Study On The Basic Theory And Its Application Of Bond-Slip Between Steel Shape And Concrete In SRC Structures

This paper analyzed the mechanism of bond between the steel shape and concrete in the SRC(Steel Reinforced Concrete) structures. By a series of SRC push-out tests, Both the bond strength and the relations between the bond stresses and slip, which was usually called bond-slip constitutive relations, were analyzed and studied to solve the problem on bond-anchoring design and the problem on numerical simulation of the bond-slip in FEM (Finite Element Method) analysis of SRC structures. The numerical simulation of the push-out test specimens were conducted with the ANSYS program, the simulation results were in good agreement with the experimental results, based on which a series of SRC beam specimens experimented before were also numerically simulated with the ANSYS program and compared with the experimental results, From these a set of methods to simulate the SRC structures with the ANSYS program, which including the establishment of the FEM model, solution of the FEM model, solution results analysis and so on was finally established. Moreover, both the methods of bond-anchoring reliability analysis and recommendations of bond-anchoring design of SRC structures were also presented in the paper.Based on the overview of former researches on the bond-slip performance between reinforced bar and concrete in RC structures as well as between steel shape and concrete in SRC structures, a new type of Slip Transfer named "The Embedded Electronic Steel-Concrete Slip Transfer" (Patent Authorization No.ZL-02-2-61881.3) was manufactured, by which the interior slip between the steel shape and concrete along the embedment length could be directly measured, the most difficult problem of experimental research was consequently solved. A type of composite H steel shape with shallow grooves in the steel shape web and flange was introduced into the push-out test, which had advantage in measuring the strains of the steel shape web and flanges with less disturbance,and therefore the accuracy of the bond stresses could be well ensured.In order to determine the relations between the four main bond-anchoring factors-concrete strength, concrete cover thickness, steel shape embedment length and the ratio of the transverse hoops-and the bond strength, and establish the bond-slip constitutive relations, 16 standard push-out test specimens were designed, and 4 comparison specimens were additionally designed to find the difference of the bond performance between the web, inside and outside of flanges the steel shape. In all these 20 specimens, the Embedded Electronic Steel-Concrete Slip Transfer were respectively embedded on the steel shape webs and inside and outside of the flanges at certain intervals along the embedment length to measure the distributions of the interior slip, and the electronic strain gauges were also installed on the shallow grooves of each steel shape web and flanges at close intervals along the length to measure the distributions of the steel shape web and flanges strain, from which the distributions of bond stress were obtained. With these methods of measuring the distributions of slip and bond stresses, the establishment of the bond-slip constitutive relations were ensured.For find the mechanism of bond-slip, the whole push-out experiment process had been fully observed. The first cracking time, the cracking development progress, and the final cracking patterns were carefully observed and depicted; and the failure specimens after experiment were entirely broke open, from which the interior failure form and characters were also observed. According to the experimental results, the load-slip curves (P-SL curves) were analyzed, and the measured strains as well as measured interior slip at both the loading phase and unloading phase of all the 20 specimens were analyzed. And the experimental results of the 4 comparison specimens were also analyzed and summarized.According to the experimental results of the 20 push-out specimens, together with the mathematical analysis of the P-SL curves, three characteristic b...