Two-stage seismic design method for replaceable energy-dissipating steel frame nodes

Abstract

The two-stage seismic design method of replaceable energy-absorbing steel frame nodes provided by the present invention comprises: determining the elastic bending moment distribution of the frame beam under the vertical load based on the traditional beam-column rigid connection steel frame structure model, determining the preliminary position of the replaceable energy-absorbing node; determining the yield bending moment M ... y and the ultimate bearing capacity of the anti-buckling brace, so as to design the connection section and length of the anti-buckling brace; determine the deformation demand of the replaceable energy-absorbing node, and determine the lower limit of the yield section length of the anti-buckling brace based on the node deformation demand; determine the elastic axial stiffness demand of the anti-buckling brace; determine the moment-rotation constitutive relationship of the replaceable energy-absorbing node based on the yield axial force, elastic stiffness and post-yield stiffness of the anti-buckling brace, which can solve the problems of unclear rotation stiffness of the replaceable energy-absorbing node due to weakened stiffness and the difficulty in analyzing the internal force of the structure caused by it, and can perform seismic design of the replaceable steel frame node based on the flange rotation mechanism on the beam.

Description

Technical Field

[0001] The invention relates to the field of earthquake resistance of building structures, and in particular to a two-stage earthquake resistance design method of replaceable energy-absorbing steel frame nodes based on a beam flange rotation mechanism. Background Art

[0002] Steel structures have been widely used at home and abroad due to their advantages such as light weight, high strength, assembly and greenness. They are also an important direction for the vigorous development of my country's building industrialization. Steel frame structure is one of the most basic seismic steel structure systems, but previous earthquake damage has shown that steel frame beam-column nodes are prone to brittle fracture due to welding heat effects and stress concentration, and the plastic damage at the ends of the beams produced in earthquakes also brings difficulties to the post-earthquake repair of the structure. How to build seismic toughness structures with good seismic performance and post-earthquake recoverability has become an important part of seismic toughness city construction. Among them, the advent of replaceable steel frame nodes provides the possibility of realizing the rapid recovery of structural post-earthquake functions. It forms replaceable energy-absorbing nodes by setting replaceable energy-absorbing components at the interface of beams and columns or on steel beams, converting the interlayer deformation of the structure into the angular deformation of the node, and then converting the angular deformation into linear displacement, thereby driving the deformation of the energy-absorbing components and dissipating the seismic energy. After the earthquake, the energy-absorbing components can be replaced according to the needs of repair, while the main structure of the beams and columns remains elastic and continues to be used, while taking into account the dual goals of the seismic performance of the structure during earthquakes and the recoverability of the structure after earthquakes.

[0003] Regarding the deformation mechanism of the node, there are currently two main deformation modes: the centroid of the beam section is the rotation center and the upper flange of the beam is the rotation center (respectively as Figure 1 , Figure 2 ). For example, the "post-earthquake replaceable upper end suspended steel frame energy-absorbing beam-column node" disclosed by Zhao Junxian et al. in the Chinese authorized invention patent CN106320517B takes the upper flange of the beam as the rotation center, and this node has the following advantages:

[0004] 1) The upward movement of the beam rotation center can be achieved at the same relative beam rotation angle (such as Figure 1 , 2 θ G ) Amplify the deformation requirements of replaceable energy-consuming components (such as Figure 1 , 2 Δ2=2Δ1), thereby increasing the bending stiffness and energy dissipation capacity of the node;

[0005] 2) The upward movement of the beam rotation center can effectively release the rotation constraint of the beam top floor slab on the node and reduce the floor slab cracking caused by the node rotation, which is beneficial to improve the symmetry and stability of the node energy consumption curve and the post-earthquake repairability of the floor slab;

[0006] 3) The node opening and closing deformation caused by the centroid rotation mechanism of the beam section exists at both the top and bottom of the beam. The top of the beam is not convenient for installing replaceable energy-absorbing components due to the existence of the floor slab, and the feasibility of replacing the components after the earthquake is also limited by the obstruction of the floor slab. On the contrary, the flange rotation mechanism on the beam can transfer the node opening and closing deformation to the bottom of the beam. Since there is no obstruction of the floor slab at this position, it is convenient for the arrangement and replacement of replaceable energy-absorbing components after the earthquake.

[0007] In the selection of replaceable energy-absorbing components, miniaturized metal, friction, viscosity, viscoelastic and other dampers can be used. Among them, since the material properties of metal dampers are stable and the mechanical properties are easy to predict, they are the main development direction of replaceable energy-absorbing components in the future. In terms of energy dissipation principles, metal damping replaceable energy-absorbing components can adopt energy dissipation mechanisms such as tensile-compression yielding, bending yielding, and shear yielding. Among them, the tensile-compression yielding form has the advantages of simple mechanical model, large axial stiffness, and sufficient energy dissipation capacity. It can maximize the seismic performance of replaceable energy-absorbing components. Therefore, tensile-compression yielding metal dampers will have a wide range of application scenarios in future recoverable functional structures.

[0008] At present, the seismic design of buildings in my country adopts a two-stage design method, that is, in the frequent earthquake stage (referred to as small earthquakes), the elastic internal force analysis of the structure is carried out and the bearing capacity design of the components is carried out in the elastic stage; in the rare earthquake stage (referred to as large earthquakes), the elastic-plastic analysis of the structure is carried out and the inter-story deformation of each floor is checked. For the replaceable steel frame node based on the flange rotation mechanism on the beam, due to the changes in the node deformation mechanism, internal force transmission mode, energy dissipation mechanism, and recoverable mechanism, the design process of this new type of node does not match the current seismic design method in my country. There are prominent problems such as weakened node stiffness, unclear node rotation stiffness and constitutive model, and coupling of the vertical internal force of the node with the seismic internal force, which are difficult to solve, seriously hindering the engineering application of this new type of structure. Therefore, it is necessary to propose a two-stage seismic design method for replaceable energy-dissipating steel frame nodes that is consistent with the existing seismic design ideas in my country, aiming at the unique working mechanism of this type of node, so as to contribute to improving the seismic toughness of single buildings and realizing seismic tough cities as soon as possible. Summary of the invention

[0009] In order to solve the problems existing in the prior art, the present invention proposes a two-stage seismic design method for replaceable energy-absorbing steel frame nodes with the upper flange of the beam as the rotation center.

[0010] In order to achieve the purpose of the present invention, the present invention provides a two-stage seismic design method for replaceable energy-absorbing steel frame nodes, comprising the following steps:

[0011] Step 1: Determine the moment distribution of the frame beam under the vertical load, determine the preliminary position of the replaceable energy-absorbing node based on the moment zero point of the steel frame beam under the vertical load, and allow the position with a preset offset α to the adjacent column side based on the preliminary position as the actual position of the replaceable energy-absorbing node;

[0012] Step 2: Determine the yield moment M of the replaceable energy dissipation node y , and the ultimate bearing capacity of the buckling-restrained brace, and use this to design the connection section and length of the buckling-restrained brace;

[0013] Step 3: Assuming that each section of the beam and column is a rigid body, according to the structural geometric characteristics of the replaceable energy-absorbing steel frame node, determine the relationship between the structural deformation, node rotation angle, and buckling-restrained brace deformation, determine the deformation demand of the replaceable energy-absorbing node, and determine the lower limit of the yield section length of the buckling-restrained brace based on the node deformation demand;

[0014] Step 4: Establish basic assumptions and analysis methods for calculating the stiffness requirements of replaceable energy-absorbing nodes, and determine the elastic axial stiffness requirements of the anti-buckling brace based on the basic assumptions and analysis methods, where the elastic axial stiffness requirements of the anti-buckling brace are:

[0015]

[0016]

[0017]

[0018]

[0019] Among them, K req is the elastic axial stiffness requirement of the buckling-resistance brace, E is the elastic modulus of the steel, and A is ave is the equivalent cross-sectional area of ​​the buckling-resisting brace, l B is the equivalent length of the buckling-resisting brace, I b is the section inertia moment of the cantilever beam section and the middle beam section, l2 is the horizontal distance from the center of the buckling-resistance brace connection section near the column side to the adjacent side joint, l3 is the horizontal distance from the center of the buckling-resistance brace connection section far from the column side to the adjacent side joint, l4 is the horizontal distance from the center of the buckling-resistance brace connection section far from the column side to the center of the beam, h1 is the vertical distance from the centroid of the shear connection to the beam axis, h2 is the vertical distance from the buckling-resistance brace axis to the beam axis, d is the joint gap between adjacent beam sections at the replaceable energy dissipation node, K B，E is the calculated value of the elastic axial stiffness of the buckling-restrained brace, K Be K is the axial stiffness of the buckling-resistance brace connection section, By，E is the elastic axial stiffness of the yield section of the buckling-resistance brace, β = 0.95 ~ 1.05 is the axial stiffness demand adjustment coefficient, lBe is the effective length of the buckling-resistance brace connection section, l By is the length of the yield section of the buckling-resistance brace, A Be is the cross-sectional area of ​​the buckling-resistance brace connection section, A By is the cross-sectional area of ​​the yielding section of the buckling-resistance brace.

[0020] Step 5: Design the shear connection according to the shear and axial force requirements;

[0021] Step 6: Perform earthquake damage control calculation on the beam ends;

[0022] Step 7: Determine the moment-rotation constitutive relationship of the replaceable energy dissipation node based on the yield axial force, elastic stiffness and post-yield stiffness of the buckling-restrained support.

[0023] Furthermore, the value of the preset offset α in step 1 does not exceed 20% of the initial position.

[0024] Furthermore, in step 1, when the preset offset is α, it satisfies:

[0025] d off = l a0 -l ac

[0026] d off ≤αl a0

[0027] Where, d off is the allowable offset of the layout position of the replaceable energy consumption node, l a0 is the distance from the zero point of the bending moment of the frame beam of the traditional beam-column rigid connection structure to the column axis under vertical load, l ac It is the distance from the actual layout position of the replaceable energy-consuming node to the column axis.

[0028] Furthermore, step 2 specifically includes the following sub-steps:

[0029] Establish a structural model, and apply vertical load and horizontal seismic load to the structural model;

[0030] The elastic internal force analysis of the structure under the combined action of vertical and horizontal loads in the small earthquake stage is carried out, and the yield moment M of the node is determined based on the bending moment design value M0 of the actual arrangement position of the replaceable energy dissipation node under the action of small earthquake. y And the cross-sectional area of ​​the yield section of the buckling-restrained brace:

[0031] M y =1.05~1.1M0

[0032] F By =0.95~1.05M y / (h1+h2)

[0033] A By =F By / f By

[0034] According to the design requirements of the buckling restraint brace, estimate the cross-sectional area and ultimate bearing capacity of the remaining sections of the buckling restraint brace:

[0035] A Be =2.5A By

[0036] F B，max =ωF By

[0037] In the formula, F By is the total yield axial force of the buckling-resistance brace, h1+h2 is the vertical height difference between the buckling-resistance brace axis and the node rotation center, F By A is the average yield strength of the steel in the yield section of the buckling-resistance brace, By is the total cross-sectional area of ​​the yield section of the buckling-resistance brace, F B，max is the ultimate bearing capacity of the buckling-resistance brace, A Be is the total cross-sectional area of ​​the connection section of the buckling restraint brace, ω is the strengthening coefficient of the yielding section steel of the buckling restraint brace considering the combined effects of strain hardening and friction;

[0038] Determine the number of bolts required for the connection section of the anti-buckling brace according to the ultimate bearing capacity of the anti-buckling brace and determine the length of the connection section l Be .

[0039] Furthermore, in step 3, the maximum deformation of the replaceable energy-consuming node is limited to no more than 3%, that is:

[0040]

[0041] Δ B =θ G (h1+h2)

[0042]

[0043] d=1.5Δ B

[0044] Among them, θ G is the rigid body rotation angle of the replaceable energy dissipation node; θ is the inter-story displacement angle limit of the structure under a large earthquake, which is 2% for the frame structure; l ac is the distance from the replaceable energy dissipation node to the axis of the frame column; l b is the distance between two replaceable energy-consuming nodes arranged on the same frame beam; Δ Bis the axial deformation of the buckling-resistance brace, h1+h2 is the vertical height difference between the buckling-resistance brace axis and the node rotation center; l By is the yield section length of the buckling-resisting brace; d is the joint gap between adjacent beam sections at the replaceable energy-absorbing node.

[0045] Furthermore, the basic assumptions and analysis methods described in step 4 are:

[0046] A steel frame beam with replaceable energy dissipation nodes is taken from the beam-column interface to the beam inflection point under earthquake action as an isolated body for analysis. The beam-column interface is considered to be fixed, and a vertical unit force acts at the beam inflection point to calculate the vertical deflection f of the steel beam. N ;

[0047] The actual structure of the replaceable energy-absorbing node with the upper flange of the beam as the rotation mechanism is equivalent to a simplified mechanical model, and the contribution of the axial deformation and bending stiffness of the shear connection of the upper flange of the beam in the elastic stage of small earthquakes is ignored. It is assumed that the midpoint of the shear connection is hinged, and its left and right sides are rigidly connected to the axis of the steel beam through vertical rigid arms respectively. The horizontal spacing between the rigid arms is taken as the beam segment gap. An equivalent two-force bar is used to act on the axis of the yielding section of the anti-buckling support, and a rigid arm is set at the connection between the anti-buckling support connection section and the beam flange to be rigidly connected to the beam axis. This rigid arm is hinged with the equivalent two-force bar, and the solid beam segment is modeled with a beam unit with consistent bending stiffness at the beam axis.

[0048] A traditional steel frame beam with the same cross-section, span, boundary conditions and load as the steel frame beam with replaceable energy-absorbing nodes is established, and the stiffness requirement of the replaceable energy-absorbing nodes is determined by making the vertical deflection under unit force at the inflection point of the beam equal.

[0049] Furthermore, in order to simplify the calculation, when calculating the elastic deformation of the steel frame beam with replaceable energy-absorbing nodes, only the deformation of the segment within the anti-buckling support area and the shear connection area is considered, so that the vertical deflection of the beam inflection point caused by the axial deformation of the replaceable energy-absorbing component in this segment is equal to the vertical deflection caused by the bending moment difference of the traditional steel frame beam in the same segment at the beam inflection point, and the axial elastic stiffness requirement of the anti-buckling support is determined.

[0050] Furthermore, in step 4, the yield section length l of the buckling-resistance brace is continuously adjusted. By , so as to adjust its axial stiffness to match the demand, and check that the design value of the bending moment of the node under vertical load does not exceed 30% of the ultimate bending bearing capacity of the node, that is, it meets the following requirements:

[0051]

[0052] N u =1.1F B，max (h1+h2)

[0053] Where M is the bending moment of the steel frame beam at the replaceable energy dissipation node under the vertical load, M u is the ultimate bending bearing capacity of the replaceable energy dissipation node, h1+h2 is the vertical height difference between the buckling-resistance support axis and the node rotation center, F B，max The ultimate bearing capacity of the buckling-resisting brace.

[0054] Furthermore, in step 6, considering the combined effects of vertical load and earthquake action, the plastic hinges at the nodes of the replaceable energy-absorbing steel frame are fully developed, and the ends of the beams at the beam-column interface are in an elastic state:

[0055] M u +(V u +V g ) a ≤M yb

[0056] N u =1.1F B，max (h1+h2)

[0057] V u =2M u / l b

[0058] V g =F g / 2

[0059] Among them, M u is the ultimate bending bearing capacity of the replaceable energy dissipation node, V u is the beam shear force generated by the fully developed plasticity of the replaceable energy-absorbing nodes under earthquake action, V g is the beam shear force generated by the vertical load at the replaceable energy dissipation node, l a M is the distance from the replaceable energy dissipation node to the adjacent beam-column interface. yb is the yield bending bearing capacity of the beam end at the beam-column interface, F B，max is the ultimate bearing capacity of the buckling-resistance brace, h1+h2 is the vertical height difference between the buckling-resistance brace axis and the node rotation center, Fg is the vertical force caused by the vertical load borne by the replaceable energy-absorbing node steel frame beam, l b is the length of the middle beam section.

[0060] Furthermore, the moment-rotation constitutive relationship in step 7 is:

[0061] K E =K B，E (h1+h2) 2

[0062] KP =γK B，P (h1+h2) 2

[0063]

[0064]

[0065] M y =f ym A By (h1+h2)

[0066] Among them, K E is the elastic rotation stiffness of the replaceable energy dissipation node, K B，E is the calculated value of the elastic axial stiffness of the buckling-resistance brace, h1 is the vertical distance from the centroid of the shear connection to the beam axis, h2 is the vertical distance from the buckling-resistance brace axis to the beam axis, K P is the post-yield rotational stiffness of the replaceable energy dissipation node, K B，P is the post-yield axial stiffness of the buckling-resisting brace, K By，P is the axial stiffness of the yield section of the buckling-resistance brace after yielding, γ is the amplification factor considering the contribution of the shear connection to the bending bearing capacity, K Be is the axial stiffness of the buckling-resistance brace connection section, E P is the post-yield tangent modulus of the steel in the yield section of the buckling-resistance brace, f ym A is the average measured strength of the steel in the yield section of the buckling-resistance brace core plate, By is the cross-sectional area of ​​the yielding section of the buckling-resistance brace.

[0067] Compared with the prior art, the present invention can achieve at least the following beneficial effects:

[0068] 1) The equal stiffness design principle with the traditional rigid-connected steel frame beams is proposed to determine the elastic rotation stiffness requirements of the replaceable energy-absorbing nodes and the elastic axial stiffness requirements of the replaceable energy-absorbing components, so that the replaceable steel frame structure maintains the same elastic stiffness characteristics as the traditional steel frame structure with the same beam-column cross-section, ensuring that the two structures have consistent elastic dynamic characteristics and elastic internal forces, so that the two structures can share the same structural analysis model in the first stage of seismic design, and solve the problems of unclear rotation stiffness caused by the weakening of stiffness of the replaceable energy-absorbing nodes and the difficulty in analyzing the structural internal forces caused by this;

[0069] 2) A simplified prediction method for the moment-rotation constitutive relationship of replaceable energy-absorbing nodes is proposed, and the calculation methods of key mechanical parameters such as the elastic rotation stiffness, yield moment, post-yield stiffness, and bending bearing capacity of the nodes are clarified. With this setting, the concentrated plastic hinge method defined for traditional structures in conventional analysis software can be used. After only the moment-rotation mechanical parameters of the replaceable energy-absorbing nodes are input, the second-stage elastic-plastic seismic analysis of the replaceable steel frame structure can be carried out. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 Schematic diagram of the node deformation mode with the centroid of the beam section as the rotation center.

[0071] Figure 2 Schematic diagram of the node deformation mode with the upper flange of the beam as the rotation center.

[0072] Figure 3(a) is a schematic diagram of the explosion of a replaceable energy-absorbing steel frame node.

[0073] Figure 3(b) is a schematic diagram of the replaceable energy-absorbing steel frame node after assembly.

[0074] Figure 4 Schematic diagram of the analysis of an isolated body removed from the overall structure.

[0075] Figure 5 It is a mechanical diagram of the replaceable energy-absorbing steel frame node.

[0076] Figure 6 Schematic diagram of the deformation of the replaceable steel frame beam.

[0077] Figure 7 Schematic diagram of deformation of traditional steel frame beam.

[0078] Figure 8 Schematic diagram of the difference in bending moment between traditional frame beams and replaceable frame beams.

[0079] Fig. 9 Schematic diagram of the beam inflection point under vertical load.

[0080] Fig.10 Schematic diagram of the bending moment at the actual layout position of the replaceable energy-absorbing node.

[0081] Fig.11 Schematic diagram of the inner core section of the buckling-restrained brace (I-shaped section).

[0082] Fig.12 Schematic diagram of the structure-node deformation relationship of the replaceable energy-absorbing node framework.

[0083] Fig.13 Schematic diagram of the bending moment in the replaceable energy dissipation node area under vertical load.

[0084] Fig.14Schematic diagram of the moment-rotation constitutive relationship of the replaceable energy dissipation node determined by the present invention.

[0085] Fig.15 A schematic diagram of a design flow chart of one embodiment of the present invention.

[0086] Fig.16 A schematic diagram of one embodiment of the present invention.

[0087] Fig.17 A schematic diagram of a buckling-resistance brace core according to one embodiment of the present invention.

[0088] Fig.18 A schematic diagram comparing the theoretical value and computer simulation value of the moment-angle relationship of a replaceable energy dissipation node in one embodiment of the present invention.

[0089] Fig.19 A comparison diagram of the elastic lateral stiffness of an assembly using one of the embodiments of the present invention and a conventional beam-column welded joint. DETAILED DESCRIPTION

[0090] The above scheme is further described below in conjunction with specific examples. It should be understood that these examples are used to illustrate the present invention and are not limited to the scope of the present invention. The implementation conditions adopted in the examples can be further adjusted according to the conditions of the specific project, and the unspecified implementation conditions are usually the conditions in the conventional experiments.

[0091] Based on the working principle of replaceable energy-absorbing steel frame nodes, the embodiment of the present invention further proposes a two-stage seismic design method for replaceable steel frame nodes that conforms to my country's seismic design ideas. This type of node uses the upper flange of the beam as the rotation center, and an anti-buckling support (tensile-compression yielding metal damper) is set at the bottom of the beam as a replaceable energy-absorbing component. As shown in Figure 3, an example of this type of node is given.

[0092] In order to facilitate the calculation of the stiffness requirements of replaceable energy-consuming nodes and replaceable energy-consuming components, the present invention proposes the following Figure 5 The mechanical diagram of the replaceable steel frame beam is shown, and the following basic assumptions and analysis methods are adopted:

[0093] 1. Take out a steel frame with replaceable energy-absorbing nodes from the beam-column interface to the beam inflection point under earthquake action (assumed to be the midpoint of the beam length direction) as an isolated body for analysis. The beam-column interface is regarded as a fixed connection, and a vertical unit force acts at the beam inflection point to calculate the vertical deflection f of the steel beam. N ;

[0094] 2. The actual structure of the replaceable energy dissipation node with the upper flange of the beam as the rotation mechanism is equivalent to a simplified mechanical model, ignoring the contribution of the axial deformation and bending stiffness of the shear connection of the upper flange of the beam in the elastic stage of small earthquakes. It is assumed that the midpoint of the shear connection is hinged, and its left and right sides are respectively connected by vertical rigid arms ( Figure 5 IC, JD) in the figure are rigidly connected to the steel beam axis. The horizontal spacing between the rigid arms is taken as the beam segment gap. The equivalent two-force rod ( Figure 5 The GH in the figure acts on the axis of the yield section of the buckling-resistance brace, and a rigid arm ( Figure 5 The BG and EH in the beam are rigidly connected to the beam axis, and this rigid arm is hinged to the equivalent two-force rod. The solid beam segments are all modeled with beam elements with consistent bending stiffness at the beam axis. The axial stiffness of the shear member is much larger than the buckling-resistance support stiffness and can be considered infinite. By moving the rigid arm to the beam segment joint interface, the calculation model of the replaceable energy-consuming node can be greatly simplified.

[0095] 3. Establish a traditional steel frame beam with the same cross-section, span, boundary conditions and load as the steel frame beam with replaceable energy dissipation nodes (such as Figure 7 As shown in the figure, the vertical deflection under unit force at the inflection point of the beam is equal (i.e., f N =f NT See Figure 6 , Figure 7 ) to determine the stiffness requirements of replaceable energy dissipation nodes. To simplify the calculation, it is not necessary to calculate the vertical deflection of the beam end caused by the bending moment within the entire length of the steel beam. When calculating the elastic deformation of the steel frame beam containing replaceable energy dissipation nodes, only the buckling restraint support area and the shear connection area (i.e. Figure 5 The deformation of the section within the GH range in the middle makes the vertical deflection of the beam inflection point caused by the axial deformation of the replaceable energy-absorbing components in this section equal to that of the traditional steel frame beam in the same section (see Figure 7 The bending moment difference of the middle BE section) (see Figure 8 The vertical deflection caused by the shaded part of the beam at the inflection point is equal, and the axial elastic stiffness requirement of the anti-buckling brace is determined. Based on this stiffness requirement, the two-stage seismic design basis of the replaceable steel frame node is established.

[0096] The two-stage seismic design method for replaceable steel frame nodes proposed in the present invention is described as follows:

[0097] Phase 1: This phase mainly involves the equal stiffness design between the steel beams with replaceable energy-absorbing nodes and the traditional steel beams, which mainly includes 1) the location determination of the replaceable energy-absorbing nodes, 2) the yield moment requirement of the nodes, 3) the deformation requirement of the nodes, and using the above requirements as constraints to determine 4) the elastic stiffness requirement of the buckling-restrained brace.

[0098] Step 1: Determine the location of replaceable energy-absorbing nodes. Arrange structural components, establish a three-dimensional structural model in structural design software such as PKPM and YJK according to conventional beam-column rigid connection, calculate the elastic internal force of each frame beam under vertical load, and determine the preliminary location of replaceable energy-absorbing nodes based on the bending moment zero point of the steel frame beam under vertical load.

[0099] In this step, the elastic internal force of the frame beam under the vertical load is calculated. At this time, the horizontal seismic load is not involved in the calculation. The purpose is to make the working performance of the replaceable energy-absorbing node independent of the vertical load. Therefore, it is arranged at the zero point of the bending moment under the vertical load. After the zero point of the bending moment, the vertical load will not generate the bending moment internal force in the replaceable energy-absorbing node. Therefore, the anti-buckling support does not generate axial force at this time, and its working performance is basically independent of the vertical load.

[0100] In the present invention, the initial position of the replaceable energy dissipation node is determined based on the bending moment zero point of the steel frame beam under the vertical load, and an offset of α to the adjacent column is allowed based on this position. Fig. 9 As shown, it satisfies

[0101] d off = l a0 -l ac

[0102] d off ≤αl a0

[0103] Where, d off is the allowable offset of the layout position of the replaceable energy consumption node, l a0 is the distance from the zero point of the bending moment of the frame beam of the traditional beam-column rigid connection structure to the column axis under vertical load, l ac It is the distance from the actual layout position of the replaceable energy-consuming node to the column axis.

[0104] In some embodiments of the present invention, the offset α does not exceed 20% of the initial position. When the offset does not exceed 20% of the initial position, it can be ensured that the node performance is basically not controlled by the vertical internal force but mainly depends on the seismic internal force, and the moment demand at the beam end can be reduced to a large extent, achieving the dual goal coordination of vertical internal force decoupling and beam end damage control, laying an important foundation for giving full play to the elastic-plastic deformation capacity of the node under a large earthquake and ensuring that the left and right nodes of the steel beam have similar seismic performance.

[0105] Step 2: Determine the yield moment M of the replaceable energy dissipation node y , and the ultimate bearing capacity of the buckling-restrained brace are used to design the connection section and its length of the buckling-restrained brace.

[0106] In some embodiments of the present invention, step 2 specifically includes the following sub-steps:

[0107] Step 2.1: In structural design software such as PKPM and YJK, a structural model is established according to conventional beam-column rigid connection. This structural model is the same as the structural model in step 1, but the type of load applied to the structure is different. In step 1, only vertical loads are applied to the structural model, while here vertical loads and horizontal seismic loads are applied to the structural model together.

[0108] Step 2.2: Perform elastic internal force analysis on the structure under the combined action of vertical and horizontal loads in the small earthquake stage, and determine the yield moment M of the node based on the design value of the moment M0 at the actual arrangement position of the replaceable energy dissipation node under the action of the small earthquake. y And the cross-sectional area of ​​the yield section of the buckling-restrained brace:

[0109] M y =1.05~1.1M0

[0110] F By =0.95~1.05M y / (h1+h2)

[0111] A By =F By / f By

[0112] Among them, the yield moment of the replaceable energy dissipation node is taken as 1.05 to 1.1 times the design value of the node moment under earthquake and vertical load. While maintaining equal stiffness, the elastic bearing capacity requirements of the node under small earthquakes can also be considered, which can solve the problem of incoordination between the stiffness and strength of the replaceable node.

[0113] According to the design requirements of the buckling restraint brace, estimate the cross-sectional area and ultimate bearing capacity of the remaining sections of the buckling restraint brace:

[0114] A Be =2.5A By

[0115] F B，max =ωF By

[0116] In the formula, F By is the total yield axial force of the buckling-resistance brace, h1+h2 is the vertical height difference between the buckling-resistance brace axis and the node rotation center (see Figure 5 ), f By A is the average yield strength of the steel in the yield section of the buckling-resistance brace, By is the total cross-sectional area of ​​the yield section of the buckling-resistance brace (see Fig.11 ), F B，nax is the ultimate bearing capacity of the buckling-resistance brace, A Be is the total cross-sectional area of ​​the connection section of the buckling-restrained brace (see Fig.11 ), ω is the strengthening coefficient of the yield section steel of the buckling restraint brace considering the combined effects of strain hardening and friction;

[0117] Step 2.3: Determine the number of bolts required for the connection section of the buckling restraint according to the ultimate bearing capacity of the buckling restraint and determine the length of the connection section l Be (See Fig.11 ).

[0118] Step 3: Assuming that the beam and column sections are rigid bodies, according to the replaceable energy-absorbing steel frame nodes (such as Fig.12 The structural geometric characteristics of the structure (as shown in the figure) are used to determine the relationship between the structural deformation, node rotation angle, and buckling-restrained brace deformation, the deformation demand of the replaceable energy-absorbing node is determined, and the lower limit of the yield section length of the buckling-restrained brace is determined by the node deformation demand.

[0119] In some embodiments of the present invention, in order to ensure that the anti-buckling brace has sufficient deformation capacity and energy dissipation capacity, the axial strain of the yield section of the anti-buckling brace under the expected structural deformation should be controlled to be no more than 3%. When the axial strain of the anti-buckling brace is controlled within 3%, better seismic resistance and low-cycle fatigue performance can be obtained, and it is not easy to break in an earthquake due to excessive deformation. Since an earthquake is a continuous time process, the anti-buckling brace must not only withstand the maximum deformation generated in an earthquake, but also be able to continue working during this earthquake without breaking. Therefore, in order to ensure that it does not break, its maximum deformation is limited to no more than 3%, that is:

[0120]

[0121] Δ B =θ G (h1+h2)

[0122]

[0123] d=1.5Δ B

[0124] Among them, θ G is the rigid body rotation angle of the replaceable energy consumption node (see Fig.12 ), θ is the inter-story displacement angle limit of the structure under a strong earthquake, which is 2% for frame structures, l ac is the distance from the replaceable energy dissipation node to the axis of the frame column (see Fig.12 ), l b The distance between two replaceable energy-absorbing nodes arranged on the same frame beam (see Fig.12 ), Δ B For the axial deformation of the buckling-resisting brace, l By is the yield length of the buckling-resisting brace (see Fig.11), d is the joint gap between adjacent beam segments at the replaceable energy dissipation node (see Figure 5 ).

[0125] Step 4: Based on the basic assumptions and analysis methods for calculating the stiffness requirements of replaceable energy-absorbing nodes, determine the elastic axial stiffness requirements of the buckling-resistance brace. (Calculation model see Figure 5 , the schematic diagram of the buckling-resistance brace core is shown in Fig.11 )

[0126]

[0127]

[0128]

[0129]

[0130] Among them, K req is the elastic axial stiffness requirement of the buckling-resistance brace, E is the elastic modulus of the steel, and A is ave is the equivalent cross-sectional area of ​​the buckling-resisting brace, l B is the equivalent length of the buckling-resisting brace, I b is the section inertia moment of the cantilever beam section and the middle beam section, l2 is the horizontal distance from the center of the buckling-resistance brace connection section near the column side to the adjacent side joint, l3 is the horizontal distance from the center of the buckling-resistance brace connection section far from the column side to the adjacent side joint, l4 is the horizontal distance from the center of the buckling-resistance brace connection section far from the column side to the center of the beam, h1 is the vertical distance from the centroid of the shear connection to the beam axis, h2 is the vertical distance from the buckling-resistance brace axis to the beam axis, d is the joint gap between adjacent beam sections at the replaceable energy dissipation node, K B，E is the calculated value of the elastic axial stiffness of the buckling-restrained brace, K Be K is the axial stiffness of the buckling-resistance brace connection section, By，E is the elastic axial stiffness of the yield section of the buckling-resistance brace, β = 0.95 ~ 1.05 is the axial stiffness demand adjustment coefficient, l Be is the effective length of the buckling-resistance brace connection section, l By is the length of the yield section of the buckling-resistance brace, A Be is the cross-sectional area of ​​the buckling-resistance brace connection section, A By is the cross-sectional area of ​​the yielding section of the buckling-resistance brace.

[0131] Under the condition that all indicators in steps 1-4 are met, the yield section length l of the anti-buckling support is continuously adjusted. By , so as to adjust its axial stiffness to match the elastic axial stiffness requirement of the buckling-restrained brace, and check that the design value of the bending moment of the node under vertical load does not exceed 30% of the ultimate bending bearing capacity of the node, that is, it meets the following requirements:

[0132]

[0133] M u =1.1F B，max (h1+h2)

[0134] Where M is the bending moment of the steel frame beam at the replaceable energy dissipation node under the vertical load (see Fig.13 ), M ，u is the ultimate bending bearing capacity of the replaceable energy-absorbing node.

[0135] Phase 2: This phase mainly includes two aspects: seismic damage control design of steel frame beams with replaceable energy-absorbing nodes during major earthquakes and moment-rotation constitutive model of replaceable energy-absorbing nodes. The former is used to control the position of the plastic hinge of the steel frame beam at the replaceable energy-absorbing nodes, and the latter is used to carry out major earthquake elastoplastic analysis of replaceable steel frame structures.

[0136] Step 5: Design shear connections based on shear and axial force requirements, including the provision of shear plates.

[0137] In some embodiments of the present invention, as shown in FIG3(a), the replaceable steel frame node includes: the cantilever beam section 1 (left beam section) and the middle beam section 2 (right beam section) are disconnected from each other with a gap of appropriate width, and the disconnection is defined as a fracture 3, and a shear plate 4 (coplanar with the beam web) is welded to the top of each left and right beam near the splicing position, and the angle steel 5 and the upper flanges of the left and right beam sections and the shear plates are overlapped and connected with bolts or welds, thereby forming a shear connection and a rotation center at the upper flange of the beam, and the left and right ends of the anti-buckling support are respectively connected to the lower flanges of the left and right beam sections at the bottom of the beam. Among them, the anti-buckling support 6 includes a core plate 61 and a restraining member 62 located outside the core plate 61.

[0138] Step 6: Perform earthquake damage control calculation on the beam ends.

[0139] In some embodiments of the present invention, Fig.12 It shows that replaceable energy-absorbing steel frame nodes are symmetrically added in a frame. Considering the combined influence of vertical load and seismic action, the plastic hinges at the replaceable energy-absorbing steel frame nodes are fully developed, and the beam ends at the beam-column interface are in an elastic state:

[0140] M u +(V u +V g ) a ≤M yb

[0141] M u =1.1F B，max (h1+h2)

[0142] V u =2N u / l b

[0143] V g =F g / 2

[0144] Among them, N u is the ultimate bending bearing capacity of the replaceable energy dissipation node, V u is the beam shear force generated by the fully developed plasticity of the replaceable energy-absorbing nodes under earthquake action, V g is the beam shear force generated by the vertical load at the replaceable energy dissipation node (the beam shear force calculated by treating the middle beam section as a simply supported beam), l a M is the distance from the replaceable energy dissipation node to the adjacent beam-column interface. yb is the yield bending bearing capacity of the beam end at the beam-column interface, F B，max is the ultimate bearing capacity of the buckling-resistance brace, h1+h2 is the vertical height difference between the buckling-resistance brace axis and the node rotation center (see 5), F g is the vertical force caused by the vertical load borne by the replaceable energy-absorbing node steel frame beam (calculated based on the vertical load within the length range of the frame beam axis), l b is the length of the middle beam section (see Fig.12 ).

[0145] Step 7: Perform routine calculations on the strong columns, weak beams and node domains of the replaceable energy-absorbing steel frame nodes.

[0146] Step 8: Determine the moment-rotation constitutive relationship of the replaceable energy-absorbing steel frame nodes.

[0147] In some embodiments of the present invention, the elastic-plastic working performance of the shear member and the buckling-restrained brace after yielding is considered at the same time, and the moment-rotation constitutive relationship of the replaceable energy dissipation node can be determined by the yield axial force, elastic stiffness and post-yield stiffness of the buckling-restrained brace (see Fig.14 ):

[0148] K E =K B，E (h1+h2) 2

[0149] K P =γK B，P (h1+h2) 2

[0150]

[0151]

[0152] M y =f ym A By (h1+h2)

[0153] Among them, K E is the elastic rotation stiffness of the replaceable energy dissipation node, K P is the post-yield rotational stiffness of the replaceable energy dissipation node, K B，P is the post-yield axial stiffness of the buckling-resisting brace, K By，P is the post-yield axial stiffness of the yield section of the buckling-resistance brace, γ is the amplification factor considering the contribution of the shear connection to the bending bearing capacity, which is taken as 1.1, and E P The post-yield tangent modulus of the steel in the yield section of the buckling-resistance brace can be taken as 2%-3% of the elastic modulus, with 3% being the preferred value. ym It is the average measured strength of the steel in the yield section of the buckling-resistance brace core plate. The Technical Code for Steel Structures of High-rise Civil Buildings lists the value of this parameter.

[0154] In one embodiment of the present invention, a specific example is provided as follows:

[0155] A replaceable energy-absorbing node is added to a steel frame. The steel frame adopts H-shaped steel beams and box columns. The cross-section and material of the beams and columns are:

[0156] Beam: Made of Q345 steel, cross section is HN500×200×16×10

[0157] Column: Made of Q345 steel, cross section: 370×370×16×16

[0158] The length of the beam column is:

[0159] Beam: Beam length is 6000mm (calculated based on column axis spacing)

[0160] Column: Column height is 3000mm (calculated by the vertical distance between the midpoint of the upper column and the midpoint of the lower column)

[0161] The beam-column joints are rigidly connected by flange welding.

[0162] like Fig.16 As shown in the figure, the replaceable energy dissipation node is arranged at 900mm from the beam-column interface, the gap between the cantilever beam section and the middle beam section is 30mm, the vertical distance from the node rotation center to the anti-buckling support axis is h1+h2=490mm, and the inner core of the anti-buckling support is made of angle steel. See the detailed figure for details. Fig.17 .

[0163] like Fig.17 As shown in Figure 1, the elastic axial stiffness of the buckling-restrained brace can be obtained from the steps in stage 1:

[0164] KB，E =166.99KN / mm

[0165] The post-yield axial stiffness of the buckling-restrained brace can be obtained from the steps in stage 2 as:

[0166] K B，P =5.08KN / mm

[0167] Furthermore, the elastic rotation stiffness of the replaceable energy-consuming node of this embodiment can be obtained from the steps of stage 2 as:

[0168] K E =40094.30KN·m

[0169] And the post-yield rotational stiffness after the plastic hinge occurs is:

[0170] K P =1219.71KN·m

[0171] Fig.18 The solid line in the middle is a graph of the moment-rotation relationship of the replaceable energy dissipation node obtained by the computer simulation example of this embodiment, and the dotted line is the moment-rotation relationship of the replaceable energy dissipation node calculated and derived by the present invention and in accordance with this embodiment. As can be seen from the figure, the two are basically consistent, which shows that the present invention can realize the simplified prediction of the moment-rotation constitutive relationship of the replaceable energy dissipation node, verifying the effectiveness of the present invention.

[0172] Fig.19 In the figure, the dotted line is a computer simulation curve of the horizontal force-displacement relationship of the beam-column assembly using the traditional node (i.e., the beam-column rigid connection); the solid line is a computer simulation curve of the horizontal force-displacement relationship of the beam-column assembly using the replaceable energy-absorbing node determined by the present invention. As can be seen from the figure, the two are basically consistent, which shows that the present invention can achieve the same stiffness design goal as the traditional rigidly connected steel frame beam, verifying the effectiveness of the present invention.

[0173] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention, and these changes and improvements fall within the scope of the present invention to be protected.

Claims

1. A two-stage seismic design method for replaceable energy-absorbing steel frame nodes, characterized in that: The following steps are involved: Step 1: Determine the moment distribution of the frame beam under the vertical load, determine the preliminary position of the replaceable energy-absorbing node based on the moment zero point of the steel frame beam under the vertical load, and allow the position with a preset offset α to the adjacent column side based on the preliminary position as the actual position of the replaceable energy-absorbing node; Step 2: Determine the yield moment M of the replaceable energy dissipation node y , and the ultimate bearing capacity of the buckling-restrained brace, and use this to design the connection section and length of the buckling-restrained brace; Step 3: Assuming that each section of the beam and column is a rigid body, according to the structural geometric characteristics of the replaceable energy-absorbing steel frame node, determine the relationship between the structural deformation, node rotation angle, and buckling-restrained brace deformation, determine the deformation demand of the replaceable energy-absorbing node, and determine the lower limit of the yield section length of the buckling-restrained brace based on the node deformation demand; Step 4: Establish basic assumptions and analysis methods for calculating the stiffness requirements of replaceable energy-absorbing nodes, and determine the elastic axial stiffness requirements of the anti-buckling brace based on the basic assumptions and analysis methods, where the elastic axial stiffness requirements of the anti-buckling brace are: Among them, K req is the elastic axial stiffness requirement of the buckling-resistance brace, E is the elastic modulus of the steel, and A is ave is the equivalent cross-sectional area of ​​the buckling-resisting brace, l B is the equivalent length of the buckling-resisting brace, I b is the section inertia moment of the cantilever beam section and the middle beam section, l2 is the horizontal distance from the center of the buckling-resistance brace connection section near the column side to the adjacent side joint, l3 is the horizontal distance from the center of the buckling-resistance brace connection section far from the column side to the adjacent side joint, l4 is the horizontal distance from the center of the buckling-resistance brace connection section far from the column side to the center of the beam, h1 is the vertical distance from the centroid of the shear connection to the beam axis, h2 is the vertical distance from the buckling-resistance brace axis to the beam axis, d is the joint gap between adjacent beam sections at the replaceable energy dissipation node, K B，E is the calculated value of the elastic axial stiffness of the buckling-restrained brace, K Be is the axial stiffness of the buckling-resistance brace connection section, K By，E is the elastic axial stiffness of the yield section of the buckling-resistance brace, β is the axial stiffness demand adjustment coefficient, l Be is the effective length of the buckling-resistance brace connection section, l By is the length of the yield section of the buckling-resistance brace, A Be A is the cross-sectional area of ​​the buckling-resistance brace connection section, By is the cross-sectional area of ​​the yielding section of the buckling-resistance brace; Step 5: Design the shear connection according to the shear and axial force requirements; Step 6: Perform earthquake damage control calculation on the beam ends; Step 7: Determine the moment-rotation constitutive relationship of the replaceable energy dissipation node based on the yield axial force, elastic stiffness and post-yield stiffness of the buckling-restrained support.

2. The two-stage seismic design method for replaceable energy-absorbing steel frame nodes according to claim 1 is characterized in that: The value of the preset offset α in step 1 does not exceed 20% of the initial position.

3. The two-stage seismic design method for replaceable energy-absorbing steel frame nodes according to claim 2 is characterized in that: In step 1, when the preset offset is α, it satisfies: d off ＝l a0 -l ac d off ≤αl a0 Where, d off is the allowable offset of the layout position of the replaceable energy consumption node, l a0 is the distance from the zero point of the bending moment of the frame beam of the traditional beam-column rigid connection structure to the column axis under vertical load, l ac It is the distance from the actual layout position of the replaceable energy-consuming node to the column axis.

4. The two-stage seismic design method for replaceable energy-absorbing steel frame nodes according to claim 1 is characterized in that: Step 2 specifically includes the following sub-steps: Establish a structural model, and apply vertical load and horizontal seismic load to the structural model; The elastic internal force analysis of the structure under the combined action of vertical and horizontal loads in the small earthquake stage is carried out, and the yield moment M of the node is determined based on the bending moment design value M0 of the actual arrangement position of the replaceable energy dissipation node under the action of small earthquake. y And the cross-sectional area of ​​the yield section of the buckling-restrained brace: M y =1.05~1.1M0 F By =0.95~1.05M y / (h1+h2) A By =F By / f By According to the design requirements of the buckling restraint brace, estimate the cross-sectional area and ultimate bearing capacity of the remaining sections of the buckling restraint brace: <h2 style=";text-align:left;direction:ltr">A<h2 style=";text-align:left;direction:ltr"> Be <h2 style=";text-align:left;direction:ltr"> <2.5A<h2 style=";text-align:left;direction:ltr"> By F B，max =ωF By In the formula, F By is the total yield axial force of the buckling-resistance brace, h1+h2 is the vertical height difference between the buckling-resistance brace axis and the node rotation center, and f By A is the average yield strength of the steel in the yield section of the buckling-resistance brace, By is the total cross-sectional area of ​​the yield section of the buckling-resistance brace, F B，max is the ultimate bearing capacity of the buckling-resistance brace, A Be is the total cross-sectional area of ​​the connection section of the buckling restraint brace, ω is the strengthening coefficient of the yielding section steel of the buckling restraint brace considering the combined effects of strain hardening and friction; Determine the number of bolts required for the connection section of the anti-buckling brace according to the ultimate bearing capacity of the anti-buckling brace and determine the length of the connection section l Be .

5. The two-stage seismic design method for replaceable energy-absorbing steel frame nodes according to claim 1 is characterized in that: In step 3, the maximum deformation of the replaceable energy-consuming node is limited to no more than 3%, that is: D B =θ G (h1+h2) d=1.5D B Among them, θ G is the rigid body rotation angle of the replaceable energy dissipation node; θ is the inter-story displacement angle limit of the structure under a large earthquake; l ac is the distance from the replaceable energy dissipation node to the axis of the frame column; l b is the distance between two replaceable energy-consuming nodes arranged on the same frame beam; Δ B is the axial deformation of the anti-buckling brace; h1+h2 is the vertical height difference between the anti-buckling brace axis and the node rotation center; l By is the yield section length of the buckling-resisting brace; d is the joint gap between adjacent beam sections at the replaceable energy-absorbing node.

6. The two-stage seismic design method for replaceable energy-absorbing steel frame nodes according to claim 1 is characterized in that: The basic assumptions and analysis methods described in step 4 are: A steel frame beam with replaceable energy dissipation nodes is taken from the beam-column interface to the beam inflection point under earthquake action as an isolated body for analysis. The beam-column interface is considered to be fixed, and a vertical unit force acts at the beam inflection point to calculate the vertical deflection f of the steel beam. N ; The actual structure of the replaceable energy-absorbing node with the upper flange of the beam as the rotation mechanism is equivalent to a simplified mechanical model, and the contribution of the axial deformation and bending stiffness of the shear connection of the upper flange of the beam in the elastic stage of small earthquakes is ignored. It is assumed that the midpoint of the shear connection is hinged, and its left and right sides are rigidly connected to the axis of the steel beam through vertical rigid arms respectively. The horizontal spacing between the rigid arms is taken as the beam segment gap. An equivalent two-force bar is used to act on the axis of the yielding section of the anti-buckling support, and a rigid arm is set at the connection between the anti-buckling support connection section and the beam flange to be rigidly connected to the beam axis. This rigid arm is hinged with the equivalent two-force bar, and the solid beam segment is modeled with a beam unit with consistent bending stiffness at the beam axis. A traditional steel frame beam with the same cross-section, span, boundary conditions and load as the steel frame beam with replaceable energy-absorbing nodes is established, and the stiffness requirement of the replaceable energy-absorbing nodes is determined by making the vertical deflection under unit force at the inflection point of the beam equal.

7. The two-stage seismic design method for replaceable energy-absorbing steel frame nodes according to claim 6 is characterized in that: To simplify the calculation, when calculating the elastic deformation of the steel frame beam with replaceable energy-absorbing nodes, only the deformation of the segment within the anti-buckling support area and the shear connection area is considered. The vertical deflection at the beam inflection point caused by the axial deformation of the replaceable energy-absorbing component in this segment is equal to the vertical deflection at the beam inflection point caused by the bending moment difference of the traditional steel frame beam in the same segment, and the axial elastic stiffness requirement of the anti-buckling support is determined.

8. The two-stage seismic design method for replaceable energy-absorbing steel frame nodes according to claim 1 is characterized in that: In step 4, the yield length l of the buckling-resistance brace is continuously adjusted. By , so as to adjust its axial stiffness to match the demand, and check that the design value of the bending moment of the node under vertical load does not exceed 30% of the ultimate bending bearing capacity of the node, that is, it meets the following requirements: N u =1.1F B，max (h1+h2) Where M is the bending moment of the steel frame beam at the replaceable energy dissipation node under the vertical load, N u is the ultimate bending bearing capacity of the replaceable energy dissipation node, h1+h2 is the vertical height difference between the buckling-resistance support axis and the node rotation center, F B，max The ultimate bearing capacity of the buckling-resisting brace.

9. The two-stage seismic design method for replaceable energy-absorbing steel frame nodes according to claim 1 is characterized in that: In step 6, considering the combined effects of vertical load and earthquake action, the plastic hinges at the nodes of the replaceable energy-absorbing steel frame are fully developed, and the ends of the beams at the beam-column interface are in an elastic state: M u +(V u +V g )l a ≤M yb M u =1.1F B，max (h1+h2) <h2 style=";text-align:left;direction:ltr">V<h2 style=";text-align:left;direction:ltr"> u <h2 style=";text-align:left;direction:ltr"> <2N<h2 style=";text-align:left;direction:ltr"> u <h2 style=";text-align:left;direction:ltr"> / l<h2 style=";text-align:left;direction:ltr"> b V g =F g / 2 Among them, M u is the ultimate bending bearing capacity of the replaceable energy dissipation node, V u is the beam shear force generated by the fully developed plasticity of the replaceable energy-absorbing nodes under earthquake action, V g is the beam shear force generated by the vertical load at the replaceable energy dissipation node, l a M is the distance from the replaceable energy dissipation node to the adjacent beam-column interface. yb is the yield bending bearing capacity of the beam end at the beam-column interface, F B，max is the ultimate bearing capacity of the buckling-resistance brace, h1+h2 is the vertical height difference between the buckling-resistance brace axis and the node rotation center, F g is the vertical force caused by the vertical load borne by the replaceable energy dissipation node steel frame beam, l b is the length of the middle beam section.

10. The two-stage seismic design method for replaceable energy-absorbing steel frame nodes according to any one of claims 1 to 9, characterized in that: The moment-rotation constitutive relation in step 7 is: K E =K B，E (h1+h2) 2 K P =γK B，P (h1+h2) 2 M y =f ym A By (h1+h2) Among them, K E is the elastic rotation stiffness of the replaceable energy dissipation node, K B，E is the calculated value of the elastic axial stiffness of the buckling-resistance brace, h1 is the vertical distance from the node rotation center to the beam axis, h2 is the vertical distance from the buckling-resistance brace axis to the beam axis, K P is the post-yield rotational stiffness of the replaceable energy dissipation node, K B，P is the post-yield axial stiffness of the buckling-resisting brace, K By，P is the axial stiffness of the yield section of the buckling-resistance brace after yielding, γ is the amplification factor considering the contribution of the shear connection to the bending bearing capacity, K Be is the axial stiffness of the buckling-resistance brace connection section, E P is the post-yield tangent modulus of the steel in the yield section of the buckling-resistance brace, f ym A is the average measured strength of the steel in the yield section of the buckling-resistance brace core plate, By is the cross-sectional area of ​​the yielding section of the buckling-resistance brace.

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