A study on impulsive force of timber drifted by tsunamis

本文提出了一种计算任意开孔率的结构物在海啸冲击波作用下，因涌浪或涌浪前缘而漂流的木材相互碰撞时所受最大冲击力的方法。在试验过程中，考察了木材的表观惯性系数、运动速度和冲击持续时间随开孔率、相对涌浪高度和木材长细比的变化特征，本文还提出了两种理论，用于估算结构物在具有较弱不稳定性和流动性的水流作用下，被漂流木材碰撞时所产生的冲击力根据弹性波理论或弹塑性理论，与涌浪或涌浪进行了比较。在前者中，弹性波理论应用于木材和结构，质量守恒定律和伯努利定理应用于木材和结构之间的水，并具有减震功能。后者将弹塑性理论应用于木材，并考虑了木材的转角速度、碰撞角和结构的挠度。

A procedure is developed for predicting the maximum impulsive force on structures with an arbitrary opening ratio due to the collision of timbers drifted by bore or surge front formed by tsunamis. In the course of the developments, variation features of the apparent inertia coefficient, the moving velocity and the impact duration time of timbers with the opening ratio, the relative bore or surge height and the timber's slenderness ratio are examined, experimentally.Two theories are also developed for estimating the impulsive force on structures due to the collision of timbers drifted by a flow with relatively weak unsteadyness and fluidity compared with bores or surges, based on the elastic wave or elasto-plastic theory. In the former, the elastic wave theory is applied to the timber and the structure, and the mass conservation law and the Bernoulli's theorem are applied to the water which is left between the timber and structure and has a shock absorption function. In the latter, the elasto-plastic theory is applied to the timber, and the angular revolution velocity and the collision angle of the timber and the deflection of the structure are also considered.