Investigation of Effective Bending Rigidity Considering Different Code Approaches

Abstract

In the study, the nonlinear behavior of reinforced concrete (RC) structures was investigated considering effect of effective bending rigidity under seismic loads. The cross-sectional effective bending rigidity (EIeff) of structural members was evaluated using different approaches of seismic design codes. The values of EIeff given in Eurocode-8, Turkish Seismic Design Code (TSDC) 2007 and Turkish Building Earthquake Code (TBEC) 2018, were used in a case study and compared with the initial (uncracked) section rigidity. The nonlinear single mode pushover analysis was carried out to determine the nonlinear performance of a RC frame structure model in SAP2000. In nonlinear pushover analysis, the lumped plasticity and plastic hinge theory were used to define nonlinear behavior of the structural members. The plastic characteristics of structural members were also evaluated using moment-curvature relationship in Xtract. The dimension of cross-sections and reinforcing details were chosen considering the design requirements of TSDC 2007 and TBEC 2018. The structural performance of the RC frame models with different stiffnesses was compared with performance of the model in which initial rigidity used. The base reaction force vs. top displacement demand, story drifts, and plastic hinge mechanisms obtained from the analyses were selected as comparison criteria. It was observed in the analysis results that a remarkable difference occurred in force and displacement demand between the models using the different effective bending stiffnesses.

Keywords

• Effect of effective bending rigidity,nonlinear performance,reinforced concrete structure,pushover analysis

References

1. [1] Chopra AK, Goel RK (2001): Modal pushover analysis of sac buildings, California.
2. [2] Ersoy, U. and Ozcebe, G. (1998), “Moment-curvature relationship of confined concrete sections”, IMO Technical Journal, December, Digest 98, 549-553.
3. [3] Çağlar, N., Demir, A., Öztürk, H ve Akkaya, A., A simple formulation for effective flexural stiffness of circular reinforced concrete columns, Vol. 38, pp. 79-87.
4. [4] Mander JB, Priestley MJN, Park R. Theoretical stress-strain model for confined concrete, Journal of Structural Engineering; 1988.
5. [5] TEC 2007, Turkish earthquake design code for buildings, The Ministry of Environment and Urban, 2007.
6. [6] EUROCODE-8. Design of structures for earthquake resistance - Part 1: General rules, seismic actions and rules for buildings. European Committee For Standardization; prEN 1998-1:2003.
7. [7] TECB 2016-Draft, Turkish earthquake design code for buildings, The Ministry of Environment and Urban, 2016.
8. [8] Xtract v.3.0. Cross-sectional X structural analysis of components, Imbsen Software Systems, 9912 Business Park Drive, Suite 130 Sacramento, CA 95827.

9. [9] SAP2000 (2015) Integrated finite element analysis and design of structures basic analysis reference manual, Computers and Structures, Inc. California, USA .