No abstract

A flexibility-based reinforced concrete beam column element is developed to study the nonlinear static and dynamic response of reinforced concrete seismic resisting frames. To model beam to column flexible connections and rigid zones that formed from beam to column intersections, end springs and end offsets are included in the element formulation, respectively. The element flexibility matrix is formed by integration of in-span section flexibilities using conventional force relations using the Simpson's method. Each cross section in the element span is subdivided into concrete and steel fibers/layers with the assumption of linear strain distribution over the section depth. The effects of shear and bond slip are neglected in the element formulation. The formulated beam column element is implemented into a developed finite element program. For the sake of verification, a series of correlations studies against members and structures available in the literature subjected to either monotonic or cyclic loads were investigated and showed a good accuracy. The proposed element can be used in nonlinear static and dynamic analysis of seismic resisting systems.

Design of economic seismic resisting structural systems with an acceptable safety margin requires continuous improvements for the available numerical models and analysis tools. In this work, an improved reinforced concrete membrane element based on the modified compression filed theory (MCFT) is presented. The developed element is implemented into a developed finite element program in order to study seismic response of different types of seismic resisting systems which are commonly used in the construction of concrete buildings in Egypt. Two types of floor systems, (beamed/beamless floors) and two types of seismic resisting systems, (frames/coupled frames with shear walls), are investigated. Reinforced concrete flexibility-based beam column and plane stress elements were used to model frames and shear walls, respectively. The static response of these systems subjected to triangular load pattern was investigated through nonlinear static analysis. It was concluded that, the predicted force reduction factor based on nonlinear static analysis of the examined systems is 50% to 75% less than those provided by Egyptian code; such variation could lead to uneconomic or inadequate design.