Wind-induced vibration control of tall buildings by designing the overhead fire water tanks as compliant deep tank dampers-inerter

Abstract

Building codes often mandate the installation of overhead fire water tanks (OFWTs) on multi-storeyed buildings. The present study proposes a cost-effective solution by utilizing these OFWTs as tuned liquid dampers (TLDs) in tall buildings to improve serviceability under wind-induced excitation. However, designing OFWTs as TLDs is often hindered by the deep nature of the OFWTs and practical constraints in dimensioning the tank as per the tuning requirement. To alleviate these hindrances, the OFWT is designed as a compliant deep tank damper-inerter (CDTDI). A compliant damper system is achieved by connecting the tank with the building through spring and dashpot elements. This allows relative motion of the whole tank with respect to the building. Further, an inerter is employed to improve the efficiency of the compliant damper. Three example buildings, 20-, 30-, and 40-storeyed, are considered and modeled as multi-degrees-of-freedom (MDOF) systems. The CDTDI-MDOF structural system’s motion equations are formulated. An excitation-independent, genetic algorithm-based single-objective optimization is performed to estimate the optimum CDTDI parameters. Sequentially, the 2nd-order or H2 and infinity or H∞ norms of the transfer function of the roof displacement are chosen as objective function. The efficacy of the CDTDI is examined by subjecting the structure to 10 simulated wind excitations. The results reveal the proficiency of the CDTDI in controlling the multiple modes of the structure, alongside providing significant damping. The CDTDI induces up to 25 and 21 % reduction, respectively, in the peak roof displacement and peak roof acceleration of the example buildings. Further, CDTDI with parameters obtained through H∞ optimization is found to be relatively better performing.