6.1.Overall Structural Behavior of Horizontal Subsystems Horizontal subsystems, which are formed by slab,beam grid and truss,act vertically to carry floor and roof loads in bending.It also pick up loads from the vertical subsystems and resist horizontal forces.6.1. Overall Structural Behavior of Horizontal Subsystems Horizontal subsystems, which are formed by slab, beam grid and truss, act vertically to carry floor and roof loads in bending. It also pick up loads from the vertical subsystems and resist horizontal forces