Experimental Study On Interface Damage Monitoring Of GFRP-UHPC Composite Structure Based On Piezoelectric Smart Aggregate

In recent years,Ultra-High Performance Concrete(UHPC)has been paid more and more attention in the field of civil engineering due to its characteristics of ultra-high strength,ultra-high durability and high toughness;and Fiber Reinforced Polymer(FRP)has been paid more and more attention because of its high specific strength,large specific modulus,good durability and fatigue resistance.Adding FRP profiles at the interface between shear and flexural members of concrete can not only improve the strength of members,but also improve the fatigue resistance of members.However,the performance of FRP-UHPC composite structure depends on the interface connection between FRP profiles and UHPC.Therefore,in order to prevent the interface peeling of FRP-UHPC composite structure from causing structural damage,it is necessary to monitor and analyze the interface peeling damage of FRP-UHPC composite structure in real time.In this paper,based on the shear performance test of GFRP-UHPC composite interface and the mechanical performance test of GFRP-UHPC composite beam,based on wavelet energy analysis method,using piezoelectric intelligent aggregate to monitor and analyze the damage of the two tests,so as to study the interface peeling caused by FRP-UHPC composite structure.The main research work includes the following aspects:(1)In this paper,piezoelectric materials and structural damage monitoring principle and structural health monitoring technology based on piezoelectric materials are introduced.Based on the research of structural monitoring based on piezoelectric materials at home and abroad,the damage monitoring of GFRP-UHPC composite structure interface based on wave method is realized by using wavelet packet analysis method based on energy,and the damage index is used to describe the damage state of the structure.(2)The push-out specimens and beam specimens with different interface connection forms are designed and manufactured.The interface forms mainly include bolt connection,GFRP permanent template connection,bolt+epoxy resin connection and bolt+epoxy resin+GFRP permanent template connection.The interface peeling of composite structures with different interface forms can be judged by monitoring different interface forms with piezoelectric intelligent aggregate.The results show that the specimen with GFRP permanent template in the interface form has improved bearing capacity and can better resist the sliding between composite structures,but its damage index is smaller than that of the specimen with bolted connection.(3)The damage of interface shear test of GFRP-UHPC composite structure under load is monitored and analyzed.The GFRP-UHPC push-out specimen was made,and the piezoelectric smart aggregate was attached to both sides of the specimen,which was subjected to monotonic static loading.The test phenomena,failure modes and damage results obtained by monitoring were compared and analyzed.The results show that the piezoelectric intelligent aggregate can monitor the damage of GFRP-UHPC,and judge its damage status.(4)The damage of GFRP-UHPC composite beam under load is monitored and analyzed.A GFRP-UHPC composite beam specimen was designed and manufactured.Piezoelectric smart aggregate was attached to the upper and lower ends of the specimen,and four-point bending test was carried out.By analyzing the collected data in time domain and frequency domain,and comparing it with the crack of the specimen,the damage index of the specimen is finally obtained.The results show that piezoelectric smart aggregate can be used to monitor and judge the damage of GFRP-UHPC composite beams.The above experimental research shows that the interface damage monitoring of GFRP-UHPC composite structure based on piezoelectric smart aggregate is feasible.