Beam load tests to verify the effectiveness of post-construction shear strengthening by embedment of deformed reinforcement bar

Yasunori KOBAYASHI¹, Toru KOBAYASHI¹, Osamu KIYOMIYA²,
1. Nippon Civic Consulting Engineers Co., Ltd. ; 2. Waseda University
Proceedings of Concrete Technology, 2002

Key words: RC structure, post-construction reinforcement-embedment method, seismic resistance, specifications, shear strengthening

Background
This paper describes the "post-construction reinforcement-embedment method" of strengthening members for seismic retrofitting of existing RC structures. The method involves embedding deformed reinforcement to strengthen shear resistance. The advantage of this construction method is that the shape of the member whose shear strength is to be increased is not altered, so it is effective for road tunnels, rail tunnels, and water tunnels where there are severe limitations on the extent to which the internal cross-sectional area can be reduced.

Research Summary
The degree of shear strengthening achieved by the "post-construction reinforcement-embedment method" was confirmed using shear tests on simple RC beams (30 cm x 46 cm x 240 cm) supported at two points and statically loaded at two points. The degree of shear strengthening obtained with this method was compared with the shear strengthening obtained with conventional stirrup strengthening. The shear resistance of members using the post construction shear strengthening method was 1.4-2.0 times that of non-treated but otherwise identical members. Also, the performance of this method relative to the conventional method of shear strengthening with stirrups anchored with hooks was 0.85-1.07. The results confirmed that the new method for shear strengthening existing RC structures is practical. We outline important considerations for construction and have prepared detailed construction specifications.