Comparative performance of isolated and fixed-base reinforced concrete structures

Abstract

The earthquake transmits to the structure a large quantity of energy that causes damage to structures. The seismic isolation technique can absorb a large quantity of the seismic energy. The seismic isolation concept is a new technique in earthquake engineering, its principle is quite simple, and it consists to create a discontinuity between the foundation and the superstructure, so that seismic energy cannot be completely transmitted into the structure. Therefore, this article includes a numerical application of the nonlinear static method, the capacity spectrum method (CSM), on two types of structures, fixed base structure and isolated base structure. The CSM is one of the methods used for the evaluation of seismic performance. Its principle consists in superimposing a curve which represents the capacity of the structure originated from a non-linear static analysis (Pushover), with a curve representing the solicitation brought by the earthquake. The intersection of these two curves represents the point performance, which evaluates the maximum displacement of the structure in the plastic domain. Algeria, the organization of technical control of construction of Chlef (CTC-Chlef) was the first to introduce this technique through the construction of the seat of its agency in Ain Defla, located in an area of high seismicity. The project of the Great Mosque of Algiers, which is under construction, will be built by using this technique. The conventional earthquake resistant designs rely on the strength and ductility of structural elements to resist seismic induced forces and to dissipate the seismic energy, which prevents the collapse of structures in case of earthquake. On the other hand, the approach of base isolation reduces the damages due to the seismic horizontal forces transmitted to the structure (Koh and Kelly, 1985). The objective of this study was to evaluate the seismic response of two structures, a fixed base structure (conventional structure), and an isolated base structure, the method of analysis used in this study is the method of spectrum capacity (CSM). A comparison of the results obtained was made for the two structures, in terms of maximum displacement in the plastic domain (Freeman, 2004). 2. The seismic isolation