controlling the constraint stiffness of the welded studs by changing the distance D from the slider to the root of the welded studs by moving the slider in the steel clamp; and determining the tensile and shear load ratio by changing the inclination angle θ between the welded studs and the horizontal plane.

[0010] In this invention, the greater the distance (D) from the slider to the root of the weld stud, the smaller the constraint stiffness of the slider on the weld stud. By moving the slider to change the distance D, the constraint stiffness of the weld stud can be precisely controlled. The greater the inclination angle (θ) between the weld stud and the horizontal plane, the greater the tensile-shear load ratio. By changing the inclination angle (θ) between the weld stud and the horizontal plane, the tensile-shear load ratio can be precisely determined.

[0011] Preferably, the distance (D) from the slider to the root of the weld stud is determined by calculation based on a nonlinear finite element model, so that the constraint stiffness of the weld stud root during testing is equal to the constraint stiffness in the actual steel and concrete composite structure.

[0012] More preferably, the nonlinear finite element model calculates the constraint stiffness of the stud connector in the actual steel and concrete composite structure, as well as the relationship curve between the distance (D) from the steel clamp to the stud root and the stud constraint stiffness.

[0013] Preferably, the angle (θ) between the weld stud and the horizontal plane determines the ratio of pull-out force to shear force on the weld stud as (tanθ:1). When the angle is 0, it is a pure shear force; when the angle is greater than 0, it is a combined tensile and shear force.

[0014] Preferably, the pure steel specimen includes a steel flange, a steel web, and welding studs;

[0015] The steel flange and steel web are welded into a steel beam. The root of the welding stud is vertically welded to the center of the steel flange of the steel beam. The head of the welding stud is ground and threaded before welding. It is fixed to the slider by nuts and washers. The inclination angle θ between the welding stud and the horizontal plane is changed by changing the angle between the steel flange and the horizontal plane.

[0016] More preferably, the side of the slider is parallel to the steel flange and perpendicular to the welding stud.

[0017] More preferably, a gap is left between one side of the slider and the root of the welding stud, and the other side is fixedly connected to the head of the welding stud.

[0018] More preferably, the threaded range of the weld stud head should be sufficient to allow a portion of the thread to be within the through hole of the slider.

[0019] More preferably, the thickness of the steel flange and the steel web is not less than the diameter of the weld stud to ensure sufficient constraint stiffness.

[0020] More preferably, the pure steel specimen includes two steel flange plates and two steel web plates, with two welding studs welded vertically to the center of the two steel flange plates respectively, and steel clamps provided on the outer side of both steel flange plates.

[0021] Preferably, the steel clamp includes a slider, a fixed steel beam, an anchor bolt, and a bottom steel beam. The slider is sleeved on a welding stud, and the head of the welding stud is fixedly connected to the slider. The slider is positioned between the fixed steel beam and the bottom steel beam, and the fixed steel beam and the bottom steel beam are connected by the anchor bolt.

[0022] More preferably, the slider is a solid component made of steel such as cast steel, and the slider has a through hole for the welding stud to pass through. The slider is a parallelepiped slider, the side parallel to the axis of the through hole is a parallelogram, and the surface in contact with the fixed steel beam and the bottom steel beam is rectangular.

[0023] More preferably, the fixed steel beam is a box-shaped steel beam, and the width of its steel base plate is wider than that of the slider, so that the slider can be strongly constrained in any position.

[0024] More preferably, the thickness of the steel plate used to fix the steel beam is not less than the diameter of the welding stud, so as to ensure sufficient constraint stiffness.

[0025] More preferably, the fixed steel beam and the bottom steel beam are connected by anchor bolts set at the four corner points to provide stronger, symmetrical constraints.

[0026] More preferably, the diameter of the anchor bolt is not less than the diameter of the welding stud to ensure sufficient constraint stiffness.

[0027] Further preferably, the bottom steel beam is completely fixed on the ground or the testing machine and does not move during the test.

[0028] Preferably, a vertical pressure is applied to the steel beam by a fatigue loading machine, and the cross-sectional dimension of the steel beam is larger than the acting surface of the loading head of the fatigue loading machine.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. The test piece of the present invention is easy to manufacture, has a low cost, the difficulty of applying the pull-shear fatigue load is low, and the test accuracy and efficiency are high. [[ID=IO]] [[ID=II]]

[0031] 2. The pure steel test piece used in the present invention is smaller in size, easier to manufacture and has a lower cost compared with the steel members in the composite structure test pieces used in the traditional push-out test and composite beam test. At the same time, since no concrete needs to be poured, the production cycle, difficulty and cost of the test piece are further reduced.

[0032] 3. The present invention cleverly simulates the restraint condition of the stud connector in concrete and the loading condition of the combined action of tension and shear through the steel fixture, including: changing the distance (D) from the slider to the root of the stud to control the stud restraint stiffness; changing the stud inclination angle (θ) to simulate the change of the tension-shear load ratio. Therefore, the fatigue load received by the stud connector can be simply and accurately controlled, greatly reducing the test difficulty.

[0033] 4. In the present invention, since the stud is not wrapped by concrete, the welding details at the root of the stud can be observed in real time during the fatigue test, and even the test piece can be taken off the device for in-depth observation. Thus, the fatigue crack propagation and other fatigue failure processes can be directly observed conveniently by means such as the naked eye, microscope or ultrasonic flaw detection, improving the test accuracy and efficiency.

[0034] 5. The present invention realizes the rapid test of the tension-shear fatigue performance of the stud connector, and can obtain more quantitative test data such as the width, length, position, etc. of the fatigue crack under different fatigue load cycles, which helps to discover new scientific phenomena and laws and is of great significance to the development of the fatigue design theory of the stud connector. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the front view of the device配套 to the test method of the present invention;

[0036] Figure 2 is the side view of the device配套 to the test method of the present invention;

[0037] Figure 3 is the calculation diagram of the stud inclination angle (θ) and the tension-shear load ratio;

[0038] Figure 4This is a schematic diagram of the relationship between the distance (D) from the slider to the root of the weld stud obtained from finite element analysis and the constraint stiffness of the weld stud.

[0039] Figure 5 This is a schematic diagram illustrating the effect of the weld stud tilt angle (θ) obtained from finite element analysis on the force on the weld stud.

[0040] In the figure: 1-pure steel specimen, 11-steel flange plate, 12-steel web plate, 13-welding stud, 2-steel clamp, 21-slider, 22-fixed steel beam, 221-steel base plate, 23-anchor bolt, 24-bottom steel beam, 3-fatigue loading machine, 4-loading frame. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0042] Example 1

[0043] A device for testing the tensile and shear fatigue properties of welded stud connectors includes a pure steel specimen 1, a steel clamp 2, and a fatigue loading machine 3.

[0044] Specifically, the pure steel specimen 1 includes a specimen steel beam with a box-shaped cross section welded from a steel flange plate 11 and a steel web plate 12, and welding studs 13 welded vertically to the steel flange plate 11. The steel flange plate 11 is set at an angle to the horizontal plane.

[0045] The steel clamp 2 includes a slider 21, a fixed steel beam 22, an anchor bolt 23, and a bottom steel beam 24. The slider 21 is sleeved on a welding stud 13, the root of which is welded to a steel flange plate 11, and the head is fixed to the slider 21. The slider 21 is positioned between the fixed steel beam 22 and the bottom steel beam 24, and the anchor bolt 23 is provided between the fixed steel beam 22 and the bottom steel beam 24.

[0046] The fatigue loading machine 3 is positioned above the steel beam of the specimen and can apply vertical fatigue loads to the steel beam of the specimen.

[0047] Example 2

[0048] A method and supporting apparatus for testing the tensile and shear fatigue properties of welded stud connectors, such as... Figures 1-2 As shown, the apparatus includes a pure steel specimen 1 and a steel clamp 2. The test applies a vertical fatigue load to the pure steel specimen 1 using a fatigue loading machine 3 and fixes the steel clamp 2 within the loading frame 4 to achieve tensile and shear fatigue loading of the welded stud connector.

[0049] The pure steel specimen 1 includes steel flanges 11, steel webs 12, and welding studs 13. There are two steel flanges 11 and two steel webs 12, which are welded together to form a box-shaped cross-section steel beam. Two welding studs 13 are welded perpendicularly to the centers of the two steel flanges 11 on the steel beam. The heads of the welding studs 13 are ground and threaded before welding. The steel flanges 11 are rectangular steel plates with an angle of (90°-θ) with the horizontal plane. The steel webs 12 are trapezoidal steel plates with a minimum angle of (90°-θ). The cross-sectional dimension of the box-shaped cross-section of the steel beam is larger than the working surface of the loading head of the fatigue loading machine. The thickness of the steel flanges 11 and steel webs 12 is not less than the diameter of the welding studs 13. The thread range of the welding stud head is three times the diameter of the welding stud 13.

[0050] The steel clamp 2 includes a slider 21, a fixed steel beam 22, an anchoring bolt 23, and a bottom steel beam 24. The slider 21 has a through hole of equal diameter in the middle, the diameter of which is equal to or slightly larger than the diameter of the welding stud 13, allowing the slider 21 to fit onto the welding stud 13. The fixed steel beam 22 is located above the slider 21, restricting its movement during fatigue loading. The anchoring bolt 23 anchors the fixed steel beam 22 to the bottom steel beam 24. The bottom steel beam 24 is fixed to the ground or the testing machine.

[0051] The slider 21 is a solid parallelepiped component machined from cast steel. The side parallel to its hole axis is a parallelogram with a minimum included angle of (90°-θ). The surface in contact with the fixed steel beam and the bottom steel beam is a rectangular surface.

[0052] The fixed steel beam 22 is a box-shaped steel beam, and the width of its steel base plate 221 is wider than that of the slider 21; the thickness of the steel plate of the fixed steel beam 22 is not less than the diameter of the welding stud 13.

[0053] There are four anchor bolts 23, located at the four corners of the fixed steel beam 22; the diameter of the anchor bolts 23 is not less than the diameter of the welding studs 13.

[0054] The installation method of each component in the device of this embodiment is as follows:

[0055] Two steel flange plates 11 and two steel web plates 12 are fabricated and welded into a box-shaped cross-section specimen steel beam; the heads of two welding studs 13 are ground and threads are engraved; the welding studs 13 are welded to the center of the two steel flange plates 11 of the specimen steel beam to form a pure steel specimen 1; the slider 21 is fitted into the welding stud 13, the distance (D) from one side of the slider 21 to the root of the welding stud 13 is set, and the head of the welding stud 13 is fixed to the other side of the slider 21 by nuts and washers; then, the slider 21 is placed below the fixed steel beam 22 and above the bottom steel beam 24, and fixed to the bottom steel beam 24 by anchor bolts 23; the bottom steel beam 24 is fixed in the loading frame 4; finally, a vertical fatigue load is applied above the specimen steel beam by a fatigue loading machine 3.

[0056] The working principle of the tensile-shear fatigue test device in this embodiment is as follows:

[0057] During fatigue loading, the weld studs 13 of the specimen are fixed in the steel clamp 2, and the slider 21 simulates the support and fixation of the weld studs by the concrete; vertical pressure is applied to the steel beam of the specimen welded to the weld studs 13 to simulate the stress on the steel components in the composite structure; such as Figure 3 As shown, the tilt angle (θ) of the stud 13 determines the ratio of pull-out force to shear force on the stud 13 as (tanθ:1); the distance (D) determined by the nonlinear finite element model makes the constraint stiffness of the stud 13 in the test equal to the constraint stiffness of the stud connector in the actual steel and concrete composite structure.

[0058] Example 3

[0059] A method for testing the tensile-shear fatigue performance of welded stud connectors is proposed. A three-dimensional nonlinear finite element model of a pure steel specimen 1 and a steel clamp 2 is established using ABAQUS commercial finite element software. The geometric dimensions of the model are consistent with those of Example 1. The steel material in the model adopts an ideal elastoplastic model. The hard contact between the pure steel specimen 1 and the steel clamp 2 is simulated. In contrast, a three-dimensional nonlinear finite element model for a traditional push-out test is established using ABAQUS commercial finite element software. The geometric dimensions of the steel component in the model are consistent with those of the pure steel specimen, but a concrete slab is simulated. The steel material in the model adopts an ideal elastoplastic model, and the concrete material adopts a damaged elastoplastic model. The hard contact between the pure steel specimen and the concrete slab is simulated. The finite element analysis results yield the stress-strain state and deformation performance of the stud under different constraints. Figure 4 The curve showing the relationship between relative slip stiffness and distance (D) for specimens without pull-out force reveals that as (D) increases, the Mises stress at the specimen root increases, and the stiffness decreases. Specifically, when D = 20 mm, the shear stiffness is close to that of a stud connector in ordinary concrete. Adjusting the distance (D) can accurately simulate the constraint of ordinary concrete on the stud. Furthermore, as... Figure 5 As shown, when the distance from the steel clamp to the root of the stud is D = 30 mm, under the same shear force, the stress of the model with a tension-shear ratio of 0.5 increases and the stiffness decreases by about 20% compared with the model with an inclination angle of zero. This is consistent with the previously reported experimental results, indicating that adjusting the inclination angle (θ) can accurately simulate different tension-shear load ratios.

[0060] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for testing the tensile and shear fatigue properties of welded stud connectors, characterized in that, A pure steel specimen (1) with welding studs (13) welded to a steel beam was prepared. During fatigue loading, the welding studs (13) of the pure steel specimen (1) were fixed in a steel clamp (2). The steel clamp (2) simulated the supporting and embedding effect of concrete on the welding studs (13). Vertical pressure was applied to the steel beam welded to the welding studs (13) to simulate the stress of the steel components in the composite structure. The constraint stiffness of the welding studs (13) was controlled by changing the distance D from the slider (21) in the steel clamp (2) to the root of the welding studs (13). The tensile-shear load ratio was determined by changing the inclination angle θ between the welding studs (13) and the horizontal plane. The pure steel specimen (1) includes a steel flange (11), a steel web (12), and a welding stud (13); The steel flange plate (11) and steel web plate (12) are welded into a steel beam. The root of the welding stud (13) is vertically welded to the center of the steel flange plate (11) of the steel beam. The head of the welding stud (13) is ground and threaded before welding. It is fixed to the slider (21) by nuts and washers. The angle θ between the welding stud (13) and the horizontal plane is changed by changing the angle between the steel flange plate (11) and the horizontal plane. The side of the slider (21) is parallel to the steel flange plate (11) and perpendicular to the welding stud (13); The steel clamp (2) includes a slider (21), a fixed steel beam (22), an anchor bolt (23), and a bottom steel beam (24). The slider (21) is sleeved on a welding stud (13), and the head of the welding stud (13) is fixedly connected to the slider (21). The slider (21) is located between the fixed steel beam (22) and the bottom steel beam (24). The fixed steel beam (22) and the bottom steel beam (24) are connected by the anchor bolt (23). The slider (21) is provided with a through hole for the welding stud (13) to pass through. The slider (21) is a parallelepiped slider. The side parallel to the axis of the through hole is a parallelogram, and the surface in contact with the fixed steel beam (22) and the bottom steel beam (24) is a rectangle. The greater the distance D from the slider (21) to the root of the welding stud (13), the smaller the constraint stiffness of the slider (21) on the welding stud (13). By moving the slider (21) to change the distance D, the constraint stiffness of the welding stud (13) can be precisely controlled. The greater the inclination angle θ between the welding stud (13) and the horizontal plane, the greater the tensile-shear load ratio. By changing the inclination angle θ between the welding stud (13) and the horizontal plane, the tensile-shear load ratio can be precisely determined.

2. The method for testing the tensile and shear fatigue properties of welded stud connectors according to claim 1, characterized in that, The threaded range of the head of the welding stud (13) is sufficient so that part of the thread is in the through hole of the slider (21).

3. The method for testing the tensile and shear fatigue properties of welded stud connectors according to claim 1, characterized in that, The fixed steel beam (22) is a box-shaped steel beam with a steel base plate that is wider than the slider (21). The thickness of the steel plate used to fix the steel beam (22) is not less than the diameter of the welding stud (13).

4. The method for testing the tensile and shear fatigue properties of welded stud connectors according to claim 1, characterized in that, The fixed steel beam (22) and the bottom steel beam (24) are connected by anchor bolts (23) set at the four corner points. The diameter of the anchor bolts (23) is not less than the diameter of the welding studs (13).

5. The method for testing the tensile and shear fatigue properties of welded stud connectors according to claim 1, characterized in that, The bottom steel beam (24) is fixed on the ground or the testing machine.

6. The method for testing the tensile and shear fatigue properties of welded stud connectors according to any one of claims 1 to 5, characterized in that, Vertical pressure is applied to the steel beam by a fatigue loader (3), and the cross-sectional dimension of the steel beam is larger than the working surface of the loading head of the fatigue loader (3).

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