Investigation of strain-based performance limits in reinforced concrete buildings with inadequately detailed beam-column joints

Appropriate analytical modeling approaches are required to reflect different damage modes in the seismic performance evaluation of existing reinforced concrete buildings. Although the beam-column connections are a significant factor for the seismic performance of existing reinforced concrete buildings in terms of both strength and drift limits, the rigid connection assumption is considered as an engineering practice in the performance evaluation. In this study, an existing four-storey reinforced concrete structure with poorly detailed beam-column connections against shear effects is considered. The numerical model is composed of rotational springs representing the beam column joint areas, distributed plasticity-based cross-section cell (fiber) and macro elements. Nonlinear time history analyses of the three-dimensional structural model with defined deformable beam-column joint are performed with STKO (Scientific Toolkit for OpenSees) using scaled earthquake records. The beam-column joint model is formed from a zero-length rotational spring defined in the middle of the joint, two connected nodes, and rigid connections extended to the column and beam elements. Moment-rotation relationships are defined by rotational springs based on shear stresses and shear strains.The relations between the sectional deformations of columns and beams of an outer and inner beam-column joint and section rotations at the joint were evaluated with the section rotation limits in TBDY (2018).