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UBC Theses and Dissertations

Directionality effects of pulse-like near field ground motions on seismic response of tall buildings Archila, Manuel


Earthquake ground shaking at near-field sites has produced severe damage to buildings and infrastructure, caused large economic and human losses. These earthquakes continue to pose a great threat to many populous urban centers around the world. Over the last 4 decades, major research efforts have been devoted to characterize near-field ground motions and their effects on the response of buildings. A challenging engineering problem that remains unsolved in the seismic design of buildings is the directionality effect of near-field pulse-like ground motions on tall buildings. This dissertation presents a computationally efficient method to calculate the critical displacement response of tall buildings. In this method, the duration and amplitude of the ground velocity pulses contained in the input motion and the building’s first mode translational period are compared to determine the orientation of the Conditional Maximum Velocity (CMV), a new ground motion metric. Nonlinear response history analyses (NRHA) using the CMV ground motion provide a close estimate of the critical displacement response of a tall building along the structural axis. The CMV Method is developed on the basis of a series of parametric studies. First synthetic pulse-like excitations and simple structures were used to systematically investigate the effects of pulse duration and amplitude on the dynamic elastic and inelastic response of structures. It is found that the critical displacement response is influenced significantly by the CMV ground motion. This finding is further validated through series of NRHA of simple structures and several case study tall buildings to near-field ground motion records. It is shown that the NRHA using CMV ground motions result in approximate, but significantly accurate estimates of the critical displacement with small errors and moderate dispersion. Ground motion pairs rotated to fault-normal (FN) orientation do not always result in the critical displacement response. Neither does the maximum direction (MD) ground motion at the fundamental period of the building. Analyses made using FN or MD may result in significant underestimates of critical displacement response compared to the proposed CMV. The use of the CMV Method may lead to a better quantification of potential seismic demands on tall buildings.

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