A loading device and test method for fatigue test of intersecting nodes of X-shaped steel structures

Abstract

The present invention discloses a fatigue test loading device and test method for intersecting nodes of X-shaped steel structures, comprising a support mechanism, a support assembly, and a force transmission and loading mechanism. The X-shaped steel structure comprises a main pipe and a branch pipe; the ends of the branch pipe are welded to two supports, with the branch pipe axis arranged parallel to the axis of the force transmission column; the ends of each branch pipe are welded to the support top plate and support bottom plate of the corresponding support, and arc-shaped stress relief holes are provided at the weld between the support top plate and the branch pipe. The arc-shaped stress relief holes are located on the side of the support top plate where the force transmission and loading mechanism is provided, with a central angle of 120° to 150°, and a 10 cm gap is reserved between the hole edge and the branch pipe wall. The fatigue test loading device for intersecting nodes of X-shaped steel structures of the present invention provides arc-shaped stress relief holes in the area of ​​the weld between the support top plate and the test piece where tensile stress is relatively high, thereby improving the fatigue performance of the connection between the support and the test piece, increasing the fatigue life of the test device, and ensuring the smooth conduct of large-tonnage fatigue load tests on the node.

Description

Technical Field

[0001] The invention belongs to the technical field of steel structure fatigue testing, and in particular relates to a fatigue testing loading device and a testing method for an intersecting node of an X-shaped steel structure. Background Art

[0002] The stiffness and stress distribution on the intersection line of steel tube intersection nodes are uneven, and the node fatigue problem is prominent. At present, the regulations on fatigue design of steel tube intersection nodes in the fields of bridge and structural engineering are incomplete, and it is necessary to determine the fatigue service life of the nodes through finite element calculation combined with fatigue load tests.

[0003] For structures like bridges and oil rigs, live loads account for a high proportion, leading to high fatigue loads. Small-scale joints cannot reflect the impact of actual construction quality on joint fatigue performance. Therefore, fatigue load testing of full-scale joints is necessary, and the fatigue test load value is increased accordingly.

[0004] Existing fatigue load test loading devices are mostly suitable for small-tonnage node fatigue load tests. For large-tonnage node fatigue load tests, the loading device is required to have good fatigue performance and its fatigue life must be longer than the fatigue life of the node to be tested to ensure that the test purpose can be successfully achieved. Summary of the Invention

[0005] In response to the above problems, the present invention discloses a fatigue test loading device and test method for X-shaped steel structure intersecting nodes. The device and method of the present invention can realize fatigue load testing of real nodes at large-tonnage engineering scales, while taking into account the effects of axial tension and bending moment, and can reflect the impact of the actual construction quality of the node on the fatigue performance of the node.

[0006] The present invention is achieved through the following technical solutions:

[0007] A loading device for fatigue testing of intersecting nodes of an X-shaped steel structure, comprising an X-shaped steel structure test piece, is characterized in that the loading device comprises a supporting mechanism, a support assembly and a force transmission loading mechanism;

[0008] The supporting mechanism is used to support the bearing component, which is a steel frame load-bearing structure;

[0009] The support is used to connect the fixed loading device and the X-shaped steel structure test piece, including two supports symmetrically arranged above and below. Each support is composed of a support top plate and a support bottom plate, and an array of longitudinal beams and cross beams welded therebetween to form a steel frame beam structure;

[0010] The force transmission loading mechanism is used to implement the test load support and consists of a force transmission column and an actuator. The two ends of the actuator are welded and fixed with coaxial force transmission columns, and the other end of each force transmission column is welded and fixed to two supports respectively.

[0011] The X-shaped steel structure test piece includes a main pipe and a branch pipe that constitute the intersecting node of the X-shaped steel structure; the two ends of the branch pipe are welded and fixed to the two supports respectively, and the axis of the branch pipe is arranged parallel to the axis of the force transmission column; wherein, the end of each branch pipe is welded and fixed to the support top plate and the support bottom plate of the corresponding support, and an arc-shaped stress relief hole is set at the welding point between the support top plate and the branch pipe. The arc-shaped stress relief hole is located on the side of the support top plate where the force transmission loading mechanism is set, with a central angle of 120°~150°, and a gap of 10 cm is reserved between the edge of the hole and the wall of the branch pipe.

[0012] Furthermore, a smooth arc transition is provided at the junction of the umbrella-shaped edges and the arc edges on both sides of the support top plate constituting the arc-shaped stress release hole.

[0013] Furthermore, an open-hole stiffening plate forming an arc-shaped stress relief hole is provided in the support steel frame beam structure; the open-hole stiffening plate includes an arc plate forming an arc and stiffening plates forming umbrella-shaped edges on both sides, the two ends of the arc plate are welded and fixed to the plate surfaces of the two umbrella-shaped edge stiffening plates, the two ends of each umbrella-shaped edge stiffening plate are respectively welded and fixed to the support side plate or the branch pipe wall, and the upper and lower ends of the arc plate and the stiffening plate are respectively welded and fixed to the support top plate or the support bottom plate.

[0014] Furthermore, longitudinal beams and transverse beams are arranged vertically and horizontally in the support steel frame structure and on opposite sides of the branch pipe of the arc-shaped stress release hole to connect the support top plate and the support bottom plate.

[0015] Furthermore, longitudinal beams and transverse beams connecting the support top plate and the support bottom plate are arranged vertically and horizontally at the welding and fixing positions of the force transmission columns in the support steel frame structure.

[0016] Furthermore, the force transmission column is composed of a force transmission column panel, a force transmission column base plate and a force transmission column stiffening plate welded and fixedly arranged crosswise between the force transmission column panel and the force transmission column base plate.

[0017] Furthermore, the support mechanism includes two support columns fixed to the ground and a support beam supported by the two support columns; the support top plate of the support component is connected and fixed to the support beam.

[0018] The present invention also discloses a method for performing an X-shaped steel structure intersecting node fatigue test using the above-mentioned X-shaped steel structure intersecting node fatigue test loading device, comprising the following steps:

[0019] Step 1: determine the maximum hot spot stress amplitude of the key point on the intersection line of the X-shaped steel structure intersection node under the design fatigue load;

[0020] Step 2: applying an external load to the X-shaped steel structure intersecting node fatigue test loading device;

[0021] Step 3: Adjust the magnitude of the external load of the fatigue test loading device so that the maximum hot spot stress amplitude of the key point on the intersection line of the X-shaped intersection node test piece is the same as the maximum hot spot stress amplitude of the key point under the design fatigue load.

[0022] The key points on the intersection line include saddle points, crown points, intersection points of the intersection node reinforcement and the intersection line.

[0023] The benefits of the invention: The X-shaped steel structure intersecting node fatigue test loading device of the present invention is provided with arc-shaped stress release holes in the area where the tensile stress of the weld between the support top plate and the test piece is relatively large, thereby improving the fatigue performance of the connection between the support and the test piece, increasing the fatigue life of the test device, and ensuring the smooth progress of large-tonnage fatigue load tests of the nodes.

[0024] The loading device and test method of the present invention are used for fatigue load testing of real-scale nodes at an engineering scale. The test pieces can reflect the influence of actual construction quality on the fatigue performance of the nodes, and the test results are closer to the actual situation of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the loading device for fatigue test of intersecting nodes of X-shaped steel structures;

[0026] Figure 2 This is the large drawing of the force transmission column;

[0027] Figure 3 for Figure 2 Middle AA section;

[0028] Figure 4 This is a schematic elevation diagram of the X-shaped steel structure's intersecting nodes and support system;

[0029] Figure 5 This is the detail drawing of the support system;

[0030] Figure 6 for Figure 5 Middle BB cross-section;

[0031] Figure 7 for Figure 5 mid-CC cross-section;

[0032] Figure 8 Schematic diagram of key points on the intersection line of X-intersection node.

[0033] Markings in the figure: 1—branch pipe, 1a—intersection line, 2—main pipe, 2a—intersection node stiffener, 3—support, 4—load transfer column, 5—actuator, 6—support beam, 7—support column, 8—load transfer column panel, 9—load transfer column bottom plate, 10—load transfer column stiffener, 11—opening stiffener, 12—support top plate, 13—support bottom plate, 14—support diaphragm 1, 15—support diaphragm 2, 16—support stiffener at load transfer column, 17—support web 1, 18—support web 2, P1—saddle point, P2—crown point, P3—intersection of intersecting node stiffener and intersection line, N—stress relief hole, θ—central angle of stress relief hole, h—reserved gap between stress relief hole and pipe wall of node test piece. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific embodiments. The specific embodiments are further explanations of the principles of the present invention and do not limit the present invention in any way. Technologies that are the same or similar to the present invention do not exceed the scope of protection of the present invention.

[0035] Combined with the attached drawings.

[0036] like Figure 1 As shown, the X-shaped steel structure intersecting node fatigue test loading device of the present invention includes an X-shaped steel structure test piece and a loading device for fatigue test, a loading device support mechanism, a support component and a force transmission loading mechanism;

[0037] The support mechanism, used to support the support, is a steel frame load-bearing structure. In this example, the support mechanism consists of two support columns 7 fixed to the ground and a support beam 6 supported by the two support columns 7. The support columns 7, support beam 6, and support 3 are connected by bolts or welding, and the distance of the support beam 6 from the ground is adjustable.

[0038] The support is used to connect the fixed loading device and the X-shaped steel structure test piece, including two supports 3 symmetrically arranged above and below. Each support 3 is composed of a support top plate 12 and a support bottom plate 13, and an array of longitudinal beams and cross beams welded therebetween to form a steel frame beam structure.

[0039] like Figure 5 、 Figure 6 、 Figure 7 As shown, the support 3 in this example includes: a support top plate 12, a support bottom plate 13; an array of longitudinal beams and transverse beams consisting of a support cross diaphragm 14, a support cross diaphragm 2 15, a support stiffener 16 at the force transmission column, a support web 1 17 and a support web 2 18, which are welded to form the steel frame beam structure of the support 3.

[0040] The force transmission loading mechanism is used to realize the test load support and is composed of a force transmission column 4 and an actuator 5; the two ends of the actuator 5 are welded and fixed with coaxially arranged force transmission columns 4, and the other end of each force transmission column 4 is respectively welded and fixed to the two supports 3; the actuator 5 is a device for providing external load.

[0041] The X-shaped steel structure test piece includes a main pipe 2 and a branch pipe 1 forming an intersecting node of the X-shaped steel structure; the two ends of the branch pipe 1 are respectively welded to the two supports 3, and the axis of the branch pipe 1 is arranged parallel to the axis of the force transmission column 4; wherein, the end of each branch pipe 1 is welded to the support top plate 12 and the support bottom plate 13 of the corresponding support 3, and an arc-shaped stress relief hole N is provided at the welding point between the support top plate 13 and the branch pipe 1. The arc-shaped stress relief hole N is located on the side of the support top plate 12 where the force transmission loading mechanism is provided, with a central angle θ of 120° to 150°, and a gap of 10 cm is reserved between the edge of the hole and the wall of the branch pipe 3.

[0042] like Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 As shown, the end of the branch pipe 1 of the X-shaped steel structure node test specimen passes through the support top plate 12 and is welded to the support top plate 12, support bottom plate 13, perforated stiffener 11, and support web 2 18. A stress relief hole N is provided in the support top plate 12. The central angle θ of the stress relief hole N is 120° to 150°, and a clearance h of 10 cm is reserved between the stress relief hole N and the node test specimen pipe wall. A smooth arc transition is provided at the junction of the umbrella-shaped edges and the arc edge of the support top plate on both sides at the end of the stress relief hole N. The arc radius is 40 mm, which further reduces stress concentration. A perforated stiffener 11 is provided at the edge of the arc-shaped stress relief hole N in the support top plate 12. The perforated stiffener 11 is welded to the support top plate 12, support bottom plate 13, support web 1 17, and the branch pipe 1.

[0043] like Figure 6 、 Figure 7 As shown, an open-hole stiffening plate 11 constituting an arc-shaped stress relief hole is provided in the support steel frame structure; in this example, the open-hole stiffening plate 11 is supported by an arc plate constituting an arc and stiffening plates constituting umbrella-shaped edges on both sides; both ends of the arc plate are welded and fixed to the plate surfaces of the two umbrella-shaped edge stiffening plates, and both ends of each umbrella-shaped edge stiffening plate are respectively welded and fixed to the support side plate or the branch pipe wall, and the upper and lower ends of the arc plate and the stiffening plate are respectively welded and fixed to the support top plate 12 or the support bottom plate 13.

[0044] like Figure 6 As shown, support cross partition 2 15, support web 1 17 and support web 2 18 are arranged vertically and horizontally on opposite sides of the branch pipe of the arc-shaped stress release hole in the support steel frame structure to form the aforementioned longitudinal beams and cross beams connecting the support top plate 12 and the support bottom plate 13.

[0045] like Figure 5As shown, inside the support steel frame structure, at the welded fixed position of the force transfer column 4, a support cross partition 14 connecting the support top plate 12 and the support bottom plate 13 constituting the longitudinal and transverse arrangement of the aforementioned longitudinal beams and transverse beams, a support stiffener 16 at the force transfer column, and a support web 17 are arranged.

[0046] like Figure 1 、 Figure 2 、 Figure 3 As shown, the force transmission column 4 is composed of a force transmission column panel 8, a force transmission column base plate 9 and a force transmission column stiffening plate 10 welded and fixed between the force transmission column panel 8 and the force transmission column base plate 9 and arranged crosswise.

[0047] The fatigue test of the intersecting node of the X-shaped steel structure is carried out by using the mounting device, which includes the following steps:

[0048] Step 1: determine the maximum hot spot stress amplitude of the key point on the intersection line of the X-shaped steel structure intersection node under the design fatigue load;

[0049] Step 2: applying an external load to the X-shaped steel structure intersecting node to be tested by the above-mentioned X-shaped steel structure intersecting node fatigue test loading device;

[0050] Step 3: Adjust the magnitude of the external load of the fatigue test loading device so that the maximum hot spot stress amplitude of the key point on the intersection line of the node test piece is the same as the maximum hot spot stress amplitude of the key point under the design fatigue load.

[0051] like Figure 8 As shown, the key points on the intersection line of the test of the present invention include: saddle point P1, crown point P2, intersection point P3 of the intersection node stiffener 2a and the intersection line 1a.

[0052] The cross bracing of a through-type, plane-curved arch bridge utilizes a pure steel tubular mesh structure. The bridge has 46 X-shaped steel structure intersections. Based on calculations, the most unfavorable X-shaped intersection was selected for fatigue testing. The main pipe of the test specimen had a diameter of 850 mm, a wall thickness of 30 mm, and a length of 3320 mm. The branch pipe had a diameter of 750 mm, a wall thickness of 25 mm, and both branches were 2150 mm long. The angle between the main and branch pipe axes was 82.4°. During the fatigue loading phase, the actuator applied a constant-amplitude sinusoidal load with a peak difference of 350 kN at a frequency of 4 Hz. The fatigue loading cycle was terminated after 2 million cycles. Throughout the test, no welds in the X-shaped steel structure intersections or the loading mechanism cracked, and the specimen exhibited no significant deformation or fatigue failure.

Claims

1. A fatigue test loading device for an X-shaped steel structure intersecting node, comprising an X-shaped steel structure test piece, characterized in that: The loading device includes a supporting mechanism, a support assembly and a force transmission loading mechanism; The supporting mechanism is used to support the bearing component, which is a steel frame load-bearing structure; The support is used to connect the fixed loading device and the X-shaped steel structure test piece, including two supports symmetrically arranged above and below. Each support is composed of a support top plate and a support bottom plate, and an array of longitudinal beams and cross beams welded therebetween to form a steel frame beam structure; The force transmission loading mechanism is used to implement the test load support and consists of a force transmission column and an actuator. The two ends of the actuator are welded and fixed with coaxial force transmission columns, and the other end of each force transmission column is welded and fixed to two supports respectively. The X-shaped steel structure test specimen includes a main pipe and a branch pipe forming an intersecting node of the X-shaped steel structure; the ends of the branch pipe are respectively welded to two supports, and the axis of the branch pipe is arranged parallel to the axis of the force transmission column; wherein, the end of each branch pipe is welded to the support top plate and support bottom plate of the corresponding support, and a circular arc stress relief hole is provided at the welding point between the support top plate and the branch pipe; The arc-shaped stress relief hole is located on the side of the support top plate where the force transmission and loading mechanism is set, with a central angle of 120° to 150°, and a gap of 10 cm is reserved between the edge of the hole and the wall of the branch pipe; a smooth arc transition is set at the junction of the umbrella-shaped edges and the arc edges on both sides of the support top plate constituting the arc-shaped stress relief hole; An open-hole stiffening plate forming an arc-shaped stress relief hole is arranged in the support steel frame structure; the open-hole stiffening plate includes an arc plate forming an arc and stiffening plates forming umbrella-shaped edges on both sides, the two ends of the arc plate are welded and fixed to the plate surfaces of the two umbrella-shaped edge stiffening plates, the two ends of each umbrella-shaped edge stiffening plate are respectively welded and fixed to the support side plate or the branch pipe wall, and the upper and lower ends of the arc plate and the stiffening plate are respectively welded and fixed to the support top plate or the support bottom plate; longitudinal beams and transverse beams connecting the support top plate and the support bottom plate are arranged vertically and horizontally on the opposite sides of the branch pipe of the arc-shaped stress relief hole in the support steel frame structure.

2. The X-shaped steel structure intersecting node fatigue test loading device according to claim 1, characterized in that: In the support steel frame structure, longitudinal beams and transverse beams are arranged vertically and horizontally to connect the support top plate and the support bottom plate at the welding and fixing positions of the force transmission columns.

3. The X-shaped steel structure intersecting node fatigue test loading device according to claim 1, characterized in that: The force transmission column is composed of a force transmission column panel, a force transmission column bottom plate and a force transmission column stiffening plate which is welded and fixed and cross-arranged between the force transmission column panel and the force transmission column bottom plate.

4. The X-shaped steel structure intersecting node fatigue test loading device according to claim 1, characterized in that: The support mechanism comprises two support columns fixed to the ground and a support beam supported by the two support columns; a support top plate of the support component is connected and fixed to the support beam.

5. A fatigue test method for intersecting nodes of X-shaped steel structures, characterized by: The X-shaped steel structure intersecting node fatigue test loading device according to any one of claims 1 to 4 comprises the following operating steps: Step 1: determine the maximum hot spot stress amplitude of the key point on the intersection line of the X-shaped steel structure intersection node under the design fatigue load; Step 2: applying an external load to the intersecting node of the X-shaped steel structure to be tested by using an X-shaped steel structure intersecting node fatigue test loading device; Step 3: Adjust the magnitude of the external load of the fatigue test loading device so that the maximum hot spot stress amplitude of the key point on the intersection line of the X-shaped steel structure intersection node test piece is the same as the maximum hot spot stress amplitude of the key point under the design fatigue load.

6. The fatigue test method for X-shaped steel structure intersecting nodes according to claim 5, characterized in that: The key points on the intersection line include saddle points, crown points, intersection points of the intersection node reinforcement and the intersection line.

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