Research On Shear Behavior Of Damaged Concrete Beams Strengthened With AFRP Sheets

Aramid fiber reinforced polymer(AFRP)sheet has the characteristics of high strength,light weight and corrosion resistance.Applying AFRP to the reinforcement of concrete beam can effectively improve the shear capacity of concrete beams and make sure the normal use of the structure so as to achieve the purpose of reinforcing and strengthening the beam and improving the structural force performance.Therefore,research on the shear resistance of damaged concrete beams strengthened with AFRP sheets has certain theoretical and engineering values.Experimental study on shear resistance of damaged concrete beams strengthened with 11 externally attached AFRP sheets was first conducted in this paper.The failure modes,characteristic loads,load-deflection curves,load-strain curves of the fiber and stirrups were analyzed.The effects of some factors,e.g.,damage degree of the beam,AFRP layer numbers,AFRP reinforcement form,AFRP bonding pitch and FRP type,etc.,on the shear resistance of the strengthened beam were studied.The results show that the damage degree has a great influence on the ultimate shear capacity of damaged concrete beams strengthened with AFRP sheets.As the degree of damage increases,the ultimate shear capacity of the reinforced beams decreases,and the reduction gradually increases.When the beams are seriously damaged,the improvement effect of reinforcement on the bearing capacity of beams is seriously affected,even the ultimate shear capacity of beams after reinforcement has not been improved.Changing the AFRP layer number can cause the change of the failure mode of the beam.The failure mode of the reinforced beam is changed from shear failure to flexural failure in the case of three AFRP layers..Based on the test data and the current specifications,considering the influence of the damage degree and the FRP layer number on the shear capacity of the damaged concrete beams strengthened with AFRP sheets,the calculation formula of the shear capacity of the damaged concrete beams strengthened with AFRP sheets is established.Experimental and theoretical calculated results are also comparatively analyzed.So as to verify the feasibility of the formula to analyze the shear performance of reinforced concrete beams externally attached AFRP.Finally,using the ABAQUS finite element software,a three-dimensional finite element model of damaged concrete beams strengthened with AFRP sheets is established on the basis of the experimental data,and the shearing process is numerically simulated.The calculated load-deflection curve and Mises stress distribution are in good agreement with the experimental results.On this basis,the effects of stirrup spacing,concrete strength and shear span ratio on the shear resistance of damaged concrete beams strengthened with AFRP sheets are considered,which provides a basis for further study on the shear resistance of damaged concrete beams strengthened with FRP sheets.