Dynamic Response of Flexibly Supported Liquid‐Storage Tanks

A refined method is presented for evaluating the impulsive components of response of upright, cylindrical liquid‐storage tanks that are supported through a rigid circular foundation at the surface of a homogeneous, elastic half‐space and are excited horizontally at the base. The convcctive components of response are insensitive to the flexibilities of the tank wall and supporting soils, and may be computed considering both the tank and the supporting medium to be rigid. Critical responses are evaluated for harmonic and seismic excitations over wide ranges of tank proportions and soil stiffnesses, and the results are used to elucidate the effects of soil‐structure interaction and to assess the adequacy of a previously reported simpler method. In addition to the exact method, an approximate technique is proposed with which the contributions of the higher modes may be evaluated readily. It is shown that soil‐structure interaction may reduce significantly the critical responses of broad tanks, but may increase those of tall, stiff tanks that have high fundamental natural frequencies. It is further shown that for tanks with height‐to‐radius ratios of the order of 1.5 or less, the higher modes of vibration are insignificant contributors to the overall response. Such systems may be analyzed reliably by the previously proposed simpler method.