Behavior of Reinforced Concrete Frames on Flexible Foundations Subjected to Both Horizontal and Vertical Ground Motions

Abstract

This paper investigates the behavior of combined horizontal and vertical accelerations on the seismic response of reinforced concrete resting on shallow foundations. Five and nine-storey buildings are considered to represent low-and medium- rise buildings. The building was assumed to be founded on shallow foundation with soil class corresponding to soft soil deposits, The soil of foundation was modeled by an equivalent massless spring coupled with a gap. The accelergrams used in this investigation in the nonlinear range are the horizontal and vertical components of the New Hall earthquake. Although most building codes postulate that SSI generally decreases the force demand of buildings, and increases the deformation demand, it was found that the inclusion of the vertical ground motion with SSI, the horizontal displacement are decreased compared to the case with only the horizontal component. the ability of the Winkler approach to provide reasonable prediction of the rocking response of various structures. This paper examines the effect of vertical ground motion on the nonlinear seismic behavior of reinforced concrete building with soil flexibly. A simple two-dimensional (2D) model was used to idealize the structures and the supporting soil. The nonlinear structural analysis program SAP2000 was chosen for this work.