برآورد خطا در روشهاي كلاس دو تيوري قابليت اعتماد سازه ها با استفاده از روشهاي كلاس سه

High-Speed calculation capability, solving large-scale problems, and ease of use are the main advantages of second class structural reliability theory. On the other hand, unknown error value and the lack of control on the calculation accuracy and somehow unreliable accurate answers in this method are the main deficiencies and had led to conservative use of this method in practice. However the third class methods are accounted as an effort to obtain better estimation and prediction of failure probability. In this class with implementing simulation method and applying different strategies using limited samples, which can result acceptable accuracy, one can evaluate the Structural Failure Probability. In this paper, in order to evaluate the Structural Reliability, using a combination of second class and high duty advanced importance sampling method (ISM), we are intended to predict the error and improve the second class accuracy. In this method, using ISM simulation operation would be done in the second class failure environment aiming increasing the accuracy of the calculations. In this way, with combining these methods, as well as using and including the main advantages of the second and third class methods, effective steps would be developed in order to eliminate the above cited deficiencies and increasing the efficiency. Several presented examples in this article, are the representatives of the satisfying capability of proposed method in solving structural reliability problems.