Influence Of Interfacial Strength And Elastic Modulus On The Flexural Behavior Of Beam

The concrete beams has widely engineering application because of its good structuralperformance. The interface between concrete and reinforcement is the transition region ofstructural stress， and the critical factor to realize the reinforcement and concrete for togetherwork. Therefore， it’s significant to study the influence of interfacial properties on theflexural behavior of beam. A large number of experimental studies have been done by manyscholars， and some conclusions have been obtained. It’s difficult to experiment on theinterface which is specialized nature and sized small， and reveal the influence of interfacialproperties on the crack mechanism of the beam due to the typically heterogeneity of theconcrete. On the other side， not many results are reported obtained by numerical analysisconcerning the interface， while there are some deviations between stimulation and realitybecause of the assumption of homogeneity on the numerical analysis. In this paper， thesteel/concrete interface， CFRP sheet/concrete interface and GFRP bar/concrete interfaceare studied considering the heterogeneity of multiphase composite material. The interface issimulated as the independent material of different mechanical property， and regarded as theprinciple line of research. The meso-scale analysis of interface behaviors are realized in thispaper， while the damage evolvement processes include crack initiation， propagation andmacro-failure modes are demonstrated under the actions of the external load. This study mayplay a role in improvement of interfacial theory. The main contents are as follows:Firstly， this paper studies the effects of interface strength on the flexural performance ofreinforced concrete beams by numerical simulation of four point bending experiment. And italso studies the effects of the elastic modulus of interface on the flexural performance ofreinforced concrete through the numerical simulation of three point bending experiments. Thenumerical simulation results are compared and analyzed with existing results in the literature，which study the effects of interface strength and elastic modulus on the bending properties ofreinforced concrete. The results show that: the higher interface strength， the higher ultimatebearing capacity， and the greater brittleness of the failure of the beam. Ultimate bearingcapacity of the beam also subsequently increases with the interfacial elastic modulus， butthere is no obvious change of the capacity when the interfacial elastic modulus increase to acertain value. Secondly， a series of numerical models of beams reinforced with different bond lengthof CFRP sheets were established by four point bending test combined. Failure modes of allbeams with different bond length and different interfacial strength were studied inmesomechanics. The results show that: the long paste specimens were most affected byinterface strength， early stiffness are improved by interfacial strength， the enhancement isnot significant when the matrix strength grade is lower by direct paste CFRP.Finally， different flexural performance of concrete beams reinforced by GFRP rebarsand concrete beams reinforced with steel bars at the same reinforcement ratio were discussed.Assuming the ideal bonding between GFRP and concrete， the damage of beams reinforcedwith GFRP rebars and concrete beam reinforced steel bars are obtained in the numericalsimulation. The failure mechanism of inner is explained in the stress term， and the energydissipation capacity of the failure process in the energy term. At the same time， the effect ofinterface strength on the flexural performance of concrete beams reinforced by GFRP rebarsare studied. The results show that: number of cracks， the bearing capacity and deflection ofconcrete beams reinforced with GFRP bars in the ideal interfacial conditions were higher thanthat of reinforced concrete beams reinforced with steel bars， ultimate bearing capacityincreases as the increase of interface strength.