Non-linear analysis of a collapsed reinforced concrete chimney

During the Ismit (Kocaeli) earthquake of 17 August 1999, a 115m high reinforced concrete chimney or heater stack, located at the Tupras Refinery, collapsed. The falling debris cut 63 pipes, which contributed to interrupted production for more than 14 months. This stack was designed and constructed according to international standards and is representative of similar structures at refineries throughout the world, including those in earthquake-prone regions. It was distinguished from similar stacks at the site by a much larger rectangular opening for the flue duct, circumscribing a horizontal arc of about 50. The opening was located about 1/3 of the height above the base and appeared to be the region of initiation of the collapse. The investigation is focused on the dynamic response of the stack due to an earthquake motion recorded at a nearby site. In this paper the results of a response spectrum analysis of the Tupras stack and a generic U.S. stack are summarized. Then, a non-linear static analysis of the collapsed stack is presented using a demand-collapse comparison. The demand is represented by an acceleration-displacement response spectrum based on the recorded motion as well as some smoothed adaptations typical of design spectra, while the capacities are calculated from pushover curves using a non-linear reinforced concrete finite element analysis. Results are presented that show the effects of the hole and the orientation of the motion with respect to the hole. Also higher-mode contributions to the pushover pattern are considered. The results confirm that the stack could readily fail under the considered earthquake and are also consistent with the debris pattern. Copyright (C) 2003 John Wiley Sons, Ltd.