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Advances in Civil Engineering
Volume 2017 (2017), Article ID 8643801, 10 pages
Research Article

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

1Department of Civil Engineering, Saravan Branch, Islamic Azad University, Saravan, Iran
2Department of Civil Engineering, University of Zabol, Zabol, Iran
3Department of Civil Engineering, Zahedan Branch, Islamic Azad University, Zahedan, Iran

Correspondence should be addressed to Hamed Makhduomi; moc.liamg@km.ymah

Received 28 January 2017; Accepted 11 May 2017; Published 7 September 2017

Academic Editor: Sertong Quek

Copyright © 2017 Hamed Makhduomi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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.