STRUCTURAL PERFORMANCE OF POST-INSTALLED REBAR ANCHOR PART 2: ANCHOR 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 the second part of this paper, experiments in a relatively long embedment length were carried out to clarify the effects of factors such as the concrete edge distance and the number of anchors for the bond behavior of the rebar and the bearing behavior of the small headed plate. The long embedment length assumes a situation where bond deterioration near the joint surface (near the load end) and bond resistance in the length direction shift for actual use.

 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 under the seismic load and the long-term load. The small headed plate is useful for ensuring uniform bond resistance over the entire length of the embedment length and contributes to an increase in anchor strength due to bearing resistance.

 (2) Bond strength decreases when anchoring near the concrete edge or multiple rebars are close to each other, but by using a long anchoring length, it is possible to ensure the tensile strength of the anchoring bars. In addition, there is no difference in performance depending on the construction direction.

 (3) 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. The small headed plate contributes 10 to 30% increase in anchor performance.

 (4) Anchorage behavior due to long embedment length can be simulated by reducing local bond strength in consideration of a concrete cone failure strength and edge and group effects.