Development Seismic Design of Steel Moment Frames and the Evaluation by Energy Spectrum Method

M R Banihashemi

doi:10.17485/ijst/2014/v7i10.31

Abstract

This study focuses on the development of seismic design of steel moment frames using Performance Based Plastic Design (PBPD) method. This methodology implements the energy–work balance equation to calculate the design base shear. Also the preselected target drifts and yield mechanism are considered since the start of the procedure. By considering gravity load and p-delta effect, the PBPD method was initially developed for steel frames with different bays. Then for better efficiency of PBPD method, some equations are presented in order to estimate the required moment of columns. A somewhat accurate estimation, helps preventing yielding in columns during sever ground motion that leads to undesirable yield mechanism in the structures. For validating this methodology, two 5 and 10 story frames are designed as case studies in both PBPD and elastic design method which have been evaluated under numerous nonlinear static pushover and dynamic analysis. The results indicate that the PBPD frames perform according to expectations in case of yield mechanism and target drift levels whereas the ED frames suffer large story drifts due to flexural yielding of the columns. Since PBPD method is a direct design method, little or no evaluation are needed after the initial design because the nonlinear behavior is built into the design process from the start. Keywords: Energy Spectrum Method, Performance Based Plastic Design, P-∆ Effect, Seismic Demand

Highlights

It is well recognized that current seismic design codes are based on elastic structural behavior and account for the inelastic behavior indirectly
Elastic design method is generally based on elastic structural behavior and accounts for the inelastic behavior in a somewhat implicit manner
It is worth mentioned that the drift limit generally governs the design of steel moment frames, after selecting the initial member sizes based on required strength, the frame designed by ED method need major revision to control the drift limitation and other requirements such as strong column-weak beam

Summary

Introduction

It is well recognized that current seismic design codes are based on elastic structural behavior and account for the inelastic behavior indirectly. It has been noted that large inelastic deformation in a pretty unpredictable behavior will happen for structure designed by such procedures under sever ground motion. This can increase the possibility of structural member’s severe buckling and yielding in an uneven manner[1,2]. Developed a methodology that enables us to directly consider inelastic behavior of structural members for resolving the above mentioned problem. This methodology which is called performance based plastic design method (PBPD method), removes the need for any further evaluation

Objectives

Methods

Conclusion