Experimental and Numerical Study of Fire Endurance of Bonded Posttensioned Concrete Slabs

The vulnerability of posttensioned (PT) slabs to fire has prompted researchers to conduct tests and devise means for numerical analysis. In this study, bonded PT slabs with varying cover thicknesses were subjected to fire tests with a numerical model developed based on the results. The test results demonstrate that current codes governing cover thickness adequately address fire resistance. The structural behavior of PT slabs was analyzed based on thermal responses for concrete and steel. Numerical modeling of heat transfer and coupled thermomechanical analyses was validated by comparison with fire test results. To investigate the influence of cover thickness on fire resistance performance, a parametric study to develop a numerical means of analysis was conducted and evaluated. With a load level of up to 40% of nominal flexural capacity at the specified cover thickness of 45 mm or larger, current codes were proven to be adequate to ensure the target safety. The authors hope that identified influencing factors of fire resistance performance of PT slabs and the proposed numerical modeling method may be helpful in design of bonded PT concrete slabs with unrestrained conditions.