This study is focused on a 115 meter high reinforced concrete chimney located at the Tüpras refinery, Turkey, which collapsed during the 1999 Kocaeli earthquake. The stack was designed and constructed according to international standards and is representative of similar structures at refineries throughout the world. This structure is of particular interest because several similar chimneys at the site survived the shock with only moderate damage. The particular distinction of this chimney appears to be an unusually large rectangular opening, located about 1/3 of the height above the base, which appeared to be the region of collapse initiation. The main focus of the research is the dynamic response of the stack due to an earthquake motion recorded at a nearby site. Results from a response spectrum analysis of the Tüpras stack as well as from a basic nonlinear static pushover analysis using a demand-collapse comparison have been published. These results provide a strong indication of the collapse mechanism of the stack and are consistent with the postcollapse remnants. Since the available spectrum had a peak close to the second period of the stack, the higher mode participation is of interest. In this paper, different methods for the consideration of the higher mode effects are evaluated by comparison with a full nonlinear dynamic analysis. Results are presented that include the effects of the higher mode contributions on the nonlinear static collapse loading.
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