| The prefabricated concrete(PC)structure breaks through the traditional construction method of wet work and is transformed into the integrated assembly construction of factory production and construction site.It can effectively reduce pollution,save cost,shorten construction period and improve project quality.The PC components are connected as a whole through reasonable connection nodes using reliable connection technology to achieve the same mechanical properties as cast-in-place structure.Therefore,the connection between PC components is to be the most important influencing factor in whole performance of PC structure.At present,Steel sleeve grouting connections are widely used in prefabricated concrete structures.However,improper construction processes of structural components often lead to insufficient grouting,affects the mechanical properties of the connection and increases the chance of structural failure.Because the construction of sleeve grouting is concealed,the grouting defect is difficult to detect.As such,it is critical to monitor the density and compactness of grouting sleeve during the construction process.In this paper,the horizontal sleeve connectors in PC-beam were set as the object,the lead zirconate titanate(PZT)-based sleeve grouting compactness detection technology was proposed and the influence of the grouting compactness in mechanical properties of sleeve connectors were analyzed.The main research works were as follows:(1)Constitutive model of grouting material was established.The compressive strength test,splitting tensile strength test and the test of elastic modulus under static compressive stress were carried out.The failure models,the peak stress,peak strain and elastic modulus of grouting materials were studied and the formulas for calculating stress-strain curves of grouting materials under compression and tension were derived.The basis of important parameters for the finite element model in sleeve connectors were provided and the foundation of mechanical performance research was laid in the next step.(2)The stress wave method was used to detect grouting compactness of sleeve grouting.The self-made PZT sensors were used to test the grouting compactness of horizontal sleeve connectors at 5 different grouting levels.The damage index CI values obtained by the normalization of wavelet packet total energy values and Hilbert energy peak values was proposed to characterize the grouting compactness of sleeve.Through comparative study,it is found that the decreasing ratio of CI values of Hilbert–Huang transform(HHT)is slightly large than that of wavelet packet energy(WPE),and the basis functions and the level number of decompositions were not considered.Therefore,it is suggested to use HHT method to process the signal.On the basis of the experiment,the mechanical-electrical coupling model of PZT transducers and sleeve was establish.The propagation mechanism of stress wave in the specimen was revealed and the correlation between the grouting compactness and the damage index was established.(3)The effect of grouting compactness on the mechanical properties of sleeve connectors was studied.The monotonic tension test and large deformation reversed tension and compression test in grout sleeve splicing of rebars were carried out.The horizontal grouting sleeves were set for six grouting different degrees(50%,60%,70%,80%,90% and 100%)to explore the rule between grouting compactness and failure mode,bearing capacity,deformation capacity and stress and strain,and the correlation model between damage index CI and failure mode was established.The results show that when the CI value was less than or equal to 0.26,the failure mode of the sleeve joint was steel bar tension.Besides,The tensile numerical models of specimens were established,and the influence of the grouting compactness on the stress of sleeve was revealed. |
PDF Full Text Request