عنوان مقاله [English]
Appropriate estimation of the reliability index is important to evaluate the failure probability in structural reliability analysis. Therefore, some methods such as: HL-RF and the Gradient method have been developed and commonly used to determine the reliability index of structures. In this paper, a new method is proposed for determining of the reliability index which is formulated using the nonlinear conjugate gradient method. First, the new iterative method was presented and then, efficiency and robustness of the proposed method were investigated using several examples. Accurate convergence and iterations of the new iterative algorithm were compared with the previous methods such as: the Hasofer-Lind approach, Gradient method, stability transformation method (STM) and Mont Carlo simulation, for examples. The results indicate that the proposed method is more robust than the old first order reliability methods i.e. the HL-RF and Gradient method. So that, this old methods were not converged for some examples but, the proposed method was converged for all problems. On the other hand, the results of proposed method are accurate and as similar as the STM but more efficient and was converged with less number of iterations in comparison with the STM.