A comparative study of probabilistic structural safety analysis

Abstract

Structural Safety is one of the most important factors of any aerospace product. Until recently, a design is considered to be robust if all the variables that affect its life has been accounted for and brought under control Safety factor cannot, by themselves, guarantee satisfactory performance and they do not provide sufficient information to achieve optimal use of available resources. The meaning of robustness is shifting. Designer and engineers have traditionally handled variability with safety factors. Some safety factors are derived from observation and analysis, and many cases it use to be pure guess work. In those cases, the bigger the guess, the bigger the risk, the bigger the safety factor resulting over designed product. In the present paper, a spherical pressure vessel is identified for structural safety evaluation. Structural Safety Index is evaluated using uncertainty. Various statistical methods like mean value and moment methods are discussed. Simulation techniques for evaluation of probability of failure are also discussed. It is well established that simulation techniques have proven their value especially for problem where the representation of the state function is associated with difficulties. Such cases are e.g when the Limit State function is not differentiable or when several design points contribute to the failure probability. The various simulation methodologies have been discussed in brief for structural safety evaluation, such as Crude Monte Carlo, Importance Sampling, Importance Sampling based on β point and Latin Hyper Cube Sampling. Finally a comparative study of safety evaluation based on these techniques are made in this paper. These methods found to be useful for structural safety and design evaluation.