Mitigation of Structural Vibrations Due to Pulse-Type-Near-Fault Earthquake by the Compliant Liquid Column Damper

Pulse-type-near-fault (P-N) earthquake ground excitations can inflict serious damage to structures in built-up areas situated close to seismic faults. The high frequency content, high velocity pulses of long period, and fling effects cause P-N motions to impose large demands on both stiff and flexible structures. Among various passive control devices, the liquid column damper (LCD) is economical and its effectiveness is well-established for flexible structures under far-field earthquake ground motions. In this paper, the compliant form of the LCD (CLCD), which was specially developed to overcome the nonapplicability of the conventional LCD to stiff structures, is investigated for the vibration control of both stiff and flexible structures subjected to P-N ground motions. The study is carried out both in the frequency and in the time domain. Results indicate that the CLCD is successful in mitigating structural response to P-N ground motions. Some of the trends of response reduction with damper parameters are found to be different from those earlier reported for far-field earthquakes. Interestingly, in the case of flexible structures, while the CLCD is found to be fairly effective, the conventional LCD is rendered practically ineffective.