Experimental Study On Fire Resistance Of Column Supported Cast-in-situ Concrete Hollow Floor

In the long history of human use of fire, along with the development of human beings, and promote the social progress. With the development of social economy, in the fire to provide convenience to people at the same time, the occurrence of fire is a serious threat to the safety of people’s life and property. In all kinds of fire, building fire is occurred most frequently, resulting in a fire the most serious losses. Cast in situ concrete hollow floor is a new type of floor system, in the project is more and more widely used, and the experimental research on related theories of cast-in-situ concrete hollow floor fire resistance is not complete. Through the analysis of the fire temperature field distribution and variation and failure features of cast-in-situ concrete hollow floor, in order to take protective measures to provide reference and data support for the design and construction in the future, reduce the harm caused by fire, therefore, is of practical significance to carry out the study of necessary fire behavior of cast-in-situ concrete hollow floor cover.Fire resistance of the columns supporting cast in situ concrete hollow floor are studied. The use of fire test furnace for column supported cast-in-situ hollow concrete floor system in accordance with the ISO843 international standard temperature curve experiment was conducted to study the fire through the deformation of column supported cast-in-situ concrete hollow floor temperature changes under high temperature condition, floor and test the damage from the following conclusions:(1) The distribution of temperature field of hollow floor rib beam has obvious temperature gradient, the ribbed beam hollow floor are beam hollow floor slab test, do not appear in the burn phenomenon, so the rib beam at side by fire, and the three face under fire beams, the temperature gradient of hollow rib beam floor is more obvious. Due to the temperature gradient of rib beam hollow floor in large, also have large temperature stress. In the process of heating, evaporation away a lot of heat, reduce the temperature of the rib beam growth, about 100 degree centigrade temperature - time curve of a level, and the bottom of the beam distance, horizontal stage lasts for a long time. When the moisture is finished, the temperature continued to rise rapidly. The temperature field distribution of water content influence the hollow slab test plate, thereby affecting the fire resistance performance of hollow floor.(2) Because of thermal inertia of the existing concrete hollow floor, temperature changes in a certain lag, so the material temperature is gradually reached the maximum value in the test after the ceasefire.(3) By the fire, have a greater torque acting on the frame beam, beam column joints are severely damaged, concrete, reinforced exposed side edge beam cracks obviously.(4) Due to temperature stress test slabs under fire effect, the coupling action of load and temperature, hollow floor upper corner cracks, around a regular class arc shaped crack, the cracks are nearly perpendicular to the side frame beam and frame beam, between approximately 45 degrees, the top frame beam position and beam vertical cracks.(5) After the start of ignition, hollow floor began to appear downward deflection deformation and overall displacement variation with time linearly after the ceasefire began to reach the maximum displacement deformation, then gradually recovered, the final recovery ratio reached 81.5%, indicating the experimental board after fire is still great stiffness, hollow floor with refractory the ultimate good.(6) From the destruction form of fire time and test board, test plate to maintain the integrity, supporting cast in situ concrete hollow floor has good fire resistance performance.