Influence of seismic incident angle on response uncertainty and structural performance of tall asymmetric structure

The estimation of critical seismic response of a structure is complicated in nature due to the uncertain distribution of the internal forces under multidirectional seismic excitations. One of the important concerns inherent to this complication is the uncertainty associated with the final design direction as different seismic directions result in different seismic responses. In this regard, this research provides a detailed examination of (1) response-to-response and record-to-record variability under varying seismic orientations, (2) quantification of seismic response uncertainties and (3) the seismic performance of asymmetric structure in the context of conservative/nonconservative seismic design. With the mentioned research objectives, a realistic case study asymmetric structure under the influence of varying bidirectional seismic excitations was evaluated. It has been argued in this research that the seismic excitations applied at structure's reference axes are very unlikely to demonstrate maximum response for all response quantities simultaneously, even if it results in a peak response for a particular seismic response quantity. This research is particularly helpful for the critical assessment of directionality influence on asymmetric structures prior to making any decision during thestructural design process. Substantial arguments have been presented to emphasize the inclusion of the investigation of seismic response uncertainty in practical design of critical asymmetric structures.