Experimental Study On Flexural Behavior Of Long-span Laminated Slabs With Precast Composite Panel

Industrialization of construction is now a key area of the construction industry.Assembled concrete structures have become an important direction of construction industrialization due to their efficient construction efficiency,good durability and overall performance,and composite floor slabs are an important part of assembly construction.Compared with the pouring floor slab,it has the advantages of saving formwork and convenient construction.It has been widely used in prefabricated buildings in China in recent years.Aiming at the problem of the current solid composite floor slabs’ large weight and single type of long-span panel,this paper proposes a new type of prefabricated composite floor slab,which can reduce the weight by 30% without significantly reducing the bearing capacity.The amount of concrete poured only accounts for 30% of the total pouring.Through static tests,the flexural performance test of the specimens in the construction stage and normal use stage was carried out.Combined with the finite element method,the engineering design calculation methods of cracking load,bending stiffness and ultimate load were established.The experimental research show that the composite slab is similar to the one-way slab’s failure characteristics.The cracks and deflections have developed sufficiently.Different structural forms have a certain effect on the yield load and ultimate load.And there were no breaks or horizontal cracks along the superimposed surface.The main research and research results are as follows:1.Through the static test of 6 full-scale specimens,the bending performance of the composite slabs during the construction and use phases was studied;the effects of different structural forms(transverse ribs,longitudinal ribs,concrete at the top of the block,etc.)on the basic mechanical properties of the test pieces were compared and analyzed.The test research shows that:(1)Without any temporary support,the construction load will cause the test piece to crack and the deformation also exceeds the specified limit.Therefore,the temporary support design calculation of the prefabricated composite bottom slab is required.(2)The failure process of composite slabs is similar to the typical failure process of ordinary concrete unidirectional slabs.From loading to failure,it has experienced three processes: the elastic stage before cracking,the elastoplastic stage after cracking,and the failure stage after yielding.Compared with castin-place slab,the cracking load is slightly lower,but the yield load and ultimate bearing capacity are higher.Due to the light weight,the ability to bear external loads is significantly improved;the displacement ductility of the two specimens performs well.(3)Comparing different structural forms,it is found that the degree of influence is different.The order of influence of different structural forms on the yield load and ultimate load is: longitudinal ribs> top concrete> transverse ribs.(4)The overall performance of the composite slab is good,and there is no sudden fracture or horizontal crack along the laminated surface.2.The refined numerical model is established,and ABAQUS is used to analyze the samples.The reliability of the numerical analysis is verified by comparing the numerical simulation results with the experimental results.On this basis,the influence of the aerated block,the longitudinal ribs and the top concrete are studied.The results show that the load deflection curves of the four kinds of structural composite slabs used in the experimental study are basically consistent with each other,and the difference between the ultimate bearing capacity is not large.It is suggested that the contribution of the aerated blocks should not be considered in the process of engineering design,and the design and calculation should be carried out according to the hollow slab.The influence degree of different numbers of longitudinal ribs on the bending performance is compared and analyzed.The possible causes of the influence of the longitudinal rib on the stress are compared and analyzed;the numerical calculation results of different thickness of the top concrete are analyzed,and the influence of the thickness of the top concrete on the stress performance of the specimen is studied.3.Based on the experimental study and numerical expansion analysis,without considering the influence of aerated concrete block,the equivalent calculation model of composite slab is proposed,and the cracking moment,rigidity and bending capacity of the composite slab are calculated and analyzed according to the equivalent I-section(1)According to the results of the comparative analysis,the basic value of the plastic influence coefficient of the section resisting moment is proposed.(2)In this paper,the general and practical stiffness calculation method is introduced to calculate and analyze the elastic and elastic-plastic stage deformation of the composite slab.By comparing the test deflection with the calculation deflection,the error is found within 15%,which proves the rationality of the formula.(3)A practical general design formula for the flexural bearing capacity of the normal section is proposed,and the influence of the effective flange width to reduce the uneven distribution of the flange stress is considered comprehensively.By comparing the theoretical calculation value with the measured value,it is found that the formula has high reliability and can be used as the actual reference of program design.(4)Based on the quasi plate method and the orthotropic plate theory,the deformation of the two-way composite specimen is calculated and analyzed,and compared with the numerical simulation results,the rationality of the analytical solution is verified.