Research On The Bond-slip Behavior And Constitutive Relation Of Steel Reinforced Recycled Concrete Under Cyclic Reversed Loading

The bond force between the shape steel and the recycled concrete is the premise to ensure that the steel reinforced recycled concrete structure work together.Scholars at home and abroad have conducted extensive research on the bond-slip theory of ordinary steel reinforced concrete structures.However,there are few studies on the steel reinforced recycled concrete and most of them are push-out tests.Since the structure is mainly subjected to cyclic reversed loading under the action of earthquake,when the structure is subjected to cyclic reversed loading and monotonic loading,there must be a large difference in the bond-slip behavior between the interface,therefore,it is necessary to study the bond-slip behavior between shape steel and recycled concrete under cyclic reversed loading.In order to investigate the bond-slip behavior between shape steel and recycled concrete under earthquake action,totally 14 steel reinforced recycled concrete specimens were designed and tested under cyclic reversed loading,which have different loading method,replacement ratio of recycled concrete,stirrup ratio,recycled concrete strength and thickness of shape steel concrete cover,and the bond-slip behavior and constitutive relation of steel reinforced recycled concrete were deeply studied.The main research work includes:(1)The research group developed an inductive bond slip sensor,which can directly measure the relative slip between steel and recycled concrete;The strain at the flange and the web center was measured by slotting the composite steel and placing strain gauge.(2)Observe the experimental phenomena and failure characteristics during the loading process;the load-slip curve and load-slip skeleton curve of each specimen were obtained from the test data.According to the sudden change of stress state,the failure process of bond slip is divided and the characteristic points are defined.(3)Defined the average bond strength,through statistical regression establish initial bond strength,ultimate bond strength and residual bond strength.(4)By defining the attenuation coefficient of bonding strength?,the degree of bonding damageD_k,the interface energy dissipation factor W_b and the bonding energy dissipation factorη,The influence of various factors on the bond-slip properties of the steel reinforced recycled concrete interface is analyzed.(5)Based on the statistics of the test data,the average bond strength and fixed slip distribution of the steel reinforced recycled concrete specimens are obtained,and the average bond strength-fixed slip constitutive equation is established.(6)Based on the analysis of the test results,the regular curve of the distribution of bonding stress and slip along the anchoring depth is obtained.Two position functions L(x)and H(x)about bond slip and bond stress are introduced,and finally the constitutive equation of bond-slip considering the change of position is established.