Evaluation of peak resultant response for wind-excited tall buildings

The traditional peak factor approach and combination rules developed for Gaussian scalar combination effects are not applicable for vectorial combination effects which feature non-Gaussian characteristics. This paper addresses the evaluation of the peak value of a vectorial resultant response of a wind-excited tall building resulting from correlated three-dimensional responses with a special focus on building acceleration. The peak value of the resultant response over a given duration is analyzed based on the upcrossing theory for non-Gaussian processes and for vector-valued Gaussian processes. A parametric study including the correlation of response components and their derivative processes is conducted to identify the controlling parameters in estimating the upcrossing rate and peak resultant response. The accuracy of the current empirical combination approaches is evaluated. A practical combination scheme is proposed and demonstrated using a wind-excited tall building with three-dimensional mode shapes. The results show that the existence of eccentricity leads to coupled alongwind, crosswind and torsional accelerations, and considerably amplifies the peak resultant acceleration.