Axial Compression Test and Stress-strain Relationship of BFRP-confined Predamaged Concrete

Ma Gao, Chen Xiaohuang


    To investigate the effects of basalt fiber-reinforced polymer (BFRP) layers and predamage levels on the axial compression behavior of BFRP-confined concrete,fourteen plain concrete cylinders were pre-loaded under axial compression loading. Three predamaged levels were considered. The predamaged cylinders were wrapped with three different BFRP layers and subjected to axial compression loading again. It is found that the ultimate strength and ultimate strain of the BFRP-confined predamaged concrete were 1.18~1.81 times and 5.94~10.55 times of those of the unconfined concrete,respectively. However,compared with the BFRP-confined undamaged concrete,the ultimate strength and initial elastic modulus of the BFRP-confined predamaged concrete were reduced by 7%~15% and 38%~55%,respectively,while the ultimate strain had little difference. The test results showed that the compression strength and deformation capacities of the damaged concrete exhibited good repair effect after BFRP confinement. However,the strength and initial elastic modulus of the BFRP-confined concrete tended to decrease with an increase of predamage level. Therefore,it will be unsafe to apply the existing mechanical model of FRP-confined undamaged concrete to the retrofit design of damaged structures. Based on the experimental results and collected literature data,a strength model,initial elastic modulus model and stress-strain relationship model of BFRP-confined concrete were proposed with considering the effect of predamage levels. The proposed models showed a good agreement with the experimental results.



Keywords:  FRP-confinement,  predamage,  strength model,  ultimate strain model,  stress-strain model

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