A study on the design parameters of the compliant LCD for structural vibration control under near fault earthquakes

Abstract

Earthquake ground motions, recorded in near-fault zones, differ from those observed in the far-fault regions. The most important characteristics of thenear-fault ground motion is the pulse like nature with high magnitude often found in the velocity time history along with large ground displacement which contribute significantly to the long period content of the resulting ground motions. This impulsive behavior is mostly caused by forward directivity effect and found in the fault normal component of the ground motion. Again, because of the short travel distance the ground motion is rich in high frequencies. Consequently both short period as well as flexible structures have very high damage and collapse potential under near-fault earthquake ground motions. Nowadays, the focus of researchers is seismic protection of structures by the use control devices. Amongst the relatively low-cost but reliable and effective passive control devices, the Liquid Column Damper (LCD) has gained ground but the conventional damper is only applicable to flexible structures. A variation of the LCD, termed the Compliant LCD (CLCD) is found suitable for short-period structures as well. However, both LCD and CLCD have hitherto been studied for suppression of structural vibrations due to far-fieldearthquakes only. In this paper, an investigation is made into the performance of the CLCD incorporated into a structure, modeled as a SDOF system. A simulation study is carried out with earthquake data specified as near-fault pulse type groundmotions. The sensitivity of some of the design parameters of the CLCD to the damper performance has also been examined. The study indicates that the CLCD is capable of acting as a control device for such earthquake vibrations. The results of the parametric study indicate design trends some of which are different from the existing ones for far-field ground motions.