Effects of Plastic Hinge Properties in Nonlinear Analysis of Reinforced Concrete Buildings

Due to its simplicity, the structural engineering profession uses the nonlinear static analysis or pushover analysis. Modeling of such analysis requires the determination of the nonlinear properties of each component in the structure, quantified by strength and deformation capacities depending on the modeling assumptions. Pushover analysis is carried out for either user-defined nonlinear hinge properties or default-hinge properties, available in some programs based on the FEMA guidelines. While such documents provide the hinge properties for several ranges of detailing, the programs may implement averaged values. The user needs to be careful; becduse the misuse of default-hinge properties may lead to unreasonable displacement capacities for existing structures. This paper studies the possible differences in the results of push-over analysis due to default and user-defined nonlinear component properties. Four- and eight-story buildings were considered to represent low- and mediumrise buildings for this study. Plastic hinge length and transverse reinforcement spacing were assumed as effective parameters in the user-defined hinge properties. The observations showed that plastic hinge length and transverse reinforcement spacing have no influence on the base shear capacity, while these parameters have considerable effects on the displacement capacity of the frames. The comparisons pointed out that an increase in the amount of transverse reinforcement improves the Frames displacement capacity. Also Our findings clearly showed that the user-defined hinge model is better than the default-hinge model in reflecting the nonlinear behavior compatible with the element properties. However, although the default-hinge model is preferred due to its simplicity, the user should be aware of the circumstances provided in the program and thus should avoid the misuse of default-hinge properties.