Bridges are indispensable components of the infrastructure of modern society, and their assessment via techniques of structural dynamics is assuming greater importance. Dynamic behaviors of Suez-Canal and Aswan cable-stayed bridges were investigated through three-dimensional finite-element models. Seismic response analyses have been conducted from the deformed equilibrium configurations due to bridges own-weight. TAFT earthquake record was used in the analysis. The earthquake record was input in the bridges longitudinal, lateral, and vertical directions simultaneously. Results show that the bridge statical system has dominant influence on the bridge vibrations and there is a strong coupling in the three orthogonal directions within most modes of vibrations. Results include dynamic characteristics, time-history and frequency –domain responses.