EXPERIMENTAL AND THEORETICAL STUDY ON FIRE RESISTANCE OF PRE-STRESSED CONCRETE HOLLOW COMPOSITE SLAB

Pre-stressed concrete hollow composite slab (hereinafter referred to as "composite slab") is made of prefabricated pre-stressed concrete hollow slab as the base plate with the reinforced concrete surface layer being poured integrally above it, which is widely used in prefabricated buildings. In order to find out the influence of the longitudinal reinforcement ratio and layout of the cast-in-place layer on the fire resistance of pre-stressed concrete hollow composite slabs with the consideration of the fire exposure of single span, fire resistance tests were carried out on three full-size two span pre-stressed concrete continuous composite slabs, based on which the development laws of temperature distribution in the cross section, internal force redistribution, cracks and deflections of the fire exposed span were obtained. Based on the test results, the influence of the fire endurance of the specimens and the ratio and arrangement of the longitudinal reinforcement in the cast-in-place layer on the fire resistance of the specimens is obtained. In order to avoid the shortcomings in the test and obtain the influence law of a wider range of parameters, ABAQUS was used to establish the fire resistance analysis model of the composite slab, which was verified according to the test data, and then the fire response of the composite slab with different reinforcement ratios and different reinforcement arrangements under the ISO-834 standard fire was analyzed. The results show that the composite slab can reach the fire endurance limit of 2 hours. Prefabricated pre-stressed hollow slab has good thermal insulation performance. Under the same fire and load conditions, increasing the ratio of longitudinal reinforcement in the cast-in-place layer can significantly improve the fire resistance of composite slabs. When the amount of reinforcement is the same, increasing the reinforcement ratio in the negative moment area and reasonably setting the length of the negative moment reinforcement can effectively improve the fire resistance of the composite slab. The reinforcement ratio in the negative moment area has a great influence on the redistribution of internal forces of composite slabs under fire. The deflection of the specimen with large heating rate is slow with the increase of temperature.