Experiment and analysis on fire resistance of two-span unbonded prestressed concrete continuous slabs

Experiment on fire resistance of nine two-span unbonded prestressed concrete (PC) continuous one-way slabs is completed. Temperature distribution along section of the slabs was obtained by embedded thermocouples in the slabs. Variation of new deflection of the slabs and stress of the unbonded prestressing steel wires in the slabs subjected to fire were obtained by load cells at the anchorage end and displacement transducers on the slabs. Variation of side supports reaction of the slabs subjected to fire was obtained by load cells at the side supports. The fire witnessed the whole process of water overflowing, vapor appearing and developing, and water drying, vapor disappearing on the unexposed surface. Calculation formula of side supports reaction, stress of unbonded prestressing steel wires and new deflection in the mid-span of slabs subjected to fire were obtained by fitting curve of experimental data considering every key factor. For in 4 slabs cracks penetrate the slab close to the cut-off point of negative flexural reinforcements at the top of intermediate support, proposition for cutting off of negative flexural reinforcements at the top of intermediate support of two-span continuous slabs is proposed.