Experimental Study On Constitutive Relation And Bond Behavior Of Concrete During Construction Under Cyclic Loading

With the frequent earthquakes around the world and the rapid development of infrastructure construction in various countries,many concrete structures are still in the construction period when earthquakes occur.Concrete structure during the construction has the characteristics of time-varying concrete performance,complex load effect,the role of formwork support system,immature structure transmission mechanism,etc.The damage degree and characteristics of concrete structure during the construction are obviously different from those of buildings and structures subjected to earthquakes during the normal usage stage.Studying the seismic damage characteristics of concrete structures during the construction is the premise of objectively evaluating the reliability of subsequent use of damaged concrete structures during the construction,and numerical simulation analysis is the current available method to study the seismic damage characteristics of concrete structures during the construction.However,numerical simulation analysis needs to be based on material constitutive relationship and bond constitutive relationship.Considering the influence of concrete age and concrete strength grade,this paper carries out stress-strain relationship test of concrete during the construction under cyclic load.The complete compressive stress-strain curves of concrete specimens with different ages and strengths grade under cyclic load are given.Variations of characteristic parameters of the curves(peak stress,peak strain,curve shape parameters,etc.)with age are analyzed.Finally,the stress-strain constitutive model of concrete under cyclic compression during the construction is established considering the influence of concrete age and concrete strength grade.Considering the influence of concrete age and concrete strength grade,the bond-slip constitutive relationship test between concrete and reinforcement during the construction under cyclic load is also carried out.The influence of concrete age and concrete strength grade on the characteristic parameters of bond-slip curve(peak bond stress,peak bond stress corresponding to slip value,residual bond stress,initial friction resistance,residual friction,unloading stiffness,etc.)is discussed.The Degradation Laws of peak bond stress,friction resistance and residual bond stress of reinforced concrete specimens of different ages and strength grades under Cyclic loading are analyzed.Considering the influence of concrete age and concrete strength grade,the bond-slip constitutive model between concrete and reinforcement during the construction under cyclic load is established.