1. The energy absorption by a ship damaged as a result of a collision can be found by static experiment, and the effect of the collision velocity on energy absorption can be corrected in accordance with the increase of the material constant due to the enhanced strain rate. 2. There exist two fracture mechanisms during collision: one called piercing fracture mode, the other called crushing fracture mode. 3. During crushing fracture mode the energy absorption is large until fracture of the side skin but then decreases catastrophically. 4. During piercing fracture mode energy absorption continues to increase, roughly in proportion to the, square of the penetration depth, even after fracture of the side skin. 5. From the viewpoint of energy absorption during collision, a structure preventing fracture of the piercing mode is more suitable in the case of large critical values of the penetration depth than a structure preventing fracture of the crushing mode. One can change the mode of fracture by varying the dimensions of the deck plates and the side skin and of the stiffeners used in the structure. 6. In the presence of a scale factor γ the load and energy absorption in the penetration depth function are proportional to γ2 and γ3, respectively.