A Study On Prediction of Impact Loads of Bow Flare Structure

The bow flare structure of a ship is designed in considering impact load largely caused by relative motion of the ship and wave at rough sea. Empirical design is still used for the bow flare structure to avoid the structural failure because impact phenomenon and structural behaviour due to impact load can not examined accurately. The objective of this study is, as the first step, to predict impact loads giving the structural damages to the bow flare structure from the damage data inversely, using explicit dynamic finite element code LS/DYNA3D, and to perform the various parametric studies of impact pressure curve for its characteristics, such as peak value, duration time, tail height, rise time, etc. Introduction In the past, a large number of the bow flare structure damages of ships due to wave impact have been noticed in the world as their bow flares are larger and their speeds are higher. Their damages are usually dents of shell plates in the range of 15–25 mm, and large deformations and bucklings of frames in the range of 150 -250 mm due to wave impact against the bow flare structures, as shown in Fig. 1. This kind of local dynamic pressure problems are not easy to solve as no clear theoretical solutions are available. The mechanism of the bow structure damage is classified into two typical phenomena, impact with water surface of Wagner type and impact with breaking wave of Bagnold type, which was introduced by the structure Committee of the Society of Naval Architects of West Japan(1974). Their each formula has been known to be suitable for Bulk carrier or Tanker. Among several class rules for the bow impact pressure, DNV class rule(1997) (DNV Pt3, CH 1, Sec 7 E303) is also known to be well defined.