**1. Introduction**

280 Earthquake Engineering

[24] CSA. 2006. Canadian Highway Bridge Design Code. Standard CAN/CSA-S6-06,

Canadian Standard Association (CSA), Mississauga, Ontario.

There are several methods exist to define the seismic performance levels of reinforced concrete (*RC*) structures. Among these methods, the nonlinear dynamic and the static analyses in which both methods involve sophisticated computational procedures because of the non-linear behaviour of the *RC* composite materials. In order to simplify these analyses for engineers, different suggested guidelines such as *FEMA-356* (Federal emergency management agency [*FEMA-356*], 2000) and *ATC*-40 (Applied Technology Council [ATC-40, 1996]) were prepared to define the plastic hinges properties for *RC* structures in the United States, and thus they have been used by many computer programs (i.e., ETABS [CSI, 2003], SAP2000 [CSI, 2008]) as a default or ready plastic hinge documents. However, there are still contradictions exist in the available literature due to the use of these ready documents in which the buildings are not designed based on the earthquake code of United States. The assessment of seismic performance of structures under future earthquakes is an important problem in earthquake engineering (Abbas, 2011). The use of methods and assumptions to define the seismic performance levels of *RC* buildings become more and more important issue with time dependent effects of corrosion. Moreover, to the knowledge of the author, no any study has been performed up to date, which studies define the possible difference in the time-dependent seismic performance levels of *RC* buildings under the impact of corrosion by using default and user-defined plastic hinge properties.

The primary objectives of this study was to investigate the effects of default hinge properties based on *FEMA-356* (FEMA-356, 2000) and user-defined hinge properties on the timedependent seismic performance levels of corroded *RC* buildings. An assumed corrosion rate was used to predict the capacity curve of the buildings by using default and user-defined plastic hinge properties as a function of time (*t*: 25 years, and *t*: 50 years). Two, four and

© 2012 Yalçiner and Marar, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Yalçiner and Marar, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

seven stories of *RC* buildings were considered to represent the effects of default and userdefined hinge properties on story levels. For the modelling of user-defined hinge properties, the time-dependent moment-curvature relationships of structural members were predicted as a function of corrosion rate for two different time periods in order to perform push-over analyses, while default hinge properties were used for the other case based on the ready documents by *FEMA-356* (FEMA-356, 2000). Then, the nonlinear time-history analyses for both corroded and non-corroded buildings were performed by using 20 individual earthquake motion records. Seismic performance levels of non-corroded buildings and predicted time-dependent seismic performance levels of corroded buildings were compared based on their story levels as a result of user-defined and default hinge properties. Limit– states at each performance levels (e.i. immediate occupancy, life safety, collapse prevention and collapse) were obtained. The obtained results were summarized to compare the differences in the results of seismic response of the buildings due to user-defined and default hinge properties for both corroded and non-corroded cases.

Seismic Performance Evaluation of Corroded Reinforced Concrete Structures by Using Default and User-Defined Plastic Hinge Properties 283

where two straight lines indicate different behaviour of concrete for confined and unconfined concrete. For the descending branch of the curve assumed to be linear and its slope specified by determining the strain when the concrete stress is decreased to half of its

Mander's (Mander, 1984) model was used for each time periods (i.e., *t*: 25 years, and *t*: 50 years) for modelling the stress-strain relationships of steel as can be seen from Fig. 2. The developed model by Mander (Mander, 1984) includes linear elastic region up to yield, elasticperfect-plastic region, and strain hardening region. The Mander's model (Mander, 1984) has control on both strength and ductility where the descending branch of the curve that first branch increases linearly until yield point then the curve continues as constant. In order to model the material properties, the following required assumptions were made. The modulus of elasticity of concrete 3250 14000 *c c E f'* MPa was calculated according to TS500 (TSI, 2000). The mechanical properties of steel in the analyses were selected according to TS500 (TSI, 2000), where the minimum rupture strength (*fsu*) was equal to 500 MPa, the yield strain (*εy*) was equal to 0.0021, the strain hardening (*εsh*) was equal to 0.008, the minimum rupture extension (*εsu*) was equal to 0.12% and the modulus of elasticity of steel (*Es*) was taken as 200,000 MPa.

stress value as suggested by Park et al. (Park et al, 1982).

**Figure 1.** Used stress-strain relationship of concrete (Kent & Park 1971).

*0.002*

*B* 

Unconfined

Three *RC* buildings having two, four and seven stories were considered in this study. The assessed three *RC* buildings were selected among the typical constructed *RC* buildings in North Cyprus where the buildings were designed according to Turkish earthquake code (TEQ, 1997). The soil classes were classified as soft clay (group D), the building importance factor was taken as 1, and the effective ground acceleration coefficient (*A0*) was taken as 0.3*g*  (seismic zone 2) according to Turkish earthquake code (TEQ, 1997). The buildings were remodelled to select the most critical frames by using the existing plans of the buildings. Fig.

D

*ε50h*

*N*

*N*

*θ*

*N*

*ε50u ε50c ε<sup>c</sup>*

*ε20c*

*s* 

*N*

*lx* 

Confined

*ly*

*C* 

**3. Description of structures** 

*A*

*0.2fc*

*0.5fc*

*fc* 

*c*
