Fuzzy Structural Reliability Analysis using the Dynamic Directional Stability Transformation Method

In this paper, a new method is proposed for fuzzy structural reliability analysis; it considers epistemic uncertainty arising from the statistical ambiguity of random variables. The proposed method, namely, fuzzy dynamic-directional stability transformation method, includes two iterative loops. An internal algorithm performs the reliability analysis using the dynamic-directional stability transformation method and an external algorithm performs the fuzzy analysis by applying the alpha-cut level optimization method based on the genetic algorithm. Implementation of the proposed method, which solves some nonlinear performance functions, indicates the efficiency and robustness of the dynamic-directional stability transformation method, as compared to other first order reliability methods

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

Nonlinear modeling of ultimate strength and strain of FRP-confined concrete using chaos control method

Abstract not availableBehrooz Keshtegar, Pedram Sadeghian, Aliakbar Gholampour, Togay Ozbakkalogl

Cyclic plastic zone-based notch analysis and damage evolution model for fatigue life prediction of metals

Fatigue strength analysis of critical components plays a vital role for ensuring structural integrity and operational reliability of major equipment. In notched components, the concept of cyclic plastic zone (CPZ) is commonly utilized for fatigue cracking analysis, in which the CPZ size normally relates to the material strength. In particular, materials with higher yield stress have shown smaller CPZ size and vice versa. According to this, a new approach for determining closed-form stress at the notch tip is proposed by considering the size of cyclic plastic zone, which can be used for the notch tip stress evaluation along the load direction under cyclic loadings. By implementing FE analysis, experimental data of 304 stainless steel, 40Cr steel and Ti-6Al-4V alloy are utilized for model validation and comparison. Results show that the scope of damaged CPZ alters the notch tip stress under fatigue loadings, and the proposed model yields better correlation of fatigue life predictions with experimental results of the three materials than other two models. (C) 2020 The Authors. Published by Elsevier Ltd