Anti-seismic performance degradation test method of steel frame structure and self-balancing loading device

Abstract

The invention discloses an anti-seismic performance degradation test method of a steel frame structure and a self-balancing loading device, and relates to the technical field of steel frame structures, the test method comprises the following steps: applying a long-term load to a key connection area of a frame; an accidental load is applied to the key connection area of the frame; testing the damage of the test piece, replacing a cracked floor slab and a residual deformed steel member, preliminarily determining a reusable damage threshold value of the member, and carrying out a quasi-static monotonic loading test; after determining the time-varying mechanical property of the key connection part, carrying out a pseudo-static reciprocating loading test; and the anti-seismic performance degradation conditions of the shear-resistant connection area and the combined beam-column joint are obtained. In the long-term stress performance test stage, the process that the concrete and steel performance change along with time and the coupling effect between the concrete and the steel are considered. According to the test method, the change process of the structural performance of the steel frame structure along with time can be more comprehensively measured.

Description

Technical Field

[0001] The invention relates to the technical field of steel frame structures, and in particular to a seismic performance degradation test method and a self-balancing loading device for a steel frame structure. Background Art

[0002] The traditional construction industry has long been in an inefficient development state of high energy consumption and high carbon emissions, and its carbon emissions account for more than 50% of my country's total carbon emissions. The construction industry has great potential for energy conservation and carbon reduction, and it is accelerating the transformation and upgrading of the entire process of the construction industry. Prefabricated steel structure buildings are naturally detachable structures. When the floor slabs are detachably connected, the entire structural system can be recycled. The outstanding advantages of this type of structure are reflected in the following two points: on the one hand, it alleviates the problem of solid waste disposal in buildings, and on the other hand, it gives full play to the intrinsic value of the building structure. Different from the recycling process of concrete recycling and steel smelting, the detachable structure greatly reduces the energy consumption and carbon emissions of the entire life cycle of the building, and is an ideal circular economy model. Therefore, the reuse of steel frame structures has significant environmental and economic benefits, but existing studies have shown that their application is relatively scarce. The reason is that the mechanism of seismic performance degradation of such structures after long-term use is unclear, and there is a lack of complete reuse design methods and specifications for reference.

[0003] The performance degradation of reused steel frame structures mainly comes from the time-varying effects of concrete and steel, which usually occur in a coupled manner. Specifically, it refers to the phenomenon that the material properties change during the service life due to the influence of time and external loads. During long-term use, creep and shrinkage of concrete are inevitable. The long-term deformation caused by this will cause the redistribution of internal forces in the floor system, thereby aggravating the cracking of concrete in the negative moment zone. At the same time, during the entire life cycle, accidental events such as earthquakes and impacts occur from time to time, and reused steel components are bound to have different degrees of plastic development. Steel is affected by strain aging, and its strength increases but its deformation capacity decreases. Determining the seismic performance degradation caused by time-varying effects through experimental means is the basis for conducting research on such structures, and it is of great significance to provide a practical and feasible test method for seismic performance degradation. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the deficiencies in the prior art, the present invention provides a method for testing the seismic performance degradation of a steel frame structure and a self-balancing loading device, which solve at least one technical problem raised in the background technology.

[0006] (II) Technical solution

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A first aspect provides a method for testing the seismic performance degradation of a steel frame structure, the method comprising:

[0009] Apply long-term loads to critical connection areas of steel frames;

[0010] Apply accidental loads to critical connection areas of steel frames;

[0011] Test specimen damage, replace cracked slabs and residual deformed steel components, preliminarily determine the damage threshold for component reuse, and conduct quasi-static monotonic loading tests;

[0012] After clarifying the time-varying mechanical properties of key connection parts, a quasi-static reciprocating loading test is conducted;

[0013] Obtain seismic degradation of shear connection areas and composite beam-column joints.

[0014] Preferably, the applying of long-term load is applying long-term load for more than 1 year.

[0015] Preferably, the sample is left to stand for more than 3 months after applying the accidental load.

[0016] Preferably, during the process of applying long-term loads to the critical connection areas of the steel frame, the critical connection areas include shear connection areas and composite beam-column nodes.

[0017] Preferably, during the process of applying accidental loads to the critical connection areas of the steel frame, the critical connection areas include shear connection areas and composite beam-column nodes.

[0018] A second aspect provides a self-balancing loading device, which is used to apply long-term loads and / or accidental loads to key connection areas of a steel frame; the self-balancing loading device comprises:

[0019] a first screw, wherein a dynamometer is disposed at an end of the first screw;

[0020] a second screw rod, wherein a spring is disposed at an end of the second screw rod;

[0021] The other ends of the first screw and the second screw are both threadedly connected to the load adjusting nut;

[0022] Wherein, the load-adjusting nut is a long nut, and the thread teeth at both ends are in opposite directions.

[0023] Preferably, the dynamometer is a through-type force sensor, which is penetrated through the end of the first screw.

[0024] Preferably, when the first screw is connected to the test piece, the end of the first screw passes through the test piece, the dynamometer is passed through the first screw, and a nut is tightened on the end of the first screw.

[0025] Preferably, when the second screw is connected to the test piece, the end of the second screw passes through the test piece, the spring is passed through the second screw, and the end of the second screw is tightened with a nut.

[0026] (III) Beneficial effects

[0027] The present invention provides a method for testing the seismic performance degradation of a steel frame structure and a self-balancing loading device, which have the following beneficial effects compared with the prior art:

[0028] The long-term stress performance of the steel frame structure and the seismic performance after long-term stress are tested. Based on this, the degree of seismic performance degradation of the steel frame structure in the reuse stage is given, providing a reference for the reuse of the steel frame structure.

[0029] In the long-term stress performance test phase, the time-varying process of concrete and steel performance and the coupling effect between the two are taken into account. Therefore, this test method can more comprehensively determine the time-varying process of the structural performance of the steel frame structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0031] Figure 1 A three-dimensional diagram of a self-balancing loading device for a shear-resistant connection area according to an embodiment of the present invention;

[0032] Figure 2 A top view of the self-balancing loading device in the shear connection area according to an embodiment of the present invention;

[0033] Figure 3 A three-dimensional diagram of a self-balancing loading device for a detachable composite beam-column node according to an embodiment of the present invention;

[0034] Figure 4 A top view of a self-balancing loading device for a detachable composite beam-column node according to an embodiment of the present invention;

[0035] Figure 5 A three-dimensional diagram of a quasi-static test device for a shear connection area according to an embodiment of the present invention;

[0036] Figure 6 It is a front view of a quasi-static test device for the shear connection area according to an embodiment of the present invention;

[0037] Figure 7 A three-dimensional diagram of a pseudo-static test device for a detachable composite beam-column node according to an embodiment of the present invention;

[0038] Figure 8 It is a front view of a pseudo-static test device for a detachable composite beam-column node according to an embodiment of the present invention;

[0039] Fig. 9 It is a reciprocating loading system of an embodiment of the present invention;

[0040] Among them, screw 1, dynamometer 2, spring 3, load adjustment nut 4, short steel beam 5, short removable floor 6, steel beam 7, steel column 8, removable floor 9, hinge point 10, distribution beam 11, connecting bolt 12, conversion beam 13, steel beam connection 14, steel column connection 15, reaction frame 16, actuator 17, pressure beam 18, fixing bolt 19, jack 20, sliding hinge 21, fixed hinge 22, lateral support 23. Specific implementation methods

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods:

[0044] The shortcomings of existing technologies:

[0045] (1) The long-term mechanical performance and seismic performance of steel frame structures can only be examined in isolation, and an organic integration cannot be achieved. The existing test methods cannot accurately determine the degree of seismic performance degradation of steel frame structures during the reuse stage, which in turn hinders the reuse design of steel frame structures.

[0046] (2) In the process of conducting long-term stress performance tests, it is impossible to take into account the performance degradation of concrete and steel. Existing long-term performance tests mainly examine the creep shrinkage of concrete, while ignoring the strain aging of steel and the coupling effect between the two.

[0047] Based on this, as shown in the attached manual Figure 1 – Figure 8As shown, the present invention provides a test method for the seismic performance degradation of a steel frame structure and a self-balancing loading device. For key connection areas, namely, shear connection areas and detachable composite beam-column nodes, a full life cycle load history simulation test is carried out considering long-term and accidental loads. Based on this, quasi-static monotonic and reciprocating loading tests are carried out respectively. In order to consider the influence of time-varying effects, two-stage static loading tests are carried out in sequence to simulate the full life cycle load history. The first stage: applying long-term loads for more than 1 year to examine the long-term deformation caused by creep and shrinkage of concrete, after which the deformation tends to stabilize. The second stage: applying short-term accidental loads to cause different degrees of plastic deformation in the steel components, and leaving them to stand for more than 3 months after unloading to allow the strain aging to fully develop. This loading sequence reproduces the effects of accidental events such as earthquakes and impacts after long-term action of constant loads, which is in line with objective facts. Based on this, the design Figure 2 and Figure 4 The self-balancing loading device and test specimen shown are used to achieve long-term load application.

[0048] Specifically, Figure 1 – Figure 4 As shown, the self-balancing loading device includes a screw rod 1, a dynamometer 2, a spring 3 and a load adjustment nut 4. The dynamometer 2 can be a through-type force sensor, which is worn on the screw rod 1. The spring 3 is also worn on the screw rod 1 to prevent the bolt 3 from loosening and causing a long-term load reduction. The screw rod 1 includes a first screw rod 101 and a second screw rod 102, which are arranged opposite to each other and are respectively threadedly connected to the two ends of the load adjustment nut 4, wherein the thread teeth at the two ends of the load adjustment nut 4 are opposite, so that the first screw rod 101 and the second screw rod 102 can be driven to move relative to each other or move toward each other by rotating the load adjustment nut 4, and then the load size can be adjusted by rotating the load adjustment nut 4.

[0049] The test specimen is a steel frame structure specimen, such as Figure 1 – Figure 4 As shown, it includes short steel beams 5, short detachable floor slabs 6, steel beams 7, steel columns 8, detachable floor slabs 9, hinge points 10, distribution beams 11, connecting bolts 12, transfer beams 13, steel beam connections 14 and steel column connections 15.

[0050] Assemble the self-balancing loading device and the test specimen, specifically:

[0051] like Figure 1 and Figure 2As shown, when the shear connection area loading test is performed, the screw rod 1 passes through the distribution beam 11, wherein the first screw rod 101 passes through a distribution beam 11, and a dynamometer 2 is installed at the end of the first screw rod 101 on the outer side of the distribution beam 11, and then pre-tightened by a nut; the second screw rod 102 passes through a distribution beam 11, and a spring 3 is installed at the end of the first screw rod 101 on the outer side of the distribution beam 11, and then pre-tightened by a nut; the first screw rod 101 and the second screw rod 102 are threadedly connected by the load adjusting nut 4. The load size is adjusted by rotating the load adjusting nut 4.

[0052] like Figure 3 and Figure 4 As shown, when the loading test of the detachable composite beam-column node is performed, the inner side of the steel beam 7 is provided with a conversion beam 13 through the connecting bolt 12, and the screw rod 1 passes through the conversion beam 13, wherein the first screw rod 101 passes through a conversion beam 13, and the dynamometer 2 is passed through the end of the first screw rod 101 on the outer side of the conversion beam 13, and then pre-tightened by a nut; the second screw rod 102 passes through a conversion beam 13, and the spring 3 is passed through the end of the first screw rod 101 on the outer side of the conversion beam 13, and then pre-tightened by a nut; the first screw rod 101 and the second screw rod 102 are threadedly connected by the load adjusting nut 4. The load size is adjusted by rotating the load adjusting nut 4.

[0053] After the long-term loading is completed, the accidental load is continued to be applied by pre-tightening the load adjustment nut 4. The long-term and accidental loads are applied according to the calculated ultimate bearing capacity, and are intended to be 50% to 70% and 70% to 90% of the calculated value respectively.

[0054] After the full life cycle load history simulation test, mature non-destructive testing methods are used to test the damage of the specimens. For floor slabs with obvious cracks and steel components with large residual deformation, follow-up tests are continued after replacement to preliminarily determine the damage threshold of the components for reuse. In this process, the detachability of floor slabs and steel components is studied, especially the detachability of composite beam-column joints. Then, monotonic loading tests considering time-varying effects are carried out. The test equipment is as follows: Figure 5 – Figure 8 As shown, the test device includes a reaction frame 16, an actuator 17, a pressure beam 18, a fixing bolt 19, a jack 20, a sliding hinge 21, a fixed hinge 22 and a lateral support 23.

[0055] After the time-varying mechanical properties of the key connection parts are ascertained, a reciprocating loading test is conducted in the reuse stage. Similarly, the damaged components that cannot be reused are first inspected and replaced, and then Figure 5 – Figure 8 The test device shown in the figure carries out reciprocating loading test, and the loading system is as follows Fig. 9By experimentally observing the failure process of the shear connection area and the composite beam-column node, the stiffness degradation, ductility index, energy dissipation capacity, etc. are analyzed to clarify the degradation of the seismic performance of the detachable composite beam-column node after being affected by the time-varying effect.

[0056] Conventional long-term load tests are combined with seismic performance tests to provide a test process for seismic performance degradation of steel frame structures, simulate the reuse process of building structures, and clarify the structural performance level in the reuse stage.

[0057] The self-balancing test device is used to simulate the load history of the entire life cycle. The specific composition and design ideas of the device are the key protection points. The self-balancing system is composed of the test piece itself. The device requires few auxiliary tools, has low cost and strong operability.

[0058] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0059] 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 aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for testing the seismic performance degradation of a steel frame structure, characterized in that: The test method includes: Apply long-term loads to critical connection areas of steel frames; Apply accidental loads to critical connection areas of steel frames; Test specimen damage, replace cracked slabs and residual deformed steel components, preliminarily determine the damage threshold for component reuse, and conduct quasi-static monotonic loading tests; After clarifying the time-varying mechanical properties of key connection parts, a quasi-static reciprocating loading test is conducted; Obtain seismic degradation of shear connection areas and composite beam-column joints.

2. The seismic performance degradation test method of a steel frame structure according to claim 1, characterized in that: The application of long-term load refers to application of long-term load for more than 1 year.

3. The seismic performance degradation test method of the steel frame structure according to claim 1, characterized in that: After applying the accidental load, the mixture is left to stand for more than 3 months.

4. The seismic performance degradation test method of a steel frame structure according to claim 1, characterized in that: When applying long-term loads to the critical connection areas of steel frames, the key connection areas are the shear connection areas and the composite beam-column nodes.

5. The seismic performance degradation test method of a steel frame structure according to claim 1, characterized in that: When applying accidental loads to the critical connection areas of the steel frame, the key connection areas are the shear connection areas and the composite beam-column nodes.

6. A self-balancing loading device, characterized in that: The self-balancing loading device is used to apply long-term load and / or accidental load to the key connection area of ​​the steel frame; the self-balancing loading device comprises: A first screw (101), wherein a dynamometer (2) is provided at an end of the first screw (101); A second screw rod (102), wherein a spring (3) is disposed at an end of the second screw rod (102); The other ends of the first screw rod (101) and the second screw rod (102) are both threadedly connected to the load adjustment nut (4); Wherein, the load-adjusting nut (4) is a long nut, and the thread teeth at both ends are in opposite directions.

7. The self-balancing loading device according to claim 6, characterized in that: The dynamometer (2) is a through-type force sensor, which is installed through the end of the first screw (101).

8. The self-balancing loading device according to claim 6, characterized in that: When the first screw rod (101) is connected to the test piece, the end of the first screw rod (101) passes through the test piece, the dynamometer (2) is passed through the first screw rod (101), and the end of the first screw rod (101) is tightened with a nut.

9. The self-balancing loading device according to claim 6, characterized in that: When the second screw rod (102) is connected to the test piece, the end of the second screw rod (102) passes through the test piece, the spring (3) passes through the second screw rod (102), and the end of the second screw rod (102) is tightened with a nut.

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