| Steel-concrete composite beams have been widely applied in the field of construction engineering.In the actual use process,various types of new steel-concrete composite beams have been proposed,such as prefabricated steel-concrete,detachable steel-concrete,detachable prefabricated steel-concrete etc.Up to present,the mechanical characteristics and theoretical analysis of the steelconcrete composite beams under positive bending moment have been fully investigated.Nevertheless,the performances of such sections under negative conditions have not been fully revealed.To solve such practical problems,the mechanical properties of the assembled composite beams exposed to negative bending moment were experimentally studied in current study.Design the one using the stud as fitting of cast-in-situ steel and concrete composite beams,one USES the high strength bolt as fitting cast-in-situ removable different degrees of connection between steel and concrete composite beams and 2 root of removable prefabricated composite beams using high strength bolts as fitting,and under the action of the four composite beams in the negative bending moment across the static loading test.The experimental phenomenon of steel-concrete composite beams and the rotational capacity,plastic bending capacity,load-deflection curve,crack distribution and slip distribution reflected in the test data of steel-concrete composite beams are analyzed and compared in detail.Four steel-concrete composite beam models subjected to negative bending force were established by employing general FEA software ABAQUS,which was verified according to the observed experimental results.Various of parameters were analyzed based on the PHBCB-B model.The main conclusions have been listed as follows:(1)The rotation ability of composite beams under negative moment can be improved by adopting cast-in-place pouring method,improving shear connection degree and using stud as shear connector.The ultimate bearing capacity of composite beams can be improved by using high-strength bolts as shear connectors,improving shear connection degree and adopting cast-in-place pouring method,but the influence on the stiffness of composite beams is small.(2)Using high-strength bolts as connectors can improve the cracking load of steelconcrete composite beams under negative moment;Increasing the shear connection degree will lead to more dense distribution of metal corrugated sleeve,and increase the weakening of metal corrugated sleeve on concrete slab,which is not conducive to the crack resistance of steel-concrete composite beams.(3)The finite element analysis software ABAQUS is used to simulate the prefabricated composite beam with complete shear connection.It is found that the ultimate bearing capacity of the specimen can be improved by increasing the force ratio and pouring material strength. |
