Modeling Shear Failure in Precast Prestressed Concrete Hollowcore Slabs under Fire Conditions

Abstract

Prestressed concrete (PC) hollowcore slabs when exposed to fire are susceptible to failure under shear limit state. However, current approaches do not consider shear limit state in evaluating failure of hollowcore slabs under fire conditions. This paper presents an approach for modeling the response of PC hollowcore slabs by considering the shear limit state. A three-dimensional finite-element model is developed for evaluating failure of fire-exposed PC hollowcore slabs under various limiting states, including through shear. This nonlinear finite-element model uses a transient thermostructural analysis to trace the response of typical hollowcore slabs under fire conditions. The model accounts for temperature-induced degradation of properties of concrete and prestressing strands, cracking in concrete, material and geometrical nonlinearities, realistic fire, load and restraint conditions, and different failure limit states. The validity of the model is established by comparing temperature, deflection, fire resistance, and failure mode from the numerical model with data obtained from fire tests on different hollowcore slabs. In addition, a case study is carried out to illustrate the significance of shear failure mode in hollowcore slabs under fire conditions. The results from the case study show that slab depth and loading pattern have significant influence on the resulting failure mode, and under certain scenarios, failure of hollowcore slabs can occur through shear limit state before attaining flexural failure.