Aseismic design of tall reinforced concrete chimneys

A lack of experimental data related to the cyclic behavior of chimney structures to severe earthquake ground shaking has resulted in design standards generally ignoring the effects of ductility and adopting conservative aseismic design provisions. This paper presents results from an experimental study that demonstrates that correctly detailed reinforced-concrete chimney sections are not brittle but possess some ductility. The experimental results have been used to develop a nonlinear dynamic analysis procedure for evaluating the inelastic response of tall reinforced-concrete chimney structures. The procedure is used to study the seismic response of ten chimneys, ranging in height from 115 to 301 m. Based on the nonlinear dynamic study, a series of code design recommendations has been developed and incorporated into the 2001 CICIND code to reduce the seismic loads by a factor of R = 2 by detailing for ductility and preventing the formation of brittle failure modes. The 2001 CICIND design recommendations result in both improved performance and cost savings of up to 20% compared with existing design practices.