Study On The Bond Slippage Of Corroded Steel And Concrete

In recent years,the durability of concrete structures has received more and more attention.During normal use,it was found that the corrosion of steel bars in the components not only reduced the effective cross-sectional area of the steel bars,changed the mechanical properties,but also significantly degraded the bond properties with the concrete,seriously affecting the safety and durability of the structure.The study of the bond properties of corroded steel bars and concrete has important practical and theoretical significance for evaluating the actual bearing capacity of existing structures and enriching the bonding theory.In this paper,using the basic principle of steel bar corrosion,in the laboratory,two different types of steel bar(light round,ribbed)test blocks under two kinds of different concrete strength levels(C20,C40)confined by stirrups are subjected to electric current corrosion.By Faraday's law to control the size of the current and power-on time,each test block appears four different degrees of rust distribution: no rust,light rust,moderate rust,and heavy rust.After the corrosion is finished,a center pull-out test is performed on concrete test blocks with different degrees of corrosion.The test results show that:(1)Due to the effect of stirrup confinement,the pull-out failure mode of the steel bar occurs in most cases of the bonded test block,and some ribbed steel bars exhibit yield failure of the test ribs.(2)The corrosion rate has a great influence on the bond stress of the steel bar.With the light corrosion rate of 3%,the bond stress is maximum.With the increase of the corrosion rate of the ribbed bar,the bond stress gradually decreases,and On this basis,the ultimate bond strength degradation formula was established.(3)Through the pull-out test data,the change rule of the bond-slip relationship curve of different kinds of steel bars under different strengths was analyzed.The larger the ultimate bond stress of the test block,the smaller the corresponding slip amount.And establish a basic relationship between bond and slip.(4)Finally,through the method of rebar slotting and strain gages,the strain of the steel bar in the anchorage zone was collected during the process of bar pull-out.The strain was gradually increased from the free end to the load end,and the bond stress was showed in the anchorage segment.The "parabolic" shape distribution,and the relative slip at the free endlags behind the loading end.On this basis,the bond-slip relationships at different points of the anchoring position are obtained,thus establishing a bond-slip constitutive structure considering the influence of the anchoring position.relationship.