Reliability-based Evaluation of Beams Designed in Accordance with Iranian Design Code

Iranian design code like any other design code increases the reliability of a structure by means of multiplying the partial safety factors by load and resistant. The reliability index can be evaluated in order to survey the reliability of structures. In this paper, the reliability index of a beam as an important member of a structure is considered and the effect of the values and coefficient of variation of design parameters on the reliability index is surveyed. Finally, the partial safety factors for different states are proposed. In this paper, a new method based on genetic algorithm (GA) is used to calculate the reliability index. This new method has more efficiency in comparison with the classic methods and thesimulation methods such as Monte Carlo. This method does not require the mathematical form of the limit state function and on the other hand, this method takes less computational time in comparison with simulation methods. In structural construction, there are many different design parameters which are random variables. Probability distribution can be considered for each of these random variables. For different statistical data of design parameters, different partial safety factors are needed to optimum design of a beam. However, Iranian design code considers the constant partial safety factors for all different conditions. In case that the exact and specific statistical data of design parameters are available, the structural reliability analysis can be applied for reaching an optimum design. The statistical data of design parameters can be obtained by gathering the statistical data in any country and after that a reliable design code can be obtained based on these statistical data. Because of lack of statistical data of design parameters in Iran, five usual conditions were considered for data and then partial safety factors are calculated.