Finite Element Analysis On Fire Resistance Capacity Of Reinforced Concrete Beams With Opening

Due to the increasement of city population density and reduction of land for construction, a surging number of high-level buildings are springing up. The citizens’ requirement of well-designed and functional buildings has been improving continuously. Owing to the application of beams with opening, the utilization of architectural space of pipe line would be reduced, and the clear height of each floor would be improved. At the same time, the cost of the construction would be reduced, and the weight of its own would be lightened. What’s more? The load effect would be alleviated. Therefore, the reinforced concrete beams with holes win a broad prospect in the near future. However, as an important component of the bearing structure, the whole structure safety are directly affected by the fireproof performance of reinforced concrete beams with opening. Therefore, it is necessary to study the fire proof property of the reinforced concrete beams with opening under fire.Throughout the domestic and foreign research status, most of the studies and analyses of mechanical properties were based on the texts under normal temperature situation. In comparison, the study of reinforced concrete beams with holes under high temperature was very scarce, even a blank. This article focused on the large span reinforced concrete beams with openings as the object of study. By using the nonlinear finite element software, thirty beam models were built, and the fire resistance limit and destructed form of the beams undergoing the fire were studied, and the performance of conditions(beams with different hole height, hole length, the location on the vertical axis and the location on cross section, hole side stirrup ratio and the form of strengthen reinforced) were compared and analysed. The corresponding conclusions were drawn, which could provide reference for design of fireproof and promote research work.As the results shown:(1)The shape of the holes and the location along the vertical axis were the main influence factors on fire proof performance. And the poorer capacity of fire proof it was, the greater influences it would suffer from the holes. With the increasing size of the hole, the fire resistance of reinforced concrete beams was reduced obviously; when the hole was located in the middle of the span, it would have a little effect on the fire proof capacity. However, the fire proof capacity of the beam could be decreased when the location of holes moving from middle to bearing side;(2)Changing the position of the hole on the cross section was of greate effects on the fire resistance of the beams, especially when the position of the hole on the cross section was set near the high temperature area. The hole center was recommended to be set in the region with low temperature of neutral axis to improve the fire resistance of reinforced concrete beam with opening.(3)Improving the hole side stirrup ratio made little effects on the fire performance;The results could be considered as references for fire resistant design of reinforced concrete beams with opening.