RELIABILITY ANALYSIS OF FRAMES

Abstract

The failure of indeterminate frame structures subjected to plastic hinge formation is characterized by the linear combination of moment of resistance or plastic moment capacities and load effects. The moment of resistance and load variables in reliability analysis are described by three quantities, mean value, standard deviation and statistical distribution function. This description contrasts with deterministic analysis where only mean values are considered explicitly and safety or load factors are used to compensate for undefined standard deviations and distribution functions. The present study is an attempt to give a technique for reliability analysis of steel frames using stiffness matrix method of linear elastic and piecewise linear elastic-plastic analysis and Monte Carlo simulation method. It involves automatic generation of stochastically dominant mechanism and their safety margin equation and calculation of bound on the system reliability. Local strategies are proposed for selection of plastic hinges and branching of failure paths to identify stochastically dominant mechanism. A generalized computer program in 'C' language is developed for computing the reliability of simple portal frame and two story one bay frame. A number of parameters such as beam span, plastic moment capacity of section, live load, wind load and flexural rigidity etc were varied with a view to study the effect on probability of failure . The results are presented and critically discussed.