Optimization Of Reduced Beam Section Moment Connections

Lawal, Morayo Oluwaseun

doi:10.32920/16847440

Abstract

Reduced beam section (RBS) moment connections also referred to as Dog-bone connections are commonly used in seismic resistant steel moment frames. In RBS connections, the top and bottom flanges of the steel beam are selectively trimmed in the area adjacent to the beam to column connection. This is to ensure that under seismic loading, plastic hinges are formed in the beam not in the column. <div>The purpose of this study is to optimize the cyclic responses of RBS moment connections including those with sloping beams. Using a response surface method, predictive equations are developed for the response characteristics, such as initial stiffness, plastic strain index, moment capacity, hysteretic energy dissipation, and strength degradation rate. The optimization studies consider objectives leading to higher stiffness, lower plastic strain index, maximum moment capacity, higher hysteresis energy dissipation and lower strength degradation. The optimization results obtained shows that beam slope angle greater than 27.8° will experience fracture, high inelastic demand with higher strength degradation and more intense buckling.</div>

Highlights

Introduction1.1 General The aftermath of the earthquakes that occurred in Northridge, Los Angeles 1994 and Kobe, Japan 1995, structural engineers discovered connection fracture in about 60% of the inspected 155 steel moment frame building (Lignos et al 2010)
CONCLUSION 6.1 Summary The objective of this research aimed at generating predictive equations
Optimizations of the RBS moment connections were also achieved by minimising the local inelastic demand while maximizing all other response variables

Summary

Introduction

1.1 General The aftermath of the earthquakes that occurred in Northridge, Los Angeles 1994 and Kobe, Japan 1995, structural engineers discovered connection fracture in about 60% of the inspected 155 steel moment frame building (Lignos et al 2010). In order to enhance the moment resisting frames, the following methods were proposed: Reinforcing the connections and weakening the beam in region of the connection Formation of plastic hinges outside the connection leading to a reduction in force and moment at that region (Roudsari et al 2015; Oh et al 2007). This idea was first proposed and tested by Plumier in 1990 which is called reduced beam section (dog-bone connections). Using RBS makes yielding and plastic hinge formation to occur within the reduced section of the beam and it restricts moment that can be developed at the face of the column (Jones et al 2002)

Objectives

Results

Conclusion