Study On Fire Resistance Of Polypropylene Fiber Reinforced Concrete Slab Column Joints

Slab column structure has the advantages of simple force transmission mode,simple structure,high space utilization rate,convenient pipeline layout,public aesthetic appearance and significant comprehensive economic benefits.But there are also many hidden dangers.Due to the particularity of the structure,the slab column joints are prone to crack or even burst in the fire,causing the overall collapse of the structure.Polypropylene fiber（PPF）can be added into concrete to improve the fire resistance apparently,thus PPF concrete at room temperature and under elevated temperatures are studied further,and then the fire resistance of PPF concrete slab column joints are also be explored.In this paper,polypropylene fiber（PPF）will be added into concrete to improve the fire resistance of slab column joints.The specific contents are summarized as follows:（1）The tests of compressive strength and splitting tensile strength of PPF concrete with different lengths and contents at room temperature were carried out.（2）The mechanical properties of PPF concrete with different length and content after high temperature were tested.Meanwhile the scanning electron microscope after high temperature were also tested.At last the macro and micro states and mechanical properties of PPF concrete at different temperatures are obtained,in order to obtain the optimal fiber length and content of PPF concrete after high temperature.（3）The stress-strain curves of PPF concrete under uniaxial compression after high temperature were studied.According to the test data,the stress-strain full curve constitutive equation of PPF concrete after high temperature is obtained,which provides valuable data to repair PPF concrete structures after fire and conduct the design and finite element simulation of PPF concrete slab-column connections.（4）Experimental study of fire resistance of PPF concrete slab column joints was carried out.During the fire tests the displacement of PPF concrete slab column joints was measured,and the crack propagation of PPF concrete slab column joints under and after high temperature was observed.The finite element analysis of PPF concrete slab column joint under fire was also carried out by ABAQUS.At last,the simulation results and test results are compared and analyzed by means of concrete temperatures,reinforcement temperatures and displacements at key points with time.