Experimental Study On Fire Resistance Of Simply Supported On Four Sides Of Full-scale Cast-in-place Concrete Hollow Floor

In all kinds of disasters, the fire is not subject to time and space constraints, the highest frequency of disasters. The building structure in case of fire, the fire floor is the largest area, but also an important structure of the effective barrier of fire spread to upstairs. So we’re on the floor of the fire resistance research has very important significance. There are many researches on fire behavior of ordinary floor at home and abroad, and for cast-in-situ concrete hollow floor fire resistance performance of cast-in-situ concrete hollow floor is less, due to the formation of cavity of different materials can be divided into many types, a combination of plastic mould box concrete hollow floor is a cast-in-situ concrete hollow floor cover, are arranged through a combination between different dimensions of the mold box and the cast-in-situ concrete rib beam, forming the integrity floor technology. The cast-in-situ concrete hollow floor with large span, heavy load, large space, flat plate beam technology, has been applied to a number of major projects, and achieved tremendous economic value and social benefits. The present stage for the research on fire behavior of cast-in-situ concrete hollow floor is still less, it is particularly important for all parts of the cavity network beam floor in the fire temperature field distribution and the form of destruction. This paper mainly through the fire test furnace, the standard temperature curve, experiments are carried out on real fire simplysupported full-scale cast-in-place concrete hollow floor under load. Through the test board by fire after the failure characteristic, floor crack, concrete rib beam combination die box cavity temperature distribution, temperature, temperature, rib beam steel plate deformation in the plane and out of plane deformation, plate edge angle analysis, draws the following conclusion:(1) simplysupported cast-in-situ concrete hollow floor under fire, Inouchi showed an obvious temperature gradient, resulting in temperature stress, the upper plate tension, cracks perpendicular to the plate edge.(2) combination die box beam floor from ignition to stop burning experienced a total of three hours and 32 minutes, under the effect of high temperature and long time floor did not(3) produce burnt through, the bottom plate only in a few parts of the concrete burst off burning plastic mould box, compared with engineering application of prefabricated composite box hollow floor and has good fire resistance performance.(3) hollow floor (floor) of the flange thickness has a certain effect on the floor damage morphology after fire, due to thermal expansion of the floor, because the fire effect, rib beam, the floor is restrained by rib beam in the expansion, resulting in the birth of compressive stress generated in the bottom plate, with the increase of furnace temperature, heat through the bottom plate of the mould box cavity gradually to the transfer, so that the gas temperature in the die box increases, the pressure increases, the bottom is out of plane gas generated by expansion force, if the floor is too thin, resulting in instability will burst, and the floor was burned through the phenomenon of emergence.(4) fire after the bottom plate concrete hollow floor force transfer mode changed and transformed by the hollow floor with four edges supported the "ribbed floor", due to the mutual restraint effect around the edge beam, the torque in the side beam, cracks on the side beam.(5) floor fire effect, due to changes in slab damage and material properties at elevated temperatures, the plate stiffness decreases, plate deformation, the deformation will stop after combustion, partial recovery, recovery ratio can reach 70%.