Prof. Ibrahim Galal Ibrahim Shaaban :: Publications:

Investigations of recent near source earthquake damages indicated that the vertical excitation played a significant role in the structural behavior and in some cases was the main cause of the damage or failure. However, most of the modern codes put more emphasis on the horizontal excitation and do not properly consider the vertical excitations. In this paper, the nonlinear response of a ten-story R.C building frame to combined horizontal and vertical excitations was investigated. The nonlinear computer program IDARC4 was utilized for the analysis. Two different levels of horizontal peak ground acceleration and three different levels of vertical peak ground acceleration were considered. The results indicated that the vertical excitation strongly increases the compression forces in the columns, especially for the interior and the upper story columns. Unlike the horizontal excitation, the vertical excitation resulted in high axial tension forces in columns, which may be very close to the yield forces. The bending moments and the shearing forces in the upper story columns increased with the increase of the vertical excitation. The level of vertical excitation itself had stronger effect than the ratio of the vertical peak to the horizontal peak values. It was also concluded that the internal forces were greatly underestimated if the same spectral shape was used for both horizontal and vertical excitation.