Experimental Study On The Flexural Behavior Of Concrete Beams Strengthened With PVA-ECC And Steel Wire Meshes

Polyvinyl alcohol fiber reinforced ferrocement cementitious composite(PVA-RFCC)is a form of reinforced composite,which consists of steel(reinforcement)mesh as reinforced material and polyvinyl alcohol fiber-engineered cementitious composites(PVA-ECC)characterized by high toughness and multi-crack development as a matrix.Experimental investigation and theoretical analysis were carried on the flexural behavior of concrete beams strengthened with PVA-RFCC.The main research content and conclusions were carried out as follows:(1)The flexural test of nine groups of PVA-ECC thin composite plates with steel wire mesh was conducted.The main variables were the diameter,transverse wire spacing and layer number of the steel wire mesh.The results showed that the PVA-ECC can work well with steel wire mesh,the bending properties of the specimen can be markedly upgraded.With the addition of PVA fiber,the ductility and toughness of the specimen can be significantly improved,but the effect on the strength and stiffness enhancement was limited.The strength,stiffness and energy absorption of the specimen can be greatly improved by adding steel wire mesh.The flexural performance was decreased with the transverse connection spacing increasing,and the increasing layer number of steel wire mesh had little influence on the mechanical performance.(2)Ten beams strengthened with PVA-RFCC were investigated to study the effects of steel wire mesh,reinforcement mesh,the thickness of composite reinforcement layer and bonded bars on the stiffness,crack development,strength,ductility and failure mode of the beam.The results showed that the bonded bars had obvious effect on improving the integrity of the strengthened beam specimens.Steel wire mesh had a limited effect on improving the load carrying capacity of beams,but it can restrain the development of cracks.Reinforcement mesh can significantly improve the load carrying capacity and the integrity of the strengthened beams.When the specimens were strengthened with PVA-ECC,the integrity and load carrying capacity were decreased with the thickness of reinforcement layer increasing.(3)Through the investigation of bending behavior of strengthened beams under the secondary load and different reinforcement lengths.The results showed that the overall performance of the beam specimens was much better with the increase of the reinforcement length.Compared with the ultimate load carrying capacity of the control beam specimen,the B6-RM-SM-1200 specimen was decreased about 3%,while the B6-RM-SM specimen was improved by 89%.The secondary load will not decrease the ultimate load of the strengthened beam,but the cracking load and the yielding load will decrease.(4)Based on the flexural test results and the requirements of specifications,the expression of cracking moment,yielding moment and ultimate bending moment were proposed.The calculated results indicated that the proposed model had a good consistency with the experimental results.Simultaneously,the strengthened layer length under different loading conditions was analyzed,and the corresponding calculation formula was putting forward.