Reliability Analysis Of Q235 And Q345 Steel Members In Axial Compression

"Standard for design of steel structures" GB50017-2017 revises the design value of steel materials,which improves the resistance partial factors of Q235 and Q345 steel materials,and "Unified standard for reliability design of building structures" GB50068-2018 revises the calculation formula of the load effect,cancel the situation that permanent load controls and increase the load partial factors.The revision of the above specifications will have an impact on the reliability level of the steel structure.Based on this,the reliability of the steel structure is analyzed.The specific work is as following:(1)According to the statistical parameters of the steel industry's yield strength and the geometric parameters of the steel plate by the China Metallurgical Construction Research Institute in 2012,the advanced first-order second-moment method was used to calculate the reliability of the 9 types of steel structures under 6 different load combinations.Compare the impact of the revised code on the reliability of the steel structure.(2)Separately consider the reliability level of the axial compression member strength and the stable reliability level.In order to obtain the distribution parameters of the bearing capacity of axial compression members,this paper adopts the stochastic finite element method,establish a finite element model that considers the variability of material yield strength,elastic modulus,initial geometric defects and geometric parameters,as well as the residual stress patterns and peak values recommended by the code preparation group.The accuracy of the finite element model is verified by experimental data.Consider 2 steel grades,2 section types(I-shaped,box-shaped),2 instability modes(instability around strong axis,instability around weak axis),10 different slenderness ratios(0.3,0.5...2.1)Through random sampling and finite element analysis calculations,statistically significant bearing capacity results of axial compression members are obtained.(3)Establish the reliability analysis function of the axial compression member that expresses the stability problem explicitly by the stability coefficient.The reliability levels of axial compression members with different load combinations,different constant live load ratios,different slenderness ratios,and different cross-section classifications are analyzed.Sensitivity analysis is carried out on the bearing capacity and reliability of axial compression members to determine which distribution parameters that have a greater influence on the reliability level of random variables.(4)Under the wind and snow load,the reliability index does not meet the requirements of the code,and the design recommendations are proposed,and the design recommendations are checked and analyzed.The reliability of the steel structure during wind and snow loads is improved.By analyzing the reliability of strength problems and stability problems separately,the meaning and reliability level of the design indicators in " Standard for design of steel structures " are clarified;for the components with stability problems,this article takes the axial compression components as an example to analyze the current standard design method reliability level.