STRUCTURAL PERFORMANCE OF POST-INSTALLED REBAR ANCHOR PART 1: BASIC BOND AND BEARING PERFORMANCE OF POST-INSTALLED REBAR WITH SMALL PLATE

Abstract

 In the case of repair and reinforcement of an R/C structural frame, and installation of new members for extension and reconstruction, it is necessary to anchor such as main bars and wall reinforcement bars of new members to the existing frame. In this case, the anchor is required to reliably transfer the tension of the rebar to the existing frame. The purpose of this research is to propose a post-installed headed rebar anchor method with high reliability both in structural performance and workability, and to evaluate the anchorage performance of the method. In this paper, experiments in a short fixing length were carried out to clarify the bond behavior of the surface of the rebar and the surface of the hole wall and the bearing effect of the small headed plate.

 In the first part of this paper, pull-out experiments are conducted to understand the effects of various factors on the basic bond performance and bearing performance. The following results were obtained.

 1) The bond strength on rebar surface of proposed method is equal to or higher than that of the cast-in-place deformed bar and is affected by the concrete strength.

 2) The bond strength difference on hole surface of proposed method is small between the case of installation by advanced rock-drilling system and advanced core drilling system. So, the performance difference due to the difference of the roughening degree is small within the scope of those methods and this experiment. Moreover, the bond strength is approximately equal to that of the cast-in-place deformed bar, and since the hole diameter is large, good bond performance can be obtained by the proposed method.

 3) The headed plate improves the anchor performance by bearing pressure resistance, and the effect is increased especially after the bond resistance on rebar surface is lost. Due to the effects of bond and bearing pressure, good anchor performance can be obtained by the proposed method.

 4) It can be said that the bond strength on rebar surface of this method is estimated to the allowable bond stress of AIJ reinforced concrete calculation standard and bond strength of AIJ design recommendation for composite construction.

 5) The local bond stress-slip relationship can be estimated by the same evaluation model used for cast-in-place deformed bars.