RELIABILITY ANALYSIS OF STEEL BRACED REINFORCED CONCRETE FRAMES WITH SEMI-RIGID CONNECTIONS

Abstract

This paper presents the reliability analysis of the frame structures with semi-rigid connections. For this purpose, the SEMIFEM finite element program that is capable of dealing with the semi-rigid connections is coded in FORTRAN. Then, this program is connected to the reliability algorithm. The direct coupling method, which is a combination of the reliability method and finite element method, is utilized to determine the reliability indexes and probabilities of failure for the structure. The first order reliability method (FORM) is the one favored in the present reliability analysis. Two sets of steel framed structures are analyzed; each of four and eight stories, consisting of a portal frame and three types of concentrically braced frames. Concrete compression strength limit state in reinforced concrete (RC) columns, steel strength limit state in steel braces and inter-story drift limit state are considered in reliability evaluation. According to the limit states, X braced frames are determined as the safest structures, while the portal frames are regarded as the most unsafe structures. As the connection percentage increases, the safety of the structure increases in terms of inter-story drift and steel strength limit states, but decreases for concrete compression strength limit states.