Significance of severe distant and moderate close earthquakes on design and behavior of tall buildings

Many sites around the world may be subjected to severe distant earthquakes alongside moderate-size, short source-to-site distance events. The two scenarios have different impacts on high-rise buildings and should be therefore investigated. Dubai, a region with an exceptionally high rate of development, is vulnerable to the aforementioned earthquake hazard scenarios. The region represents one of the most rapidly growing in construction of tall buildings worldwide. It was therefore selected for the investigation described in the paper. A hazard study for the construction site of a 187m high reinforced concrete tower is conducted. Seismicity of the region is outlined and a hazard assessment is carried out to evaluate peak ground accelerations and uniform hazard spectra for different probabilities of exceedance. A number of natural and synthetic records are selected to represent different seismic assessment scenarios at the site. The RC tower is then modeled and analyzed using state-of-the art analytical platforms. Three-dimensional elastic, inelastic pushover and response history analyses are carried out to verify the dynamic characteristic and estimate the capacity to compare it with the predicted demand. The significance of including severe distant earthquakes in design and assessment of high-rise buildings is confirmed. Records representing the latter scenario amplify the fundamental mode that may be overlooked in design using short source-to-site earthquakes. A proposal is made for scaling the results from inelastic dynamic analysis to arrive at a safe and economical design level. The study not only presents comprehensive hazard and vulnerability study for the selected test case, but also gives conclusions that genetically apply to the class of long-period buildings subjected to large-distant and small-close earthquakes.