Reliability Analysis Of Axial Bearing Capacity Of Stirrup-Confined Concrete Filled Steel Tubular Stub Columns With Different Cross Sections

In this paper,Monte Carlo Simulation(MCS)and the simplified fourth-moment method based on cubic normal distribution are used to analyze the reliability of bearing capacity formula of concrete-filled steel tubular(CFST)stub columns under axial compression proposed by Ding Faxing,which considers the shape confinement coefficient of steel tube.A total of 945 axial compression test data of ordinary CFST short columns of various sections and38 axial compression test data of tie bar CFST stub columns are collected.The calculation formulas of national standards and the calculation formulas of bearing capacity of well-known scholars are compared.Monte Carlo method and simplified fourth-moment method are used to analyze the reliability of CFST stub columns.Finally,the influence of each parameter change on the reliability index is analyzed.The main research results are as follows:(1)The main reliability calculation methods and their application are summarized,and the CFST bearing capacity calculation formulas at home and abroad are collected,including the standard regulations as well as some influential calculation formulas proposed by some scholars.The results are compared with the experimental results.The results show that based on the existing test data,the formula proposed by Ding Faxing considers the shape confinement coefficient of steel tube,and the calculated results are relatively close to the experimental results.Therefore,the formula proposed by Ding Faxing is used to calculate the reliability;(2)In this study,the collected data of 945 ordinary CFST stub column axial compression test and 38 tie bar CFST stub column axial compression test are summarized and analyzed,and the statistical parameters of random variables are obtained,including load,material strength,geometric size and statistical parameters of calculation mode uncertainty;(3)The reliability of the calculation formula of axial compression bearing capacity of CFST stub columns proposed by scholar Ding faxing is analyzed,and the influence of different parameter changes on the reliability index is considered,including section shape,steel ratio,concrete strength,steel strength,load ratio,load combination,stirrup strength and stirrup ratio.The results show that the reliability index of ordinary CFST is improved by more than 20% after being equipped with tie bars.