Experimental Study On Punching Failure Of Section Steel-strip-UHPC Composite Bridge Deck

The section steel-strip-UHPC combination structure is a new type of bridge deck structure system.The new bridge deck structure,which consists of section steel,steel strips,and UHPC slabs,is light in weight and high in stiffness to meet the demand for self-weight of large span bridges,but the UHPC slabs with steel strips are thin and lead to high local shear stress under wheel load,so the punching and shearing performance of this structural system needs to be studied in focus.With this background,the experimental study of steel strip-UHPC composite slab was carried out to investigate the influence of steel strip parameters and reinforcement rate on the punching performance of the test slab,and the static punching test of 24 plates under concentrated load was completed.The main contents of the study and the corresponding conclusions are as follows:(1)Concentrated load test studies were conducted on UHPC thin slabs and steel strip-UHPC combination slabs considering the presence or absence of reinforcement,the presence or absence of steel strips,and the spacing of steel strips.A total of 24 UHPC plates were fabricated,vertically loaded at the center position,and tested for punching failure to obtain the test results of cracking load,peak load,load-deflection relationship,crack distribution at the bottom of the slab,crack development,and punching diagonal cracks for each specimen.A total of 17 specimens suffered punching failure test and 7 specimens suffered bending failure.The test shows that the UHPC thin slab with reinforcement only occurs punching failure,the plain UHPC slab occurs bending failure,and the UHPC slab with reinforcement only has higher bearing capacity.(2)The ultimate load capacity of UHPC slabs can be significantly increased by adding steel strips to the UHPC slab members.The tests showed that the UHPC composite deck slab with steel strips had higher load carrying capacity and ductility than the plain UHPC slab with bending failure when the punching failure occurred after the steel bars yielded.With the decrease of steel strip spacing,the punching capacity of thin UHPC composite slab with steel strip increases.In the whole process of loading the specimen,the slab’s bending effect and punching effect exist simultaneously and affect each other.Due to the existence of the steel strips,the ductility of the reinforcement in the slab and the overall ductility of the specimen can be better played,therefore it has a higher punching bearing capacity.(3)This paper analyzes the punching capacity calculation method of the stripUHPC composite plate under the punching and shearing mechanism by double shear stress three parameters theory,based on which the punching capacity calculation method considers the combined contribution of UHPC matrix,steel strip,and steel reinforcement as well as the composition effect of punching and bending is proposed,which has less deviation from the test bearing capacity and can reflect the stress mechanism of UHPC punching and shearing failure more realistically.(4)By collecting domestic and foreign literature on UHPC slab punching failure tests,establishing a database of UHPC punching failure test slabs,combining reliability theories,conducting reliability analysis on the punching capacity in the specification formula.Based on the experiments in this paper and punching theory,it proposes a reliability-based punching capacity correction formula to meet the current target reliability requirements.