Partially fusible two-stage energy absorbing structure in the core and axial steel dampers

Abstract

The present invention relates to a two-stage energy absorption structure and an axial steel damper that can be partially melted at the core, the axial steel damper includes an energy absorption structure at the core and a peripheral restraint component, the energy absorption structure at the core includes at least one steel plate with an austenitic structure and one steel plate with a ferritic structure, and the steel plate with an austenitic structure and the steel plate with a ferritic structure are connected without restraint. The microstructure of the steel plate with an austenitic structure is mainly metastable austenite, the microstructure of the steel plate with a ferritic structure is mainly ferrite, the yield strength of the steel plate with an austenitic structure is 220 MPa or more and elongation is 40% or more, and the yield strength of the steel plate with a ferritic structure is less than 180 MPa and elongation is 30% or more. The axial steel damper according to the present invention has a small yield displacement, excellent ductility and cumulative plastic deformation capacity, the energy absorption structure at the core can be partially melted, the damper load can be limited, and the same fracture redundancy as the main structure of the building can be obtained.

Description

[Technical field]

[0001] The present invention belongs to the technical field of construction structural engineering, and relates to a partially fusible two-stage energy absorption structure and axial steel damper at the core. [Background technology]

[0002] High intensity earthquakes and long duration external vibrations both cause great damage to high rise buildings and structures. Using energy absorbing and shock absorbing devices and techniques can effectively absorb the external vibration energy and minimize the damage to buildings and structures. Energy absorbing buckling restrained braces are a common axial energy absorbing and shock absorbing element, and are widely used in civil engineering structures due to their direct force transmission path, large additional stiffness and good economy.

[0003] Currently, energy absorbing buckling restrained braces mainly use steel materials such as LY225 low yield point steel and Q235 steel as energy absorbing core materials (both of the above steel types are low carbon ferritic steels). Energy absorbing buckling restrained braces made of the above types of steels often only provide a certain stiffness and have very little effective yield deformation for seismic energy absorption when frequent earthquakes ("small earthquakes") or earthquakes of enhanced intensity ("moderate earthquakes"). More importantly, they are constrained by the lower ductility and low cycle fatigue deformation capacity of the steel types, which limits the cumulative plastic deformation and cumulative plastic energy absorption effect of the above types of steels due to repeated deformation. Therefore, when a rare earthquake ("big earthquake") occurs, energy absorbing buckling restrained braces made of the above types of steels will experience fatigue failure after a relatively small number of cycles of tensile and compressive repeated loading. Also, in rare or very rare earthquakes, the energy absorbing buckling restrained brace cannot achieve the same failure redundancy as the building's main structure (i.e., the energy absorbing buckling restrained brace will fail earlier than the building's main structure, and the building's main structure will not be further protected by the energy absorbing buckling restrained brace). Furthermore, the limit load of conventional energy absorbing buckling restrained braces is often relatively large. The larger the limit load, the greater the strain on the joints, which may cause the joints to fail before the energy absorbing components, making the basic idea of ​​earthquake resistance "strengthen the nodes and weaken the components" impossible to realize. Here, the joints refer to the components that fixedly connect the energy absorbing buckling restrained brace (or axial energy absorbing and impact absorbing elements) to the building's column-beam structure. Thus, the energy absorbing buckling restrained brace manufactured with conventional low carbon ferritic steel core material cannot play the role of seismic protection even under earthquakes of different seismic intensities. In addition, traditional energy absorbing buckling restrained braces need to be designed and manufactured to match the diagonal dimensions of the primary structural frame, and the size of the energy absorbing brace components is generally large, making them unsuitable for on-site installation and post-earthquake replacement. Summary of the Invention

[0004] Based on the above technical situation, it is urgent to develop an axial steel damper that has small yield displacement, good ductility and accumulated plastic deformation capacity, can limit the damper load, and has the same fracture redundancy as the main structure of the building. Therefore, the present invention provides a two-stage energy absorption structure and an axial steel damper that can be partially melted at the core.

[0005] The axial steel damper provided by the present invention can play the role of energy absorption and shock absorption under earthquakes of different seismic intensities, and provide earthquake protection for buildings; when the load of the axial steel damper reaches a certain level, the energy absorption structure at the core of the damper will be partially melted, which limits the limit load of the damper and ensures the reliability of the joint under rare or extremely rare earthquakes.

[0006] Compared with the traditional energy absorbing buckling restraint brace, the partially fusible two-stage energy absorbing structure and axial steel damper at the core of the present invention has a small yield displacement, excellent ductility and cumulative plastic deformation capacity, and can have the same fracture redundancy as the main structure of the building. The partially fusible two-stage energy absorbing axial steel damper of the present invention can exert energy absorbing and shock absorbing effects even under earthquakes of different seismic intensities, and provide earthquake protection for the building, and when the load of the axial damper reaches a certain level, the energy absorbing structure at the core of the damper will partially break, limiting the limit load of the damper. In addition, the axial steel damper for two-stage energy absorption of the present invention can be connected and combined with other steel braces to form an axial energy absorbing brace, meeting the requirements of prefabricated buildings and rapid replacement after earthquakes.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] The present invention first provides a two-stage energy absorption structure that can be partially melted at the core, which absorbs external vibration energy when the axial steel damper is subjected to cyclic and alternating plastic deformations of tension and compression; The partially meltable two-stage energy absorption structure at the core includes at least one steel plate having an austenitic structure and one steel plate having a ferritic structure, and the steel plate having the ferritic structure and the steel plate having the austenitic structure are connected without being restrained, The microstructure of the steel sheet having an austenitic structure is composed of metastable austenite and thermally induced ε martensite with a volume fraction of 15% or less, the average grain size of the metastable austenite is 400 μm or less, and during tensile or compressive plastic deformation, the metastable austenite of the steel sheet having an austenitic structure is induced to undergo ε martensite phase transformation by the action of strain, and α' martensite phase transformation is suppressed. When the steel sheet is subjected to cyclic and alternating tensile and compressive plastic deformation, a reversible phase transformation between austenite and strain-induced ε martensite occurs inside the steel sheet having an austenitic structure, and the microstructure of the steel sheet having a ferritic structure is mainly ferrite, the average grain size of the ferrite is 200 μm or less, The steel plate having an austenitic structure has a yield strength of 220 MPa or more and an elongation of 40% or more, and the steel plate having a ferritic structure has a yield strength of less than 180 MPa and an elongation of 30% or more; In the energy absorbing structure in the core, the ratio of the sum of the cross-sectional areas of the energy absorbing parts in the core of all the steel plates having a ferritic structure to the sum of the cross-sectional areas of the energy absorbing parts in the core of all the steel plates having an austenitic structure is 0.4 or more.

[0009] The present invention relates to an energy absorbing structure at a core, in which, when the geometric shape of the cross section of the steel plate having a ferritic structure or the steel plate having an austenitic structure does not change along the longitudinal direction, the energy absorbing portion at the core of the steel plate having a ferritic structure or the steel plate having an austenitic structure is the entire length of the steel plate having a ferritic structure or the steel plate having an austenitic structure, in this case, the cross section of the energy absorbing portion at the core of the steel plate having a ferritic structure or the steel plate having an austenitic structure is the cross section of the steel plate having a ferritic structure or the steel plate having an austenitic structure, In the case where the geometric shape of the cross section of a steel plate having a ferritic structure or a steel plate having an austenitic structure is characterized in that both ends are wide and the center is narrow along the longitudinal direction, the energy absorption portion at the core of the steel plate having a ferritic structure or the steel plate having an austenitic structure is the narrow portion in the center of the steel plate having a ferritic structure or the steel plate having an austenitic structure, and in this case, the cross section of the energy absorption portion at the core of the steel plate having a ferritic structure or the steel plate having an austenitic structure is, in other words, the cross section of the narrow portion in the center of the steel plate having a ferritic structure or the steel plate having an austenitic structure.

[0010] The present invention restricts the partially meltable two-stage energy absorbing structure at the core to include at least one steel plate having an austenitic structure and one steel plate having a ferritic structure. The microstructure of the steel plate having an austenitic structure is metastable austenite and thermally induced ε-martensite with a volume fraction of 15% or less, and the purpose is to promote the generation of a flaky single variant of strain-induced ε-martensite with crystallographic characteristics inside the steel plate under alternating tensile and compressive loads, avoid the influence of the thermally induced ε-martensite in the original matrix structure, promote the reversible phase transformation between austenite and strain-induced ε-martensite, reduce the occurrence of matrix crystal defects of the austenitic steel plate in the structure, and inhibit the growth of fatigue cracks, so that the steel plate having an austenitic structure can exhibit excellent low cycle fatigue performance and accumulated plastic deformation capacity. Furthermore, the present invention restricts the metastable austenite inside the steel plate having an austenitic structure to inhibit the α′-martensite phase transformation during tensile or compressive deformation. This is because when metastable austenite undergoes excessive α′ martensite phase transformation due to the action of plastic strain, localized deformation is likely to occur inside the steel plate, and the low cycle fatigue performance of the steel plate having an austenitic structure is rapidly reduced. The present invention restricts the average grain size of metastable austenite to not exceed 400 μm. This is because if the austenite grains are too coarse, the reversible phase transformation between austenite and strain-induced ε martensite is significantly inhibited, and the fatigue resistance performance of the steel plate having an austenitic structure is significantly reduced. The present invention strictly restricts the microstructure of the steel plate having an austenitic structure, with the purpose of ensuring that the steel plate having an austenitic structure can withstand large strain fatigue deformation, and that the axial steel damper can function without early fatigue failure even under medium and high intensity earthquakes and extremely rare earthquakes, and that the axial steel damper has the same fracture redundancy as the main structure of the building.

[0011] The steel plate having the ferritic structure has a low yield strength, a high Young's modulus, and a low degree of work hardening during repeated deformation cycles. Therefore, before the energy absorbing structure at the core of the axial steel damper is partially melted, the steel plate having the ferritic structure contributes to reducing the yield load, the yield displacement, and the degree of work hardening during repeated deformation cycles of the entire energy absorbing structure at the core (when the energy absorbing structure at the core is used in the axial steel damper, i.e., the axial steel damper), thereby enabling the steel damper to achieve yield and energy absorption even under small and medium-sized earthquakes. However, the low cycle fatigue properties of the steel plate having the ferritic structure are inferior to those of the steel plate having the austenitic structure. This is because during repeated deformation of a steel plate having a ferritic structure, cross slip occurs frequently and microscopic plastic deformation is irreversible, so that the structural stability of the material is continuously reduced, the localization of plastic strain is continuously increased, and with the increase in repeated accumulated strain, fatigue cracks nucleate at the strain-incompatible points (e.g., grain boundaries, ferrite / cementite phase boundaries) or at persistent slip bands at the interface of the material surface structure, and grow along the grain boundaries or grow intragranularly until intergranular or intragranular fracture of the material occurs. The present invention limits the average grain size of ferrite to not exceed 200 μm. This is because if the ferrite grains are too coarse, fatigue cracks are likely to initiate and propagate from the grain boundaries, and the fatigue resistance of the steel plate having a ferritic structure is significantly reduced. Therefore, the restriction on the grain size (and elongation) of ferrite is intended to ensure the appropriate fatigue resistance of the steel plate having a ferritic structure.

[0012] In the partially meltable two-stage energy absorption structure in the core according to the present invention, the ferritic steel plate and the austenitic steel plate are connected without restraint. This is because, when the austenitic steel plate and the ferritic steel plate are connected with restraint by some means (e.g., welding), the austenitic steel plate restrains the deformation of the ferritic steel plate, since the austenitic steel plate has a relatively higher yield strength (and deformation resistance) and work hardening degree than the ferritic steel plate, and due to this restraint, the energy absorption components in the core will fatigue fracture almost instantly at the same part, i.e., the austenitic steel plate and the ferritic steel plate often break at the same time at the same part, so it is not easy to realize the requirement of limiting the load of the axial steel damper. When the ferritic steel plate and the austenitic steel plate are connected without restraint, there is no restraint mechanism of the austenitic steel plate against the deformation of the ferritic steel plate. Compared with steel plates with austenitic structure, steel plates with ferritic structure have significantly lower yield strength and fatigue resistance, so that when subjected to alternating tensile and compressive plastic deformation, the steel plates with ferritic structure will first undergo yield deformation and fatigue fracture, resulting in partial melting of the energy absorption structure at the core of the damper, limiting the load of the axial steel damper, and then the steel plates with austenitic structure in the energy absorption structure at the core will continue to withstand cyclic tensile and compressive deformation and absorb external vibration energy until the steel damper finally breaks completely. Usually, steel plates with austenitic structure and steel plates with ferritic structure will break at different parts. Therefore, the material selection and the design of the energy absorption structure at the core of the present invention ensure that the axial steel damper has the effect of gradual energy absorption and load limiting, and at the same time, the axial steel damper can play the role of energy absorption and shock absorption even under earthquakes of different seismic intensities.

[0013] The present invention restricts the yield strength of the steel plate with austenitic structure constituting the energy absorption structure at the core to be 220Mpa or more and elongation to be 40% or more, and the yield strength of the steel plate with ferritic structure to be less than 180Mpa and elongation to be 30% or more. The main purpose of restricting the mechanical properties of the two kinds of steel plates is to ensure that the two kinds of steel plate materials have excellent plastic deformation capacity and fatigue performance as much as possible (although the plastic deformation capacity and fatigue performance of the steel plate with austenitic structure are significantly better than those of the steel plate with ferritic structure), so that the axial steel damper has good cumulative plastic deformation capacity before and after the energy absorption structure at the core is partially melted, and meets the following technical performance indicators: The ratio of the limit allowable displacement to the yield displacement is not less than 18, the limit allowable displacement is not less than 1 / 50 of the length of the axial steel damper, under the condition of this limit allowable displacement, the axial steel damper can undergo cyclic alternating tensile and compressive plastic deformation for at least 3 cycles, with a load-bearing capacity reduction of less than 15%, and after the energy absorbing structure at the core of the axial steel damper is partially melted, under the condition of a displacement of 1 / 60 of the length of the axial steel damper, the axial steel damper can still undergo cyclic alternating tensile and compressive plastic deformation for at least 30 cycles, with a load-bearing capacity reduction of less than 15%. Since the limit allowable displacement is not less than 1 / 50 of the length of the axial steel damper, the two-stage energy absorbing structure that can be partially melted at the core according to the present invention can be realized to have the same fracture redundancy as the main structure of the building when used in the axial steel damper.

[0014] It should be noted here that the smaller the yield strength of the steel plate with ferritic structure, and the larger the difference in yield strength between the steel plate with ferritic structure and the steel plate with austenitic structure, the smaller the yield displacement of the axial steel damper, and the more energy it can absorb in small and medium earthquakes. On the contrary, increasing the strength of the steel plate with ferritic structure not only increases the yield displacement, but also usually reduces the elongation and low cycle fatigue performance of the steel plate with ferritic structure, which is not conducive to showing sufficient cumulative plastic deformation capacity of the energy absorbing structure at the core.

[0015] In the present invention, when the ratio of the sum of the cross-sectional areas of the energy absorption parts at the core of all the steel plates having ferritic structures to the sum of the cross-sectional areas of the energy absorption parts at the core of all the steel plates having austenitic structures is too small (less than 0.4), the deformation and loading of the energy absorption structure at the core will be mainly dominated by the steel plates having austenitic structures before it is partially melted down, so that the yield displacement of the energy absorption structure at the core will be greatly increased, and as a result, under small displacement conditions (i.e., "small earthquakes"), not only is the energy absorption effect of the energy absorption structure at the core not significant, but the ductility of the energy absorption structure at the core and the axial steel damper will also be greatly reduced. Therefore, in the present invention, the ratio of the sum of the cross-sectional areas of the energy absorption parts at the cores of all the steel plates having ferritic structures to the sum of the cross-sectional areas of the energy absorption parts at the cores of all the steel plates having austenitic structures is limited to 0.4 or more, and further, from the viewpoint of reducing the yield displacement of the energy absorption structure at the core, it is preferable that the ratio of the sum of the cross-sectional areas of the energy absorption parts at the cores of all the steel plates having ferritic structures to the sum of the cross-sectional areas of the energy absorption parts at the cores of all the steel plates having austenitic structures is 0.8 or more.

[0016] This invention is based on the limit allowable displacement (u d,max ) and yield displacement (u dy ) is defined as follows. When the load on the axial steel damper reaches a certain level, the energy absorbing structure in the core of the damper partially melts, and the limit allowable displacement (u d,max) is the maximum allowable displacement of the axial steel damper when it continues to undergo repeated tensile and compressive plastic deformation after the energy absorption structure in the core is partially melted down. Under this condition of maximum allowable displacement, the steel damper can undergo at least three cycles of repeated tensile and compressive deformation without failure. If the repeated deformation displacement exceeds the above limit allowable displacement, the axial steel damper cannot complete three cycles of repeated tensile and compressive deformation until it is fatigue-fractured. When the axial steel damper is subjected to cyclic alternating tensile and compressive plastic deformation at the maximum allowable displacement before the energy absorption structure in the core is partially melted down, the displacement corresponding to the yield deformation of the damper is the yield displacement (u dy ) is called the maximum allowable displacement before the energy absorbing structure at the core of the steel damper is partially melted down. Here, the maximum allowable displacement before the energy absorbing structure at the core of the steel damper is still specified to be the maximum allowable displacement when the energy absorbing structure at the core of the steel damper can withstand at least three cycles of repeated plastic deformation of tension and compression before it is partially melted down. Figure 1 shows the cyclic stress-strain curve when the axial steel damper is subjected to cyclic alternating tensile and compressive deformation at the maximum allowable displacement before the energy absorbing structure at the core is partially melted down, and the cyclic stress-strain curve when the axial steel damper is subjected to cyclic alternating tensile and compressive deformation at the same displacement after the energy absorbing structure at the core is partially melted down. The elastic stiffness of the axial steel damper is obtained from the unloading part of the cyclic stress-strain curve when it is subjected to cyclic deformation at the maximum allowable displacement before the energy absorbing structure at the core is partially melted down. The elastic stiffness corresponding to the unloading part of the tensile part of the cyclic stress-strain curve is K d (t) The elastic stiffness corresponding to the unloading part of the compression part of the cyclic stress-strain curve is K d (c) It is. d (t) ≠K d (c) If , the elastic stiffness of the axial steel damper K d is 1 / 2(K d (t) +K d (c) ) and K d (t)=K d (c) If , the elastic stiffness of the axial steel damper is K d =K d (t) =K d (c) The elastic stiffness K d Draw a straight line with a slope of , and the intersection of this line with the tensile part of the repeated stress-strain curve is the yield displacement u dy (t) The intersection of this line with the compression part of the repeated stress-strain curve is the yield displacement u dy (c) The yield displacement of the axial steel damper u dy is 1 / 2(u dy (t) +u dy (c) ) is calculated as follows: Limit allowable displacement u d,max and the yield displacement u dy From the above, the limit allowable displacement u of the axial steel damper d,max and the yield displacement u dy The ratio of this to the ductility of the steel damper can be calculated.

[0017] In one embodiment of the present invention, the mass percentages of the chemical components of the steel plate having an austenitic structure are limited to C≦0.15%, 20.0%≦Mn≦34.0%, 3.5%≦Si≦6.0%, Al≦2.5%, Ni≦5.0%, Cu≦2.0%, P≦0.03%, S≦0.03%, N≦0.02%, and the remainder is Fe and unavoidable impurity elements, and the mass contents of Al, Ni and Cu satisfy Ni / Cu≧0.25 and Al+0.4Ni+0.25Cu≦3.5%.

[0018] The microstructure of the material satisfying the above component requirements is metastable austenite and thermally induced ε martensite with a volume fraction of 15% or less, and the metastable austenite undergoes reversible ε martensite phase transformation when tensile and compressive loads are applied alternately (i.e., metastable austenite and strain-induced ε martensite undergo a two-phase intertransformation when loads are applied alternately), and α' martensite phase transformation is suppressed, so that the steel plate material has excellent low-cycle fatigue performance.

[0019] Without changing the above basic microstructural properties, the chemical composition of the steel plate having an austenitic structure may contain a small amount of Cr element, and the present invention limits the mass percentage of Cr element to Cr≦2%. With the above alloying composition and the average grain size of metastable austenite being ≦400 μm, the steel plate having an austenitic structure has a yield strength of ≧220 MPa and an elongation of ≧40%.

[0020] In one embodiment of the present invention, the present invention further limits the mass percentages of the chemical components of a steel plate having a ferritic structure to C≦0.1%, Mn≦1.0%, Si≦0.8%, Ti≦0.15%, Nb≦0.1%, V≦0.2%, P≦0.03%, S≦0.03%, N≦0.02%, with the balance being Fe and unavoidable impurity elements.

[0021] The microstructure of the material that meets the above composition requirements is mainly ferrite. Without changing the above basic microstructural properties, the chemical composition of the steel plate with ferrite structure can contain small amounts of Cu, Cr and Ni elements, and the present invention limits the mass percentages of Cu, Cr and Ni elements to Cu≦0.5%, Cr≦1%, Ni≦1%. With the above alloy composition and the average ferrite grain size of ≦200 μm, the steel plate with ferrite structure has a yield strength of less than 180 MPa and an elongation of ≧30%.

[0022] In one embodiment of the present invention, the cross section of the energy absorbing structure at the core may have any kind of axially symmetric geometric shape, which may mainly include a cross shape, a square shape, etc.

[0023] In one embodiment of the present invention, as shown in Fig. 2, the core energy absorbing structure of the partially meltable axial steel damper for two-stage energy absorption can adopt a cross-sectional shape that is narrow in the middle and wide at both ends. When the two kinds of steel plates have a geometric shape that is wide at both ends and narrow in the middle (the narrow part in the middle of the steel plates is called the core energy absorbing part), the narrow part in the middle of the core energy absorbing structure composed of the two kinds of steel plates is called the core energy absorbing part of the core energy absorbing structure. Because the axial steel damper is connected with the main beam-column structure of the building and other steel braces through joints and other connection components, the above-mentioned cross-sectional geometric design of the core energy absorbing structure of the steel damper ensures that the plastic deformation of the axial steel damper is concentrated only on the core energy absorbing part of the core energy absorbing structure, and avoids the occurrence of significant yield deformation or destruction of the joints or other connection components during the use of the steel damper. The rational selection of the ratio of the cross-sectional area of ​​the energy absorbing portion at the core to the cross-sectional area of ​​both ends of the energy absorbing structure at the core is mainly determined by the material strength of the energy absorbing structure at the core and the joint or other connecting component, and the connection strength between them. In principle, the yield load at the time of yielding of the joint or other connecting component should be greater than the yield load at the time of yielding of the energy absorbing structure at the core.

[0024] In the present invention, as shown in FIG. 2, increasing the ratio of the length L0 of the energy absorbing portion at the core of the steel plate having an austenitic structure to the length l0 of the energy absorbing portion at the core of the steel plate having a ferritic structure in the energy absorbing structure at the core contributes to the energy absorption by the axial steel damper under small and medium earthquakes.

[0025] The present invention further provides an axial steel damper for partially fusible two-stage energy absorption, comprising a partially fusible two-stage energy absorption structure at the core and a perimeter restraint component, wherein the partially fusible two-stage energy absorption structure at the core serves to absorb external vibration energy when the axial steel damper is subjected to cyclic alternating plastic deformations of tension and compression, and the perimeter restraint component restrains the lateral displacement of the energy absorption structure at the core, preventing the energy absorption structure at the core from buckling and becoming unstable.

[0026] In one embodiment of the present invention, the peripheral restraint component of the partially meltable two-stage axial steel damper for energy absorption is selected as a restraint casing formed by a combination of steel tube and internally filled concrete, or a reinforced concrete restraint casing, or a pure steel structural restraint member.

[0027] In one embodiment of the present invention, the partially meltable two-stage energy absorption axial steel damper is installed in a building or structure and connected to the main column-beam structure and joints of the building or structure to form a whole, and serves to absorb external vibration energy, thereby significantly improving the seismic performance of the building or structure.

[0028] In one embodiment of the present invention, the partially fusible axial steel damper for two-stage energy absorption can be connected and combined with other steel braces through flanges or intermediate connection plates to form an axial energy absorption brace, which meets the requirements of prefabricated buildings and rapid replacement after earthquakes. Therefore, the structural size of the axial steel damper according to the present invention is generally smaller than that of the conventional energy absorbing buckling restrained brace, and its self-weight is lighter. FIG. 3 is a schematic diagram of an axial energy absorption brace formed by combining a replaceable partially fusible axial steel damper for two-stage energy absorption with other steel braces, and a schematic diagram of its three-dimensional model is shown in FIG. 4. One end of the axial steel damper is connected with a building gusset plate through an intermediate connection plate and a spherical hinge, and the other end of the axial steel damper is connected with other steel braces through an intermediate connection plate or a flange to form an axial energy absorption brace.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) Compared with the conventional energy absorbing buckling restrained brace (the energy absorbing structure at the core is usually manufactured with LY225 or Q235 steel plate), the energy absorbing structure at the core of the axial steel damper for partially meltable two-stage energy absorption according to the present invention has a small yield displacement, excellent ductility and cumulative plastic deformation capacity, and can have the same fracture redundancy as the main structure of the building, and when the load of the axial damper reaches a certain level, the energy absorbing structure at the core of the damper will be partially melted, limiting the limit load of the damper. The conventional energy absorbing buckling restrained brace does not have the above technical features. 2) The axial steel damper according to the present invention can be connected and combined with other steel braces to form an axial energy absorbing brace, which meets the requirements of prefabricated buildings and rapid replacement after earthquakes. The structural size and self-weight of the axial steel damper according to the present invention can be smaller than those of traditional energy absorbing buckling restrained braces. 3) In the present invention, the steel plate having an austenitic structure constituting the energy absorbing structure at the core of the steel damper undergoes a reversible phase transformation between austenite and strain-induced ε martensite when alternately subjected to tensile and compressive plastic deformation, and therefore the steel plate having an austenitic structure has excellent fatigue deformation performance, and as a result, the steel damper can have a very high limit allowable displacement and the same fracture redundancy as the main structure of a building. In the case where the steel plate having an austenitic structure used in the energy absorbing structure in the core of the axial steel damper only undergoes dislocation plane slip deformation under cyclic loading, the mass percentages of the chemical components of the corresponding steel plate having an austenitic structure may be 0.4%≦C≦0.7%, 16.0%≦Mn≦26.0%, Si≦2.0%, P≦0.02%, S≦0.03%, N≦0.03%, with the balance being Fe and unavoidable impurity elements, and the ductility and cumulative plastic deformation capacity of the axial steel damper can be superior to that of conventional energy absorbing buckling restrained braces, but significantly lower than that of the partially fusible two-stage energy absorption axial steel damper of the present invention. [Brief description of the drawings]

[0030] [Figure 1] Figure 1 shows the cyclic stress-strain curves of a partially meltable two-stage energy absorption axial steel damper when it is subjected to alternating tensile and compressive deformations at the maximum allowable displacement before the energy absorption structure in the core is partially melted, and then when it is subjected to alternating tensile and compressive deformations at the same displacement after the energy absorption structure in the core is partially melted. [Diagram 2] FIG. 2 is a schematic diagram of the energy absorption structure in the core of the axial steel damper for partially fusible two-stage energy absorption. [Diagram 3] FIG. 3 is a schematic diagram of an axial energy absorbing brace formed by a combination of a partially fusible two-stage energy absorption axial steel damper and other steel braces. [Figure 4]Figure 4 is a schematic diagram of a three-dimensional model of an axial energy absorbing brace formed by combining a partially fusible axial steel damper with other steel braces for two-stage energy absorption. [Diagram 5] FIG. 5 shows the geometric shape of the steel plate having an austenitic structure constituting the energy absorbing structure at the core of the partially fusible two-stage axial steel damper for energy absorption in Example 1. [Figure 6] FIG. 6 shows the geometric shape of the steel plate having a ferritic structure constituting the energy absorbing structure in the core of the partially fusible two-stage axial steel damper for energy absorption in Example 1. [Figure 7] FIG. 7 is a front view of the energy absorption structure in the core of the axial steel damper for partially fusible two-stage energy absorption in the first embodiment. [Figure 8] FIG. 8 is a top view of the energy absorption structure in the core of the axial steel damper for partially fusible two-stage energy absorption in the first embodiment. [Figure 9] FIG. 9 is a side view of the energy absorption structure in the core of the axial steel damper for partially fusible two-stage energy absorption in the first embodiment. [Figure 10] FIG. 10 is a front view of a partially meltable two-stage axial steel damper for energy absorption in the first embodiment. [Figure 11] FIG. 11 is a top view of a partially fusible axial steel damper for two-stage energy absorption in accordance with a first embodiment. [Figure 12] FIG. 12 is a cross-sectional view taken along line AA of the partially meltable axial steel damper for two-stage energy absorption in the first embodiment. [Figure 13]Fig. 13 shows the cyclic stress-strain curves of the partially meltable two-stage energy absorbing axial steel damper in Example 1 when it is subjected to cyclic alternating tensile and compressive plastic deformation before being partially melted. The tensile (or compressive) displacements corresponding to the cyclic stress-strain curves of deformation are 3 mm, 9 mm, 17 mm, 25 mm, and 31 mm, respectively. At each displacement condition, three cycles of cyclic deformation are applied. [Figure 14] Fig. 14 shows the cyclic stress-strain curves of the partially meltable two-stage energy absorbing axial steel damper in Example 1 when it is partially melted and subjected to cyclic alternating tensile and compressive plastic deformations. The tensile (or compressive) displacements corresponding to the cyclic stress-strain curves of deformation are 34mm and 37mm, respectively. Three cycles of cyclic deformation are applied at each displacement condition. [Figure 15] Fig. 15 shows the cyclic stress-strain curves of the partially meltable two-stage energy absorbing axial steel damper in Example 1 when it is subjected to tensile and compressive plastic deformations alternately in cycles after being partially melted. The tensile (or compressive) displacements corresponding to the cyclic stress-strain curves of deformation are 41mm, 50mm, 56mm, 63mm and 67mm, respectively. At each displacement condition, three cycles of cyclic deformation are applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0032] Example 1 A partially fusible two-stage axial steel damper for energy absorption, consisting of an energy absorbing structure at the core and a perimeter restraint component.

[0033] The cross section of the energy absorbing structure at the core has a cross-shaped axially symmetric geometric shape with the axial direction of the steel damper as the axis of symmetry, narrow in the middle and wide at both ends along the axial direction. As shown in Fig. 2, the energy absorbing structure at the core is composed of one steel plate 2 having an austenitic structure and two steel plates 1 having a ferritic structure, the steel plate 2 having an austenitic structure and the steel plate 1 having a ferritic structure have the same length along the longitudinal direction, the two steel plates 1 having a ferritic structure are respectively arranged above and below the steel plate 2 having an austenitic structure with the longitudinal center line of the steel plate 2 having an austenitic structure as the axis of symmetry, and the two steel plates 1 having a ferritic structure and the steel plate 2 having an austenitic structure are connected without restraint.

[0034] The geometric shape of the steel plate with austenitic structure constituting the energy absorbing structure at the core is shown in Figure 5. The total length of the steel plate with austenitic structure is L = 2000 mm, the length of the central part of the steel plate (i.e., the energy absorbing part at the core) is L0 = 1530 mm, the width is W0 = 160 mm, and the thickness of the steel plate is T = 16 mm.

[0035] The chemical components and mass percentages of the steel plate having an austenitic structure are 29.4% Mn, 4.3% Si, 1.4% Al, 0.049% C, 0.009% P, 0.008% S, 0.005% N, and the balance is Fe and unavoidable impurity elements. The yield strength of the steel plate having an austenitic structure is 304 MPa and the elongation is 52%. The microstructure of the steel plate having an austenitic structure is a single austenitic structure, and when entering the yield stage, the metastable austenite undergoes ε-martensite phase transformation due to the action of strain, and when tensile and compressive loads are applied alternately, a reversible phase transformation between the metastable austenite and strain-induced ε-martensite occurs. The average grain size of austenite in the steel plate having an austenitic structure is 76 μm.

[0036] The geometric shape of the steel plate with ferritic structure constituting the energy absorbing structure at the core is shown in Figure 6. The total length of the steel plate with ferritic structure is l = 2000 mm, the length of the central part of the steel plate (i.e., the energy absorbing part at the core) is l0 = 1530 mm, the width is w0 / 2 = 80 mm, and the thickness of the steel plate is t = 16 mm.

[0037] The chemical components and mass percentages of the steel plate having a ferritic structure are 0.30% Mn, 0.05% Si, 0.015% C, 0.05% Ti, 0.012% P, 0.006% S, 0.006% N, with the balance being Fe and unavoidable impurity elements. The steel plate having a ferritic structure has a yield strength of 157 MPa and an elongation of 47%. The microstructure of the steel plate having a ferritic structure is mainly a ferritic structure. The average grain size of ferrite in the steel plate having a ferritic structure is 50 μm.

[0038] The length of the energy absorption portion in the core of the steel plate having an austenitic structure is the same as the length of the energy absorption portion in the core of the steel plate having a ferritic structure. The thickness of the steel plate having an austenitic structure is the same as the thickness of the steel plate having a ferritic structure. The ratio of the sum of the cross-sectional areas of the energy absorption portions in the cores of the two steel plates having a ferritic structure to the cross-sectional area of ​​the energy absorption portion in the core of the one steel plate having an austenitic structure is 1.0 (greater than 0.4).

[0039] The front, top and side views of the energy absorbing structure at the core are shown in Figures 7, 8 and 9, respectively.

[0040] The perimeter restraint component is a restraint casing formed by combining a perimeter restraint steel pipe 4 and an internally filled concrete 3, and serves to restrain the lateral displacement of the energy absorption structure at the core and prevent the buckling of the energy absorption structure at the core. In order to eliminate friction between the perimeter restraint component and the energy absorption structure at the core, a non-bonding material layer is provided between the perimeter restraint component and the energy absorption structure at the core.

[0041] After being assembled, the front view, top view, and cross-sectional view along plane AA of said partially fusible two-stage axial steel damper for energy absorption are shown in FIG. 10, FIG. 11, and FIG. 12, respectively.

[0042] The partially meltable two-stage energy absorbing axial steel damper is subjected to tensile and compressive plastic deformations alternately at displacements of 3mm, 5mm, 7mm, 9mm, 11mm, 17mm, 20mm, 23mm, 25mm, 28mm and 31mm, respectively, and under each displacement condition, three cycles of cyclic deformation are applied, the maximum load does not decrease, and the energy absorbing structure at the core of the axial steel damper is not partially melted. Figure 13 shows the corresponding cyclic stress-strain curves when the axial steel damper is subjected to tensile and compressive plastic deformations alternately at displacements of 3mm, 9mm, 17mm, 25mm and 31mm, respectively. When the displacement of the cyclic tensile and compressive plastic deformation is increased to 34mm, the single ferritic steel plate constituting the energy absorbing structure at the core experiences fatigue failure at the second cycle of cyclic deformation, where under the displacement condition of 34mm, the axial steel damper is subjected to a total of three cycles of cyclic deformation. When the displacement of the cyclic plastic deformation of tension and compression is increased to 37 mm, the second steel plate having a ferrite structure constituting the energy absorbing structure at the core also undergoes fatigue failure at the second cycle of the cyclic deformation, and the axial steel damper undergoes a total of three cycles of cyclic deformation under the displacement condition of 37 mm. It can be seen that the energy absorbing structure at the core of the steel damper partially melts at the displacements of 34 mm and 37 mm, respectively, and the load-bearing capacity of the axial steel damper decreases accordingly. Figure 14 shows the cyclic stress-strain curves of the partially meltable axial steel damper for two-stage energy absorption when it is subjected to cyclic and alternating plastic deformation of tension and compression when it is partially melted. The maximum allowable displacement of the energy absorbing structure at the core of the steel damper before it is partially melted needs to be 31 mm to 34 mm. The yield displacement of the axial steel damper obtained from the cyclic stress-strain curve for cyclic deformation with a displacement of 34 mm is approximately 3.0 mm (in fact, the yield displacement of the axial steel damper obtained from the cyclic stress-strain curve for cyclic deformation with a displacement of 31 mm is also very close to 3.0 mm).

[0043] After the energy absorbing structure in the core is partially melted, due to the excellent low cycle fatigue performance of the steel plate with austenitic structure, the axial steel damper continues to undergo cyclic alternating plastic deformation of tension and compression at displacements of 38mm, 41mm, 44mm, 47mm, 50mm, 53mm, 56mm, 59mm, 63mm and 67mm, respectively, and the maximum load does not decrease after three cycles of repeated deformation under each displacement condition, and the axial steel damper does not yet undergo fatigue failure. The above plastic deformation displacements are all greater than 1 / 60 of the length of the axial steel damper (about 33.3mm), that is, after the axial steel damper is partially melted, it can complete cyclic alternating plastic deformation of tension and compression for at least 30 cycles under the displacement condition of 1 / 60 of the length of the steel damper. Figure 15 shows the cyclic stress-strain curves of the axial steel damper when it is subjected to cyclic alternating tension and compression plastic deformations when the displacements are 41mm, 50mm, 56mm, 63mm, and 67mm, respectively. The ultimate allowable displacement of the axial steel damper is greater than 67mm (corresponding to 1 / 30 of the length of the axial steel damper). The calculated ratio of the ultimate allowable displacement to the yield displacement of the axial steel damper is greater than 22 (significantly greater than 18).

[0044] Therefore, the ratio of the limit allowable displacement and the yield displacement of the partially meltable axial steel damper for two-stage energy absorption according to the present embodiment is 18 or more, and the limit allowable displacement is greater than 1 / 50 of the length of the partially meltable axial steel damper, and under this limit allowable displacement condition, the partially meltable axial steel damper for two-stage energy absorption can be alternately subjected to tensile and compressive plastic deformation for at least 3 cycles, and the load-bearing capacity is reduced by less than 15%. After the energy absorbing structure at the core of the partially meltable axial steel damper for two-stage energy absorption is partially melted, under the displacement condition of 1 / 60 of the length of the partially meltable axial steel damper, the partially meltable axial steel damper for two-stage energy absorption can be alternately subjected to tensile and compressive plastic deformation for at least 30 cycles, and the load-bearing capacity is reduced by less than 15%. The partially meltable two-stage axial steel damper for energy absorption can play the role of absorbing energy and shock even in earthquakes of different intensity, and has the same fracture redundancy as the main structure of the building, thereby limiting the limit load of the steel damper and ensuring the reliability of the joints of the main structure of the building.

[0045] 3 and 4 are schematic diagrams of an axial energy absorbing brace formed by combining an axial steel damper and other steel braces in this embodiment. One end of the axial steel damper 5 is connected to a building gusset plate via an intermediate connection plate 6 and a spherical hinge 8, and the other end of the axial steel damper 5 is connected to another steel brace 7 via an intermediate connection plate 6 to form an axial energy absorbing brace.

[0046] Example 2 A partially fusible two-stage axial steel damper for energy absorption, consisting of an energy absorbing structure at the core and a perimeter restraint component.

[0047] The energy absorption structure in the core is composed of one steel plate having an austenitic structure and one steel plate having a ferritic structure, the steel plate having an austenitic structure and the steel plate having a ferritic structure have the same length in the longitudinal direction, the steel plate having the ferritic structure is arranged perpendicular to the steel plate having an austenitic structure, and the steel plate having the ferritic structure and the steel plate having an austenitic structure are connected without any constraint.

[0048] The geometric shape of the steel plate with austenitic structure constituting the energy absorbing structure at the core is shown in Figure 5. The total length of the steel plate with austenitic structure is L = 2000 mm, the length of the central part of the steel plate (i.e., the energy absorbing part at the core) is L0 = 1530 mm, the width is W0 = 80 mm, and the thickness of the steel plate is T = 14 mm.

[0049] The chemical components and mass percentages of the steel plate having an austenitic structure are 27.5% Mn, 4.0% Si, 0.6% Al, 0.002% C, 2.0% Ni, 0.7% Cu, 0.007% P, 0.006% S, 0.005% N, and the balance is Fe and unavoidable impurity elements. The yield strength of the steel plate having an austenitic structure is 229 MPa and the elongation is 58%. The microstructure of the steel plate having an austenitic structure is a single austenitic structure, and when entering the yield stage, the metastable austenite undergoes ε-martensite phase transformation due to the action of strain, and when tensile and compressive loads are applied alternately, a reversible phase transformation between the metastable austenite and strain-induced ε-martensite occurs. The average grain size of austenite in the steel plate having an austenitic structure is 126 μm.

[0050] The geometric shape of the steel plate with ferritic structure constituting the energy absorbing structure at the core is shown in Figure 6. The total length of the steel plate with ferritic structure is l = 2000 mm, the length of the central part of the steel plate (i.e., the energy absorbing part at the core) is l0 = 1000 mm, the width is w0 / 2 = 100 mm, and the thickness of the steel plate is t = 16 mm.

[0051] The chemical components and mass percentages of the steel plate having a ferritic structure are 0.18% Mn, 0.05% Si, 0.01% C, 0.04% Ti, 0.01% P, 0.006% S, 0.006% N, with the balance being Fe and unavoidable impurity elements. The steel plate having a ferritic structure has a yield strength of 122 MPa and an elongation of 50%. The microstructure of the steel plate having a ferritic structure is mainly a ferritic structure, and the average grain size of ferrite in the steel plate having a ferritic structure is 86 μm.

[0052] The length of the energy absorption portion in the core of the steel plate having an austenitic structure is greater than the length of the energy absorption portion in the core of the steel plate having a ferritic structure. The ratio of the cross-sectional area of ​​the energy absorption portion in the core of the steel plate having a ferritic structure to the cross-sectional area of ​​the energy absorption portion in the core of the steel plate having an austenitic structure is 1.43 (greater than 0.4).

[0053] The perimeter restraint component is a restraint casing formed by combining steel pipes and internally filled concrete, and a non-bonded material layer is provided between the perimeter restraint component and the energy absorbing structure at the core to eliminate friction between the perimeter restraint component and the energy absorbing structure at the core.

[0054] The partially meltable two-stage energy absorbing axial steel damper is subjected to three cycles of tensile and compressive plastic deformations at displacements of 5mm, 10mm, 25mm and 35mm, respectively, and then when the displacement of the tensile and compressive plastic deformations is increased to 38mm, the steel plate having a ferrite structure constituting the energy absorbing structure at the core will undergo fatigue failure at the third cycle of cyclic deformation, i.e., the energy absorbing structure at the core of the steel damper will be partially melted, and the load-bearing capacity of the axial steel damper will decrease accordingly. The yield displacement of the axial steel damper obtained from the cyclic stress-strain curve of the cyclic deformation at a displacement of 38mm is about 3.1mm. The yield displacement of the steel damper obtained from the cyclic stress-strain curve of the cyclic deformation at a displacement of 35mm is also about 3.1mm.

[0055] After the energy absorbing structure in the core is partially melted, the axial steel damper continues to undergo cyclic alternating plastic deformation of tension and compression with a displacement of 48 mm for 30 cycles, and the axial steel damper still does not experience fatigue failure and does not lose its load-bearing capacity. All of the above plastic deformation displacements are greater than 1 / 60 (about 33.3 mm) of the length of the axial steel damper. The axial steel damper also undergoes cyclic alternating plastic deformation of tension and compression with a displacement of 70 mm, and the steel damper breaks at the fourth cycle. Therefore, the limit allowable displacement of the axial steel damper is about 70 mm (the displacement of 70 mm corresponds to 1 / 29 of the length of the axial steel damper), and the calculated ratio of the limit allowable displacement to the yield displacement of the axial steel damper is about 22 (significantly larger than 18).

[0056] Therefore, the ratio of the limit allowable displacement and the yield displacement of the partially meltable axial steel damper for two-stage energy absorption described in this embodiment is 18 or more, and the limit allowable displacement is 1 / 50 or more of the length of the partially meltable axial steel damper for two-stage energy absorption, and after the energy absorption structure at the core of the partially meltable axial steel damper for two-stage energy absorption is partially melted, under the displacement condition of 1 / 60 of the length of the partially meltable axial steel damper, the partially meltable axial steel damper for two-stage energy absorption can be alternately subjected to tensile and compressive plastic deformation for at least 30 cycles, and the load-bearing capacity is reduced by less than 15%.

[0057] Example 3 A partially fusible two-stage axial steel damper for energy absorption, consisting of an energy absorbing structure at the core and a perimeter restraint component.

[0058] The cross section of the energy absorbing structure at the core has an axisymmetric geometric shape of a cross with the axial direction of the steel damper as an axis of symmetry, narrow in the middle and wide at both ends along the axial direction. The energy absorbing structure at the core is composed of one steel plate having an austenitic structure and two steel plates having a ferritic structure, the steel plate having an austenitic structure and the steel plate having a ferritic structure have the same length in the longitudinal direction, the two steel plates having a ferritic structure are respectively arranged above and below the steel plate having an austenitic structure with the longitudinal center line of the steel plate having an austenitic structure as the axis of symmetry, and the two steel plates having a ferritic structure and the steel plate having an austenitic structure are connected without being restrained.

[0059] The geometric shape of the steel plate with austenitic structure constituting the energy absorbing structure at the core is shown in Figure 5. The total length of the steel plate with austenitic structure is L = 2000 mm, the length of the central part of the steel plate (i.e., the energy absorbing part at the core) is L0 = 1530 mm, the width is W0 = 160 mm, and the thickness of the steel plate is T = 12 mm.

[0060] The chemical composition and mass percentage of the steel plate having an austenitic structure are 23.4% Mn, 5.4% Si, 2.3% Al, 0.04% C, 0.01% P, 0.008% S, 0.005% N, and the balance is Fe and unavoidable impurity elements. The yield strength of the steel plate having an austenitic structure is 284 MPa, and the elongation is 44%. The microstructure of the steel plate having an austenitic structure is a single austenitic structure, and when entering the yield stage, the metastable austenite undergoes ε-martensite phase transformation due to the action of strain, and when tensile and compressive loads are applied alternately, a reversible phase transformation between the metastable austenite and strain-induced ε-martensite occurs. The average grain size of austenite in the steel plate having an austenitic structure is 216 μm.

[0061] The geometric shape of the steel plate with ferritic structure constituting the energy absorbing structure at the core is shown in Figure 6. The total length of the steel plate with ferritic structure is l = 2000 mm, the length of the central part of the steel plate (i.e., the energy absorbing part at the core) is l0 = 1530 mm, the width is w0 / 2 = 80 mm, and the thickness of the steel plate is t = 12 mm.

[0062] The chemical components and mass percentages of the steel plate having a ferritic structure are 0.50% Mn, 0.3% Si, 0.095% C, 0.1% Ti, 0.06% Nb, 0.01% P, 0.006% S, 0.005% N, with the balance being Fe and unavoidable impurity elements. The steel plate having a ferritic structure has a yield strength of 175 MPa and an elongation of 31.5%. The microstructure of the steel plate having a ferritic structure is mainly a ferritic structure. The average grain size of ferrite in the steel plate having a ferritic structure is 192 μm.

[0063] The length of the energy absorption portion in the core of the steel plate having an austenitic structure is the same as the length of the energy absorption portion in the core of the steel plate having a ferritic structure. The thickness of the steel plate having an austenitic structure is the same as the thickness of the steel plate having a ferritic structure. The ratio of the sum of the cross-sectional areas of the energy absorption portions in the cores of the two steel plates having a ferritic structure to the cross-sectional area of ​​the energy absorption portion in the core of the one steel plate having an austenitic structure is 1.0 (greater than 0.4).

[0064] The perimeter restraint component is a restraint casing formed by combining steel pipes and internally filled concrete, and a non-bonded material layer is provided between the perimeter restraint component and the energy absorbing structure at the core to eliminate friction between the perimeter restraint component and the energy absorbing structure at the core.

[0065] The partially meltable two-stage energy absorbing axial steel damper is subjected to tensile and compressive plastic deformations alternately at displacements of 3mm, 9mm, 15mm, 18mm and 22mm, respectively, and is subjected to three cycles of repeated deformation under each displacement condition, and the maximum load does not decrease, and the energy absorbing structure at the core of the axial steel damper does not melt partially. When the displacement of the repeated plastic deformation of tension and compression is increased to 26mm, the first and second ferritic steel plates constituting the energy absorbing structure at the core sequentially undergo fatigue failure at the third and fourth cycles of repeated deformation, that is, the energy absorbing structure at the core of the steel damper is partially melted at a displacement of 26mm. The yield displacement of the axial steel damper obtained from the repeated stress-strain curve of the repeated deformation at a displacement of 26mm is about 3.0mm.

[0066] After the energy absorbing structure in the core is partially melted, the axial steel damper continues to undergo cyclic alternating plastic deformation of tension and compression for 30 cycles with a displacement of 38 mm, and the axial steel damper still does not experience fatigue failure and does not lose its load-bearing capacity. All of the above plastic deformation displacements are greater than 1 / 60 (about 33.3 mm) of the length of the axial steel damper. The axial steel damper also undergoes cyclic alternating plastic deformation of tension and compression with a displacement of 58 mm, and the steel damper breaks at the sixth cycle. Therefore, the limit allowable displacement of the axial steel damper is greater than 58 mm (corresponding to 1 / 35 of the length of the axial steel damper), and the calculated ratio of the limit allowable displacement to the yield displacement of the axial steel damper is greater than about 19.

[0067] Therefore, the ratio of the limit allowable displacement to the yield displacement of the partially meltable axial steel damper for two-stage energy absorption described in this embodiment is 18 or more, and the limit allowable displacement is 1 / 50 or more of the length of the partially meltable axial steel damper for two-stage energy absorption, and under the limit allowable displacement condition, the partially meltable axial steel damper for two-stage energy absorption can be alternately subjected to tensile and compressive plastic deformation for at least 3 cycles, and the load-bearing capacity is reduced by less than 15%. After the energy absorbing structure at the core of the partially meltable axial steel damper for two-stage energy absorption is partially melted, under the displacement condition of 1 / 60 of the length of the partially meltable axial steel damper for two-stage energy absorption, the partially meltable axial steel damper for two-stage energy absorption can be alternately subjected to tensile and compressive plastic deformation for at least 30 cycles, and the load-bearing capacity is reduced by less than 15%.

[0068] (Examples 4 to 6) A partially fusible two-stage axial steel damper for energy absorption, consisting of an energy absorbing structure at the core and a perimeter restraint component.

[0069] The cross section of the energy absorbing structure at the core has an axisymmetric geometric shape of a cross with the axial direction of the steel damper as an axis of symmetry, narrow in the middle and wide at both ends along the axial direction. The energy absorbing structure at the core is composed of one steel plate having an austenitic structure and two steel plates having a ferritic structure, the steel plate having an austenitic structure and the steel plate having a ferritic structure have the same length in the longitudinal direction, the two steel plates having a ferritic structure are respectively arranged above and below the steel plate having an austenitic structure with the longitudinal center line of the steel plate having an austenitic structure as the axis of symmetry, and the two steel plates having a ferritic structure and the steel plate having an austenitic structure are connected without being restrained.

[0070] The geometric shape of the steel plate with austenitic structure constituting the energy absorbing structure at the core is shown in Figure 5. The total length of the steel plate with austenitic structure is L = 2000 mm, the length of the central part of the steel plate (i.e., the energy absorbing part at the core) is L0 = 1530 mm, the width is W0 = 160 mm, and the thickness of the steel plate is T = 16 mm.

[0071] The geometric shape of the steel plate with ferritic structure constituting the energy absorbing structure at the core is shown in Figure 6. The total length of the steel plate with ferritic structure is l = 2000 mm, the length of the central part of the steel plate (i.e., the energy absorbing part at the core) is l0 = 1530 mm, the width is w0 / 2 = 80 mm, and the thickness of the steel plate is t = 16 mm.

[0072] The length of the energy absorption portion in the core of the steel plate having an austenitic structure is the same as the length of the energy absorption portion in the core of the steel plate having a ferritic structure. The thickness of the steel plate having an austenitic structure is the same as the thickness of the steel plate having a ferritic structure. The ratio of the sum of the cross-sectional areas of the energy absorption portions in the cores of the two steel plates having a ferritic structure to the cross-sectional area of ​​the energy absorption portion in the core of the one steel plate having an austenitic structure is 1.0 (greater than 0.4).

[0073] The main chemical components (steel inevitably contains traces of P, S, N and other impurity elements) and mechanical properties of the steel plate having the austenitic structure are shown in Table 1. The microstructure of the steel plate having the austenitic structure is a single austenitic structure. When entering the yield stage, metastable austenite undergoes ε-martensite phase transformation due to the action of strain, and when tensile and compressive loads are applied alternately, a reversible phase transformation between metastable austenite and strain-induced ε-martensite occurs. The average grain size of austenite in the steel plate having the austenitic structure is shown in Table 1.

[0074] The main chemical components (steel inevitably contains trace amounts of P, S, N and other impurity elements) and mechanical properties of the steel plate having the ferritic structure are shown in Table 1. The microstructure of the steel plate having the ferritic structure is mainly a ferritic structure. The average grain size of ferrite in the steel plate having the ferritic structure is shown in Table 1. [Table 1]

[0075] The perimeter restraint component is a restraint casing formed by combining steel pipes and internally filled concrete, and a non-bonded material layer is provided between the perimeter restraint component and the energy absorbing structure at the core to eliminate friction between the perimeter restraint component and the energy absorbing structure at the core.

[0076] The partially meltable two-stage energy absorbing axial steel damper is partially melted when it is subjected to cyclically alternating plastic deformations of tension and compression. Before the axial steel damper is partially melted, the axial load-bearing capacity of the steel damper is not reduced during repeated deformation. While the axial steel damper is partially melted, the load-bearing capacity of the damper is reduced. After the axial steel damper is partially melted, the steel damper is continuously subjected to 30 cycles of repeated plastic deformations of tension and compression at a displacement of 35 mm, and fatigue failure does not occur, the load-bearing capacity of the steel damper is not reduced, and the steel damper is continuously subjected to repeated plastic deformation to obtain the ultimate allowable displacement of the steel damper. The yield displacement, ultimate allowable displacement, and the ratio of the ultimate allowable displacement to the yield displacement of the axial steel damper are shown in Table 2. [Table 2]

[0077] From Table 2, it can be seen that the ratio of the limit allowable displacement to the yield displacement of the partially meltable axial steel damper for two-stage energy absorption described in Examples 4 to 6 is 18 or more, and the limit allowable displacement is 1 / 50 or more of the length of the partially meltable axial steel damper for two-stage energy absorption. Under this limit allowable displacement condition, the partially meltable axial steel damper for two-stage energy absorption can be subjected to tensile and compressive plastic deformations alternately for at least 3 cycles, and the load-bearing capacity is reduced by less than 15%. After the energy absorption structure in the core of the partially meltable axial steel damper for two-stage energy absorption is partially melted, under the displacement condition of 1 / 60 of the length of the partially meltable axial steel damper for two-stage energy absorption, the partially meltable axial steel damper for two-stage energy absorption can be subjected to tensile and compressive plastic deformations alternately for at least 30 cycles, and the load-bearing capacity is reduced by less than 15%.

[0078] Example 7 A partially fusible two-stage axial steel damper for energy absorption, consisting of an energy absorbing structure at the core and a perimeter restraint component.

[0079] The energy absorption structure in the core is composed of one steel plate having an austenitic structure and one steel plate having a ferritic structure, the steel plate having an austenitic structure and the steel plate having a ferritic structure have the same length in the longitudinal direction, the steel plate having the ferritic structure is arranged perpendicular to the steel plate having an austenitic structure, and the steel plate having the ferritic structure and the steel plate having an austenitic structure are connected without any constraint.

[0080] The geometric shape of the steel plate with austenitic structure constituting the energy absorbing structure at the core is shown in Figure 5. The total length of the steel plate with austenitic structure is L = 2000 mm, the length of the central part of the steel plate (i.e., the energy absorbing part at the core) is L0 = 1530 mm, the width is W0 = 100 mm, and the thickness of the steel plate is T = 14 mm.

[0081] The chemical components and mass percentages of the steel plate having an austenitic structure are 27.5% Mn, 4.0% Si, 0.6% Al, 0.002% C, 2.0% Ni, 0.7% Cu, 0.007% P, 0.006% S, 0.005% N, and the balance is Fe and unavoidable impurity elements. The yield strength of the steel plate having an austenitic structure is 229 MPa, and the elongation is 58%. The microstructure of the steel plate having an austenitic structure is a single austenitic structure, and when entering the yield stage, the metastable austenite undergoes ε-martensite phase transformation under the action of strain, and α′-martensite phase transformation is suppressed, and when tension and compression loads are applied alternately, a reversible phase transformation between metastable austenite and strain-induced ε-martensite occurs. The average grain size of austenite in the steel plate having an austenitic structure is 126 μm.

[0082] The geometric shape of the steel plate with ferritic structure constituting the energy absorbing structure at the core is shown in Fig. 6. The total length of the steel plate with ferritic structure is L = 2000 mm, the length of the central part of the steel plate (i.e., the energy absorbing part at the core) is L0 = 1530 mm, the width is W0 / 2 = 42 mm, and the thickness of the steel plate is T = 16 mm.

[0083] The chemical components and mass percentages of the steel plate having a ferritic structure are 0.18% Mn, 0.05% Si, 0.01% C, 0.04% Ti, 0.01% P, 0.006% S, 0.006% N, with the balance being Fe and unavoidable impurity elements. The steel plate having a ferritic structure has a yield strength of 122 MPa and an elongation of 50%. The microstructure of the steel plate having a ferritic structure is mainly a ferritic structure. The average grain size of ferrite in the steel plate having a ferritic structure is 86 μm.

[0084] The length of the energy absorption portion in the core of the steel plate having an austenitic structure is greater than the length of the energy absorption portion in the core of the steel plate having a ferritic structure. The ratio of the cross-sectional area of ​​the energy absorption portion in the core of the steel plate having a ferritic structure to the cross-sectional area of ​​the energy absorption portion in the core of the steel plate having an austenitic structure is 0.48 (greater than 0.4).

[0085] The perimeter restraint component is a restraint casing formed by combining steel pipes and internally filled concrete, and a non-bonded material layer is provided between the perimeter restraint component and the energy absorbing structure at the core to eliminate friction between the perimeter restraint component and the energy absorbing structure at the core.

[0086] The partially meltable two-stage energy absorption steel axial damper is subjected to cyclical alternating plastic deformation of tension and compression for three cycles at a displacement of 30 mm, and also to alternating plastic deformation of tension and compression at a displacement of 38 mm, and the steel plate having a ferrite structure that constitutes the energy absorption structure at the core experiences fatigue failure at the fourth cycle of repeated deformation at a displacement of 38 mm, i.e., the energy absorption structure at the core of the steel damper is partially melted. The yield displacement of the steel axial damper obtained from the repeated stress-strain curve of the repeated deformation at a displacement of 38 mm is about 4.1 mm.

[0087] After the energy absorbing structure in the core is partially melted, the axial steel damper continues to be subjected to cyclically alternating tensile and compressive plastic deformation for 30 cycles at a displacement of 38 mm, and the axial steel damper still does not experience fatigue failure and does not lose its load-bearing capacity. The above plastic deformation displacements are all greater than 1 / 60 (about 33.3 mm) of the length of the axial steel damper. The axial steel damper also undergoes cyclically alternating tensile and compressive plastic deformation for 3 cycles at a displacement of 75 mm, and just fails. Therefore, the limit allowable displacement of the axial steel damper is 75 mm (the displacement of 75 mm corresponds to 1 / 27 of the length of the axial steel damper), and the calculated ratio between the limit allowable displacement and the yield displacement of the axial steel damper is 18.2.

[0088] Therefore, the ratio of the limit allowable displacement and the initial yield displacement of the partially meltable axial steel damper for two-stage energy absorption described in this embodiment is 18 or more, the limit allowable displacement is 1 / 50 or more of the length of the partially meltable axial steel damper for two-stage energy absorption, and after the energy absorption structure at the core of the partially meltable axial steel damper for two-stage energy absorption is partially melted, under the condition of a displacement of 1 / 60 of the length of the partially meltable axial steel damper, the partially meltable axial steel damper for two-stage energy absorption can be alternately subjected to tensile and compressive plastic deformation for at least 30 cycles, and the reduction in load-bearing capacity is less than 15%.

[0089] Comparative Example 1 A partially fusible two-stage axial steel damper for energy absorption, consisting of an energy absorbing structure at the core and a perimeter restraint component.

[0090] The energy absorption structure in the core is composed of one steel plate having an austenitic structure and one steel plate having a ferritic structure, the steel plate having an austenitic structure and the steel plate having a ferritic structure have the same length in the longitudinal direction, the steel plate having the ferritic structure is arranged perpendicular to the steel plate having an austenitic structure, and the steel plate having the ferritic structure and the steel plate having an austenitic structure are connected without any constraint.

[0091] The geometric shape of the steel plate with austenitic structure constituting the energy absorbing structure at the core is shown in Figure 5. The total length of the steel plate with austenitic structure is L = 2000 mm, the length of the central part of the steel plate (i.e., the energy absorbing part at the core) is L0 = 1530 mm, the width is W0 = 100 mm, and the thickness of the steel plate is T = 14 mm.

[0092] The chemical components and mass percentages of the steel plate having an austenitic structure are 27.5% Mn, 4.0% Si, 0.6% Al, 0.002% C, 2.0% Ni, 0.7% Cu, 0.007% P, 0.006% S, 0.005% N, with the balance being Fe and unavoidable impurity elements. The steel plate having an austenitic structure has a yield strength of 229 MPa and an elongation of 58%. The average grain size of austenite in the steel plate having an austenitic structure is 126 μm.

[0093] The geometric shape of the steel plate with ferritic structure constituting the energy absorbing structure at the core is shown in Figure 6. The total length of the steel plate with ferritic structure is l = 2000 mm, the length of the central part of the steel plate (i.e., the energy absorbing part at the core) is l0 = 1530 mm, the width is w0 / 2 = 34 mm, and the thickness of the steel plate is t = 16 mm.

[0094] The chemical components and mass percentages of the steel plate having a ferritic structure are 0.18% Mn, 0.05% Si, 0.01% C, 0.04% Ti, 0.01% P, 0.006% S, 0.006% N, with the balance being Fe and unavoidable impurity elements. The steel plate having a ferritic structure has a yield strength of 122 MPa and an elongation of 50%. The microstructure of the steel plate having a ferritic structure is mainly a ferritic structure. The average grain size of ferrite in the steel plate having a ferritic structure is 86 μm.

[0095] The length of the energy absorption portion in the core of the steel plate having an austenitic structure is the same as the length of the energy absorption portion in the core of the steel plate having a ferritic structure. The ratio of the cross-sectional area of ​​the energy absorption portion in the core of the steel plate having a ferritic structure to the cross-sectional area of ​​the energy absorption portion in the core of the steel plate having an austenitic structure is 0.389 (less than 0.4).

[0096] The perimeter restraint component is a restraint casing formed by combining steel pipes and internally filled concrete, and a non-bonded material layer is provided between the perimeter restraint component and the energy absorbing structure at the core to eliminate friction between the perimeter restraint component and the energy absorbing structure at the core.

[0097] The partially meltable two-stage energy absorption steel axial damper is subjected to cyclical alternating plastic deformation of tension and compression for three cycles at a displacement of 30 mm, and also to alternating plastic deformation of tension and compression at a displacement of 38 mm, and the steel plate having a ferrite structure that constitutes the energy absorption structure at the core experiences fatigue failure at the sixth cycle of repeated deformation at a displacement of 38 mm, i.e., the energy absorption structure at the core of the steel damper is partially melted. The yield displacement of the steel axial damper obtained from the repeated stress-strain curve of the repeated deformation at a displacement of 38 mm is about 4.5 mm.

[0098] After the energy absorbing structure in the core is partially melted, the axial steel damper continues to be subjected to cyclically alternating tensile and compressive plastic deformations for 30 cycles at a displacement of 38 mm, and the axial steel damper still does not experience fatigue failure and does not lose its load-bearing capacity. The axial steel damper also undergoes cyclically alternating tensile and compressive plastic deformations at a displacement of 75 mm, and fails at the 3.5th cycle. Thus, the limit allowable displacement of the axial steel damper is about 75 mm. The calculated ratio of the limit allowable displacement to the yield displacement of the axial steel damper is about 16.7. Thus, the ratio of the limit allowable displacement to the yield displacement of the axial steel damper for partially melted two-stage energy absorption described in this comparative example is less than 18.

[0099] The above description of the embodiments is intended to enable those skilled in the art to understand and use the present invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without any creative ingenuity. Therefore, the present invention is not limited to the above embodiments, and 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 present invention shall be within the protection scope of the present invention. [Explanation of symbols]

[0100] 1. Steel plate having a ferrite structure; 2. Steel plate having an austenitic structure; 3. Concrete, 4. Periphery restraint steel pipe; 5, Axial steel damper, 6. Intermediate connection plate; 7. Steel braces, 8. Spherical hinge.

Claims

1. A two-stage energy absorbing structure for an axial steel damper, which can be partially melted at the core, to absorb external vibration energy when the axial steel damper is subjected to cyclic alternating plastic deformations of tension and compression, comprising: The partially meltable two-stage energy absorption structure at the core includes at least one steel plate having an austenitic structure and one steel plate having a ferritic structure, and the steel plate having the ferritic structure and the steel plate having the austenitic structure are connected without being restrained, the microstructural structure of the steel sheet having an austenitic structure is composed of metastable austenite and thermally induced ε martensite having a volume fraction of 15% or less, the average grain size of the metastable austenite is 400 μm or less, during tensile or compressive plastic deformation, the metastable austenite of the steel sheet having an austenitic structure induces ε martensite phase transformation by the action of strain and inhibits α' martensite phase transformation, and when the steel sheet is subjected to cyclic and alternating tensile and compressive plastic deformation, a reversible phase transformation between austenite and strain-induced ε martensite occurs inside the steel sheet having an austenitic structure, The microstructure of the steel sheet having a ferritic structure is mainly ferrite, and the average grain size of the ferrite is 200 μm or less; The steel plate having an austenitic structure has a yield strength of 220 MPa or more and an elongation rate of 40% or more, and the steel plate having a ferritic structure has a yield strength of less than 180 MPa and an elongation rate of 30% or more, A two-stage energy absorption structure capable of partially melting at a core, characterized in that a ratio of a sum of cross-sectional areas of energy absorption parts at the core of all steel plates having a ferritic structure to a sum of cross-sectional areas of energy absorption parts at the core of all steel plates having an austenitic structure is 0.4 or more.

2. 2. The two-stage energy absorption structure capable of partially blowing at a core according to claim 1, wherein, when the geometric shape of a cross section of the steel plate having a ferritic structure or the steel plate having an austenitic structure does not change along the longitudinal direction, the energy absorption portion at the core of the steel plate having a ferritic structure or the steel plate having an austenitic structure is the entire length of the steel plate having a ferritic structure or the steel plate having an austenitic structure, and when the geometric shape of a cross section of the steel plate having a ferritic structure or the steel plate having an austenitic structure is characterized in that both ends are wide and the center is narrow along the longitudinal direction, the energy absorption portion at the core of the steel plate having a ferritic structure or the steel plate having an austenitic structure is the narrow portion in the center of the steel plate having a ferritic structure or the steel plate having an austenitic structure.

3. The partially fusible two-stage energy absorption structure at the core according to claim 1, characterized in that the mass percentages of the chemical components of the steel plate having an austenitic structure are C≦0.15%, 20.0%≦Mn≦34.0%, 3.5%≦Si≦6.0%, Al≦2.5%, Ni≦5.0%, Cu≦2.0%, P≦0.03%, S≦0.03%, N≦0.02%, and the balance is Fe and unavoidable impurity elements, where the mass contents of Al, Ni and Cu satisfy Ni / Cu≧0.25 and Al+0.4Ni+0.25Cu≦3.5%.

4. The two-stage energy absorption structure capable of partially fusing at the core according to claim 1, characterized in that the mass percentages of the chemical components of the steel plate having a ferritic structure are C≦0.1%, Mn≦1.0%, Si≦0.8%, Ti≦0.15%, Nb≦0.1%, V≦0.2%, P≦0.03%, S≦0.03%, N≦0.02%, and the balance being Fe and unavoidable impurity elements.

5. 2. The partially fusible dual stage energy absorbing structure at the core according to claim 1, wherein a cross section of the energy absorbing structure at the core is selected as an axisymmetric geometric shape.

6. The two-stage energy absorption structure capable of being partially melted at the core according to claim 1, characterized in that the length l0 of the energy absorption portion at the core of the steel plate having a ferritic structure constituting the energy absorption structure at the core is less than or equal to the length L0 of the energy absorption portion at the core of the steel plate having an austenitic structure.

7. 7. A partially fusible two-stage axial steel damper for energy absorption, comprising a partially fusible two-stage energy absorption structure at the core according to any one of claims 1 to 6 and a perimeter restraint component, the perimeter restraint component restraining lateral displacement of the energy absorption structure at the core and preventing the energy absorption structure at the core from buckling and becoming unstable.

8. The partially meltable axial steel damper for two-stage energy absorption as claimed in claim 7, characterized in that the perimeter restraint component is selected as a restraint casing formed by a combination of steel tube and internally filled concrete, or a reinforced concrete restraint casing, or a pure steel structural restraint member.

9. The ratio of the limit allowable displacement to the yield displacement of the partially meltable two-stage energy absorption axial steel damper is 18 or more, and the limit allowable displacement is 1 / 50 or more of the length of the partially meltable two-stage energy absorption axial steel damper; Under the condition of the limit allowable displacement, the partially meltable two-stage energy absorbing axial steel damper can be subjected to at least three cycles of alternating tensile and compressive plastic deformations, and the load carrying capacity is reduced by less than 15%; The partially meltable axial steel damper for two-stage energy absorption as claimed in claim 7, characterized in that after the energy absorption structure at the core of the partially meltable axial steel damper for two-stage energy absorption is partially melted, under a displacement condition of 1 / 60 of the length of the partially meltable axial steel damper for two-stage energy absorption, the partially meltable axial steel damper for two-stage energy absorption can be subjected to alternating tensile and compressive plastic deformation for at least 30 cycles, and the reduction in load-bearing capacity is less than 15%.

10. The partially meltable two-stage energy absorption axial steel damper according to claim 7, characterized in that the partially meltable two-stage energy absorption axial steel damper is used alone or in combination with other steel braces to form an axial energy absorption brace, which is installed in a building or structure and connected to the main column-beam structure of the building or structure to form a whole, thereby absorbing external vibration energy.

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