Study On The Rust And Bond Dynamics Of Corroded Steel Bars Under Confined Stress And Holding

A reliable bonding between reinforcing steel bar and concretes is the prerequisite and foundation for the interaction between rebar and concretes.The corrosion is the main reason for the degradation of bond performance of reinforced concretes.The corrosion of rebar can cause section losses and degradation of mechanic performances.More seriously,the corrosion causes 2~4 times of volume expansion of the products,which may result in cracks in the concrete cover and destroy the interfacial bonding properties of the reinforced concretes.This further severely damages the safety of reinforced concrete structures.Given that the rebars of structures in service were corroded under loading and confinment,the exist of load and confinement may affect the expansion of rebar’s corrosion and interfacial bond.In order to simulate the actual engineering structure as much as possible in the circumstances,this thesis will study the parameters of lateral confinement,loading effect,corrosion rate and cover to bar diameter et al on the expansion and bonding effect of rust of reinforced concrete.The main contents include the following word:Based on the volume coordination of the corrosion product and the conservation of the Fe element,considering the elastic shrinkage of the cracked concrete,the model of the surface crack’s width with the corrosion rate was established;Study on the factors such as corrosion rate,lateral confinement and cover to bar diameter,which may affect the fill expansion ratio n of corrosion prodects by the Micro-XCT technique;This thesis studies the effect of rust expansion test on reinforced concrete,and verifies the rationality of the theoretical model with experimental data.The bonding specimen consider different parameters like corrosion rate,lateral confinement,cover to bar diameter,loading stress coupling,after monotonic load,the results show that the bond performance with lateral confinement,first increases with the increase of the corrosion rate and then decreases;The stiffness of lateral confinment,the level of sustain load and cover to bar diameter are positive correlation with bond performance.After the cyclic loading of corroded reinforced concrete bonded specimens,we use some indexes such as bong strength,bond stiffness and energy dissipation capacity evaluate the bond performance of each specimen.The results show: The influence of the corrosion rate on the dynamic bond performance is first increased and then decreased;The lateral confinment has a great extent on the dynamic bond performance of the specimen,especially the corrosion test under loading’ specimen is more obvious;The cover to bar diameter has a certain degree of improvement on the dynamic bond performance of the specimen;The existence of the sustained load makes the increase of dynamic bond performance,but with increase of the ratio of load stress,the amplitude of the reinforcement decreases gradually.