The present invention relates to the technical field of earthquake resistance of civil engineering, and in particular to a connection design method for a lateral resisting system of a self-centering steel frame.
When natural disasters occur, earthquakes and typhoons mainly stimulate the structure in a horizontal direction. Thus, a lateral resisting system which mainly resists the horizontal load becomes the most critical link to protect the safety of the structure. The lateral resisting system is arranged, which not only can ensure that the structure meets the requirements of stiffness, strength and ductility in normal use and bearing capacity limit states, but also can give full play to the performance of materials and obtain good economic benefits.
In the existing lateral resisting system of a self-centering frame, a frame structure is formed generally by a foundation, steel columns and cross beams. For example, application publication number CN111691544A (application publication date 2020 Sep. 22) discloses a lateral resisting system of a self-centering steel frame, comprising a self-centering column base structure and a self-centering connection structure. The steel columns are vertically arranged on the top surface of the foundation, and the bottom ends of the steel columns are connected with the foundation to form the self-centering column base structure. A steel plate is embedded inside the foundation. A suspension board is horizontally fixed on the side wall of the steel column. The anchor rod passes through the suspension board and the embedded steel plate, and are fixed through first high strength nuts. A first disc spring group is sleeved between the first high strength nuts and the top end of the top surface of the suspension board. The cross beams are arranged horizontally, and the ends of the cross beams are connected with the side walls of the steel columns to form a self-centering connection structure. End plates are fixed at the ends of the cross beams, and high strength pull rods pass through the side walls of the cross beams and the end plates, and are fastened by second high strength nuts. A second disc spring group is fixed between the end plate of at least one end of the high strength pull rods and the second high strength nuts. Stiffening ribs are arranged up and down between the high strength pull rods. Both ends of a C-type energy dissipation steel plate are fixedly connected with the side walls of the steel columns and the flanges of the cross beams respectively. The principle is that, in an earthquake, when the cross beams swing, the earthquake energy can be dissipated in the earthquake by the C-type energy dissipation steel plates between the beams and the columns; when the cross beams swing up and down, the deformation of the second disc spring group on the plurality of groups of high strength pull rods connected with the beams and the columns is increased, so as to realize the rapid post-earthquake self-centering of the frame structure; and finally, the energy dissipation and self-centering function of the beam column connections are realized, which solves the problem of large residual deformation of the beams and the columns after the earthquake, and enables the structure to dissipate energy in the earthquake and quickly restore the use function after the earthquake.
At present, the traditional earthquake resistance thought takes the protection of life as the primary goal, and avoids the collapse of the structure under strong earthquakes through ductility design. However, the ductility design comes at the cost of allowing plastic deformation of the main stressed members of the structure. On the other hand, due to the uncertainty of earthquake action, the structure may suffer stronger earthquake action than fortification intensity during use and is seriously damaged or even overturned. The results of earthquake disasters in recent years show that although the number of building collapses and human deaths in earthquakes has been effectively controlled, the direct and indirect economic losses caused by the earthquakes are huge, wherein the indirect economic losses caused by the interruption of urban functions have exceeded the direct economic losses. In recent years, many researchers have proposed the concept of recoverable functional structure. Earthquake recoverable functional structure refers to the structure that can restore the use function without repair or with slight repair after an earthquake. Its main purpose is to enable the structure to have the capability of quickly recovering the use function after the earthquake, so as to reduce the impact caused by the interruption of the structure functions after the earthquake.
Therefore, it is an urgent problem for those skilled in the art to propose a connection design method for a lateral resisting system of a self-centering steel frame with strong horizontal load resistance, self-centering performance, energy dissipation capacity and excellent ductility and fatigue resistance.
In view of this, the present invention provides a connection design method for a lateral resisting system of a self-centering steel frame to solve the above technical problems.
To realize the method design provided by the present invention, firstly, the present invention provides a corresponding lateral resisting system of a self-centering steel frame, comprising: a foundation, steel columns and cross beams;
The steel columns are vertically arranged on the top surface of the foundation, and the bottom ends of the steel columns are connected with the foundation to form a self-centering column base structure;
The cross beams are horizontally arranged, and ends are connected with the side walls of the steel columns; and the steel columns and the cross beams connected at both sides form a self-centering connection structure.
When the system provided by the present invention is under the action of frequently occurred earthquakes, each connection of the structure is closed, which is consistent with the traditional structure, to resist the action of the earthquakes relying on the elastic deformation of the structure. Under the action of rarely occurred earthquakes, each connection of the structure is opened to prevent a main structure from generating plastic loss. Meanwhile, the self-centering column base structure, a self-centering connection structure and an energy dissipation device generate plastic deformation to dissipate seismic energy, to jointly ensure that the connections and the column base have good self-centering performance and the lateral resistance, energy dissipation and self-centering functions of the whole system can be finally realized.
Preferably, in the above lateral resisting system of a self-centering steel frame, the self-centering column base structure comprises an embedded steel plate, a suspension board, anchor bolts and a first disc spring group;
The embedded steel plate is embedded inside the foundation.
The suspension board is horizontally fixed to the side wall of the steel column near the foundation.
A plurality of anchor rods are arranged, and are vertically distributed; both ends of the anchor rods pass through the suspension board and the embedded steel plate respectively, and are fastened through first high strength nuts.
The first disc spring group is sleeved at the top ends of the anchor rods, and abutted between the top surface of the suspension board and the first high strength nuts at the top end.
The structure swings; the suspension board at the bottom of the steel columns tilts and presses the first disc spring group; and the first disc spring group produces a reaction force to compel the structure to return to an initial position, thereby achieving the effect of self-centering the column base structure. Meanwhile, due to the limitation of the first high strength nuts on the first disc spring group, the maximum swing position of the structure is limited by the heights of the first high strength nuts, which increases the swing controllability.
Preferably, in the above lateral resisting system of a self-centering steel frame, the top surface of the foundation is provided with a limiting groove through which the steel columns are inserted; a bottom plate is fixed at the bottom ends of the steel columns; and a cushioning rubber pad is fixed between the bottom plate and the limiting groove. The cushioning rubber pad arranged at the bottom end of the steel column can play a cushioning role in the earthquake, and the limiting groove controls the lateral drift at the bottom of the steel column.
Preferably, in the above lateral resisting system of a self-centering steel frame, a supporting plate is fixed between the bottom surface of the suspension board and the side wall of the steel column. The structural stability of the suspension board can be effectively improved.
Preferably, in the above lateral resisting system of the self-centering steel frame, the self-centering connection structure comprises end plates, high strength pull rods and C-type energy dissipation steel plates;
The end plates are fixed to the ends of the cross beams;
A plurality of high strength pull rods are arranged, horizontally penetrate through the side walls of the steel columns and the two end plates, and are fastened at both ends through second high strength nuts. and at least one end of the high strength pull rods is sleeved with a second disc spring group abutted between the end plates and the second high strength nuts;
A plurality of C-type energy dissipation steel plates are arranged; and both ends of the C-type energy dissipation steel plates are fixedly connected with the side walls of the steel columns and flanges of the cross beams respectively.
In an earthquake, when the cross beams swing, the earthquake energy can be dissipated in the earthquake by the C-type energy dissipation steel plates between the beams and the columns; when the cross beams swing up and down, the deformation of the second disc spring group on the plurality of groups of high strength pull rods connected with the beams and the columns is increased, so as to realize the rapid post-earthquake self-centering of the frame structure; and finally, the energy dissipation and self-centering function of the beam column connections are realized, which solves the problem of large residual deformation of the beams and the columns after the earthquake, and enables the structure to dissipate energy in the earthquake and quickly restore the use function after the earthquake.
Preferably, in the above lateral resisting system of the self-centering steel frame, in the self-centering connection structure, a plurality of stiffening ribs are welded and fixed between two side walls of the steel columns, and the stiffening ribs are arranged up and down between the high strength pull rods. The strength of the side walls of the steel columns is improved.
Preferably, in the above lateral resisting system of the self-centering steel frame, the highest layout horizontal plane of the plurality of stiffening ribs is flush with the top surface of the cross beams, and the lowest layout horizontal plane is flush with the bottom surface of the cross beams. The strength of the steel columns can be improved, and the structural strength of connection between the steel columns and the cross beams can also be improved.
Preferably, in the above lateral resisting system of the self-centering steel frame, both ends of the C-type energy dissipation steel plates are welded and fixed with the side walls of the steel columns and the flanges of the cross beams, or fixed with bolts respectively. The C-type energy dissipation steel plates can in non-permanent connection easy for replacement and maintenance, or in stable permanent connection.
Preferably, in the above lateral resisting system of the self-centering steel frame, the steel columns are I-steel or square steel tubes or concrete filled steel tubes. The use range of the structure of the present invention can be extended.
Based on the structure of the above lateral resisting system of the self-centering steel frame, to achieve the above connection design, the present invention adopts the following technical solution:
A connection design method for a lateral resisting system of a self-centering steel frame comprises the following steps:
Through the above technical solution, in the connection design method for the lateral resisting system of the self-centering steel frame provided by the present invention, structural components are independent in functions, clear in stress and definite in force transmission. The vertical load of the main structure is mainly borne by the prepressure provided by the disc springs, which is different from the traditional energy-dissipating angle steel which bears both shear resistant and energy dissipation purposes. The C-type energy dissipation steel plates are easy to deform under the stress and do not increase the bearing capacity and shearing resistance, which is convenient for the calculation of the stress of the main structure. The checking of the bearing capacity and the stability under the action of large earthquakes is conducted on the basis of meeting the requirements of small earthquakes. The calculation methods are simple and feasible, can ensure more accurate results, and have good popularization and application values. The lateral resisting system of the steel frame designed by the method has strong resistance to horizontal load, self-centering performance and energy dissipation capability, and also has excellent ductility and fatigue resistance.
Preferably, in the above connection design method for the lateral resisting system of the self-centering steel frame, in step 1, the section sizes and heights of steel columns and steel beams are determined, and the used steel has sectional inertia moment I, elastic modulus E and yield strength fy. This is used as the calculation basis of connection design.
Preferably, in the above connection design method for the lateral resisting system of the self-centering steel frame, in step 2, the shearing force of the column bottom is resisted by embedding shear keys in the foundation, and the shear keys only constrain the horizontal lateral movement of the column base. After consideration, the elastic effect of the structure is calculated under the action of small earthquakes, and then the design internal force required by each connection is obtained through the combination of load effects.
Preferably, in the above connection design method for the lateral resisting system of the self-centering steel frame, in step 3, the prepressure F0 to be applied for each anchor rod at the column bottom is determined according to the performance-based design requirements in the current seismic codes, so that the flanges of the column base are not separated from the foundation under the action of small earthquakes; and prepressure F0′ to be applied for the beam column connection is determined so that beam flanges are not separated from the side walls of the columns under the action of small earthquakes.
The bending moment M at the column bottom under the action of small earthquakes is known from the above calculation of the internal force. In order to prevent the column base from lifting, the bending moment value generated by the prepressure and the axial force on the rotation point of the column base shall be greater than the bending moment M at the column bottom under the action of small earthquakes, namely:
N×0.5 h+M0≥M;
The beam end bending moment Mt under the action of small earthquakes is known. In order to keep the beam column connection closed, the bending moment value generated by the prepressure on the rotation point of the beam column connection shall be greater than the bending moment Mt at the column top under the action of small earthquakes, namely:
M
0
′≥M
t
M0 is the bending moment value generated by the prepressure on the rotation point of the column base, M0′ is the bending moment value generated by the prepressure on the rotation point of the beam column connection and h is the sectional height of the column. Since the axial force is known, the prepressure F0 of each anchor rod can be calculated.
Preferably, in the above connection design method for the lateral resisting system of the self-centering steel frame, in step 4, an inter-storey drift angle limit θ in a large earthquake is determined according to the current building seismic design code of China, and then an inter-storey lateral drift limit Δ is calculated.
When the angle is very small, tanx=x, so Δ/hc=θ; hc is the column height, and hc and θ are both known, so Δ can be obtained.
Preferably, in the above connection design method for the lateral resisting system of the self-centering steel frame, in step 5, the rotational stiffness K1′ of the column top and the rotational stiffness K2′ of the column base generated by the disc spring and energy dissipating parts are obtained by taking the moment of the rotation point; K1′ and K2′ are not considered, and the column bottom is set as hinged. The upper column generates rotational stiffness K1″=3.5i2 to point A; point A provides rotational stiffness for point B: K2″=αi1; α is rotational constraint stiffness coefficient, and i1 is column line stiffness, wherein:
Horizontal lateral movement weakens rotational stiffness transfer. Kt and Kd are the rotational stiffness at both ends of the column. The lateral stiffness D of the column top can be calculated, and then the rotational stiffness K1″′ transferred by K2′ to the column top and rotational stiffness K2′″ transferred by K1′ to the column bottom can be obtained. Thus, rotational stiffness of the column base can be obtained: K2=K2′+K2″+K2″′, and rotational stiffness of the column top is K1=K1′+K1″+K1″′, wherein:
Preferably, in the above connection design method for the lateral resisting system of the self-centering steel frame, in step 6, the inter-storey lateral drift limit Δ in a large earthquake is determined in step 4; and the angular drift limits θ1 and θ2 of the beam column connection and the column base connection are calculated according to a force method or a drift method.
The rotational stiffness K1 and K2 at both ends of the column, the horizontal lateral movement at the column top and the column body line stiffness i1 are known, and equations of the force method are listed:
Bending moments X1 and X2, at the column top and the column bottom can be calculated, and then angles θ1 and θ2 at the column top and the column bottom can be calculated.
A drift method is also used for checking results:
The results are consistent, and the angular drift limits θ1 and θ2 of the beam column connection and the column base connection in the large earthquake are obtained.
Preferably, in the above connection design method for the lateral resisting system of the self-centering steel frame, in step 7, the proportion of the bending moment bearing capacity provided by a disc spring in the bending capacity of the whole section is φdes under the action of the large earthquake, and the proportion of the bending moment bearing capacity provided by the C-type energy dissipation steel plate is (1−φdes), so as to calculate the bending moment bearing capacity Mb provided by the energy dissipation steel plate to design the section size of the energy dissipation steel plate.
When the inter-storey drift angle reaches 1/50, the disc spring provides the bending moment bearing capacity Ms, so the energy dissipation steel plate provides the bending moment bearing capacity:
Mh=fyAd, d is the vertical distance from the axial force direction of the energy dissipation steel plate to the connection rotation point, and the section size of the energy dissipation steel plate can be preliminarily determined.
Preferably, in the above connection design method for the lateral resisting system of the self-centering steel frame, in step 8, according to the column bottom angle θ2 under the action of the large earthquake, the bending moment Mp generated by the prepressure, the bending moment Ma generated by the axial force and the bending moment ΔM increased by the deformation of the disc spring group when the column base produces the angle θ2 can be obtained respectively. The allowable bending moment Md of the column bottom under the action of the large earthquake can be obtained by adding the three. According to the angle θ1 of the beam column connection under the action of the large earthquake, the bending moment Mp′ generated by prepressure when the connection produces angle θ1, the bending moment Mb generated by the C-type energy dissipation steel plate yielding and the bending moment ΔM′ increased by the deformation of the disc spring group can be obtained respectively. The allowable bending moment Md′ of the beam column connection under the action of the large earthquake can be obtained by adding the three.
According to the column bottom angle θ2 under the action of the large earthquake, the bending moment Mp generated by the prepressure, the bending moment Ma generated by the axial force and the bending moment ΔM increased by the deformation of the disc spring group when the column base produces the angle θ2 can be obtained respectively. The allowable bending moment Md of the column bottom under the action of the large earthquake can be obtained by adding the three. According to the angle θ1 of the beam column connection under the action of the large earthquake, the bending moment Mp′ generated by prepressure when the connection produces angle θ1, the bending moment Mb generated by the C-type energy dissipation steel plate yielding and the bending moment ΔM′ increased by the deformation of the disc spring group can be obtained respectively. The allowable bending moment Md′ of the beam column connection under the action of the large earthquake can be obtained by adding the three.
Preferably, in the above connection design method for the lateral resisting system of the self-centering steel frame, in step 9, according to the angular drift of each connection, the axial deformation δy of the connection disc spring can be obtained, and then the anchor rod axial force generated by the axial deformation of the disc spring can be calculated. By adding the anchor rod axial force with the initial prepressure on the disc spring, the axial force Fy and Fy′ of each anchor rod of each connection can be obtained.
According to the angular drift of each connection, the axial deformation δy of the connection disc spring can be calculated, and then the anchor rod axial force generated by the axial deformation of the disc spring can be calculated. The axial force of each anchor rod at each connection can be obtained by adding the initial prepressure on the disc spring.
Preferably, in the above connection design method for the lateral resisting system of the self-centering steel frame, in step 10, the moment of the rotation point of the column base is taken to obtain the column axial force P when the angular drift limit θ2 is reached, and the local pressure Fc of the column flange is obtained through equilibrium conditions; the equivalent beam axial force P′ when the angular drift limit θ1 is reached is obtained by taking the moment of the rotation point of the beam column connection, and the local pressure Fc′ of the beam flange is obtained by the equilibrium conditions.
Preferably, in the above connection design method for the lateral resisting system of the self-centering steel frame, in step 11 and step 12, the design and calculation of the self-centering steel frame connections are completed when the checking results meet the requirements.
Checking steps in step 11 and step 12 are as follows:
1. Column Base Part:
(1) Firstly, Ensuring that the High Strength Anchor Rod May not Yield
(2) Checking the Strength According to the Strength Checking Formula of Tensile Bending and Compression Bending Members:
In the formula:
(3) In-Plane Stability Checking:
Wherein:
(4) Local Stability Checking:
Width to thickness ratio of the compression flange of the box section,
(5) Local Pressure at the Column Bottom:
wherein: Afn—Local pressure sectional area
2. Beam Column Connection Part:
(1) Firstly, Ensuring that the High Strength Pull Rod May not Yield
(2) Checking the Self-Centering Beam Section
The beam end bending moment shall be less than the plastic bending moment:
M
d
≤M
n
=F
y
W
x
Checking the strength by a bending strength checking formula:
Local Stability of Compression Flange:
The maximum pressure Fb of the compression flange plate is checked by the following formula (local stability):
(3) Shear Check of Beam-Column Joint Surface
The shear strength of the beam-column joint surface is mainly provided by the prepressure provided by the disc spring. The simplified analysis and calculation formula of the shear capacity V of the beam-column joint surface can be obtained as follows:
V
n=μfFpr
3. Checking Self-Centering Capability:
If φdes design value is greater than or equal to 0.5, namely Mprs/Mp≥0.5 it can ensure that the section meets the requirements of self-centering according to the codes. If φdes design value is less than 0.5, it needs to ensure that the connection meets Mprs≥Mat+Mac at the zero bound point of opening and closing.
If checking cannot meet the requirements, φdes needs to be adjusted and the section size of the C-type energy dissipation steel plate is also reduced or the prestress of the disc spring is increased, and the calculation is repeated until the requirements of self-centering are met.
It can be known from the above technical solutions that compared with the prior art, the present invention discloses and provides a connection design method for a lateral resisting system of a self-centering steel frame, and has the following beneficial effects:
1. Strong self-centering ability: the disc spring group of each connection generates restoring force when the structure is deformed, and the restoring force is superimposed with the prepressure of the disc spring group to form the self-centering bending moment, which jointly ensures that the connection and column base have good self-centering performance, so as to realize no damage or slight damage to the connection and the column base under the action of the large earthquake and ensure that the use function of the structure is not interrupted after the earthquake.
2. Strong energy dissipation capacity: existing studies show that the self-centering structure has a larger inter-storey drift angle than the traditional structure under the action of the earthquake. The present invention arranges the energy dissipation devices at the beam column connections to give full play to the energy dissipation characteristics of metal plastic deformation.
3. The structural components are independent in functions, clear in force and definite in force transmission: the vertical load of the main structure is mainly borne by the prepressure provided by the disc spring; different from the traditional energy-dissipating angle steel which bears both shear resistant and energy dissipation purposes, the C-type energy dissipation steel plates are easy to deform under the stress and do not increase the bearing capacity and shearing resistance, which is convenient for the calculation of the stress of the main structure.
4. According to the design method for the self-centering structure provided by the present invention, the present invention conducts the checking of the bearing capacity and the stability under the action of large earthquakes on the basis of meeting the requirements of small earthquakes. The calculation methods are simple and feasible, can ensure more accurate results, and have good popularization and application values.
To more clearly describe the technical solution in the embodiments of the present invention or in the prior art, the drawings required to be used in the description of the embodiments or the prior art will be simply presented below. Apparently, the drawings in the following description are merely the embodiments of the present invention, and for those ordinary skilled in the art, other drawings can also be obtained according to the provided drawings without contributing creative labor.
Wherein:
The technical solution in the embodiments of the present invention will be clearly and fully described below in combination with the drawings in the embodiments of the present invention. Apparently, the described embodiments are merely part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those ordinary skilled in the art without contributing creative labor will belong to the protection scope of the present invention.
By referring to
The steel columns 2 are I-steel or square steel tubes or concrete filled steel tubes. When the steel columns 2 are I-steel, in a self-centering column base structure 4, the inner sides of flanges of the steel columns 2 are fixed with flange reinforcing plates 46. The steel columns 2 are vertically arranged on the top surface of the foundation 1, and the bottom ends of the steel columns 2 are connected with the foundation 1 to form a self-centering column base structure 4. The cross beams 3 are horizontally arranged, and ends are connected with the side walls of the steel columns 2; and the steel columns 2 and the cross beams 3 connected at both sides form a self-centering connection structure 5.
The self-centering column base structure 4 comprises an embedded steel plate 41, a suspension board 42, anchor bolts 43 and a first disc spring group 44. The embedded steel plate 41 is embedded inside the foundation 1. The suspension board 42 is horizontally fixed to the surrounding side wall of the steel column 2 near the foundation 1. Eight anchor rods 43 are arranged, and are vertically distributed; both ends of the anchor rods 43 pass through the suspension board 42 and the embedded steel plate 41 respectively, and are fastened through first high strength nuts 45. The first disc spring group 44 is sleeved at the top ends of the anchor rods 43, and abutted between the top surface of the suspension board 42 and the first high strength nuts 45 at the top end. Rigid backup plates are cushioned above and below the first disc spring group 44. The top surface of the foundation 1 is provided with a limiting groove 11 through which the steel columns 2 are inserted; a bottom plate 21 is fixed at the bottom ends of the steel columns 2; and a cushioning rubber pad 12 is fixed between the bottom plate 21 and the limiting groove 11. A supporting plate 22 is fixed between the bottom surface of the suspension board 42 and the side wall of the steel column 2.
The self-centering connection structure 5 comprises end plates 51, high strength pull rods 52 and C-type energy dissipation steel plates 53; the end plates 51 are fixed to the ends of the cross beams 3; and three high strength pull rods 52 are arranged, horizontally penetrate through the side walls of the steel columns 2 and the two end plates 51, and are fastened at both ends through second high strength nuts 54. At least one end of the high strength pull rods 52 is sleeved with a second disc spring group 55 abutted between the end plates 51 and the second high strength nuts 54; four C-type energy dissipation steel plates 53 are arranged; and both ends of the C-type energy dissipation steel plates 53 are fixedly connected with the side walls of the steel columns 2 and flanges of the cross beams 3 respectively. A plurality of stiffening ribs 56 are welded and fixed between two side walls of the steel columns 2, and the stiffening ribs 56 are arranged up and down between the high strength pull rods 52; the highest layout horizontal plane of the plurality of stiffening ribs 56 is flush with the top surface of the cross beams 3, and the lowest layout horizontal plane is flush with the bottom surface of the cross beams 3. Both ends of the C-type energy dissipation steel plates 53 are welded and fixed with the side walls of the steel columns 2 and the flanges of the cross beams 3, or fixed with bolts respectively.
The principle of the lateral resisting system of the steel frame in the present embodiment is: when an earthquake comes, firstly, the C-type energy dissipation steel plates 53 located at the beam column connections dissipate the seismic energy; then, the deformation of the second disc spring group 55 on the beam column connection is increased, and the anchor rods 43, the first disc spring group 44 and the suspension board 42 at the lower parts of the steel columns 2 jointly form the self-centering column base; and the prepressing bending moment is formed through the prepressure of the disc spring group, to jointly ensure that the connections and the column base have good self-centering performance and finally realize the lateral resistance, energy dissipation and self-centering functions of the whole system. The lateral resisting system has the characteristics of strong lateral resistance, self-centering and energy dissipation capability, is clear in concept, convenient in construction and reasonable in building cost, and will be widely used in high-rise and super high-rise building structures.
The present invention has the characteristics of strong lateral resistance, self-centering and energy dissipation capability. The present invention is clear in concept, convenient in construction and reasonable in building cost, and will be widely used in high-rise and super high-rise building structures.
By referring to
S1: determining basic dimension parameters of components of a steel frame, comprising:
the section sizes and heights of steel columns and steel beams, and the basic parameters of the used steel comprise sectional inertia moment I and elastic modulus E; by referring to
By referring to
The column steel is selected from Q345 steel, the column height is hc, the beam section height is h′, and the beam length is L; and the elastic modulus E is known according to the properties of materials, and the sectional inertia moment I can be obtained through calculation.
S2: determining a connection design load, wherein the shearing force of the column bottom is resisted by embedding shear keys in the foundation, and the shear keys only constrain the horizontal lateral movement of the column base.
After consideration, the elastic effect of the structure is calculated under the action of small earthquakes, and then the design internal force required by each connection is obtained through the combination of load effects. The maximum bending moment of the column bottom of the steel column under the action of a small earthquake is M, the maximum bending moment of the beam end at the beam column connections is Mt, and column axial force is N;
S3: determining the performance targets of connections when designing self-centering connections; determining the prepressure F0 to be applied for each anchor rod at the column bottom according to the performance-based design requirements in the current seismic codes so that the flanges of the column base are not separated from the foundation, and prepressure F0′ to be applied for the beam column connection so that beam flanges are not separated from the side walls of the columns.
The bending moment M at the column bottom under the action of small earthquakes is known from the above calculation of the internal force. In order to prevent the column base from lifting, the bending moment value generated by the prepressure and the axial force on the rotation point of the column base shall be greater than the bending moment M at the column bottom under the action of small earthquakes, namely:
N×0.5 h+M0≥M;
The bending moment M at the column bottom under the action of small earthquakes is known. In order to prevent the column base from lifting, the bending moment value generated by the prepressure and the axial force on the column edge shall be greater than the bending moment M at the column bottom under the action of small earthquakes. A calculation diagram is shown in
Wherein: t is the thickness of the sectional steel plate, h is the sectional height of the column, and d1, d2, d3 and axial force are known, so the minimum prepressure F0 of each anchor rod can be calculated.
According to F0, the number of disc springs required by the first disc spring group and the combination form are determined, and the axial stiffness KS of the disc spring group is determined.
The bending moment Mt at the beam column connection under the action of small earthquakes is known. In order to keep the beam column connection closed, the bending moment value generated by the prepressure on the flanges of the beams shall be greater than the bending moment Mt at the column top under the action of small earthquakes. A calculation diagram is shown in
In the formula: t1 is the thickness of the beam flange plate, and a1 and a2 are known, so the minimum prepressure F0′ of each anchor rod can be calculated.
According to F0′, the number of disc springs required by the second disc spring group and the combination form are determined, and the axial stiffness KS′ of the disc spring group is determined.
S4: determining an inter-storey drift angle limit θ in a large earthquake according to the current building seismic design code of China, and then calculating an inter-storey lateral drift limit Δ;
When the angle is very small, tanx=x, so Δ/hc=0; hc is the column height, and hc and θ are both known, so the following can be obtained:
inter-storey lateral drift limit Δ=hc×θ;
S5: calculating the rotational stiffness K1 and K2 of the column top and the column bottom;
A calculation diagram is shown in
B-end rotational stiffness caused by the disc spring group:
Column line stiffness i1=EI/hc
Upper column line stiffness is i2 and beam line stiffness is i3;
A-end rotational stiffness caused by the disc spring group:
K
1
′=k
s
′[a
1
2+(a1+a2)2+(a1+2a2)2]
A-end rotational stiffness caused by adjacent beams and columns: K1″=3.5i2;
Point A provides rotational stiffness for point B: K2″=αi1;
The lateral stiffness of rotating constraint rods at both ends is calculated as follows:
The rotational stiffnesses at both ends are K1 and K2, rod length is 1 and line stiffness is i;
The lateral stiffness at the column top is D=ΣDj
The rotational stiffness transmitted by K2′ to the column top is K1″′:
The rotational stiffness transmitted by K1′ to the column bottom is K2″′:
To sum up:
K
1
=K
1
′+K
1
″+K
1″′
K
2
=K
2
′+K
2
″+K
2′″
S6: calculating the angular drift limits θ1 and θ2 of the column top and the column bottom in a large earthquake according to a force method or a drift method;
The rotational stiffness K1 and K2 at both ends of the column, the horizontal lateral movement A at the column top and the column body line stiffness i1 are known;
A calculation diagram is shown in
X1 and X2 are bending moments at the column end, and the direction is counterclockwise.
Wherein δ11=δ22=1/(3i), and δ12=δ21=−1/(6i);
The simultaneous equations are solved to obtain the bending moment value X1 at the column top and the bending moment value X2 at the column bottom;
θ1−X1/K1,θ2=X2/K2
A drift method is also used for checking results:
The results are consistent, and the angular drift limits θ1 and θ2 of the column top and the column bottom in the large earthquake are obtained.
S7: The proportion of the bending moment bearing capacity provided by a disc spring in the bending capacity of the whole section is φdes under the action of the large earthquake, and the proportion of the bending moment bearing capacity provided by the C-type energy dissipation steel plate is (1−φdes), so as to calculate the bending moment bearing capacity Mb provided by the energy dissipation steel plate to design the section size of the energy dissipation steel plate.
When the inter-storey drift angle reaches 1/50, the disc spring provides the bending moment bearing capacity Ms, and the energy dissipation steel plate provides the bending moment bearing capacity Mh:
d is the vertical distance from the axial force direction of the energy dissipation steel plate to the connection rotation point, and the section size of the energy dissipation steel plate can be preliminarily determined.
φdes=0.6. When the inter-storey drift angle reaches 1/50, the compression drift of the disc spring is L=θh. h is the vertical distance between the axial force exerted by the disc spring group and the rotation center of the connection. Therefore, the axial force Fy=F0+KSL after compression of the disc spring group can be calculated. The moment of the axial force of each disc spring group for the rotation center can be obtained as follows:
The sectional area A of the energy dissipation steel plate can be calculated. The thickness of the energy dissipation steel plate should not exceed the thickness of the beam flange, and the width should be consistent with the beam flange.
S8: determining the allowable bending moment Md of the column bottom and the allowable bending moment Md of the beam column connection under the large earthquake according to a column axial force, an inter-storey horizontal force, anchor rod prepressure, disc spring deformation force and the angular drift limits.
According to the column bottom angle θ2 under the action of the large earthquake, the bending moment Mp generated by the prepressure, the bending moment Ma generated by the axial force and the bending moment ΔM increased by the deformation of the disc spring group when the column bottom produces the angle θ2 can be obtained respectively. The allowable bending moment Md of the column bottom under the action of the large earthquake can be obtained by adding the three.
hm is the vertical distance between the suspension board and the ground, as shown in
M
d
=M
p
+M
a
+ΔM;
According to the angle θ1 of the column top under the action of the large earthquake, the bending moment Mp′ generated by prepressure when the column top produces angle θ1, the bending moment Mb generated by the energy dissipation steel plate yielding and the bending moment ΔM′ increased by the deformation of the disc spring group can be obtained respectively. The allowable bending moment Md′ of the column top under the action of the large earthquake can be obtained by adding the three.
In the formula, fy is the yield strength of the energy dissipation steel plate, A is the sectional area of the energy dissipation segment, and d′ is the vertical distance from the center of the energy dissipation section to the rotation point.
M
d
′=M
p
′+ΔM′+M
b
S9: calculating the axial forces Fy and Fy′ of the anchor rods when the angular drift limits are reached according to the angular drift limits of the column bottom and the column top;
According to the angular drift of the column bottom, the axial deformation δy of the disc spring in the first disc spring group can be calculated, and then the axial force generated by the axial deformation of the disc spring can be calculated. The axial force Fy of each pull rod can be obtained by adding the axial force with the prepressure applied initially by the disc spring. Force analysis is shown in
According to the angular drift of the column top, the axial deformation δy′ of the disc spring in the second disc spring group can be calculated, and then the axial force generated by the axial deformation of the disc spring can be calculated. The axial force Fy′ of each anchor rod can be obtained by adding the axial force with the prepressure applied initially by the disc spring. Force analysis is shown in
S10: taking the moment of a rotation point to obtain the axial force of the beam column when the angular drift limits are reached, and the local pressure of each connection flange is obtained through equilibrium conditions.
The rotation point of the column bottom:
The axial pressure P of the column body when the angular drift reaches θ2 under the action of the large earthquake is calculated.
So, Fc=Fy1+Fy2+Fy3+P−Fy4
The rotation point of the beam column:
The lateral drift stiffness of the frame is known. According to the inter-storey horizontal drift, the inter-storey horizontal force can be calculated; the equivalent beam axial force P′ when the angular drift limit θ1 is reached is obtained by taking the moment of the rotation point of the beam column, and the local pressure F,′ of the beam flange is obtained by the equilibrium conditions, as shown in
The equivalent beam axial force P′ when the angular drift reaches θ1 is obtained under the action of the large earthquake.
So, Fc′=Fy1′+Fy2′+Fy3′+F+P′
S11: conducting strength checking, stability checking and local pressure checking.
1. Column Base Connection Part:
(1) Ensuring that the High Strength Anchor Rod May not Yield:
The anchor rod at the farthest end from the rotation point is checked, and the axial force of the anchor rod is
The yield stress of the anchor rod is σpt,y, and the minimum cross-sectional area of the high strength anchor rod is
When the cross-sectional area of the high strength anchor rod meets A≥Ay, the requirement is satisfied.
(2) Checking the Strength According to the Strength Checking Formula of Tensile Bending and Compression Bending Members:
The cross-sectional area A of the column is known.
The plastic development coefficient γx of the section and the net sectional modulus ωnx with respect to the x-axis can be obtained by table look-up or calculation. P is known, so σ can be calculated.
When
the strength checking of the column base meets the requirement.
(3) In-Plane Stability Checking:
Because the bottom of the column base rotates and separates from a foundation beam, both ends of the column are assumed to be hinged. Then, μ=1.0
the requirement is satisfied, wherein [λ]=150.
For b type section, coefficient
is calculated, and ωx can be obtained by referring to the code.
The reverse curvature is generated by the end bending moment and the lateral load,
When
the requirement is satisfied.
(4) Local Stability Checking:
When
the requirement is satisfied.
(5) Local Pressure at the Column Bottom:
When
the requirement is satisfied, wherein Afn=th is the local contact area.
2. Beam Column Connection Part:
(1) Firstly, Ensuring that the High Strength Pull Rod May not Yield:
The pull rod at the farthest end from the rotation point is checked, and the axial force of the pull rod is
The yield stress of the pull rod is σpt,y, and the minimum cross-sectional area of the high strength pull rod is
When the cross-sectional area of the high strength pull rod meets A≥Ay, the requirement is satisfied.
(2) Checking the Self-Centering Beam Section:
Plastic moment is Mn=FyWx, Fy is yield stress and Wx is plastic sectional modulus. The beam end bending moment Md′ can be calculated:
When
and Md′≤Mn, the requirement is satisfied.
(3) Checking the Strength According to the Strength Checking Formula of Tensile Bending and Compression Bending Members:
Because the beam section parameter is known, the beam sectional area A′ can be calculated. The net sectional modulus ωnx with respect to the x-axis and the plastic development coefficient γx of the section can be obtained by table look-up.
When the requirement is satisfied.
(4) Checking Local Stability of the Compression Flange:
Critical elastic buckling force of the compression flange of the compression bending member is
In the formula: kp is the elastic buckling coefficient, μ is the poison ratio, h0/tw is the height to thickness ratio of the compression flange, and Fcr is the critical elastic buckling force of the compression flange. When the maximum pressure of the compression flange plate is Fb≤Fcr, the requirement is satisfied.
3. Checking Self-Centering:
If φdes design value is greater than or equal to 0.5, namely Mprs/Mp≥0.5, it can ensure that the section meets the requirements of self-centering according to the codes. If φdes design value is less than 0.5, it needs to ensure that the connection meets Mprs≥Mat+Mac at the zero bound point of opening and closing.
When all the above checking results meet the requirements, the connection design for the lateral resisting system of the self-centering steel frame is completed. If the requirements cannot be met, φdes needs to be adjusted and the section of the C-type energy dissipation steel plate is also reduced or the prestress of the disc spring is increased, and the calculation is repeated until the requirements of self-centering are met.
According to the connection design method for the lateral resisting system of the self-centering steel frame provided by the present invention, the method conducts the checking of the bearing capacity and the stability under the action of large earthquakes on the basis of meeting the requirements of small earthquakes. The calculation methods are simple and feasible, can ensure more accurate results, and have good popularization and application values. The lateral resisting system of the steel frame designed by the method has the characteristics of strong lateral resistance, self-centering and energy dissipation capability. The present invention is clear in concept, convenient in construction and reasonable in building cost, and will be widely used in high-rise and super high-rise building structures. The vertical load of the main structure is mainly borne by the prepressure provided by the disc spring; different from the traditional energy-dissipating angle steel which bears both shear resistant and energy dissipation purposes, the C-type energy dissipation steel plates are easy to deform under the stress and do not increase the bearing capacity and shearing resistance, which is convenient for the calculation of the stress of the main structure.
Each embodiment in the description is described in a progressive way. The difference of each embodiment from each other is the focus of explanation. The same and similar parts among all of the embodiments can be referred to each other. For a device disclosed by the embodiments, because the device corresponds to a method disclosed by the embodiments, the device is simply described. Refer to the description of the method part for the related part.
The above description of the disclosed embodiments enables those skilled in the art to realize or use the present invention. Many modifications to these embodiments will be apparent to those skilled in the art. The general principle defined herein can be realized in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principle and novel features disclosed herein.
Number | Date | Country | Kind |
---|---|---|---|
202310434483.5 | Apr 2023 | CN | national |