HORIZONTAL AND VERTICAL SEISMIC RESPONSE OF TORSIONALLY COUPLED BUILDINGS

Past analytical investigations have shown that the dynamic torsional coupling in asymmetric tall buildings, when subjected to the horizontal translational component of an earthquake, increases the response significantly. The effects of the vertical component of earthquake motion, acting simultaneously on the structure, are studied. A simple lumped-mass model of a single storey building resting on a rigid foundation has been developed and displacement responses are evaluated due to; firstly, horizontal motion; secondly, torsional motion; and thirdly, vertical motion. It has been concluded that the vertical response is very sensitive to the vertical frequency ratio (lambda(v)) values. For smaller lambda(v) values, the response is much higher when the translational natural period of uncoupled building (T-U) is greater than 1.2 s.