Experimental Study On Flexural Behavior Of Assembled Monolithic Large-span Steel-concrete Composite Beams With Precast Hollowcore Slabs~*

Steel-concrete composite beams have the advantages of high flexural capacity,good ductility,strong stiffness and small cross-section height.Precast hollow slabs have the advantages of light weight,various types and fast construction.Considering the characteristics of steel-concrete composite beams and hollowcore slabs,the Assembled Monolithic Large-span Steel-concrete Composite Beams with Precast Hollowcore Slabs(CBHCSs)are proposed,which maintains the advantages of traditional composite beams,while can be applied to the large-span structures.To study the flexural behavior of large-span CBHCSs with different parameters(i.e.,degree of shear connection,transverse reinforcement ratio and the depth of topping concrete et.al),nine simply supported large-span CBHCSs were designed and tested.The results are as follow:There are three typical failure modes of large-span CBHCSs,consisting of bending-slip failure,stripping bending-slip failure and longitudinal shear failure.The plane section assumption is applicable when the specimens are elastic.The degree of shear connection has a great influence on the bearing capacity and ductility of the specimens.Compared with the full shear connected specimens,the bearing capacity of the specimens with 60%degree of shear connection decreases by 10%-14%,and the ductility of which decreases by 27%-41%.Compared with the full shear connected specimens,the bearing capacity of the specimens with 30%degree of shear connection decreases by 27%-41%,and the ductility of which decreases by 63%-84%.With good ductility,the specimens with reduced area of transverse reinforcement and thickness of laminated layer have the same bearing capacity and ductility as those of 60%degree of shear connection.The specimens with 30%degree of shear connection are brittle,and the cooperation is poor.The rest of the specimens have good cooperative performance.The finite element model of ABAQUS is established and compared with the test results.After verifying the model,fifty finite element models are established.The results are as follow:When the span of the CBHCSs is 6 m to 8.4 m,the thickness of flange is 150 mm to 210 mm,and the hollow ratio is 9.8%to 18.7%,the CBHCSs can meet the requirements of full shear connection only by 85%of the number of shear studs of the traditional composite beams.Considering the layout of pipelines,the bearing capacity and ductility of specimens,the thickness of topping concrete should be 40 mm to 70 mm.To ensure the bearing capacity and ductility of the specimens,and reduce the wet operation on the construction site,the thicker hollowcore slabs could be utilized.The calculation methods of the bending capacity of steel-concrete composite beams in GB 50017-2017 and EC 4 are compared.The mechanism of large-span CBHCSs and traditional composite beams is analyzed and compared,and the calculation formulas of the bending capacity of large-span CBHCSs are proposed.The theoretical results are in good agreement with the experimental and finite element results.