Study On Bonding Properties Of RC Members Under Combination Of Fatigue Load And Chloride Ion Erosion

The reinforced concrete structure has good integrity and strong bearing capacity and has been widely used in bridge engineering.Fatigue and chloride ion erosion are two major problems affecting the service life of bridges.In actual engineering,the cracking of concrete caused by fatigue loading and the corrosion of steel in the corrosive environment have become very common.At present,some research results have been obtained at home and abroad.Most of the research objectives focus on the degradation of the bond performance of RC members under single factor,but the bridge structure must withstand the combined effects of various damage factors in the service process.The chloride ion erosion and fatigue load are two key factors in the service life of the bridge.However,there is a lack of research on the bonding properties of RC components under composite action.Therefore,the degradation law of RC components under rust and fatigue composites needs to be further studied.In this article,a series of experimental designs have been conducted for this major issue.(1)The steel bar uses the method of wire cutting,and the strain change at each position of the steel bar is measured by sticking the strain gauge to the inner groove of the steel bar.(2)By studying the concrete specimens under different fatigue load cycles,the relationship between external force and strain,the bond stress-slip curve,the position function reflecting the change of the bond stress with position,and the bond strength degradation coefficient are obtained.The results show that the bond stress decreases with the increase of fatigue times;the peak of bond stress appears near the load end;the peak position of bond stress tends to move toward the free end with the increase of the number of fatigue cycles;the test pieces are mostly cracked and broken.(3)Through the study of reinforced concrete specimens with different degrees of corrosion,the distribution of strain along the anchorage length,the bond stress-slip curve,the position function reflecting the change of the bond stress with position,and the bond strength degradation coefficient are obtained.The results show that the strain has strain hysteresis at the near loading end;when the degree of corrosion is low,the ultimate bonding stress of the specimen is slightly higher than that of the reference specimen;the peak of the bonding stress appears near the free end;the slip value is greatly reduced when it is destroyed;the test piecesare mostly shear damage.(4)By studying the reinforced concrete specimens under the simultaneous action of two kinds of damages,the distribution of strain along the anchorage length,the bond stress-slip curve,the position function describing the change of the bond stress with position are obtained,and the coefficient of bond strength degradation.The results show that the strain hysteresis becomes inconspicuous;when both damage values are high,the decline phase disappears in the constitutive relation,and the specimen directly destroys after the stress reaches the peak value;yhe peak of the bond stress is bimodal along the anchor length distribution,which is located near the loading end and the free end.;some specimens have broken rib damage.The test results and the fitted functions can be used for reference by other scholars,and provide theoretical support for the prevention of fatigue and rust damage in engineering practice.