Study On The Bearing Capacity Of Large Prestressed Concrete Roof Slab Subjected To Fire

Building fire is one of the most frequent disasters at present,and the high-temperature effect of fire will seriously affect the bearing capacity of engineering structures and components.Large prestressed concrete roof slab is a basic structural component widely used in industrial buildings,and it has the characteristics of large span and thick plate.At present,there are few relevant theories and experimental data about the deterioration law of bearing capacity of such large roof slab under fire action at home and abroad.Therefore,it is of great theoretical and practical significance to carry out research on the fire-resistance performance of large prestressed concrete roof slab.In this paper,a total of 8 large prestressed concrete roof slab specimens were made,3 of which were used as room temperature comparison specimens,1 for the ultimate bearing capacity test under thermal coupling effect,and 4 for the residual bearing capacity test after fire.The main research contents and related achievements of this paper are as follows:(1)Through the static loading test of three prestressed concrete roof slabs at room temperature,the vertical deflection change,crack development law and failure characteristics of roof slabs under uniform load were observed and analyzed.(2)The bearing capacity test of simply supported prestressed concrete roof slab under constant temperature rise was carried out.By measuring the distribution of temperature field along the direction of plate thickness and the vertical deflection of the slab,the crack development law,failure characteristics and fire resistance limit of the roof slab under thermal coupling were studied.The results show that the failure of roof slab starts from the bending failure of main ribs on both sides under the action of thermal coupling,and the failure is rapid.When the roof slab is damaged,the main cracks parallel to the main rib and the secondary rib appear in the four zones of the roof roof,and the plastic hinge ring is formed.The measured fire resistance limit is about 50 minutes.(3)Through the static loading test at room temperature of prestressed concrete roof slab cooled by watering after fire,the crack development rules and failure characteristics of components after watering and cooling under the action of high temperature after fire were studied and analyzed.Test research shows: watering cooling did not cause concrete surface burst and fall off,with the increase in fire time,the roof plate bearing capacity deterioration is more serious,bending stiffness is also lower.(4)Based on the test results,using the finite element simulation software ABAQUS,a simulation analysis of performance than by fire roof panel,thermal coupling under the action of roof plate bearing capacity limit simulation analysis of temperature field distribution inside the roof panel,the fire simulation analysis,the simulation analysis of performance roof plate after fire water cooling,and the finite element simulation results comparing with experimental results.