In high-rise buildings, it is important to ensure adequate stiffness to resist lateral forces induced by wind, or seismic or blast effects. These forces can develop high stresses, and produce sway movement or vibration, thereby causing discomfort to the occupants. Concrete walls, which have high in-plane stiffness, placed at convenient locations, are often economically used to provide the necessary resistance to horizontal forces. This type of wall is called a shear wall. The walls may be placed in the form of assemblies surrounding lift shafts or stair wells; this box-type structure is efficient in resisting horizontal forces. Columns, of course, also resist horizontal forces, their contribution depending on their stiffness relative to the shear walls. The object of the analysis for horizontal forces is to determine in what proportion are the external loads at each floor level distributed among shear walls and the columns.