Abstract
To evaluate the bond behavior between the reinforcing bar and surrounding concrete, a total of six-group pullout specimens with plain steel bars and two-group specimens with deformed steel bars, serving as a reference, are experimentally investigated and presented in this study. The main test parameters of this investigation include embedment length, surface type of reinforcing bars, and bar diameter. In particular, the bond mechanism of plain steel reinforcing bars against the surrounding concrete was analyzed by comparing with six-group pullout specimens with aluminium alloy bars. The results indicated that the bond stress experienced by plain bars is quite lower than that of the deformed bars given equal structural characteristics and details. Averagely, plain bars appeared to develop only 18.3% of the bond stress of deformed bars. Differing from the bond strength of plain steel bars, which is based primarily on chemical adhesion and friction force, the bond stress of aluminium alloy bars is mainly experienced by chemical adhesion and about 0.21~0.56 MPa, which is just one-tenth of that of plain steel bars. Based on the test results, a bond-slip model at the interface between concrete and plain bars is put forward.
Highlights
A large number of existing reinforced concrete buildings were constructed with plain reinforcing bars before the 1970s [1]
This paper introduces research aiming at characterizing the effects of rebar type, embedment length, the surface type of reinforcing bars, and bar diameter on the bond strength of plain reinforcing bars
Different from the plain bar, when specimens of deformed bars were damaged, the concrete surrounding the reinforcing bars was pulled out followed by the bars, which indicated that the mechanical interlock played a role
Summary
A large number of existing reinforced concrete buildings were constructed with plain reinforcing bars before the 1970s [1]. The behavior of smooth reinforcing bars embedded in concrete is a key issue in the development of reliable procedures for the evaluation of available bearing and/or displacement capacities of historical buildings. In order to further study the bond behavior between the plain steel bar and surrounding concrete, six-group pullout specimens with plain steel bars and two-group specimens with deformed steel bars conducted for comparison purposes are experimentally investigated. Considering it is difficult to distinguish adhesive stress from friction stress for the bond strength of plain reinforcing bars, six-group pullout specimens with plain aluminium alloy bars were constructed to analyze the bond mechanism between plain bars and surrounding concrete in this test [9]. Empirical equations for maximum average bond stress are derived using regression analysis, and the form of the load-slip curve is presented
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