A SIMPLIFIED METHOD FOR NONLINEAR CYCLIC ANALYSIS OFREINFORCED CONCRETE STRUCTURES: DIRECT AND ENERGYBASED FORMULATIONS

摘要

This paper presents a simplified method based on direct and energy formulations for nonlinear analysis ofrnreinforced concrete frame structures. In the simplified method, a reinforced concrete member is modeledrnby an equivalent member of homogeneous nonlinear material with a derived stress-strain relationship,rnwhich satisfies the requirement that the equivalent member has the same moment-curvature behaviour asrnthe original member. One advantage of the simplified method is its simplicity which can be easilyrnimplemented in most structural analysis computer programs with nonlinear modeling capabilities. Therndeveloped model can accurately predict the nonlinear hysteretic responses of reinforced concreternstructures with frame members of arbitrary shapes and reinforcing details under severe earthquakernexcitations. Numerical examples of a cantilever beam and a new bridge pier system of double-skinnedrnconcrete filled tubular (DSCFT) members, recently developed in Taiwan for seismic construction, arernanalyzed under monotonic and cyclic loadings. The effects of concrete confinement, steel hardening,rnstiffness degradation, strength deterioration, and pinching are simulated in the developed simplifiedrnmethod. Modules of the method are developed for implementation in the Open System for EarthquakernEngineering Simulation framework (OpenSees). Results from the simplified method agree well with finiternelement and fibre layer models, as well as with experimental testing results.