Numerical Methods for the Seismic Performance Assessment of Reinforced Concrete Buildings

Introduction

The need for evaluating the seismic adequacy of existing structures has come into focus following the damage and collapse of numerous reinforced concrete (RC) structures during recent earthquakes in many southern European, Middle Eastern and west Asian countries settling on highly seismic zones. The vulnerable building stock in these regions have similar structural and construction deficiencies because of the fact that they have not been adequately designed or constructed in terms of the seismic regulations of the design codes, while some have even not benefitted from engineering services. In most of these regions, a clear majority of the zone of occupation has been exposed to strong ground shakes during recent earthquakes. Most particularly, the destructive earthquakes occurred in Turkey over the past two and a half decades, which caused significant amounts of casualties and economic losses, revealed the insufficient structural capacity of the existing building stock and emphasized the need for performance assessment to estimate the potential damage and to make required provisions against future earthquakes.

Site-observed damages in buildings, mostly consisting of low- and mid-rise RC structures, point out inadequate reinforcement detailing, lack of confinement zones, heavy and large-span cantilevers and indirect supporting preventing the formation of regular structural frames. Within the scope of this research, a building stock which represents the general characteristics of existing structures is taken into consideration. The stock consists of 3~5 story RC frame structural buildings which have experienced moderate damages during the M_w 6.2 1998 Ceyhan Earthquake. The aim of the study is to perform the structural performance assessment of the representative building stock by utilizing:

• 1.

  Linear elastic procedure described in Turkish Earthquake Code, TEC (2007);

• 2.

  Nonlinear dynamic analysis procedure under the effect of the recorded strong ground motion during 1998 Ceyhan Earthquake;

• 3.

  Appendix-2 of the Application Regulation of the law no: 6306 by Republic of Turkey, Ministry of Environment and Urbanization (2012); and

• 4.

  Japanese seismic index method (2001) and then compare the findings.

If there is a necessity for a detailed investigation, different procedures are recommended for performance analysis of buildings in many seismic codes that present two approaches to accomplish this task: linear elastic and nonlinear methods. Even though there is a broad agreement that the nonlinear based procedures are better tools for the implementation of the performance based seismic engineering, the linear elastic methods are and will continue to be used due to their simplicity in modeling and analysis. Independent from the approach, seismic performance of the building is defined to be related with the probable damage in individual structural members subjected and evaluated under the effect of the earthquake load and is classified considering damage regions such as:

• •

  Minimum,

• •

  Advanced,

• •

  Extensive, and

• •

  Collapse.

Thus, as the first step of this research, linear elastic procedure is applied for the entire building ensemble and structural performances throughout the entire structural elements are investigated subsequent to sectional performances by considering the targeted performance level.