A Comparative Study of First-Order Reliability Method-Based Steepest Descent Search Directions for Reliability Analysis of Steel Structures

Abstract

Three algorithms of first-order reliability method (FORM) using steepest descent search direction are compared to evaluate the reliability index of structural steel problems which are designed by the Iranian National Building code. The FORM formula is modified based on a dynamic step size which is computed based on the merit functions named modified Hasofer-Lind and Rackwitz-Fiessler (MHL-RF) method. The efficiency of the gradient, HL-RF, and MHL-RF method was compared for a bar structure under tensile capacity, a multispan beam under bending capacity, a connection under tension load, and a column under axial force. The results illustrated that the MHL-RF method is more efficient than the HL-RF and gradient method. The designed steel components by the Iranian National Building code showed good confidence levels with the reliability index in the range from 2.5 to 3.0.

An empirical regression model toward optimized ergonomic conditions for monitoring room operators using RSM

“…RSM is a sequential procedure. Frequently, the initial estimate of the optimum operating condition for the system will be far away from the actual optimum (Elliott et al , 2016; Makhduomi et al , 2017). The objective here is to lead the experiments rapidly and efficiently along a path of improvement toward the general vicinity of the optimum.…”

Nonrecursive Equivalent of the Conjugate Gradient Method without the Need to Restart

“…Obviously, IRM represents an iterative procedure, where a discrete Ritz method is applied at each step, and a suitable set of coordinate vectors which span a subspace are generated. A local energy minimum is sought within that subspace (therefore (5) should be solved at each step), thereby decreasing the total energy of the system, which eventually converges to the required minimum. The subspace dimension, or the size of (5), is not limited.…”

“…Also, recurrence relation in (11) becomes r (i+1) ← r (i) − ω (i) β (i) . Obviously, using ω = 1, A-orthogonality is lost, but convergence is improved in many cases [5]. The third advantage is the very natural adoption of (multi) preconditioning-like techniques [6].…”