Analysis On The Effect Of Hygrothermal Environment On Interfacial Stress And Bearing Capacity For Concrete Beams Reinforced With AFRP

Aramid fiber reinforced plastic (AFRP) has been widely used in the field of strengtheningstructures due to its advantages, such as good dielectricity, thermal stability, corrosion resistance,fatigue resistance and impact resistance. The affixing AFRP to the surfaces of concretestructures which need to be reinforced is an efficient, simple, economical and practicalstrengthening method, which has great prospects.However, when AFRP sheets-reinforced concrete structures have been exposed tohygrothermal environment for long-term, the physical properties of reinforcement materialitself are not only to change, but also the interface temperature stress and moisture stressproduced by hygrothermal environment similarly affect its performance. The interfacialresidual stress and the decline of interfacial bonding strength generated by moistureabsorption are the main factors which cause the decline of bearing capacity of strengtheningmembers.Based on the existing test data, an FEM model of AFRP-reinforced concrete beam isestablished by using a finite element software ANSYS and the interfacial force conditions ofstrengthening member under hygrothermal environment are simulated. First, a3-D finiteelement model of strengthening member is created to calculate the interfacial stress caused bytemperature variation and the ultimate bearing capacity of strengthening members underfour-point bending. Then the moisture concentration field and interfacial moisture stress ofstrengthening members under moist environment are analyzed by using a2-D model ofmoisture absorption. And then the decline of bearing capacity of strengthening membersunder different exposure time is calculated. Finally, a number of factors that affect theinterfacial hygrothermal stresses are summarized and the preliminary discussion is carried out.some results not to be easily observed in test are obtained.Following conclusions can be drawn as follows.(1) The interfacial stress and bearing capacity of AFRP-reinforced concrete beams underhygrothermal environment are calculated by using ANSYS and the present results are in goodagreement with the existing test data. It is verified that using ANSYS to analyze the durabilityof AFRP-reinforced concrete beam under hygrothermal environment is feasible. Thesimulated method can also overcome the long time-consuming and costly defects inexperiment.(2) The bearing capacity of reinforced member declines to a certain extent as the increaseof temperature. And the bearing capacity would be likely to increase as the decrease of temperature because of a beneficial stress state.(3) When member is exposed to damp environment, the interfacial stress obtained bycalculation is relatively small, but the bearing capacity of reinforced member is obviouslydecreased, because the shear strength of epoxy adhesive declines after moisture absorption.(4) The main factors affecting the interface temperature stress and bearing capacity ofreinforced members are the elasticity modulus of AFRP, elasticity modulus of epoxy adhesiveand number of layers of AFRP. The main factors affecting the interfacial moisture stress andbearing capacity of reinforced member are the change of relative humidity of environment.The results of the present analysis and calculation for the interfacial hygrothermal stressof AFRP-reinforced concrete beams under hygrothermal environment can provide atheoretical basis for future research on damage mechanism and fatigue failure mechanism ofAFRP/concrete interface and have the important significance and applicable value.