Behaviour of Buildings under Lateral Loads

Abstract

Gravity loads are the primary loading on a building. However, as a building becomes taller, it must have adequate strength and stiffness to resist lateral loads imposed by winds and moderate earthquakes. As the height of a building increases, the additional stiffness required to control the deflection, rather than the strength of the members, dictates the design. Figure 2.1 shows the additional weight of steel required to resist the wind loads as the number of storeys increases. Buildings up to 10 storeys, designed for gravity loads, can resist lateral loads without any increase in the size of members, because of the increase in the permissible stresses allowed for combined loading. Beyond 10 storeys, the additional material required to resist the lateral load increases non-linearly. Thus for reasons of economy it is desirable to use an appropriate structural system to resist the lateral loads, in addition to gravity loads.