Nonlinear analysis and retrofit strategy selection of a historical reinforced concrete building according to Turkish Earthquake Code 2007

Abstract

The necessity of estimating the actual nonlinear behavior of the buildings during the seismic activity leads to a new earthquake code in Turkey. A new procedure, to evaluate seismic performance levels of the existing buildings, performance based design is introduced with the put in force of Turkish Earthquake Code 2007. The expected earthquake will also hit the historical buildings in the Marmara region, so that a historical reinforced concrete building ‘Haldun Taner Theatre Hall’ is chosen for the cased study in terms of seismic protection of historical buildings. The aim of this study is to evaluate the seismic performance of that building and to perform convenient retrofit strategy to improve the capacity to the desired level according to Turkish Earthquake Code 2007. In this study; the material models which are used during the performance based design procedure, plastic hinge hypothesis, basis of ductility concept and the general statements and theory for the performance based design are explained to define the theoretical background of nonlinear analysis. Also to clarify the retrofit strategy selection procedure, the related factors and different retrofit strategies are explained. In the case study, to determine the seismic demand and the target displacements with pushover analysis method; the capacity curve of the model is obtained; then it is converted to spectral acceleration-spectral displacement diagram (ADRS format) and it is compared with the earthquake demand in capacity spectrum method in the same diagram. After that the seismic performance evaluation of the building is done for two directions under two target performance levels (2% 50 years and 10% 50 years) according to TEC 2007. In the incremental equivalent seismic load method (push over analysis); the internal forces and deformation demand during the seismic activity and the resulted member damage levels are specified directly. As a conclusion the building can not satisfy the Immediate Occupancy Level for the design earthquake (10% 50 years) and can not satisfy the Life Safety Level for the biggest earthquake (2% 50 years), also the building is in the collapse region for that target performance level. The retrofit study of the building with shear walls and braced frames are explained respectively. There is not any section in the current code TEC2007 that exactly describes the retrofit strategies but this study gives an idea to estimate the effectiveness of the strategies to provide the desired building performance levels. There is not an exact comparison of these retrofit strategies in that study but a simple cost and construction time analysis is introduced in the last chapter. Both adding of shear walls and braced frames increase the lateral capacity and stiffness significantly which make the building reach the desired performance levels.