Crack detection for wading-concrete structures using water irrigation and electric heating

Cracking in wading-concrete structures has a worse impact on structural safety compared with conventional concrete structures.The accurate and timely monitoring of crack development plays a significant role in the safety of wading-concrete engineering.The heat-transfer rate near a crack is related to the flow velocity of the fluid in the crack.Based on this,a novel crack-identification method for underwater concrete structures is presented.This method uses water irrigation to generate seepage at the interface of a crack;then,the heat-dissipation rate in the crack area will increase because of the convective heat-transfer effect near the crack.Crack information can be identified by monitoring the cooling law and leakage flow near cracks.The proposed mobile crack-monitoring system consists of a heating system,temperature-measurement system,and irrigation system.A series of tests was conducted on a reinforcedconcrete beam using this system.The crack-discrimination index ψ was defined,according to the subsection characteristics of the heat-source cooling curve.The effects of the crack width,leakage flow,and relative positions of the heat source and crack on ψ were studied.The results showed that the distribution characteristics of ψ along the monitoring line could accurately locate the crack,but not quantify the crack width.However,the leakage flow is sensitive to the crack width and can be used to identify it.