The Research On Flexural Performance Of Prefabricated NSC Components With UHPC Wet Joints

With the advantages of mature technology,fast construction and good economy,prefabricated normal strength concrete(NSC)components have been widely used in engineering structures all over the world.However,a large number of engineering projects have proved that the wet joints of NSC in prefabricated normal strength concrete structures are prone to crack and leakage,which seriously threaten the safety and durability of the structures.Due to its excellent mechanical properties and high interfacial bonding strength,ultra high performance concrete(UHPC)has become a promising new material for cast-in-place wet joint of prefabricated NSC components.The main purpose of this paper is to study the bending properties of prefabricated NSC panels with UHPC joints of different shapes.The bending properties include the cracking strength of UHPC-NSC interface,the development of interface crack,failure mode and so on.UHPC joints of different shapes include joint with rectangular section,joint with rectangular dense reinforced section,joint with rectangular perforated section,joint with wedge-shaped section and joint with diamond section.The main research method of this paper is carrying out the flexural test of prefabricated NSC panels with UHPC wet joints,and the finite element numerical analysis of the interfacial flexural behavior.The key conclusions of the paper are as follows:(1)The flexural tensile strength of UHPC wet joint itself is obviously higher than that of prefabricated NSC panel.The bonding strength between cast-in-place UHPC and prefabricated NSC is good.(2)The crack strength of UHPC-NSC interface of the Panel J-R1 and the Panel J-R3 is basically the same as that of prefabricated NSC.The crack strength of UHPC-NSC interface of the Panel J-R2,the Panel J-W and the Panel J-D is higher than that of the monolithic prefabricated NSC panel(M-N)about 43.7% to 96.2%.(3)From the view of the failure mode of the jointed panels,except for the Panel J-R1,the other four jointed panels(J-R2,J-R3,J-W and J-D)are damaged in the prefabricated NSC.The failure load of the jointed panels are equal or higher than that of the monolithic NSC panel(M-N).(4)The bending stiffness of the Panel J-R1 and the Panel J-D is slightly smaller than that of the monolithic NSC panel(M-N),while the bending stiffness of the other jointed panels are basically equal or larger than that of the monolithic NSC panel(M-N).(5)Based on the properties of all the jointed panels,it is recommended to use the Panel J-R2,the Panel J-R3,the Panel J-W and the Panel J-D.Do not recommend the use of the Panel J-R1.(6)The finite element modeling method proposed in this paper is suitable for the analysis of the bending behavior of UHPC-NSC interface.The results of finite element analysis are in good agreement with the experimental results.The crack resistance and bending resistance of UHPC-NSC interface,whose interface reinforcement ratio exceed 5.33% or hole area ratio exceed 3.27%,can basically ensure that it is better than the prefabricated NSC.The crack resistance and bending resistance of the composite interface(perforated+dense reinforcement interface,wedge-shaped+dense reinforement interface and diamond+dense reinforement interface)are improved obviously,and the first cracking load of interface(Pcr)increases 15.0% to 33.5% than the original single interface.