Study On Compressive Behavior Of Concrete Confined By Triaxial Woven Fabric Composite

Triaxial woven fabric(TWF)is made up by three sets of 60 degree yarn interwoven,with uniform hexagonal holes.As the reinforcement of composite materials,the triaxial woven fabric has excellent mechanical properties and is widely used in the fields of aerospace and sports etc.However there are few researches on the application of triaxial woven fabric in the field of building reinforcement.In order to expand the application field of triaxial woven fabric,this paper mainly studies the compressive properties of triaxial woven fabric confined concrete.The main research work is as following:(1)Through the axial compression test of concrete column confined by triaxial woven fabric,the reinforcement effect of different restraint modes was analyzed.The test results show that when the weft yarns of the triaxial woven fabric were along the axial direction,the restraint effect was batter.However,the restraint effect was poor,when the weft yarns of triaxial woven fabric were along the circular direction.The differences in failure appearance and failure mode between the two groups of samples were studied.The failure mode of the TWF-A sample was instantaneous failure,while the TWF-C sample was progressive.(2)Digital image correlation(DIC)technology was used to test the strains of each group yarns in the triaxial woven fabric under the compression state of the concrete column restrained by triaxial woven fabric.By analyzing of the strain of yarns,it was found that the yarn strain state of the two groups of samples was different.The weft strain along the loop direction in the TWF-A sample was positive,while the strain of the warp yarns was negative.In the TWF-C samples,the strain of warp yarns was positive,while the strain of the weft yarns along the axil was negative.Based on the analysis of the stress of each group of yarns,a formula for calculating the lateral confining pressure that triaxial woven fabric composite provided on the concrete column was proposed.(3)Acoustic emission technology was used to monitor the compression failure process of the samples.The differences of energy,ringing counts,and peak frequency of AE events was compared during compression between the two groups of samples,and the reasons for these differences was explained.At the same time,the acoustic emission characteristic parameters were classified,and the related damage was corresponding to them,and the compression failure process and mechanism of triaxial woven fabric confined concrete column were analyzed from the internal of materials.The damage mainly includes concrete microcrack generation,microcrack propagation,composite matrix fracture and fiber breakage.(4)Combined with DIC technology and AE monitoring technology,the effects of the sample aspect ratio(height/diameter)on the compressive properties of concrete column confined by triaxial woven fabric were investigated,and the compressive properties of three groups of samples with different aspect ratios were compared.The effect of the aspect ratio on the compressive properties of the samples were analyzed by means of compressive strength,axial displacement,strain-time curve,failure appearance and acoustic emission signal characteristic parameters.The results showed that the damage morphology and internal failure mode were less affected by the length-diameter ratio of concrete column confined by triaxial woven fabric samples,but the compressive strength,axial displacement,turning point strain and ultimate strain in the yarn's stress-time curve were more affected.