Reliability Study And Sensitivity Analysis Of Bearing Capacity Of Concrete-Filled Square Steel Tubular Compression And Bending Members

In the possess of design and pouring of concrete-filled square steel tube(CFST)members,there are uncertainties in material properties,action loads and geometric dimensions of members,which lead to the accidental failure of concrete-filled square steel tubular(CFST)members.It is of great significance for the reliability design of members to study the transmission speed of uncertainty in the component to determine the reliability of the component and to study the influence of these uncertainties on the function of bearing capacity.In this paper,the reliability and sensitivity of bearing capacity of concrete-filled square steel tubular members are discussed in detail,the main contents are as follows:(1)Based on the experimental data,the finite element software is used to simulate and verify the correctness of the model and parameters,and then the bearing capacity of concrete-filled square steel tube compression-bending members is calculated and the working mechanism is analyzed.The results show that the finite element results are close to the experimental data and are more safe.(2)The bearing capacity of compression-bending members is calculated by using technical regulations,and the influence of various influencing factors on the bearing capacity and reduction coefficient of compression-bending members is analyzed.The results show that the edge length of steel pipe has the greatest influence on the bearing capacity and eccentricity reduction coefficient of the member,and the length of the member has the greatest influence on the slenderness ratio reduction coefficient.(3)The reliability analysis of the bearing capacity of concrete-filled square steel tubular members is carried out by Monte Carlo method,and then the non-normal variables are equivalent normalized,then the reliability analysis of the bearing capacity of compression and bending members is carried out by using the stochastic response surface method,and then the results of the two methods are compared and analyzed.The results show that the reliability indexes of Monte Carlo method and the second and third order stochastic response surface method can meet the requirements of the national standard.The results of using the second-order and third-order stochastic response surface method are similar to those of Monte Carlo method,so the second-order stochastic response surface method can meet the requirements of accuracy.(4)The function of bearing capacity of concrete-filled steel tube(CFST)members is analyzed in terms of local sensitivity,global sensitivity and regional sensitivity.Compare the advantages and disadvantages of the three sensitivities,and further rank the sensitivity of each variable,find out the most important variables affecting the function,and determine the influence of important variables on the function in different distribution regions.The results show that the three variables which have the greatest influence on the function of bearing capacity are the compressive strength of concrete,the uncertainty of the calculation mode of the compression and bending members and the side length of the cross-section of the steel tube.In the aspect of method,local sensitivity can only reflect the information of local gradient of function.The precision of MCS method and FAST method of global sensitivity index is very good,compared with FAST method,MCS method has a large amount of calculation.Using the existing data,the influence of input variables on the uncertainty of output function can be obtained by using the regional sensitivity.