ABSTRACT
Multistory buildings are designed not only for gravity loads but also for lateral loads. In the performance-based design of a multistory building, four major performance requirements such as strength, stiffness, stability and cost must be considered. In the design for vertical loads, the floor system in a building must be strong enough to transfer the loads to the columns or walls and stiff enough not to deflect excessively. Moreover, the floor system must be designed to have sufficient strength and stiffness to brace all columns and walls so that they will not buckle under the design loads. In the design for lateral loads, the structural system must be adequate stiff to resist wind and seismic forces. The strength performance requirement is the dominant factor in the design of low-rise buildings. The effects of lateral loads on buildings increase rapidly with increases in the height of the buildings. The stiffness and stability performance requirements are often dominant criteria in the design of tall buildings. There are two methods to satisfy the stiffness and stability performance criteria. The first is to increase the sizes of the members. However, increasing the sizes of structural members results in either impractical or uneconomical designs of tall buildings. The second is to select a more rigid and stable lateral load resisting system to reduce the deflections and to increase the stability. The first step in the structural design process of a tall building is to select a lateral load resisting system for wind and seismic forces. The selected lateral load resisting system is then sized. The final step is to ensure that the lateral resisting system is adequate for the stability bracing of the building.
