CN115186329A - Low-cycle fatigue failure sequence prediction method for plate-type connection steel support frame - Google Patents
Low-cycle fatigue failure sequence prediction method for plate-type connection steel support frame Download PDFInfo
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Abstract
The invention provides a low-cycle fatigue failure order prediction method for a plate-type connecting steel supporting frame, which comprises the following steps of: considering different combination schemes of design parameters; based on a ductile damage method and a critical plane method, obtaining the low-cycle fatigue life of a gusset plate and an I-shaped section support in a central support steel frame; calculating a frame low-cycle fatigue damage matching control index; establishing a low-cycle fatigue failure sequence prediction function of a central support steel frame with a plate-type connection I-shaped section based on a Bayesian update theory; and establishing a central support steel frame low-cycle fatigue failure order prediction model under different reliability degrees based on probability statistics. The method can directly utilize the design parameters of the plate-type connecting support frame to judge and predict the low-cycle fatigue damage sequence, avoids the complex and time-consuming numerical simulation, can help engineers to evaluate and control the anti-seismic design safety level of the central support steel frame in the design stage, and provides theoretical basis for the value of the design parameters of the support frame.
Description
Technical Field
The invention belongs to the technical field of low-cycle fatigue life prediction, and particularly relates to low-cycle fatigue failure sequence prediction and regulation of a plate-type connecting steel supporting frame.
Background
The plate type connecting center supporting steel frame structure is simple in structure, clear in force transfer and high in industrial degree, and has certain advantages in the assembly type steel structure building which is widely popularized in China. Meanwhile, the structure has good horizontal rigidity and bearing capacity, and has wide application prospect in civil buildings.
In recent years, earthquake damage investigation shows that the plate-type connecting center supporting steel frame is not only subjected to low-cycle fatigue damage fracture in supporting, but also has a great deal of damage in plate-type nodes. If the support is damaged and broken too early, the rigidity of the floor where the support is located is seriously degraded, and a weak layer is easily formed to cause structural collapse; if the connection node is damaged or broken before supporting, a force transmission path is damaged, and the integral bearing capacity and ductility performance of the structure are deteriorated. Therefore, the prediction and control of the low-cycle fatigue damage sequence and the service life matching degree of each component of the support frame in the structural design have important significance.
Most of the existing researches are on the influence of single-factor design variables (such as geometric parameters, detailed structures, support arrangement and the like) on the seismic performance of the support frame, the low-cycle fatigue failure sequence of each component in the support frame cannot be considered and predicted at present, and a collaborative design strategy capable of meeting the common adjustment of multiple design parameters is lacked, so that the popularization and the application of the structure are limited to a certain extent. For a plate type connecting steel supporting frame, the design of the gusset plates (relative support) is over-strong (the gusset plates are large and thick) or over-weak (the gusset plates are small and thin) to generate deterioration influence on the whole anti-seismic performance of the supporting frame, the gusset plates not only participate in structural plasticity development, but also ensure that the plate type gusset plates generate low-cycle fatigue damage after supporting, and the whole energy consumption capacity of the structure can be fully exerted. From the perspective of cooperative design, if the low-cycle fatigue damage of different components can be predicted and regulated during the anti-seismic design, the inconsistent anti-seismic performance caused by overlarge low-cycle fatigue life difference of the components is avoided, the cooperative work of the components can be realized, and the optimization of the overall anti-seismic performance of the structure is further achieved.
Disclosure of Invention
In order to solve the technical problems, the invention provides a low-cycle fatigue failure sequence prediction method for a plate-type connecting H-shaped section center support steel frame, which avoids complex and low-efficiency numerical operation, and can adjust various design parameters (including geometric dimension, connection coefficient and the like) of the support frame in the structural design stage according to the method so as to improve the anti-seismic performance of the support frame.
In order to achieve the purpose, the invention adopts the following technical scheme:
a low-cycle fatigue failure sequence prediction method for a plate type connecting steel supporting frame comprises the following steps:
step 1: considering design parameters including component geometric parameters, connection structure, connection coefficient, design interlayer displacement angle and the like, obtaining different design parameter combination schemes of the plate type connection I-shaped section center support steel frame, establishing an ABAQUS finite element model and carrying out numerical analysis;
step 2: obtaining the low-cycle fatigue life of a gusset plate and an I-shaped section support in a central support steel frame based on a ductile damage method (reduced damage model) and a critical plane method (LZH model);
and step 3: low cycle fatigue life N of gusset plate C And support low cycle fatigue life N B The ratio of (b) is used as the low-cycle fatigue damage matching control index beta of the central support frame, namely beta = N C /N B And calculating the result;
and 4, step 4: establishing a low-cycle fatigue failure sequence prediction function of the plate type connection I-shaped section center support steel frame based on a Bayesian update theory;
and 5: and based on probability statistics, establishing a low-cycle fatigue failure sequence prediction model of the plate-type connecting center supporting steel frame with different reliability.
Preferably, the design parameters of step 1 specifically include: supporting slenderness ratio lambda B B/t width-to-thickness ratio of supporting flange and h width-to-thickness ratio of supporting web 0 /t w Length-to-thin ratio lambda of node plate C A connection coefficient k, a beam-column height ratio xi and an interlayer displacement angle delta.
Preferably, the step 2 of obtaining the gusset plate and the supporting low cycle fatigue life specifically comprises the following processes:
the first process is as follows: adding a ductile damage model into the constitutive model of the supporting frame material,
in the formula (I), the compound is shown in the specification,
is a critical value of equivalent plastic strain; eta is the stress triaxial degree, represents the stress state of the unit and is the ratio of the average stress of the unit and the Mises equivalent stress; eta 0 Is a material constant, typically 1/3 for metallic materials;
C 2 the critical value of the equivalent plastic strain in a unidirectional tensile state can be obtained by the following formula:
C 2 ＝-ln(1-A R )
in the formula, A R Represents the reduction of area of the material and can be obtained by a monotone tensile test of the material;
C 1 representing the critical value of equivalent plastic strain in pure shear, can be obtained by the following formula:
σ＝Aε n a and n respectively represent the strength coefficient and the hardening index of the material, and can be obtained by calculation according to the relation between the real stress sigma and the real strain epsilon of a monotone tensile test before necking the steel; when the numerical simulation strain of the support key position in the frame reaches the critical value, the damage is started to be counted, and the cycle when the damage is accumulated to 1 is the low cycle fatigue life N of the frame B ；
And a second process: establishing low-cycle fatigue life N of the node plate based on LZH model of critical surface method C The formula of the prediction is that,
in the formula, Δ γ max Is the maximum shear strain amplitude of the critical position unit; sigma n,max Is the maximum positive stress of the critical surface of the unit (i.e. the plane where the maximum shear strain amplitude is located); delta epsilon n Is the normal positive strain amplitude of the critical plane of the element; sigma' f Is fatigue strength coefficient, a is fatigue strength index of epsilon' f Is the fatigue ductility coefficient, b is the fatigue ductility index, E is the elastic modulus of the steel material, f y Is the yield strength of steel, and the 6 terms are all material coefficients; omega is the life reduction factor considering the interaction of the support and the node plate fatigue damage.
Preferably, the matching control index β = N for the low cycle fatigue damage of the support frame in step 3 C /N B When is beta>1, the low cycle fatigue life of the plate type node is longer than that of the support, namely the design is safe but is conservative; when the beta =1, the low-cycle fatigue life of the plate type node is equal to that of the support, the synergistic deformation effect of the low-cycle fatigue life and the support can be fully exerted, and the overall energy consumption capability of the frame is optimized; when beta is<1, the low cycle fatigue life of the plate type node is smaller than that of the support, and design parameters need to be adjusted.
Preferably, the frame low cycle fatigue failure order prediction function is,
based on the Bayesian update theory, the method has the advantages that,
f(α)＝γL(α)p(α)
where α = (a, σ) is unknown model coefficient, f (α) is a posterior distribution function of α, γ is a regularization factor, L (α) is a likelihood function, p (α) is a prior distribution function of α; adopting Markov Chain Carlo simulation (Markov Chain Monte Carlo), combining the beta data in the step 3 to obtain key factors influencing the matching relation of the frame low-cycle fatigue damage, namely the support slenderness ratio lambda B B/t width-to-thickness ratio of supporting flange and lambda length-to-thin ratio of gusset plate C A connection coefficient k, a beam-column height ratio xi, and solving fitting coefficients alpha = (a) in the formula 0 ,a 1 ,a 2 ,a 3 ,a 4 ,a 5 )。
Preferably, the frame low-cycle fatigue failure order prediction function of the step 4 does not need to consider external loads, so that the frame low-cycle fatigue failure order prediction function is conveniently used for supporting frame seismic design.
Preferably, the frame low-cycle fatigue failure order prediction function in the step 4 can meet the requirement of joint adjustment of multiple design parameters, and has high calculation efficiency and strong applicability.
Preferably, said step 5 logarithms both sides of the step 4 damage order prediction function,
in the formula, mu p Is the standard normal offset, s is the sample standard deviation, μ p s is the model error of the linear model, each reliability p i Corresponding mu pi Obtaining n as the number of the support frame samples according to a standard normal offset table;
and
respectively represent lna 0 And the average of β; different reliabilities correspond to different estimated values in the prediction formula
Compared with the prior art, the invention has the following beneficial effects:
1. the low-cycle fatigue failure order prediction method provided by the invention can obtain the matching relation between the low-cycle fatigue failure order of the plate-type connecting center supporting steel frame and the low-cycle fatigue life of the component at the structural design stage, and can simultaneously consider and adjust multiple design parameters, so that the support frame seismic design not only meets the strength requirement, but also meets the requirement of component failure after the node, the design principle of 'strong node and weak component' is realized, and the 'controllable and controllable' safety level of the structural design is further reached.
2. The method can directly utilize the design parameters of the plate-type connecting support frame to judge and predict the low-cycle fatigue damage sequence, avoids the complex and time-consuming numerical simulation, can help engineers to evaluate and control the anti-seismic design safety level of the central support steel frame in the design stage, and provides theoretical basis for the value of the design parameters of the support frame.
3. The low-cycle fatigue failure order prediction function of the plate-type connection I-shaped section support steel frame provided by the invention does not need to consider external loads, can meet the requirement of joint adjustment of multiple design parameters, has high calculation efficiency and strong applicability, and is suitable for seismic design of the support frame.
Drawings
FIG. 1 is a flow chart of a method for predicting a low cycle fatigue failure sequence of a plate-type connecting steel supporting frame according to the present invention;
FIG. 2 is a diagram of the numerical simulation results of the low cycle fatigue failure sequence of the center support steel frame with plate-type connecting I-shaped cross section according to the present invention;
FIG. 3 is a graph comparing the predicted results and numerical simulation calculated results of the low cycle fatigue failure sequence of a plate-type connecting and supporting frame made of Q355B steel by the method of the present invention;
FIG. 4 is a schematic diagram of a model for predicting the low-cycle fatigue failure order of a support frame under the conditions of a connection coefficient k =1.2 and a beam-column height ratio ξ =1.
Detailed Description
In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments of the present invention.
As shown in fig. 1, a method for predicting a low cycle fatigue failure order of a plate-type connection steel support frame comprises the following steps:
step 1: according to the selected design parameters such as geometric parameters, connection structures, connection coefficients and designed interlayer displacement angles of the components, different parameter combination schemes of the plate type connection I-shaped section center support steel frame seismic design are obtained, an ABAQUS finite element model is established, and numerical analysis is carried out;
step 2: obtaining the low-cycle fatigue life of a gusset plate and an I-shaped section support in a central support steel frame based on a ductile damage model in a ductile damage method and an LZH model in a critical plane method;
and step 3: low cycle fatigue life (N) of gusset plate C ) And support low cycle fatigue life (N) B ) Ratio of (β = N) C /N B ) The low-cycle fatigue damage matching control index is used as a central support frame low-cycle fatigue damage matching control index, and the result is calculated;
and 4, step 4: establishing a low-cycle fatigue failure sequence prediction function of the plate type connection I-shaped section center support steel frame based on a Bayesian update theory;
and 5: and based on probability statistics, establishing a low-cycle fatigue failure sequence prediction model of the plate-type connecting center supporting steel frame with different reliability.
The low-cycle fatigue failure order prediction method provided by the embodiment can obtain the matching relation between the low-cycle fatigue failure order of the plate-type connecting center supporting steel frame and the low-cycle fatigue life of the assembly at the structural design stage, and can simultaneously consider and adjust multiple design parameters, so that the support frame seismic design not only meets the strength requirement, but also meets the requirement of member failure after the node, the design principle of 'strong node and weak member' is realized, and the 'controllable and controllable' safety level of the structural design is further reached.
In the plate type connecting H-shaped section center supporting steel frame, a support is connected with a beam column through a gusset plate; the support is connected with the gusset plate through a connecting piece in two modes of welding and bolt connection; the node plate is connected with the beam column through the end plate.
In this embodiment, the number of finite element models of the support frame in step 1 is 192 in total, and the design parameter variables substantially include all influence factors that need to be considered in the structural design, specifically: supporting slenderness ratio lambda B The three-stage solar water heater is divided into six stages, namely 50, 60, 70, 80, 90 and 100; the width-thickness ratio b/t of the supporting flange is divided into six levels, namely 6, 7, 8, 9, 10 and 11; width-thickness ratio h of supporting web 0 /t w The device is divided into six stages which are respectively 20, 21, 22, 23, 25 and 27; the clear distance ratio is the distance L from the support end to the diagonal line of the gusset plate off And the thickness t of the gusset plate p The ratio of the support to the beam column is divided into three stages, namely 2, -2 and-6, and the negative number represents that the support end extends into the inner side of the diagonal line of the gusset plate, namely the support is closer to the beam column; connection coefficient k = W w t p /A b Wherein A is b To support the cross-sectional area, W w The Whitmore effective width of a spreading angle for supporting the end part at 30 degrees is divided into seven grades which are respectively 1, 1.1, 1.2, 1.3, 1.4, 1.5 and 1.6; the height ratio xi of the beam column is divided into three stages, namely 0.7, 0.84 and 1, the included angle between the corresponding column and the beam is 35 degrees, 40 degrees and 45 degrees, and the displacement angle delta between layers is divided into three stages, namely 1/100, 1/70 and 1/50. To facilitate the establishment of the prediction model, the geometric information of the node board is converted into a slenderness ratio lambda C And (4) showing.
The support low cycle fatigue life of the step 2 is obtained by a ductile damage method, a ductile damage model is added into a material constitutive model of the support frame,
in the formula (I), the compound is shown in the specification,
is a critical value of equivalent plastic strain; eta is the stress triaxial degree, represents the stress state of the unit and is the ratio of the average stress of the unit and the Mises equivalent stress; eta 0 Is a material constant, which is usually 1/3 for a metal material;
C 2 the critical value of the equivalent plastic strain in a unidirectional tensile state can be obtained by the following formula:
C 2 ＝-ln(1-A R )
in the formula, A R Represents the reduction of area of the material and can be obtained by a monotone tensile test of the material;
C 1 representing the critical value of equivalent plastic strain in pure shear, can be obtained by the following formula:
σ＝Aε n a and n respectively represent the strength coefficient and the hardening index of the material, and can be obtained by calculation according to the relation between the real stress sigma and the real strain epsilon of a monotone tensile test before necking the steel; the monotonic tensile test was performed on the Q355B steel, and the results of the parameter acquisition and processing are shown in Table 1:
TABLE 1 values of various parameters of the Q355B Steel ductile damage model
When the numerical simulation strain of the support key position in the frame reaches the critical value, the damage is counted, and the cycle when the damage is accumulated to 1 is the lowCycle fatigue life N B ；
The low-cycle fatigue life of the gusset plate in the step 2 is obtained by a critical plane method, and the low-cycle fatigue life N of the gusset plate is established based on an LZH model C The formula of the prediction is that,
in the formula, Δ γ max Is the maximum shear strain amplitude of the critical position unit; sigma n,max Is the maximum positive stress of the critical surface of the unit (i.e. the plane where the maximum shear strain amplitude is located); delta epsilon n Is the normal positive strain amplitude of the unit critical plane; sigma' f Is fatigue strength coefficient, a is fatigue strength index, epsilon' f Is fatigue ductility coefficient, b is fatigue ductility index, E is steel elastic modulus, f y Is the yield strength of steel, and the 6 terms are all material coefficients; and omega is a life reduction coefficient considering the interaction of the support and the fatigue damage of the gusset plate, and 2 is taken. The Q355B steel is subjected to a low-cycle fatigue test, and the acquisition and processing results of the parameters are shown in Table 2:
TABLE 2 Q355B Steel LZH model values for various parameters
In the embodiment, data analysis shows that the frame low-cycle fatigue failure sequence is only related to 5 factors, namely the support slenderness ratio lambda B B/t width-to-thickness ratio of supporting flange and lambda length-to-thin ratio of gusset plate C The connection coefficient k and the height ratio xi of the beam column. And beta shows good logarithmic linearity relation with all factors, so as to obtain the frame low-cycle fatigue failure order prediction function of step 4,
based on Bayes update theory, a Markov Monte Carlo simulation (Markov Chain Monte Carlo) is adopted, and the beta data in the step 3 is combined to solve each fitting coefficient in the formula:
α＝(a 0 ,a 1 ,a 2 ,a 3 ,a 4 ,a 5 )
f(α)＝γL(α)p(α)
where α = (a, σ) is unknown model coefficient, f (α) is a posterior distribution function of α, γ is a regularization factor, L (α) is a likelihood function, p (α) is a prior distribution function of α; the values of the coefficients of the low cycle fatigue failure order prediction function are shown in table 3:
TABLE 3 values of the coefficients of the low cycle fatigue failure order prediction function for the plate-type joint support frame
After the low cycle fatigue failure order prediction model is established, the low cycle fatigue failure order of the corresponding plate type connection supporting frame can be predicted by bringing the given design parameters into the model, and the design parameters can be adjusted according to the beta value to meet the design requirements.
A comparison graph of the prediction result and the numerical simulation calculation result of the Q355B steel plate type connecting and supporting frame low-cycle fatigue failure sequence by adopting the method of the invention is shown in FIG. 3. The prediction result is mostly positioned in a 1.5-time dispersion band of the numerical analysis result, which shows that the prediction model has good accuracy.
The plate-type connection I-shaped section supporting steel frame low-cycle fatigue failure order prediction function does not need to consider external load, can meet the requirement of common adjustment of multiple design parameters, is high in calculation efficiency and strong in applicability, and is suitable for seismic design of a supporting frame.
By adopting the method, the low-cycle fatigue failure sequence of the first-stage, second-stage, third-stage and fourth-stage frames in the existing specification is predicted, the connection coefficient k =1.2 and the height ratio xi =1 of the beam column are taken as basic conditions, the prediction result of the low-cycle fatigue failure sequence beta of the support frame is shown in figure 4, most beta is far greater than 1, and the conservatism of the design requirement of the existing frame is illustrated.
in the formula, mu p Is the standard normal offset, s is the sample standard deviation, μ p s is the model error of the linear model, each reliability p i Corresponding mu pi Obtaining n as the number of the support frame samples according to a standard normal offset table;
and
respectively represent lna 0 And the average of β; the present embodiment is differentThe reliability corresponding to different estimated values in the prediction formula
Specific values are shown in Table 4.
TABLE 4 prediction model a at different reliabilities 0 Coefficient value of
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A low cycle fatigue failure sequence prediction method for a plate type connecting steel supporting frame is characterized by comprising the following steps:
step 1: considering design parameters including component geometric parameters, connection structure, connection coefficient, design interlayer displacement angle and the like, obtaining different design parameter combination schemes of the plate type connection I-shaped section center support steel frame, establishing an ABAQUS finite element model and carrying out numerical analysis;
and 2, step: based on a ductile damage method and a critical plane method, obtaining the low-cycle fatigue life of a gusset plate and an I-shaped section support in a central support steel frame;
and step 3: low cycle fatigue life N of gusset plate C And support low cycle fatigue life N B The ratio of (b) is used as the low-cycle fatigue damage matching control index beta of the central support frame, namely beta = N C /N B And calculating the result;
and 4, step 4: establishing a low-cycle fatigue failure sequence prediction function of the plate type connection I-shaped section center support steel frame based on a Bayesian update theory;
and 5: and based on probability statistics, establishing a low-cycle fatigue failure sequence prediction model of the plate-type connecting center supporting steel frame with different reliability.
2. The method for predicting the low cycle fatigue failure order of the plate-type connection steel supporting frame according to claim 1, wherein the design parameters of the step 1 specifically comprise: supporting slenderness ratio lambda B B/t width-to-thickness ratio of supporting flange and h width-to-thickness ratio of supporting web 0 /t w Length-to-fineness ratio lambda of node plate C A connection coefficient k, a beam-column height ratio xi and an interlayer displacement angle delta.
3. The method for predicting the low cycle fatigue failure order of the plate-type connection steel support frame according to claim 1, wherein the step 2 node plate and support low cycle fatigue life obtaining specifically comprises the following processes:
the first process comprises the following steps: adding a ductile damage model into the constitutive model of the supporting frame material,
in the formula (I), the compound is shown in the specification,
is a critical value for equivalent plastic strain; eta is the stress triaxial degree, represents the stress state of the unit and is the ratio of the average stress of the unit and the Mises equivalent stress; eta 0 Is a material constant, which is usually 1/3 for a metal material;
C 2 the critical value of equivalent plastic strain in a unidirectional tensile state can be obtained by the following formula:
C 2 ＝-ln(1-A R )
in the formula, A R Represents the reduction of area of the material and can be obtained by a monotone tensile test of the material;
C 1 representing the critical value of equivalent plastic strain in pure shear, can be obtained by the following formula:
σ＝Aε n a and n respectively represent the strength coefficient and the hardening index of the material, and can be obtained by calculation according to the relation between the real stress sigma and the real strain epsilon of a monotone tensile test before necking the steel; when the numerical simulation strain of the support key position in the frame reaches the critical value, the damage is started to be counted, and the cycle when the damage is accumulated to 1 is the low cycle fatigue life N of the frame B ；
And a second process: establishing low-cycle fatigue life N of gusset plate based on LZH model of critical surface method C The formula of the prediction is that,
in the formula, Δ γ max Is the maximum shear strain amplitude of the critical position unit; sigma n,max Is the maximum positive stress of the critical surface of the unit (i.e. the plane where the maximum shear strain amplitude is located); delta epsilon n Is the normal positive strain amplitude of the unit critical plane; sigma' f Is fatigue strength coefficient, a is fatigue strength index of epsilon' f Is fatigue ductility coefficient, b is fatigue ductility index, E is steel elastic modulus, f y The yield strength of steel is shown, and the 6 terms are material coefficients; omega is the life reduction factor considering the fatigue damage interaction of the support and the gusset plate.
4. The method for predicting the low cycle fatigue failure order of the plate-type connection steel support frame according to claim 1, wherein the support frame low cycle fatigue damage matching control index β = N in step 3 C /N B When is beta>1, the low cycle fatigue life of the plate type node is longer than that of the support, namely the design is safe but is conservative; when the beta =1, the low-cycle fatigue life of the plate type node is equal to that of the support, the synergistic deformation effect of the low-cycle fatigue life and the support can be fully exerted, and the integral energy consumption capability of the frame is optimized; when beta is<1, the low cycle fatigue life of the plate type node is smaller than that of the support, and design parameters need to be adjusted.
5. The method for predicting the low-cycle fatigue failure order of a plate-type connection steel supporting frame according to claim 1, wherein the frame low-cycle fatigue failure order prediction function is,
based on the Bayesian update theory, the method comprises the following steps of,
f(α)＝γL(α)p(α)
where α = (a, σ) is unknown model coefficient, f (α) is a posterior distribution function of α, γ is a regularization factor, L (α) is a likelihood function, p (α) is a prior distribution function of α; adopting Markov Chain Monte Carlo simulation (Markov Chain Monte Carlo), combining the beta data in the step 3, obtaining key factors influencing the matching relation of the low cycle fatigue damage of the frame, namely supporting slenderness ratio lambda B B/t width-to-thickness ratio of supporting flange and lambda length-to-thin ratio of gusset plate C A connection coefficient k, a beam column height ratio xi, and simultaneously solving each fitting coefficient alpha = (a) in the formula 0 ,a 1 ,a 2 ,a 3 ,a 4 ,a 5 )。
6. The method for predicting the low cycle fatigue failure order of the plate-type connection steel support frame according to claim 1, wherein the frame low cycle fatigue failure order prediction function of the step 4 does not need to consider external loads, so that the method is conveniently used for seismic design of the support frame.
7. The method for predicting the low cycle fatigue failure order of the plate-type connection steel supporting frame according to claim 1, wherein the frame low cycle fatigue failure order prediction function of the step 4 meets the requirement of multi-design parameter joint adjustment.
8. The method for predicting the low cycle fatigue failure order of a plate-type connected steel supporting frame according to claim 1, wherein the step 5 takes logarithm of both sides of the failure order prediction function of the step 4,
in the formula, mu p Is the standard normal offset, s is the sample standard deviation, μ p s is the model error of the linear model, each reliability p i Corresponding mu pi Obtaining n as the number of the support frame samples according to a standard normal offset table;
and
respectively represent lna 0 And the average of β; different reliabilities correspond to different estimated values in the prediction formula
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