Numerical investigation of fire behavior of unbonded post-tensioned concrete

This study investigates the fire behavior of cast-in-place unbonded post-tensioned (PT) concrete through a combined thermal and mechanical finite element analysis. Addressing the complexity of modeling the unbonded PT concrete, the research uses temperature data from 2D heat transfer simulations, which is applied in 3D structural model using spring and contact modeling methods. Results align closely with experimental data, showing that both modeling techniques predict member deflections and tendon tensile forces effectively, though spring models are more accurate. Parametric studies reveal that varying concrete cover thicknesses do not compromise safety during 2-hour and 3-hour fire scenarios. The study also indicates that current fire design codes are sufficiently conservative, suggesting opportunities for optimizing structural design when applying certain tendon configurations. Overall, the findings support the adequacy of existing fire codes and suggest potential for cost-effective design improvements.