Optimal bracing type and position to minimize lateral drift in high-rise buildings

Abstract

Selection of high-rise bracing type and position is based on many factors: their degree of resistance to lateral forces, cost, complexity of connection and assembly, and the integration with Architectural objectives. This paper includes selection of the optimal bracing type and position for a high-raise office building in Dammam Saudi Arabia. This 900 square meters per floor prototype is used as case study to compare four bracing types: single diagonal bracing, chevron shape bracing, cross (X) bracing and eccentric bracing; as well as two positions: bracing at the core and external parameter bracing (building facade). The case study building height is 40 stories in an area of high wind velocity (145 km/h) where no critical seismic force is recorded. The STAAD Pro 2005 software is used to analyze these systems according to allowable stress requirements for an objective function to minimize drift for wind speed of 145 kilometers per hour. The result of this study shows that adding bracing members to the moment frame structure increases stability and reduces drift. Chevron bracing and cross bracing have the highest resistance to the lateral drift compared to the others; but cross bracing is more costly due to more joints. Therefore chevron is the optimal bracing type. Also this study shows that adding the braces to the core of building reduces the drift much more than adding them to the building facades. © 2009 WIT Press.