Reliability Analysis Of Solid And Hollow Cfst Short Column Under Axial Compression

Presently, base on structural reliability, the probability constant value design method which uses constant load and constant resistance is widely used to structural design of building engineering. This method is visual and univocal to be used. Therefore, it is used in the code for structural design in China. Although concrete fill steel tube (CFST) structure is globally used in building engineering, its reliability analysis is lacking. The components of CFST are concrete and steel, the uncertainty of material strength and the lack of statistical data of the geometrical parameters makes the probability distribution of the error difficult to estimate.Therefore, the axial compression test data are collected to carry out the reliability analysis of the CFST by using Monte Carlo method in this paper. Influence of various factors to the reliability index is studied. The partial factor of resistance is carried out and the influence of various factors to it is studied. The main research includes the following aspects:(1) The axial compression test data of CFST are collected to carry out the bearing capacity of the specimen base on the code formula and the modified formula. Four common probability distributions (Normal, Lognormal, Weibull and Gamma) are used to fit the computation in order to find the best-fit distribution which can represent model error. Base on the design code and related papers, the statistical parameters of geometrical variability,material property variability and load modelling are carried out.(2) Base on two design formulas of the compressive capacity in Technical Code for Concrete Filled Steel Tubular Structures (GB50936-2014), the reliability analysis of solid CFST short columns under axial compression is carried out. The influence of model error distribution type, steel ratio, concrete strength, steel strength, live-to-dead ratio and live load type to the reliability index is studied.(3) Base on the design formula of the compressive capacity in Technical Code for Concrete Filled Steel Tubular Structures (GB50936-2014) and the modified formula which is suggested by the research team, the reliability analysis of hollow CFST short columns under axial compression is carried out. The influence of calculation model error distribution type,steel ratio, concrete strength, steel strength, hollow ratio, live-to-dead ratio and live load type to the reliability index is studied.(4) Base on the expression of partial coefficient for reliability design of building structures, the statistical parameters of the resistance modelling and the partial factor of resistance are figured out by Design Point method. The influence of model rerror, live load type, safety grade and live-to-dead ratio to the partial factor of resistance is studied.Considering the common live-to-dead ratio, it is suggested that using different partial factor of resistance in different live-to-dead ratio.