Influence of the wind load correlation on the estimation of the generalized forces for 3D coupled tall buildings

For tall buildings subject to wind action, the estimation of the first three generalized forces, essential for performing a modal analysis, can be obtained correcting with suitable coefficients the base moments, which can be experimentally measured on rigid models using the high frequency base balance during wind tunnel tests. Several formulations for these coefficients have been proposed; they are based on various hypotheses on the correlation of the wind loads and result in different estimates for the generalized forces. In this work the generalized forces were estimated applying various correction schemes to the base moments obtained from the integration of the experimental pressure measure- ments carried out on a regular and an irregular shaped building. The correction schemes were chosen among the most commonly adopted in design practice. The generalized forces obtained from the base moments were then compared to those obtained directly from the pressure measurements. The entity of the error introduced by various schemes is investigated in the frequency domain through the spectral densities and variances of the resulting generalized forces. While for regular buildings all the correction schemes give good approximation, the negative effect of a complex geometric form, coupling and non-linearity in the modes is clearly seen.