| Ultrahigh-performance concrete(UHPC)offers high strength and high durability.In recent years,it has been developed rapidly,especially steel-UHPC combined structures,which has obvious advantages in making full use of the strength of the two materials and improving the crossing capacity.It is widely used in the field of bridge engineering.The interface of steel-UHPC composite structure is mostly connected by studs,and its interface performance directly affects the service performance of the composite structure.At present,domestic and foreign scholars have carried out a large number of research on the interfacial shear transfer and fatigue performance of stud connected steel-UHPC composite structures.Some studies have shown that the interface action has a significant impact on the interfacial fatigue life of steel-UHPC composite structures,but the impact mechanism is not clear.Based on this background,this paper aims to effect and reveal the fatigue fracture mechanism of stud connected steel-UHPC composite structure under the influence of interface action.The main work is as follows:(1)The effect of interface action on the fatigue performance of stud connected steelUHPC composite structure is experimentally studied.The fatigue experiment of stud connected steel-UHPC composite push-out specimens is designed.By comparing and analyzing the failure mode,fatigue life and load-slip characteristics of push-out specimens,the influence of interface action on the fatigue performance of stud connected steel-UHPC composite push-out specimens is researched,the influence range of interface action effect of steel-UHPC composite is explored,and the influence of interface action on the fatigue performance of normal steel-concrete push-out specimens is also compared and analyzed.(2)The fatigue crack development and failure mechanism of stud connected steel-UHPC composite structure under the influence of interface action are revealed.Aiming at the problem that it is difficult to directly observe the fatigue failure process of conventional pushout specimens,the stud connected steel-UHPC visual push-out specimens are designed and manufactured to carry out the experiment,and the equivalence of the visual specimens is verified;The deformation response and failure characteristics of the interface between steel plate,stud and concrete during fatigue are obtained,and the fatigue crack development and failure mechanism of stud connected steel-UHPC composite structure under the influence of interface action are revealed.(3)A practical prediction method of fatigue life of stud connected steel-UHPC composite structure is proposed.The fatigue fracture process of stud connected steel-UHPC composite structure and stud connected normal steel-concrete composite structure is essentially caused by the fatigue fracture of stud.The difference lies in the influence degree of interface action.Therefore,based on the existing fatigue life prediction model of stud connector of normal steel-concrete composite structure,considering the appropriate reduction of stud fatigue stress amplitude under the action of interface,this paper establishes the fatigue life prediction method of stud connected steel-UHPC composite structure,that is,the general fatigue life prediction model of stud connected steel-concrete composite structure,and verifies its applicability. |
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