Reliability Assessment of Three-dimensional Moment Resisting Frames Designed According to the Iranian National Building Code, Part 10: Steel Structures, 2008 and 2013 Editions

Abstract

Awareness of the probability of failure and the safety index of a structure designed and implemented on the basis of regulations and codes can enhance the designer's attitude towards the failure or safety of the structure. This paper examines the probability of failure and safety index of 3D steel moment frames. A three-story steel moment frame and a six-story steel moment frame loaded and designed on the basis of the previous drafts of National Building Regulations of Iran have been selected. In order to perform the finite element analysis of the 3D moment frame and system reliability analysis, a program with CSHARP programming language is written incorporating the Monte Carlo method. In reliability analysis, the uncertainties in the yield strength and the Young's modulus of steel, gravity loads and lateral forces, cross-sectional and plastic section modulus of the frame members were considered. The calculation of the probability of failure and the safety index of the framing system in two cases, according to the old, 2008 edition and new, 2013 edition of Iranian National Building code, Part 10: Steel Structures, have been done and compared. It was noted that assessment of buildings constructed on the basis of the old regulations with new drafts of National Building Regulations of Iran resulted in decreased safety levels. Also, the effect of statistical correlation between gravity loads and lateral forces in determining the frame safety index has been investigated. The sensitivity analysis performed for the steel coefficient of variation showed that its variation after the value of 0.07 can have a significant effect on the reliability of the steel moment frame.

Keywords

• reliability
• 3d steel moment frames
• system safety index
• monte carlo method
• sensitive analysis