Base isolation for multistorey building structures.

Abstract

Earthquakes are one of nature’s greatest hazards; throughout historic time they have caused significant loss of life and severe damage to property, especially to man-made structures. On the other hand, earthquakes provide architects and engineers with a number of important design criteria foreign to the normal design process. From well established procedures reviewed by many researchers, seismic isolation may be used to provide an effective solution for a wide range of seismic design problems. The application of the base isolation techniques to protect structures against damage from earthquake attacks has been considered as one of the most effective approaches and has gained increasing acceptance during the last two decades. This is because base isolation limits the effects of the earthquake attack, a flexible base largely decoupling the structure from the ground motion, and the structural response accelerations are usually less than the ground acceleration. In this research, a series of dynamic analyses are carried out to investigate in detail the seismic responses for stiff and flexible 12-storey multi storey buildings to the various isolation systems and to consider the effects of foundation compliance on their responses when subjected to different earthquakes. At the same time, an investigation of the seismic response of the recently suggested segmental buildings is carried out. The segmental building concept can be considered as an extension of the conventional base isolation technique with additional flexibility distributed in the superstructure. In addition to the conventional isolation system placed at the base, the superstructure of segmental buildings is further divided into several segments which are interconnected by extra isolation systems located in the upper storeys. In general, the increase of additional viscous damping in the structure may reduce displacement and acceleration responses of the structure. This study also seeks to evaluate the effects of additional damping on the seismic response when compared with structures without additional damping for the different ground motions. In addition, analysis and design considerations for base isolated and segmental structures are suggested to enable the designer to get a better understanding at the preliminary design stage.