Research On Reliability Of Existing Steel Members And Defective Plane Steel Frames

Steel frame structures are widely used due to the advantages of light weight,high strength,high ductility,strong seismic performance,convenient construction and short construction time.However,in the process of construction and use,it is easy to cause different types of defects in structural components,resulting in that the reliability of the structure does not meet the requirements of structural design.In addition,compared with industrial building codes,civil building steel structure codes are not perfect in terms of reliability standards.Therefore,in order to study the reliability of existing steel frame structures,the main contents of this paper are as follows:（1）Combined with the MATLAB calculation program,the reliability indexes of steel structural members and thin steel structural members under different safety levels are studied by using the first-order second moment method of structural member reliability.According to the reliability level stipulated in the three standards of"Uniform standard for reliability design of building structures"GBJ68-84,"Uniform standard for reliability design of building structures"GB50068-2001,"Unified standard for reliability design of building structures"GB50068-2018,in building in the case where the structural safety level is level 2（γ₀=1.0）,the reliability index of the steel structure member and the thin steel structure member’s resistance effect ratio is b and c respectively,and compared with the industrial building reliability specification,the specific value of the most reasonable resistance action ratio of steel members in"Civil building reliability appraisal standard"GB50292 is proposed.（2）Taking the standard given by the current code as the target value,the reliability analysis of the plane steel frame structure is carried out through the parameters.Considering the influence of the initial eccentricity existing in the column member on the reliability of the steel structure member and the whole,the sensitivity of the reliability of the steel frame structure to the initial eccentricity is obtained.The function is established to calculate the reliability of the components with initial eccentricity,and the influence law of the initial eccentricity on the reliability of the steel structure is proposed.（3）The finite element software ANSYS is used to establish a double-layer double-span steel frame structure,and the LHS method of Monte Carlo method is used to analyze the distribution of each random input variable.Extract the maximum displacement and maximum stress value of the structure,establish a function according to the specified value of the specification,calculate the reliability of the plane steel frame structure,and draw the sensitivity diagram of the probability parameter through the distribution diagram of the maximum displacement and the maximum axial force,and analyze the random input variables.The influence on the reliability of the steel frame structure,the response surface function was fitted and compared with the Monte Carlo method.The influence of the initial bending existing in different column members on the reliability of the structure is analyzed by the response surface method,and which variables can realize the optimization of the reliability and make suggestions.