Influence Of Corrosion On Mechanical Properties Of Reinforced Concrete Beam And Column

Early deterioration of reinforced concrete(RC)structures in harsh environments has been reported around the world.The durability of reinforced concrete structures has been paid more and more attention by experts and scholars in the field of civil engineering.For marine chloride environment,steel corrosion caused by chloride ion erosion is one of the main deterioration phenomena of reinforced concrete(RC)structures in this area.How to solve the durability problem caused by steel corrosion has become an important issue for scholars at home and abroad.Among the many properties of corroded RC members,the research on shear behavior of RC beams and bending behavior of RC columns is still insufficient.More research data need to be accumulated if quantitative evaluation of bearing capacity of corroded RC members is to be realized.Because of the irregularity and unpredictability of steel corrosion in actual structures,it is more reasonable and effective to study the bearing capacity of RC members with steel corrosion by FEM numerical simulation.In addition to reproducing macro-mechanical phenomena such as load,deflection and crack distribution,numerical simulat:ion can also acquire micro-information such as strain and stress of concrete and steel in components,which is helpful to reveal the shear bearing mechanism of corroded reinforced beams and to realize reasonable evaluation of bearing capacity.In view of this,the mechanical properties of corroded reinforced concrete beams and columns are studied by using finite element software Diana based on the experiments completed by the research group.In addition,a new meso-concrete constitutive model is used to simulate the reinforced concrete beams in OpenSees.Through the mutual verification of the experimental results and the finite element simulation results,the following conclusions are drawn:1.Effect of corrosion of longitudinal tension reinforcement on shear behavior of RC beams with web reinforcement(1)The degradation of bond between steel and concrete caused by corrosion of longitudinal tension steel leads to the enhancement of "arch mechanism" effect,which improves the shear capacity of RC beams.The enhancement of arch mechanism is reflected in the location of shear principal oblique crack.With the increase of longitudinal reinforcement corrosion rate,the location of shear principal oblique crack migrates to the loading point.(2)The effect of "arch mechanism" increases with the increase of corrosion degree of longitudinal tension steel;at the same corrosion rate,with the increase of shear span ratio,the proportion of shear force borne by "arch mechanism" in the external shear force decreases gradually in the limit state.(3)The shear stress retention coefficient increases with the increase of the corrosion degree of longitudinal reinforcement;the change of shear stress retention coefficient of RC beams with larger shear span is more gentle with the increase of the corrosion degree of longitudinal reinforcement.This is consistent with the experimental phenomenon that the width of shear main oblique crack decreases with the increase of corrosion rate of longitudinal steel bar.2.Effect of longitudinal reinforcement corrosion on compression-bending behavior of eccentric RC columns(1)For large eccentric compression columns,the corrosion of steel at tension side decreases the tensile strength of stee and the bonding performance with concrete,which leads to the decrease of stiffness and bearing capacity of corroded RC columns;the corrosion cracks of steel at compression side lead to the damage of mechanical properties of concrete in compression zone,and the ductility of specimens is poor after peak value,and the failure mode changes from ductile failure to brittle failure.(2)For small eccentric compression columns,the bearing capacity of specimens is mainly affected by the corrosion of steel on the compression side,the greater the corrosion degree,the more obvious the reduction of bearing capacity;the failure of bond slip between steel and concrete caused by the corrosion of steel on the tension side will cause the bending deformation to concentrate in the middle of the span.(3)For the specimens with bilateral corrosion,the bearing capacity and stiffness of columns with large and small eccentricities are significantly reduced,and the degradation of mechanical properties is affected by the coupling effect of steel corrosion on the tension side and compression side.3.New meso-concrete model theory The damage crack graph obtained by the new meso-concrete model canreproduce the macro-experimental phenomena reasonably,which shows that the model is feasible in simulating reinforced concrete members.