Degradation Of Capacity Of The Corroded Reinforced Concrete Columns

Because of chloride ion and long expected service life, Marine concretestructures in the long term service process will suffer to different degrees ofcorrosion damage, leading to deterioration of performance. Damagedstructures may deviate from the expected requirement under the action ofloads and cause serious harm. It’s great value to research the degradation ofcapacity of corroded reinforced concrete structures. A total of eight specimenswere experimentally investigated for study the influence of corrosion rate andaxial repeated load to the performance of reinforced concrete column. Andconsideration of the influence of initial defective crack、concrete grade、thickness of concrete cover and bar diameter to inner crack initiation、propagation and mechanical properties of concrete, a finite element model forsimulating cracking propagation of protection layer on the base of extendfinite element method(XFEM) and cohesive crack model was established andanalyzed. Results or findings from experiment and numerical analysisresulted in the following conclusions:(1) It was demonstrated that reinforced corrosion had no clearrelationship with cracking load, but had influence on yield load and ultimateload under horizontal reciprocating load. Ultimate strength decreasedsignificant when corroded seriously, with no obvious influence when steelcorrosion level was low(about4%). The results from test showed that theultimate load of specimen whose longitudinal bar average corrosion level was7.16%and stirrup average corrosion level was about18.27%decreased about11.5%compared with non-corrosion specimen.(2) The results from the test showed that displacement-load curve wasasymmetrical in positive and negative direction, and yield load and ultimate load of the face on which corrosion rate was more serious were higher thanthat of the other face. It’s the result of coaction of non-uniform corrosion ofreinforcement and spiral stirrups.(3) Columns yielded earlier on account of steel corrosion, while theultimate displacement basically remained unchanged because of spiral stirrupsconstraints. Therefore, ductility was improved when the steel corrosionlevel is within limits, while total cumulative energy absorption was reduced.The severer of steel corrosion, the more reduced of energy dissipationcapability. the energy dissipation capability of specimen whose longitudinalbar(about7.16%) and stirrup(about18.27%) both corroded seriouslydecreased about16.7%compared with non-corrosion specimen in test.(4) The results from the test showed that strain of reinforcement andconcrete was incompatibility because of the corrosion-induced cracks and thatthe performance of corroded column had no substantial impacted under axialrepeated loads.(5) Implementation of XFEM and cohesive crack model for the analysisof concrete fracture and propagation are effective, and capable of simulatingcrack initiation and extension path without remeshing. Existence of pre-crackchanges the mechanism of crack initiation and accelerates crack propagationthrough the cover.(6) The rust expansion and forces produced by the infiltration into crackof the corrosion products coefficiently lead to the breakthrough of cover fornon-defective structures, in addition, the crack propagation angle tends to120degrees, which agrees well with test.