Department of Building and Civil Engineering, I.I.S., University of Tokyo, 4–6–1 Komaba, Meguro-ku, Tokyo, 153–0041 Japan

Graduate School of Science and Engineering, Waseda University, 3–4–1, Okubo, Shinjuku-ku, Tokyo, 169–8555 Japan

Department of Building and Civil Engineering, I.I.S., University of Tokyo, 4–6–1 Komaba, Meguro-ku, Tokyo, 153–0041 Japan

Ono-Sokki Co., 1–16–1, Hakusan, Midori-ku, Yokohama, 226–8507 Japan