| In the world,the problem of steel corrosion has caused great harm to the existing and under construction infrastructure,and brought huge economic losses.Therefore,it is of great significance to develop new materials and new structural systems with high durability.As a substitute material of steel,FRP has been widely studied and applied in FRP-concrete composite structures because of its light weight,high strength and corrosion resistance.Compared with ordinary concrete,UHPC has super high strength and excellent durability.Therefore,the reasonable design of FRP profile-UHPC composite structure can meet the requirements of light,high strength and durability of bridge engineering,and it is a new type of structure with great potential for application.The development of prefabricated buildings is an important measure to promote the supply side structural reform and the development of new urbanization.Prefabricated composite structure has the advantages of saving formwork,improving construction environment and improving production efficiency.Referring to the prefabricated construction method of steel-concrete composite structure shear connectors,this paper proposes a prefabricated FRP profile-concrete composite structure with local UHPC material cast in place at the connectors.The interface is the key part of FRP profile-UHPC composite structure,and it is also the weak part of failure.However,up to now,there is still a lack of research on the mechanical properties of FRP profile-UHPC composite interface at home and abroad.Therefore,three groups(34 specimens in total)of GFRP profile-UHPC push-out specimens are designed in this paper.The failure mode,interfacial stiffness and ultimate shear capacity of GFRP profile-UHPC composite interface under different influence factors are studied by experiments,numerical simulation and theoretical analysis.The main contents are as follows:(1)Six types of FRP profile-UHPC composite interfaces were designed,and the failure mode,slip resistance and ultimate shear capacity of FRP profile-UHPC pushout shear specimens with different interface modes were compared and analyzed.Compared with the bolt connection interface,the steel bolt-adhesive interface specimen has higher anti sliding stiffness and ultimate shear capacity,and the interfacial shear performance is significantly improved;Compared with the interface of steel boltadhesive connection,the interface with SIP-SK connection obviously has greater ultimate shear capacity and interfacial stiffness,and the hybrid connection with bolt +SIP-SK has excellent interfacial shear performance;The shear capacity of single connector is the highest under the steel bolt-adhesive interface,and the shear capacity of single steel bolt is 1.94 times of that of single FRP shear key;The interfacial stiffness of adhesive interface is far greater than that of other interfaces,and the interfacial stiffness of bolt connection interface is the lowest;the interfacial stiffness of single connector can be significantly improved by coating epoxy resin on the interface.(2)In this paper,thirteen push-out specimens of GFRP profile-UHPC under the steel bolt-adhesive interface were tested.The effects of concrete strength,bolt diameter,bolt spacing,embedded depth of bolt,bolt number and bolt strength on failure mode,interfacial slip performance and ultimate shear capacity of push-out specimens under the steel bolt-adhesive interface were studied and analyzed.Compared with the FRP profile-ordinary concrete composite interface,the shear performance of GFRP profileUHPC composite interface is better;There are three failure modes in the GFRP profileUHPC push-out specimens with steel bolt-adhesive interface,which are the UHPCadhesive debonding failure,the shear failure of bolts and the shear failure of flange of FRP profile;Based on the test results,the shear capacity calculation formula of GFRP profile-UHPC with steel bolt-adhesive interface under the failure mode of steel bolt shear failure is given.(3)Sixteen push-out specimens of GFRP profile-concrete with local UHPC and bolted connections were tested.The effects of bolt diameter,UHPC pocket width,embedded depth of bolt,bolt number and interface type on failure mode,interfacial slip performance and ultimate shear capacity of push-out specimens with local UHPC and bolted connections were studied.The results show that the interfacial shear performance of push-out specimens with local cast-in-place UHPC is similar to that of push-out specimens with full cast-in-place UHPC,and it is obviously better than that of push-out specimens with full cast-in-place ordinary concrete;The width of UHPC pocket has little effect on the interfacial stiffness and ultimate shear capacity of FRP profile-concrete push-out specimens;the steel bolt shear failure,ordinary concrete failure and flange shear failure of FRP profile mainly occur in the push-out specimens of GFRP profile-concrete with local UHPC and bolted connections;Based on the test results,the shear capacity calculation formula of push-out specimens of GFRP profileconcrete with local UHPC and bolted connections under the failure mode of steel bolt shear failure is given. |
