Progressive collapse analysis of precast concrete frames with semi-rigid connections

Progressive collapse occurs when one or more structural members lose their capability to sustain additional loads caused by the failure of members elsewhere. Many studies on progressive collapse have been reported since the destruction of the World Trade Centre in 2001. However, the studies on the modeling of beam-column connection and the impact of connection behavior on progressive collapse are rather limited. The connections play an important role in assessing the robustness of precast concrete buildings against accidental load. In this study, a precast concrete frame is studied by considering the beam-column connections as semi-rigid. The semi-rigid effect is modeled by zero length nonlinear spring elements at the panel zone. Spring stiffness is obtained through the finite element modeling of beam-column connections. A model of five-storey frame building is examined for the progression of damage following the removal of a key element. Static and dynamic analyses were conducted with the effect of material and geometric nonlinearities. The behavior of the building with different connection rigidities were compared in terms of the deflection, demand capacity ratio, ductility and rotation limits. Results demonstrate the importance of applying real behavior of beam-column connections especially when assessing the robustness of the building.