Wind-induced responses of tall buildings experiencing complex motion

A wind tunnel model study on the effects of eccentricity between centre of mass and centre of stiffness of a tall rectangular building on the wind-induced response characteristics and wind excitation mechanisms was carried out. The results indicated significant effects of eccentricity on the along-wind, cross-wind, and twisting moment responses for both cases of the incident wind normal to the narrow and wide faces of the building model. The periodic twisting moments, created either by the flow separation at the upstream corners and the reattachment process of the separated shear layers, or by the eccentricity between the resultant lift force and centre of stiffness, were found to be a dominant wind excitation mechanism causing a significant increase in the twisting moment response of the building model. In addition, the twisting moment responses could be greatly amplified by the effects of resonance between the frequency of the periodic twisting moment and the torsional natural frequency of the building model. For the building model with the centre of stiffness located downstream from the centre of mass, increases in the twisting moment response and the resultant acceleration response at the corner of the building model were more prominent.