Experimental study on the efficiency of tuned liquid dampers for vibration mitigation of a vertically irregular structure

This paper investigates the efficiency of Tuned Liquid Dampers (TLDs) in mitigating dynamic responses of vertically irregular structures. For this purpose, a three-story steel structure was specifically designed and subjected to free and forced vibration tests. In addition, the dynamic responses of eight structure-TLD systems were investigated through three cases. In the first and second cases, TLDs were tuned to the first and second natural frequencies of the steel structure and they were installed on each floor separately. In the third case, which was referred to as the combined case, two TLDs that were tuned to the first and second natural frequencies were first placed simultaneously on the third floor and then separately on the third and second floors. The results indicated that the installation of the combined TLDs on the third floor reduced the peak acceleration and displacement responses of the third floor more than the other cases. It was also observed that, in all the studied cases, the peak displacement response of the third floor was significantly increased when the structure-TLD systems were excited at the second resonance frequency. In addition, at the second resonance frequency, the TLD which was tuned to the first natural frequency and installed at the third floor increased the peak acceleration responses of all floors. It was concluded that, unlike the case in regular structures, a TLD which is tuned to the first natural frequency and installed at the highest level of an irregular structure may not satisfactorily mitigate the structural response of all floors.