ABAQUS Fire Behavior Based Concrete Composite Beam Floor Cages Analysis

Fire is one of the most frequent disasters.With the development of society,the losses caused by building fires are becoming more and more serious.The floor is one of the important components of the building structure,and it is also one of the most damaged components in the building fire.If it collapses,it will cause a major accident.Although the cage composite beam floor have been widely used,there are few studies on their fire resistance at present.The study of the fire behavior of the cage composite beam floor r is to grasp the bearing capacity of the cage composite beam floor when the high temperature is used,and the two damage caused by the collapse of the floor can be avoided.The research on the bearing capacity after the cooling of the high temperature is the safety assessment and reinforcement of the building after the fire.As mentioned above,it is necessary to study the fire behavior of the cage composite beam floor,especially the high temperature and the high temperature bearing capacity.In this paper,based on the finite element software ABAQUS,a temperature field analysis model and an anti fire analysis model are set up on the basis of the predecessors' research.Through the analysis model system,the temperature field and the fire resistance of the cage composite beam floor are studied by the fire time,the width of the rib beam,the thickness of the protective layer and the height of the floor section.The conclusions are as follows:(1)Temperature fieldDuring the 3 hours of fire,the temperature field changes of the cage composite beam floor can be roughly divided into two stages,namely,before and after the burning of the composite box floor.The temperature field of the laminated box girder floor and its rib beam is basically the same as that of the ordinary concrete slab and beam on the single side.After burning through the floor of the stack box,the top plate of the stack box is burned up quickly,and the temperature field at the junction of the rib beam and the top of the stack box begins to appear in the high temperature zone moving to the rib beam.The change of the height of the cross section box girder,the width of the rib beam and the thickness of the protective layer has little effect on the whole temperature field.Increasing the height of the section and the width of the rib can slow down the attenuation of the effective section area of the concrete,and it is more effective to increase the height of the cross section compared with the width of the rib beam.The change of the thickness of the protective layer only has a great influence on the temperature change of the steel bar at high temperature.When the thickness of the concrete protective layer is 25 mm,the maximum temperature of the reinforcement at the fire surface is less than 700 degrees within 3 hours,and the steel bar has the bearing capacity.(2)Bearing capacity at high temperatureThe bearing capacity of the composite box girder is not greatly influenced by the changing process of the fire time.The bearing capacity of the cage composite beam floor is slow down in the 60 min before the fire,and the bearing capacity decreases rapidly after 60 min.The increase of the cross section height of the composite box girder can effectively increase the bearing capacity of the components at high temperature,and the increase of the width of the rib beam is the second,and the thickness of the protective layer is not obvious.Compared with the bearing capacity at normal temperature,the increase of the height of the section can be the most effective reduction in the decrease of the bearing capacity of the component,while the increase of the thickness of the protective layer is the second,and the width of the rib beam is not obvious.The bearing capacity of the analyzed components is greater than 20% of the normal temperature when the 3H is fired,and the bearing capacity of the components is still 3h after fire.The rib beam plays a key role in the high temperature of the component.(3)Residual bearing capacity after high temperatureThe variation of the bearing capacity of the cage composite beam floor,the width of the rib beam and the thickness of the protective layer has no effect on the change of the bearing capacity of the component with time.The change of the bearing capacity of the member is faster in the 30 min before the fire,and decreases slowly and tends to be slow after 30 min.Compared with the enlargement of the width of the rib beam of the cage composite beam floor,the increase of the height of the section can be more effective to improve the bearing capacity after the high temperature action of the component,and the change of the reinforcement protection layer has almost no effect on the bearing capacity of the member after the high temperature action.Compared with the bearing capacity at normal temperature,the increase of the height of the section can be the most effective reduction in the decrease of the bearing capacity and the effect of increasing the thickness of the protective layer,while the variation of the width of the rib beam has no effect on this.And it is suggested that the value of the component protection layer is greater than 25 mm.The bearing capacity of the analyzed component is still 60% higher than that of normal temperature when the 3H is fired at high temperature.After that,the bearing capacity of the component decreases slowly.