A NEW METHOD FOR ASSESMENT OF THE STRACTURAL RELIABILITY

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

Modeling the behavior of FRP-confined concrete using dynamic harmony search algorithm

The accurate prediction of ultimate conditions for fiber reinforced polymer (FRP)-confined concrete is essential for the reliable structural analysis and design of resulting structural members. Nonlinear mathematical models can be used for accurate calibration of strength and strain enhancement ratios of FRP-confined concrete. In this paper, a new procedure is proposed to calibrate the nonlinear mathematical functions, which involved the use of a dynamic harmony search (DHS) algorithm. The harmony memory is dynamically adjusted based on a novel pitch generation scheme using a dynamic bandwidth and random number with normal standard distribution in DHS. A new design-oriented confinement model is proposed based on three influential factors of FRP area ratio (ρa), lateral confinement stiffness ratio (ρE), and strain ratio (ρε). Five nonlinear mathematical design-oriented models are regressed on approximately 1000 axial compression tests of FRP-confined concrete in circular sections based on the proposed DHS algorithm. The proposed models for the prediction of the ultimate axial stress and strain of FRP-confined concrete are compared with the existing models. It has been shown that the DHS algorithm offers the best performance in terms of both accuracy and fast convergence rate in comparison with the other modified versions of harmony search algorithms for optimization problems. The proposed design-oriented model provides improved accuracy over the existing models.Behrooz Keshtegar, Togay Ozbakkaloglu, Aliakbar Gholampou