Seismic design method for vertical tension-shear composite connection nodes of modular steel structure buildings

Abstract

The seismic design method of the vertical tension-shear composite connection node of the modular steel structure building provided by the present invention includes: calculating the internal force borne by the node in the ultimate working state I and the ultimate working state II; determining the preload of the tie rod, determining the cross-sectional size of the tie rod shaft tension section according to the preload and preliminarily determining the cross-sectional size of the tie rod tension-shear section; determining the thickness of the shear plate of the connection box and the strength of the grouting material according to the fact that the hole wall does not yield under pressure and the grouting material does not fail under pressure under the ultimate working state I of the node; verifying whether the tension-shear section of the tie rod yields under the ultimate working state I of the node; determining the size of the side plate of the connection box according to the fact that the flange plate of the side plate of the connection box does not fail under local pressure under the ultimate working state II and the web does not fail under shear yield under the ultimate working state I and ultimate working state II. The present invention will provide a reference for realizing rigid connection of the vertical tension-shear composite node of the modular steel structure building under earthquake action.

Description

Technical Field

[0001] The invention relates to the field of earthquake resistance of building structures, and in particular to an earthquake-resistant design method for vertical tension-shear composite connection nodes of modular steel structure buildings. Background Art

[0002] Modular steel structure building is a highly integrated new type of prefabricated building, which uses each room as a prefabricated module unit. After the beams, columns, floor slabs, wall panels, decoration, water and electricity pipelines of each module are assembled in advance in the factory, the module units are transported to the site and connected to each other to assemble them into a whole building. The vertical connection nodes between module units are the key to affecting the seismic performance of modular buildings.

[0003] Chinese invention patent CN 106149901 A discloses "a corner piece rotating modular building connection node". This connection method lacks a reliable node tension / bending force transmission mechanism, making it difficult to achieve a rigid connection between adjacent modules, and the modular structure has large lateral deformation under horizontal loads. Moreover, for semi-rigid nodes, it is not convenient to perform structural system analysis, which increases the cost of structural design. In addition, this connection method lacks a reliable shear force transmission mechanism. There is an assembly gap between the rotating corner piece and the connection box of this connection. Under the action of horizontal force, relative slip will occur between the upper and lower modules, resulting in discontinuous shear stiffness of the structure, which has an adverse effect on the seismic resistance of modular steel structure buildings.

[0004] At present, most of the vertical connection nodes proposed for modular steel structure buildings lack a reliable node force transmission mechanism, making it difficult to achieve rigid connection between adjacent vertical modules under different stress states and continuity of node shear stiffness, resulting in potential seismic safety hazards in modular steel structure buildings. Moreover, the semi-rigid connection of the nodes is not conducive to the system analysis of the structure. Summary of the invention

[0005] In order to solve the problem in the prior art that vertical connection nodes of modular steel structure buildings are difficult to achieve rigid connection and have poor seismic performance, the present invention proposes a seismic design method for vertical tension-shear composite connection nodes of modular steel structure buildings.

[0006] In order to achieve the purpose of the present invention, the present invention provides a seismic design method for a vertical tension-shear composite connection node of a modular steel structure building, wherein the node comprises an upper connection box and a lower connection box arranged relatively to each other, the upper connection box and the lower connection box are connected by a tie rod, the gaps between the upper connection box, the lower connection box and the tie rod are filled with grouting material, the upper connection box is provided with an upper module column and a floor beam, the lower connection box is provided with a lower module column and a ceiling beam, the tie rod comprises a tie rod shaft pulling section and a tie rod tension-shear section, the upper connection box and the lower connection box both comprise a connection box side plate and a connection box shear plate, the connection box side plate comprises two flange plates and two web plates, and the connection box and the lower connection box are interfaced and sheared by the connection box shear plate-grouting material-tie rod pressure-bearing joint shearing is achieved; the method comprises the following steps:

[0007] Step 1: Preliminary calculation of the internal forces of the node in the limit working state I and the limit working state II. The node limit working state I refers to the state in which the shear force at the end of the beam is transferred to the node and converted into axial tension when both the ceiling beam and the floor beam at the node enter the full section plastic state; the node limit working state II refers to the state in which the shear force at the end of the beam is transferred to the node and converted into axial pressure when both the ceiling beam and the floor beam at the node enter the full section plastic state;

[0008] Step 2: Determine the preload force of the tie rod according to the performance target that the node does not disengage or pry under the limit working state I. P 0; According to the preload of the tie rod P 0 Determine the cross-sectional dimensions of the tie rod shaft section; preliminarily determine the cross-sectional diameter of the tie rod shear section based on the cross-sectional diameter of the tie rod shaft section D bar,V , the cross-sectional diameter of the tie rod shear section shall not be less than the cross-sectional diameter of the shaft shear section;

[0009] Step 3, determine the thickness of the shear plate of the connection box and the compressive strength of the grouting material, wherein the thickness of the shear plate of the connection box should be such that no pressure yielding of the hole wall occurs under the node limit working state I, and the strength of the grouting material should be such that no compressive failure occurs under the node limit working state I;

[0010] Step 4, verify whether the tie rod shear section yields under the node limit working state I; if it yields, return to step 2 and re-determine the cross-sectional diameter of the tie rod shear section; if it does not yield, perform the following step 5;

[0011] Step 5, determine the size of the side plate of the connection box, wherein the flange plate of the connection box should satisfy that the node does not suffer from local compression failure under the limit working state II, and the web plate of the connection box should satisfy that the node does not suffer from shear yield failure under the limit working states I and II; and the stiffness of the connection box should satisfy that the increase in the tie rod preload force of the node under the limit working state I does not exceed the set proportion of the initial preload force (the present invention preferably does not exceed 5% of the initial preload force).

[0012] Furthermore, in step 1, the internal forces borne by the nodes in the ultimate working state I and the ultimate working state II are preliminarily calculated, including the bending moments borne by the floor beams and ceiling beams in the ultimate working state I and the ultimate working state II. M fb,p , M cb,p , and the most unfavorable axial tension of the node in the limit working state I T j0 The bending moment of the node under the limit working state I M j0 .

[0013] Furthermore, the connection box includes an upper connection box and a lower connection box, the upper connection box and the lower connection box have exactly the same size, preferably, the cross section of the connection box side plate is a square tube cross section, and the side length of the connection box side plate cross section is equal to the side length of the module column cross section.

[0014] Furthermore, the most unfavorable axial tension of the node in the limit working state I is calculated based on the shear force at the end of the floor beam of the node and the axial force transmitted by the upper module column. T j0 .

[0015] Furthermore, the bending moment borne by the node under the ultimate working state I is M j0 According to the end bending moment of the upper module column at the node M c,u Bending moment at the end of floor beam M fb,p Determine, that is M j0 = M c,u - M fb,p .

[0016] Furthermore, in step 2, the preload force of the tie rod is determined P 0, the following two formulas must be satisfied at the same time:

[0017]

[0018]

[0019] in, T j0 is the most unfavorable axial tension of the node under the limit working state I, b box is the cross-sectional side length of the connection box, M j0 is the bending moment borne by the node under the ultimate working state I;

[0020] Cross-sectional diameter of the tie rod shaft section Dbar,T Satisfy the following formula:

[0021]

[0022] In the formula, is the tensile strength of the tie rod, A e is the effective cross-sectional area of ​​the tie rod shaft section, D bar,T is the diameter of the pull rod shaft section, e It is the thread pitch of the pull rod shaft section.

[0023] Furthermore, the thickness of the shear plate of the connection box satisfies the following formula:

[0024]

[0025] Furthermore, the strength of the grouting material satisfies the following formula:

[0026]

[0027] In the formula, V bar is the shear force on the tie rod when the node is in the ultimate working state I, is the yield strength of the connection box, t sp is the thickness of the shear plate of the connection box, For the strength of grouting material.

[0028] Furthermore, in step 4, whether the pull rod shear section yields is determined according to the following formula:

[0029]

[0030] In the formula, is the elastic resistance moment of the tension shear section of the tie rod, is the yield strength of the tie rod; if this formula holds true, the tie rod shear section does not yield; otherwise, the tie rod shear section yields, and it is necessary to return to step 2 to increase the cross-sectional size of the tie rod shear section.

[0031] Furthermore, in step 5, the following formula must be satisfied to ensure that the flange plate of the connection box does not suffer from local pressure damage:

[0032]

[0033] In the formula N j0 is the most unfavorable axial pressure that the node bears under the limit state II, t f,box is the thickness of the connection box flange, b box is the width of the connection box flange, is the yield strength of the connection box.

[0034] To ensure that the web of the connection box does not undergo shear yield, the following two equations should be satisfied at the same time:

[0035]

[0036]

[0037] In the formula M cb,p is the bending moment borne by the ceiling beam under the node limit working state I or the node limit working state II, M fb,p is the bending moment borne by the floor beam under the node limit working state I or node limit working state II, is the height of the ceiling beam, is the height of the floor beam, t w,box is the thickness of the web of the connection box, t f,box is the thickness of the flange of the connection box, is the shear yield strength of the connecting box steel;

[0038] To ensure that the increase in the tie rod preload under the node limit state does not exceed 5%, the following formula should be satisfied:

[0039]

[0040]

[0041]

[0042] in K box is the axial stiffness of the connection box, K bar is the axial stiffness of the tie rod, is the length of the pull rod shaft section, is the length of the shearing section of the tie rod, E is the elastic modulus of steel, A bar,T is the cross-sectional area of ​​the tie rod shaft section, A bar,V is the cross-sectional area of ​​the shear section of the tie rod, A box is the cross-sectional area of ​​the side plate of the connection box, is the height of the side panel of the connection box.

[0043] Compared with the prior art, the advantages of the present invention are at least:

[0044] (1) The present invention considers the stress state of the modular steel structure building nodes under different limit states, and considers the influence of the axial force change of the modular steel structure node on the node stress.

[0045] (2) The present invention establishes a reliable node force transmission mechanism, which can realize the rigid connection between the upper and lower adjacent modules, facilitate the system analysis of modular steel structure buildings, and establish a reliable mechanical shear resistance mechanism (interface friction between the upper connection box and the lower connection box and shear plate-grouting material-tie rod pressure-bearing combined shear resistance), which solves the problem of sudden change in node stiffness existing in some connection nodes, enhances the integrity and seismic performance of modular steel structure buildings, and is conducive to promoting the popularization and application of modular steel structure buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of the structure of the tension-shear composite connection node in an embodiment of the present invention.

[0047] Figure 2 This is a design flow chart of a tension-shear composite connection node in an embodiment of the present invention.

[0048] Figure 3 It is a schematic diagram of the stress state of the tension-shear composite connection node of the planar module frame in the embodiment of the present invention under the limit working state I.

[0049] Figure 4 It is a schematic diagram of the stress state of the tension-shear composite connection node of the planar module frame in the embodiment of the present invention under the limit working state II.

[0050] Figure 5 Schematic diagram of the dimensions of the components of the tension-shear composite connection node in an embodiment of the present invention, wherein (a) is a plane view of the node, and (b) is a diagram along the AA direction in (a).

[0051] Figure 6 Schematic diagram of shear force transmission mechanism among shear plates, grouting materials and tie rods in an embodiment of the present invention.

[0052] Figure 7 Schematic diagram of the force on the shearing section of the tie rod in the embodiment of the present invention.

[0053] Figure 8 Schematic diagram of the plastic strain distribution of the tension-shear composite connection node under the limit working state I and the limit working state II in an embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] In order to solve the common problems of vertical connection nodes in modular steel structure buildings, a vertical tension-shear composite connection node is proposed. This node resists pulling and bending through the pre-tightening force of the tie rod and the connection box, and resists shearing through the interface friction between the upper connection box and the lower connection box and the shear plate-grouting material-tie rod pressure. Therefore, the reasonable design of this vertical tension-shear composite connection node is the key to ensuring the reliable performance of modular steel structure buildings using this vertical node form under earthquake action.

[0056] Figure 1 The figure shows a schematic diagram of the structure of the vertical tension-shear composite connection node of the modular steel structure building in this embodiment, wherein the upper module column 1 and the floor beam 3 are welded to the upper connection box 6, the lower module column 2 and the ceiling beam 4 are welded to the lower connection box 7, the upper connection box 6 and the lower connection box 7 are connected by applying a pre-tightening force through the tie rod 5, and the assembly gap between the connection box and the tie rod 5 is filled with grouting material 8 to complete the vertical tension-shear composite connection node.

[0057] Figure 5 The figure shows the dimensions of the various components of the node, wherein the tie rod 5 includes a tie rod shaft section 51 and a tie rod shear section 52, and the tie rod shaft section 51 extends into the upper module column 1; the upper connecting box 6 and the lower connecting box 7 have the same structure and dimensions. Taking the upper connecting box 6 as an example, the upper connecting box 6 includes a connecting box side plate and a connecting box shear plate 63, wherein the connecting box side plate includes two connecting box flange plates 61 and two connecting box webs 62.

[0058] Combination Figure 5 , the connection box web 62 and the connection box flange plate 61 are perpendicular to each other, and the plate surface of the connection box web 62 is in line with the drawing main view ( Figure 5 The plane of the node plan view in Figure (a) is parallel, the plate surface of the connection box flange plate 61 is perpendicular to the plane of the drawing main view, and the connection box flange plate 61 and the connection box web 62 are located at the same height. The plate surface of the connection box shear plate 63 is perpendicular to the plate surfaces of the connection box flange plate 61 and the connection box web 62. The upper and lower connection boxes are arranged symmetrically, so for the upper connection box 6, the connection box shear plate 63 is located below its connection box flange plate 61 and the connection box web 62, and for the lower connection box 7, the connection box shear plate 63 is located above its connection box flange plate 61 and the connection box web 62. (The plate surface here refers to the surface perpendicular to the plate thickness direction)

[0059] The cross section of the connection box side plate is a square tube cross section, and the side length of the cross section of the connection box side plate is equal to the side length of the cross section of the module column.

[0060] See also Figure 2 The present embodiment provides a method for designing a vertical tension-shear composite connection node of a modular steel structure building, comprising the following steps:

[0061] Step 1: Preliminary calculation of the internal forces borne by the nodes in the ultimate working state I and the ultimate working state II.

[0062] Among them, the node limit working state I refers to the state in which the shear force at the beam end is transmitted to the node and converted into axial tension when both the ceiling beam and the floor beam at the node enter the full-section plastic state; the node limit working state II refers to the state in which the shear force at the beam end is transmitted to the node and converted into axial pressure when both the ceiling beam and the floor beam at the node enter the full-section plastic state.

[0063] This step is done by Figure 3 , Figure 4 The stress state of the nodes of the mid-plane module frame under the limit working state I and the limit working state II, and the situation of the nodes bearing internal forces are obtained.

[0064] First, according to the cross-sectional dimensions and material properties of floor beam 3 and ceiling beam 4, the bending moments borne by floor beam 3 and ceiling beam 4 under the limit state are determined respectively. M fb,p , M cb,p ;

[0065] Then the axial force on the node in the limit working state I is calculated T j0 and bending moment M j0 , axial force T j0 It can be calculated based on the shear force at the end of the floor beam 3 of the floor where the node is located and the axial force transmitted by the upper module column 1, where the axial force borne by the upper module column 1 is the sum of the gravity of the current floor and the upper floor borne by the upper module column 1 and the shear force borne by all ceiling beams 4 and floor beams 3 of the upper floor connected to the upper module column 1. The bending moment borne by the node under the ultimate working state I M j0 The end bending moment of the upper module column 1 at the node can be M c,u Bending moment at the end of floor beam M fb,p Determine, that is M j0 = M c,u - M fb,p .

[0066] Step 2: First, determine the preload of the tie rod based on the performance target that the vertical node does not disengage or pry under the ultimate working state I. P 0, then according to the preload of the tie rod P 0 Determine the cross-sectional dimensions of the pull rod shaft pull section 51.

[0067] The node does not disengage under the limit state I, which means that the upper connection box 6 and the lower connection box 7 are always in close contact under the action of the axial tension, that is, there is always a preload between the upper connection box 6 and the lower connection box 7. The following formula is used to ensure that the preload meets this performance target:

[0068]

[0069] in, T j0 is the most unfavorable axial tension of the node under the limit working state I, b box is the side length of the connection box section, M j0 is the bending moment borne by the node under the ultimate working state I;

[0070] The performance target of the node not to be pried under the limit working state I refers to the node under axial force T j0 and bending moment M j0 Under the combined action, the upper connecting box 6 and the lower connecting box 7 do not produce relative rotation, and the following formula is used to ensure that the preload force meets this performance target:

[0071]

[0072] In the formula b box is the cross-sectional side length of the connection box, such as Figure 5 shown.

[0073] Preload of tie rod P 0, the cross-sectional dimensions of the pull rod shaft section 51 are determined according to the magnitude of the preload force, which must satisfy the requirement that the pull rod shaft section 51 does not yield during the application of the preload force, and the cross-sectional diameter of the pull rod shaft section 51 is D bar,T The following formula must be satisfied:

[0074]

[0075] In the formula, is the tensile strength of the tie rod, A e for Figure 5 The effective cross-sectional area of ​​the pull rod shaft section 51 is shown as follows, D bar,T for Figure 5 The diameter of the pull rod shaft section 51 is shown, e It is the thread pitch of the pull rod shaft pull section 51.

[0076] The cross-sectional diameter of the pull rod shear section 52 is preliminarily determined based on the cross-sectional diameter of the pull rod shaft pull section 51. D bar,V , the cross-sectional diameter of the tie rod shear section 52 is not less than the cross-sectional diameter of the tie rod shaft section 51, that is, D bar,V ≥ D bar,T .

[0077] Step 3: Determine the thickness of the connection box shear plate 63 and the compressive strength of the grouting material 8. The thickness of the connection box shear plate 63 should ensure that the connection box shear plate 63 does not yield under the limit working state I of the node, and the compressive strength of the grouting material 8 should ensure that the grouting material 8 does not suffer compressive damage under the limit working state I of the node.

[0078] Since the upper connection box 6 and the lower connection box 7 of the node have the same size, the size of each plate of the connection box is determined by taking the upper connection box 6 as an example. V c The shear force borne by the friction between the upper connecting box 6 and the lower connecting box 7 and the shear plate 63-grouting material 8-pull rod pull shear section 52 is shared by the joint pressure. V bar A conservative choice is: V bar = V c -μ( P 0-0.95 T j0 ), where μ is the friction coefficient between steels, V c is the shear force borne by the node. Figure 6 The force transmission mechanism of the connecting box shear plate 63, the grouting material 8, and the pull rod shear section 52 is shown, wherein the width of the compression area of ​​the connecting box shear plate 63 of the upper connecting box and the compression area of ​​the grouting material 8 is D bar,V In order to avoid the compression yielding of the connection box shear plate 63 and the compression failure of the grouting material 8, the thickness of the connection box shear plate 63 should satisfy the following formula:

[0079]

[0080] The strength of the grouting material 8 should satisfy the following formula:

[0081]

[0082] In the formula, is the yield strength of the connection box, is the strength of the grouting material 8, such as Figure 5 As shown, t sp is the thickness of the connection box shear plate 63.

[0083] Step 4: Check whether the tie rod shear section 52 yields under the node limit working state I; if it yields, return to step 2 and increase the cross-sectional diameter of the tie rod shear section 52; if it does not yield, proceed to the next step.

[0084] like Figure 7 As shown, since the connecting box shear plate 63 has a certain thickness, the tie rod shear section 52 needs to bear the bending moment caused by the shear force in addition to the shear force and the pre-tension force. The most unfavorable section of the tie rod shear section 52 is the junction of the upper connecting box 6 and the lower connecting box 7. The following formula should be used to determine whether the most unfavorable section of the tie rod shear section 52 yields:

[0085]

[0086] In the formula, is the elastic resistance moment of the cross section of the tie rod shear section 52, is the yield strength of the tie rod 5;

[0087] If the equation holds true, the tie rod shear section 52 does not yield, and the next step is executed; otherwise, the tie rod shear section 52 yields, and the process returns to step 2 to readjust the cross-sectional dimensions of the tie rod shear section 52.

[0088] Step 5: Determine the size of the connection box side plate, which includes two flange plates and two web plates. For this plane frame node, the connection box flange plate mainly bears local pressure, and the connection box web plate mainly bears shear force. The connection box flange plate should meet the requirement that the node does not suffer local pressure damage under the limit working state II, and the connection box web plate should meet the requirement that the node does not suffer shear yield damage under the limit working state I and the limit working state II. In addition, the axial stiffness of the connection box should meet the requirement that the increase in the tie rod preload under the limit working state I does not exceed 5% of the initial preload.

[0089] Taking the above connection box 6 as an example, the upper connection box flange plate 61 needs to meet the requirement that no local pressure damage occurs under the node limit working state II, and its thickness needs to meet the following formula:

[0090]

[0091] In the formula, N j0 is the most unfavorable axial pressure that the node bears under the limit state II, is the yield strength of the upper connection box, such as Figure 5 As shown, t f,boxis the thickness of the flange of the connection box, b box is the width of the connection box flange.

[0092] To ensure that the web of the connection box does not undergo shear yielding, the following two equations should be satisfied at the same time:

[0093]

[0094]

[0095] In the formula, M cb,p is the bending moment borne by the ceiling beam under the node limit working state I or the node limit working state II, M fb,p is the bending moment borne by the floor beam under the node limit working state I or node limit working state II, is the shear yield strength of the connecting box steel. Figure 5 As shown, is the height of the ceiling beam, is the height of the floor beam, t w,box is the thickness of the web of the connection box, t f,box is the thickness of the connection box flange.

[0096] When the node is subjected to axial force, the change of the axial force of the tie rod 5 will depend on the axial stiffness of the tie rod 5 and the axial stiffness of the upper connecting box 6. The axial stiffness of the tie rod 5 is mainly determined by the axial stiffness of the tie rod axial section 51 and the tie rod shear section 52. The axial stiffness of the upper connecting box 6 is approximately equal to the axial stiffness of the side plate of the upper connecting box 6. In order to ensure that the increase in the tie rod preload at the node under the limit state I does not exceed 5%, the stiffness of the tie rod 5 and the upper connecting box 6 should satisfy the following formula:

[0097]

[0098]

[0099]

[0100] in K box is the axial stiffness of the upper connection box 6, K bar is the axial stiffness of the tie rod 5, A bar,T is the cross-sectional area of ​​the pull rod shaft section 51, A bar,V is the cross-sectional area of ​​the tie rod shear section 52, A box is the cross-sectional area of ​​the side plate of the upper connection box 6, Eis the elastic modulus of steel, such as Figure 5 As shown, is the height of the side plate of the upper connection box 6, is the length of the pull rod shaft section 51, It is the length of the pull rod shear section 52.

[0101] In some embodiments of the present invention, Figure 8 The plastic strain of the vertical tension-shear composite node designed by this design method under two limit working states is given. The node is taken from a 5-story 3-span modular steel structure building. The outer contour height of the steel structure module is 3m, the longitudinal outer contour length is 6m, and the transverse outer contour width is 3m. The node model includes half of the first-floor module column, half of the second-floor module column, half of the first-floor module ceiling beam, and half of the second-floor module floor beam. The module column is made of Q355 cold-formed steel square tube with a cross-sectional size of ; Floor beams and ceiling beams are made of hot-rolled H-shaped steel with a cross-sectional size of The beams at the first floor nodes are made of Q355 steel, and the beams at the other nodes on the upper part are made of Q235 steel.

[0102] The rationality of the vertical node design method is verified by monotonic loading of the node finite element model. Figure 8 The equivalent plastic strain distribution of the connecting box, tie rod and beam end under the node limit working state I and limit working state II shows that under the two limit working states, when the beam end has reached full cross-section yield, the connecting box and tie rod have not yielded, verifying the effectiveness of the design method of the present invention.

[0103] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The seismic design method of vertical tension-shear composite connection nodes of modular steel structure buildings is characterized by: The method comprises the following steps: Step 1: Preliminary calculation of the internal forces of the node in the limit working state I and the limit working state II. The node limit working state I refers to the state in which the shear force at the end of the beam is transferred to the node and converted into axial tension when both the ceiling beam and the floor beam at the node enter the full section plastic state; the node limit working state II refers to the state in which the shear force at the end of the beam is transferred to the node and converted into axial pressure when both the ceiling beam and the floor beam at the node enter the full section plastic state; Step 2: Determine the preload force of the tie rod according to the performance target that the node does not disengage or pry under the limit working state I. P 0; According to the preload of the tie rod P 0 Determine the cross-sectional dimensions of the tie rod shaft section; preliminarily determine the cross-sectional diameter of the tie rod shear section based on the cross-sectional diameter of the tie rod shaft section D bar,V ; Step 3, determine the thickness of the shear plate of the connection box and the compressive strength of the grouting material of the node, wherein the thickness of the shear plate of the connection box satisfies that no pressure yielding of the hole wall occurs under the node limit working state I, and the strength of the grouting material satisfies that no compression failure occurs under the node limit working state I; Step 4, verify whether the tension shear section of the tie rod yields under the node limit working state I; if it yields, return to step 2 and increase the cross-sectional diameter of the tension shear section of the tie rod; if it does not yield, execute step 5; Step 5, determine the size of the connecting box side plate of the node, where the connecting box flange plate satisfies that the node does not suffer local compression failure under the limit working state II, and the connecting box web satisfies that the node does not suffer shear yield failure under the limit working state I and the limit working state II; and the connecting box stiffness satisfies that the increase in the preload force of the tie rod under the limit working state I does not exceed the set percentage of the initial preload force.

2. The seismic design method for vertical tension-shear composite connection nodes of modular steel structure buildings according to claim 1 is characterized in that: In step 1, the internal forces of the nodes under the ultimate working state I and the ultimate working state II are preliminarily calculated, including the bending moments of the floor beams and ceiling beams under the ultimate working state I and the ultimate working state II. M fb,p , M cb,p , and the most unfavorable axial tension of the node in the limit working state I T j0 The bending moment of the node under the limit working state I M j0 .

3. The seismic design method for vertical tension-shear composite connection nodes of modular steel structure buildings according to claim 2 is characterized in that: Determine the bending moments of the floor beams and ceiling beams under the limit state according to the cross-sectional dimensions and material properties of the floor beams and ceiling beams. M fb,p , M cb,p ; Calculate the most unfavorable axial tension of the node in the limit working state I according to the shear force at the end of the floor beam of the node and the axial force transmitted by the upper module column T j0 .

4. The seismic design method for vertical tension-shear composite connection nodes of modular steel structure buildings according to claim 2 is characterized in that: Bending moment of the node under the ultimate working state I M j0 According to the end bending moment of the upper module column at the node M c,u Bending moment at the end of floor beam M fb,p Determine, that is M j0 = M c,u - M fb,p .

5. The seismic design method for vertical tension-shear composite connection nodes of modular steel structure buildings according to claim 1 is characterized in that: In step 2, determine the preload force of the tie rod P 0, the following two formulas must be satisfied at the same time: in, T j0 is the most unfavorable axial tension of the node under the limit working state I, b box is the cross-sectional side length of the connection box, M j0 is the bending moment borne by the node under the ultimate working state I; Cross-sectional diameter of the tie rod shaft section D bar,T Satisfy the following formula: In the formula, is the tensile strength of the rod, A e is the effective cross-sectional area of ​​the tie rod shaft section, D bar,T is the diameter of the pull rod shaft section, e It is the thread pitch of the pull rod shaft section.

6. The seismic design method for vertical tension-shear composite connection nodes of modular steel structure buildings according to claim 1 is characterized in that: The size of the upper connection box is exactly the same as that of the lower connection box, and the cross-sectional side length of the connection box side plate is equal to the cross-sectional side length of the module column.

7. The seismic design method for vertical tension-shear composite connection nodes of modular steel structure buildings according to claim 1 is characterized in that: The cross section of the connection box side plate is a square tube section.

8. The seismic design method for vertical tension-shear composite connection nodes of modular steel structure buildings according to claim 1 is characterized in that: The thickness of the shear plate of the connection box in step 3 satisfies the following formula: The strength of the grouting material satisfies the following formula: In the formula, V bar is the shear force on the tie rod when the node is in the ultimate working state I, is the yield strength of the connection box, t sp is the thickness of the shear plate of the connection box, The strength of the grouting material.

9. The seismic design method for vertical tension-shear composite connection nodes of modular steel structure buildings according to claim 1, characterized in that: In step 4, determine whether the shear section of the tie rod yields according to the following formula: In the formula, V bar is the shear force on the tie rod when the node is in the ultimate working state I, t sp is the thickness of the shear plate of the connection box, is the elastic resistance moment of the tension shear section of the tie rod, is the yield strength of the tie rod; if this formula holds true, the tie rod shear section does not yield; otherwise, the tie rod shear section yields.

10. The seismic design method for vertical tension-shear composite connection nodes of modular steel structure buildings according to any one of claims 1 to 9, characterized in that: In step 5, the following formula must be satisfied to ensure that the flange plate of the connection box does not suffer local pressure damage: In the formula P 0 is the preload of the tie rod, N j0 is the most unfavorable axial pressure that the node bears under the limit working state II, t f,box is the thickness of the flange of the connection box, b box is the width of the connection box flange, is the yield strength of the connection box; To ensure that the web of the connection box does not undergo shear yield, the following two equations should be satisfied at the same time: In the formula M cb,p is the bending moment borne by the ceiling beam under the node limit working state II, M fb,p is the bending moment borne by the floor beam under the node limit working state I, is the height of the ceiling beam, is the height of the floor beam, t w,box is the thickness of the web of the connection box, t f,box is the thickness of the flange of the connection box, is the shear yield strength of the connecting box steel; To ensure that the increase in the preload force of the tie rod under the node limit working state I does not exceed 5%, the following formula should be satisfied: in T j0 is the most unfavorable axial tension of the node under the limit working state I, K box is the axial stiffness of the connection box, K bar is the axial stiffness of the tie rod, is the length of the pull rod shaft section, is the length of the shearing section of the tie rod, E is the elastic modulus of steel, A bar,T is the cross-sectional area of ​​the tie rod shaft section, A bar,V is the cross-sectional area of ​​the shear section of the tie rod, A box is the cross-sectional area of ​​the side plate of the connection box, is the height of the side panel of the connection box.

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