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

Document Type : Research Article


Assistant Professor, Faculty of Engineering and Technology, University of Mazandaran


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 the
simulation 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


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