SEISMIC UPGRADING OF GRAVITY LOAD DESIGNED CONCRETE BUILDINGS USING ADVANCED COMPOSITE MATERIALS

Abstract

Many of the existing reinforced concrete structures performed poorly during recent earthquakes as they were designed to resist gravity loads only with inadequate seismic detailing. Several of the construction details in existing gravity-load buildings do not conform to current code requirements for seismic design and . may lead to nonductile behavior. The objective of this research is to investigate the use of advanced composite materials for the rehabilitation ofnonductile R.C. buildings. The study is limited to low­ to-medium-rise frame buildings. Four reinforced concrete buildings, three, six, nine and twelve stories, were selected to represent existing nonductile structures that were designed according to early codes. The seismic response of the buildings was evaluated in terms of deformations and damage. The buildings were considered as a series of planer frames connected at each floor by a rigid diaphragm, therefore, only 2D analysis was performed. The buildings seismic performance parameters were obtained using nine ground motion records with different characteristics. The selected records covered a wide range of frequency content and strong ground motion durations. The free-vibration characteristics of the buildings were determined and the relation between the building seismic performance parameters and the PGA level of the earthquake• records was investigated. The relation between the deformation and damage for the four buildings was evaluated. The response of the same reinforced concrete buildings wrapped with advanced composite materials under seismic loads was evaluated. An enhanced hysteretic model was implemented to represent the inelastic behavior of wrapped columns. In order to examine the inelastic cyclic behavior of the wrapped columns a quasi-static displacement analysis was performed to simulate the results of specimens from several experimental programs. Several iterations were performed to adopt the hysteretic parameters that correctly simulate the experimental hysteresis loops.