Study On The Flexural Behaviors Of The Prestressed Concrete Composite Slabs

Concrete composite slab is that after precast prestressed concrete member hoist in place,on the top pouring a layer of concrete to composite formation of the whole again.Composite slabs have the characteristics of shuttering demolition mode is simple,short construction period,small field work,strong integrity,good seismic performance.Prefabricated part adopts prestressed reinforcement,can improve the overall rigidity and crack resistance,as far as possible without design or reduce support and can reduce the dosage of steel,it has the good economic benefits.In this paper,prestressed concrete composite slabs don't set support in construction stage,they are the secondary stress components.All load are borne by the prefabricated part,the prestressed concrete composite slabs reduce the workload and labor costs,speed up the construction speed.Composite surface using artificial rough surface instead of shear reinforcement ensure new and old concrete work together,so as to save the amount of reinforcement,it has important economic and social benefits for the application and development of composite slab.In this paper,the prestressed concrete composite slabs are analyzed and researched,through the prestressed composite slabs are studied based on uniformly distributed load test and ABAQUS finite element simulation,crack resistance,the rigidity and shear performance of composite surface are analyzed.Based on the result,the prestressed and thickness of composite layer effect on the flexural properties of composite slabs are analyzed.Main conclusions are as follows:(1)For uniformly distributed load test of precast prestressed concrete slab,In the process of test specimens don't crack.Based on the linear development of load-deflection curves,load-reinforcement strain curves and load-concrete strain curves,specimens are in elastic deformation stage.Maximum deflection values conform to the requirements of standard,the specimens meets the requirement.(2)For uniformly distributed load test of prestressed concrete composite slab with 2m×3m,when specimen loaded to using load,under the slabs cracks are not found.when the specimen continue loading to 12.67kN/mm2,the slabs cracks are not found too.And none of peeling phenomenon on concrete composite surface.For uniformly distributed load test of prestressed concrete composite slab with 2m×4.64m,when specimen loaded to using load,under the slabs cracks are not found,when the specimen continue loading to 10.88kN/mm2,cracks are found and through the mid-span,and cracks are concentrated in the mid-span.But none of peeling phenomenon on concrete composite surface.For uniformly distributed load test of prestressed concrete composite slab on DHB-5?DHB-10,when specimen loaded to using load,under the slabs cracks are not found.when the specimen continue loading to 8.33kN/mm2,cracks are found and through the mid-span,cracks value is around 0.2mm,and cracks are concentrated in the mid-span.But none of peeling phenomenon on concrete composite surface.(3)Through the analysis of rigidity on the specimens,this paper preliminary discusses on rigidity's calculation formula of the composite slabs;Through the analysis of crack resistance on the specimen,the result shows that:the ratio of cracking load value measured and calculated according to the theory of elasticity at mid-span is 1.04?1.20,the average is 1.13,the test results and the theoretical results are in good agreement.Through the contrast can be seen that the cracking load value of specimens are slightly larger than theoretical cracking load values,it has a certain safety coefficient.(4)In the test,composite surface adopt two ways:natural rough surface and artificial rough surface of 4mm.To the end of the uniformly distributed load,specimens don't appear horizontal cracks or sliding along the composite surface,this shows that using natural rough surface,the shear bearing capacity of composite surface can still meet the requirements.(5)Test model DHB-8 in chapter 2 is analyzed by using finite element software ABAQUS,through the comparisons of load-deflection curve at mid-span and the analysis of the stress nephogram for concrete and reinforcement,calculation results coincide well with the experimental results.Using the ABAQUS finite element model of composite slab to expand parameter of numerical analysis is feasible.(6)Through the finite element software ABAQUS to analyze in comparison crack resistance and ultimate bearing capacity between prestressed and nonprestressed composite slab.Crack resistance of prestressed composite slab increased 13.3%,the bearing capacity of prestressed composite slab improved 21.7%.Through the finite element software ABAQUS to analyze in comparison crack resistance and ultimate bearing capacity between thickness of the composite layer is 60mm,70mm and 80mm.Crack resistance of Specimen DHB80 increased by 17.6%than the specimen DHB70,crack resistance of Specimen DHB70 increased by 30.8%than the specimen DHB60.Ultimate bearing capacity of the specimen DHB80 increased by 14.3%than the specimen of DHB70,ultimate bearing capacity of the specimen DHB70 increased by 33.3%than the specimen of DHB60.