Experimental Study Of Bond-slip Between Steel Shape And Concretein Srrc Structures

As a new type of green,environmental protection,energy saving building materials,RAC(Recycled Aggregate Concrete)has been noticed by more and more experts and scholars.And abundant research and analysis of SRC(Steel Reinforced Concrete Structure)whose advantage was widely welcomed had been done.Then this paper combines the characteristics of the RAC and SRC.Steel with RAC work together,and finally formed SRRC(SteelReinforced Recycled Concrete).This paper analyzed the mechanism of bond between the steel shape and recycled concrete in the SRRC structures.By a series of SRRC push-out tests,both the bond strength and the bond-slip constitutive relations were analyzed and studied.The following is the main content of this paper:(1)A new type of slip transfer named “The Embedded Electronic Steel-Concrete Slip Transfer” was used to measure the interior slip between the steel shape and recycled concrete along the embedment length directly;And a type of composite H steel shape was introduced into the push-out test,that had advantage in measuring the strains of steel shape web and flanges,then the bond stress of SRRC could be well ensured.(2)In order to investigate the relationship between the four main influence factors—recycled aggregate replacement ratio,recycled concrete strength,concrete cover thickness and steel shape embedment length--and the bond strength,9 standard push-out specimens were designed.(3)To find out the mechanism of bond-slip,the whole push-out experiment process had been carefully observed.The first cracking time,the cracking location and development progress,and the mainly cracking patterns were fully observed and depicted.After experiment,the failure specimens were entirely broken open,from which the interior damage condition were also observed.Combined with the test data,the characteristics of load-slip curves(P-S curves)were analyzed.Finally the measured strains as well as measured interior slip of steel shape were also analyzed and summarized.(4)According to the mathematical analysis of the P-S curves,first-slip bond strength,maximum bond strength and the remnant bond strength of SRRC were summed up,the relationship between the main influence factors and three characteristics bond strength were established.A set of bond strength calculation formulae was statistically regressed,the comparison and error analysis with the calculated results were conducted,by which thecalculation results were verified in good agreement with the experimental results.According to the test data,firstly,the relations of the bond strength with load-end slip(τ-S relations)and the steel shape equivalent strains were studied.Based on the statistical regression and the force balance equations,the longitudinal distributions of the bond stresses of SRRC were established;Secondly,the longitudinal distributions of the interior slip along the embedment length were also obtained and the characteristic slip values were established by statistical regression;According to the distributions of the bond stresses and the interior slip,a new type of bond-slip constitutive relation model which including two longitudinal position functions,F(x)and G(x),were established and expresses as formula τ(x)=τ(S,x).