Evaluation of Conventionally Designed Reinforced Concrete Beams Against Vertical Seismic Excitation

Most reinforced concrete structures are designed without taking into account the vertical ground motion. In the present paper the structural behavior of such conventionally designed planar frames under concurrent action of both horizontal and vertical seismic components is evaluated. The whole investigation focuses on beams and its objective is to determine the variation of crucial design parameters and identify the code provisions that could be violated in case of neglecting the vertical motion during the design process. Firstly, a regular 4-storey reinforced concrete planar frame is conventionally designed in compliance with current codes. Subsequently, the structural behavior of the beams for concurrent action of horizontal and vertical seismic excitation is assessed with the aid of both linear and non-linear dynamic analyses for three scaled near-field ground motions. The whole study reveals that conventionally designed beams in compliance with modern codes may not satisfy essential design criteria when subjected to concurrent action of horizontal and vertical seismic motion.