Time Delay of Earthquake Excitation in High-Rise Building

The nature of time delay of earthquake excitation in structures from the perspective of wave propagation is addressed, and then the time delay is used to modify conventional structural dynamics equation, which assumes implicitly the simultaneity of earthquake initial excitations at all degrees of freedom of a structure. A simple and practical method is then developed to compute structural responses considering the time delay effects of earthquake excitations in the structure. Through the computation of floor displacement and top floor maximum displacement according to current standards on seismic design of buildings, it was shown that conventional method neglecting the time delay effects of wave propagation in structures would not provide accurate structural responses, and should be modified. The introduction of the time delay effects of wave propagation in structures is thus of great importance for the safety of more and more supertall buildings to be constructed. The method proposed in the paper deals with this problem and provides a practical solution by incorporating time delay effects on analyzing structural responses for high-rise buildings subjected to earthquake excitations.