تأثیر انتخاب خصوصیات مفصل پلاستیک در رفتار غیرخطی قابهای بتن مسلح

Abstract
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.