Optimization of Concrete Chimneys Considering Random Underground Blast and Temperature Effects

Generally, design of concrete chimney is accomplished considering wind or earthquake loadings disregarding the blast effects. However, in recent years, it has been realized that underground blast effects caused by terrorist attacks and mine blasts are also of growing concerns and may become critical for such tall stack-like structures. Moreover, stresses due to temperature gradient that almost always prevail in reinforced concrete (RC) chimneys in operation may further add to blast-induced stresses. Thus, design optimization of RC chimneys under the combined effects of underground blast and temperature is of important significance. The blast as well as temperature effects are uncertain in nature, owing to their sources, e.g., the charge weight, distance, soil properties, heat inside the chimney, ambient temperature, etc. Also, the optimum design of chimney should duly consider the effect of uncertainty. A robust design optimization (RDO) approach is noted to be suitable to consider the effects of uncertainty in the design of chimney under such random loading conditions which is the subject of the present study. To make the RDO procedure computationally efficient, a cumulative distribution function matching-based procedure is adopted in the framework of dual response surface method. The random blast load is numerically simulated through weighted amplitude wave superposition technique using Tajimi-Kanai spectrum. The results of the numerical study of the proposed RDO approach of RC chimney indicate notable differences with that derived from the conventional code-specified design approach. The present RDO approach yields designs which are almost insensitive from uncertainty effects.