2 正会員 元名古屋大学工学部環境土木・建築学科(同上) 3 正会員 東海国立大学機構名古屋大学大学院工学研究科土木工学専攻(同上) 4 フェロー会員 東海国立大学機構名古屋大学大学院工学研究科土木工学専攻(同上) 5 正会員 東亜建設工業(株)技術研究開発センター(〒230-0035 横浜市鶴見区安善町 1-3) 曳航・据付作業時に浮遊状態にあるケーソンの動揺低減効果に与えるフーチング幅の影響を自由動揺実 験と強制動揺実験により考究した．自由動揺実験より，Pitch の固有周期は相対フーチング幅の増加ととも に大きくなる傾向があることを確認した．また，Heave および Pitch の非線形減滅係数も相対フーチング幅 の増加とともに大きくなり，フーチングの延長は動揺の減衰に効果があることを示した．強制動揺実験よ り，Heave の全振幅は入射波周期が Heave の固有周期と一致したときに，Pitch の全振幅は入射波が Pitch の固有周期と同周期または 2 倍周期となったときに同調現象が生じて増大することが判明した．以上の点 を考慮して，適切なフーチング幅を決めることの重要性を示唆した．

Floating caissons may oscillate primarily due to ocean waves during towing operations. Reducing the oscillation based on the extension part (footing) of the bottom slab of the caissons can efficiently increase the safety of towing maneuvers. However, the influence of the footing length on the motion of floating caissons has not been adequately studied. This study investigates this topic through hydraulic model experiments and numerical simulations. Experimental results for regular waves show that the rotational motion (pitch) of the caisson around the wave crest direction increases owing to resonance. This suggests that the pitch could be reduced by designing caissons, such that resonance may be prevented along the footing length. In the numerical simulations of irregular waves, the Fourier amplitudes of the heave and pitch show that the footings amplify their low-frequency components and reduce their high-frequency components. Furthermore, the significant total amplitudes of the heave and pitch show a different trend from that of the regular waves observed in the hydraulic model experiments. This suggests that it is essential to examine the motion of a caisson under irregular waves when assessing the effect of footings in an actual marine environment.