ABSTRACT For evaluation of the consequences of ship-ship collisions, and ship collisions against offshore installations and bridges, it is important to know the force-displacement relation and the energy absorption caused by crushing of complex bulbous bow structures. This paper presents a method to calculate the dynamic bow crushing forces using simplified analytical procedures taking into account the variation of the crushing velocity during impact. Firstly, a non-linear finite element method is applied to simulate the dynamic as well as the quasi-static crushing process of the large scale quasi-static bow crushing experiments performed by Yamada and Endo (2005). The dynamic crushing force-displacement relations, the strain rates and the energy absorption of the bow models are evaluated. An empirical relation is derived between the actual crushing velocity and the strain rates in the bow structure. For different ship impact velocities and impact masses, the dynamic impact results are compared with the experimental static crushing results. It is observed that for realistic velocities and masses the crushing forces and energy absorption of the bulbous bow structure is increased significantly due to the dynamic effects. Secondly, an analytical procedure is presented which is based on a quasi-static simplified calculation method modified by the derived relation between actual deformation velocity and the strain-rates. The varying crushing velocity is determined by an energy based procedure to give consistent estimates of the dynamic bow crushing forces. Finally, the simulated numerical non-linear finite element dynamic and static crushing responses are compared with the results of the presented simplified analytical method. INTRODUCTION In ship collision analyses, the structural behavior of the bow plays a dominant role. For ship-ship collisions, it is the strength of the colliding bow which determines whether the energy will be absorbed primarily by the bow of the colliding ship or by structural damage to the struck vessel. In collisions with offshore structures, the designers will normally aim for a strength design of the installation such that the ship bow shall absorb most of the energy released for crushing. Similarly, in the structural design of bridges against ship collisions, the pylons and the bridge piers have to be designed to withstand bow impacts of the design vessels.

ABSTRACT The development of inland navigation takes an economic effectiveness, but the issue of the accident possibility of ship collision has received considerable critical attention. It is significant to study how to evaluate the risk of inland ship collision and to provide instant maneuver advice for the current vessel in case of multi-factors. This paper presents a quantification method of ship collision risk assessment for inland navigation, and delimits the safe voyage range of every ship in inland water. Specifically, by considering the influence of the multi-factors (flow state, channel conditions and ship maneuverability), the ships' relative navigation trajectories, relative course-speed vectors and relative bearing vectors are predicted by Extended Kalman filter. Then all feasible voyages of the give-way vessel can be calculated using the interaction with other ones, and the safe voyage ranges are provided according to the optimal path planning decision. In the end, a maritime simulator is employed to verify the presented assessment model's availability. INTRODUCTION With the continuous expansion of the global shipping fleet and the large scale of ships, the traffic density of ships in narrow watercourses increases constantly, and the complicated navigation environment in the narrow channel makes it more difficult for large ships to operate and avoid collisions in narrow waterways, resulting in the occurrence of ship collision accidents in narrow watercourses. The navigation of ships in narrow watercourses may be influenced by inter-ship effect, shore wall effect, shallow water effect, abandoned flow, bridge area and so on. Therefore, it is more difficult to operate and avoid collision than open water, so it is urgent to obtain the auxiliary support in theory and technology. However, the complex environment in the narrow channel leads to the difficulty in the study of collision avoidance decision-making, which leads to the relative lack of research results of the decision-making of narrow channel collision avoidance.

ABSTRACT In this paper, an anti-collision steel box barrier used in an over-bay cable-stayed bridge is introduced. The whole history of a ship colliding on the cap with anti-collision box barrier is simulated. To clarify the influence of pile-soil interaction, the ship-cap-subsoil model is developed. By taking the Fast Fourier Transformation toward the plastic displacement of the RC cap, the dynamic properties of the cap are obtained and the damage induced by ship collision is evaluated. Furthermore, the anti-collision efficiency of the steel box barrier installed on the cap of the cable-stayed bridge is discussed. INTRODUCTION With the rapid development of infrastructure network, several cross-sea highway bridge projects have been completed. In these projects, bridges play an important role, but it also behaves as a man-made obstacle in the navigation channel. In the recent years, the collapse accidents due to ship collision become more and more serious. According to the statistics by Dong (2009) based on 503 collapse accidents of bridges in 66 countries, there were 91 ones caused by various collisions, and 56 accidents were induced by vessel collision. According to the statistics, only for the Wuhan Yangtze River Bridge, it suffered 76 ship collision accidents after its opening for traffic. A similar investigation by Wardhana (2003) on 503 bridge collapses in the United States from 1989 to 2000, which indicated that the most frequent causes of bridge failures were attributed to floods and collisions. When a ship acts on a bridge pier, it may not only influence the normal operation of the navigation channel, but also seriously threat the structural safety of the bridge. In addition to the static calculation equations given by many scholars and used in codes (Meier-Dornberg, 1983; AASHTO 1991), several dynamic vessel-impact analysis techniques have been recently proposed, where a force-deformation curve was employed to model the vessel bow stiffness. Most studies mainly focused on the force-deformation curves of the barge bows rather than the ship bows. Consolazio (2003) computed the forcedeformation relationships for several scenarios of hopper barge crushing, and compared the results obtained from the nonlinear finite element crush analysis and the empirical crush models in bridge design specifications. Fan (2014) developed a high resolution finite element model to obtain the ship bow force-deformation curves with consideration of the effect of pile-cap depth. Storheim (2016) calculated the collision response of the bulbous bow of a full scale offshore service vessel by using ABAQUS and LS-DYNA, and investigated the influence factors such as numerical setup, element formulation and mesh size. To detect the damage induced by ship collision, Ferraro (2013) used an ultrasonic pulse velocity test to assess the integrities of the structure before and after impact. Sha (2013) extracted the vibration data before and after collision, and used the frequency domain decomposition method to estimate the bridge damage state after barge impact accident.

ABSTRACT A new experimental configuration is designed for large scale Y shape stiffened panels under lateral impact load, which can avoid second impact during test and could be conducted in laboratory condition. The specimens consist of three Y shape stiffeners with one span in the longitudinal direction. The permanent deflections of the steel sandwich were measured by 3D-scan technology. High speed camera is introduced to obtain the velocity history of pendulum bar. Acceleration sensor is set on the indenter to record its acceleration history, which is transferred as the impact force according to Newton second law. The impact force - penetration relationships based on experimental result are compared to existing analytical method. INTRODUCTION The collisions between ships would cause the damage of ship structures, and then result in loss of human lives and severe environmental pollutions. There exist two type analysis methods for the ship collision: external and internal mechanics. The external mechanics deals with the global motion of the ship under the action of the collision force and the hydrodynamic pressure exerted on the wetted surface (Petersen, 1992). On the other hand, the internal mechanics concentrates purely on the structural response, evaluating the structural crashworthiness of the ship during accidents (Reckling, 1983). The response of a ship structure struck by another vessel is usually nonlinear, which depends on the structural arrangement of the ship side and the location of the strike relative to the transverse web frames and bulkheads and on the strength of a striking bow compared with the strength of the struck side. Many parameters associated with the ship collision problem influence the results, including different ship types, drafts, striking bow angles and rakes are considered. (Jones, 1983) The concept of Y shape stiffener was introduced by Ludolphy (2001), which was used in double hull structure by Damen Schelde Naval Shipbuilding as shown in Fig.1 (a). Practical application of Y shape stiffener in side structure is shown in Fig.1 (b). Using numerical analysis, Klanac et al. (2005) compared the crashworthiness for ten different steel sandwich structures. Naar et al. (2002) and Hu et al. (2005) conducted a series of nonlinear numerical simulations for Y shape structure under lateral impact. These studies found that the double Y type structure can effectively improve the impact resistance ability. It was found that the Y shape structures offered around 40 % higher capacity to absorb collision energy relative to conventional double side. In structural design of ship and offshore structures, it is of high importance to predict the damage caused by collision or grounding.

ABSTRACT A collision or grounding event may lead to large plastic deformation and fracture in collided ship, which could result in severe consequences. Therefore, it is of great importance to predict the response of ship structures rapidly and accurately when subjected to impact loads. Numerical simulation and simplified analytical method are carried out to investigate their internal mechanics in two specific scenarios. Based on the deformation patterns observed in numerical simulation, analytical expressions for assessing the resistance of components such as plate, stiffener, web frame and web girder are established. Several assumptions are made to predict fracture. In combination of these individual members, curves of resistance force versus indentation are obtained, which correspond well with the results conducted by the numerical simulation. INTRODUCTION Ship collision and grounding are accidents that will result in catastrophic consequences such as economic loss and potential ecological pollution. However, the collision scenarios which a ship may encounter are uncertain because of complicated navigation environment and diverse structural design of itself. Therefore, a fast and reliable procedure should be developed for the potential collision accidents forecast in the preliminary design. According to Hong (2008), the prevailing approaches to assess the internal mechanics of ship collisions are experiments, numerical simulation and simplified analytical method. Among them, the full-scale collision and grounding experiments are too expensive to implement. While the model tests involve complex scaling effects and the process is lengthy for unexpected problems. Comparatively, numerical analysis gives priority to the experimental method due to its low cost and repeatable. Furthermore, it can provide satisfactory results including the deformation and fracture details as well as the resistance force. Therefore, it has been extensively treated as "numerical experiments". For example, Haris and Amdahl (2013) used the software LS-DYNA to produce virtual experimental data for several ship collision scenarios evaluating the interaction between the deformation on the striking and the struck ships. Gao et al. (2014) took the numerical simulation to verify the accuracy of the proposed analytical method that can rapidly predict the response of FPSO side structures collided by rigid bulbous bow. Sun et al. (2015) conducted numerical analysis to validate the proposed analytical method that deals with double side structures collided by a raked bow. Liu and Soares (2016) provide analytical method to estimate the extent of structural damage within double-hull tanker side structures during minor head-on collision and it was validated by numerical simulation with precise modeling parameters confirmed by previous experimental results. However, the failure prediction of numerical simulation has not improved much because the commonly used failure stain is highly dependent on the element length-thickness ratio and the criteria for dealing with sheet metal ductile fracture beyond local necking is not well established. Thus, material failure should be validated against the experimental tests before performing structural analysis.

Abstract The correct use of nonlinear finite element analysis enables increased confidence in the results and better utilization of the actual structural capacity compared with simplified methods, which has rapidly become a widely adopted tool for the simulation of such accidental impacts. By applying structural dynamic finite element numerical simulation technology and acoustic numerical simulation technology, taking an actual ship collision accident as an example, detailed vibration and acoustic ship models through the finite element method are constructed in this paper. Collision process, structure damages, vibration of ship structure and noise resulting from collision are calculated, according to the loading condition and the navigation status of accident ships. Comparison of the results shows a good agreement between the accident structure damages and numerical simulation results. Moreover, acceleration vibration level difference and average sound pressure level of the wheelhouse are obtained by transient vibration response analysis and acoustic statistical energy analysis. At last, staff's perceptions of ship collision in the wheelhouse and crew cabins are discussed with relevant codes and regulations, which provides a guidance to accident identification. Introduction Maritime transportation is the main transportation mode for international trade. It is estimated that 90% of the goods of world trade is transported by sea (Zhang et al, 2015). The risk of ship collision has been greatly increased together with the growth of the global ship fleet and ship speed. Ship collision can not only provoke oil spill and permanent ship structure damage but also cause the degradation of the marine environment, human losses and ships traffic blocking (Fig.1). Therefore, increased attention has being paid to investigate the response mechanisms and the numerical simulation methods of ship collision, to reduce the risk of structural impact damage, protect both lives and the environment and offer certain reference for solving maritime dispute (Carlebur, 1995).

Abstract According to the European Maritime Safety Agency (EMSA) statistics, ship collision accounted for forty percent of total water accidents in the scope of their jurisdiction. However, human factors play a key role in the happening of about eighty percent accidents. Therefore we must strengthen safety consciousness and improve the mariner ability. It is also essential that we strengthen ship maintenance practices, and strictly follow a standard system for ship inspections. Some reasonable and effective measures must be taken when a potential danger is found. Reporting to the captain in time also is necessary. When a collision accident is inevitable, amidships is a dangerous place. Therefore ship's office as well as ship's engine room must be located as far as possible from amidships to avoid crashes. But due to lack of accurate analysis, the ship's office may lapse in judgment and cause a greater damage. Therefore, the paper departs from the perspective of the ship's structure and instead become vulnerable parts of the ship when adding a cross-shaped reinforcement according to a simulation study of inevitable ship collisions by applying the nonlinear finite element Program MSC.Patran/Dytran. We simulate a collision of two ships at different angles, velocities and collision points, and then study the damage of the ship's side during the collision and mechanical deformation of the structure of energy absorption mechanism via combining the basic principles of ship collision dynamics and plasticity kinetics. A comparative analysis of the hull's damage deformation in a variety of conditions, allows a relatively clear understanding of the ship's side energy absorption and the structural response under different collision factors. These studies will promote the development of new ship design and manufacturing techniques, and serve for new ship's structure as a reference for future crash worthiness optimization designs to help reduce maritime casualties and property losses.

Abstract The risk assessment is one of the main issues for all of the offshore units operating on Norwegian Continental Shelf (NCS). The risk assessment is required to fulfill Petroleum Safety Authority (PSA)/Norwegian Maritime Authority (NMA) regulations and the requirements from the classification societies. This paper discusses risk evaluations for a semi-submersible drilling rig operating on NCS that is classified as a Mobile Offshore Drilling Unit (MODU). In this paper, four accidental events are used for the risk evaluation such as fire, explosion, ship collision and dropped objects. Dimensioning/design accidental loads from the accidental events are introduced and verified through Accidental Limit State (ALS) assessments. A simple method and finite elements analysis are adopted to show the current designs can sustain the accidental loads. It is also described how the risks are evaluated based on the principle of As Low As Reasonable Practicable (ALARP).

Abstract It is very important to define the procedure and boundary condition setting in experimental programs to simulate the response of ship structures under accidental loading conditions, such as in collision scenarios, to obtain the reliable results. The present paper aims to identify an appropriately experimental program for the unstiffened panels subjected to lateral impact. The influence of different configurations on the impact force and lateral displacement of the unstiffened panels are investigated in the FE analysis, including the boundary conditions, thickness of the plates and velocity of impact, which provide the basis idea for the further experimental program of the structural components analyzed. The results of the plates with the simply supported, clamped and box girder supporting are very close, which are slightly different to that with the steel block supporting with bolt constraint. It is vital that the experimental program have enough number bolts to reduce the influence of the local stress concentration.

Abstract To solve the controversy of the responsibility in ship-ship collision, a ship-ship collision model was established on the basis of the collision accident of the "Xin Haixin 818" and " Guibei fishing 58013", then using the nonlinear dynamic analysis software AUTODYN to display finite element simulation. In the ship-ship collision simulation, according to the damage extent of the two ships, "Guibei fishing 58013" is regarded as a rigid body in which the overall deformation is smaller, while the larger deformation of "Xin Haixin 818" is a deformable structure. By setting ship motion parameters on multiple conditions, and choosing a reasonable time steps, the intrusion - yield - destruction process of the hull collision region is restored. The comparison of the calculations and the accident scene investigation of the crevasse shape and invasion depth reveal that the model prediction is in good agreement. The quantitative reproduction method of modeling the collision damage process allows maritime authorities to judge collision conditions, and provides a new reference for the maritime ascertaining accident responsibility.

ABSTRACT This paper summarizes a pilot study conducted in the fall of 2010 and winter of 2011 for the multi-party research program entitled Sustainable Technology for Polar Ships and Structures or STePS 2 at Memorial University of Newfoundland, Canada. The work investigates laboratory production techniques of cone-shaped ice specimens and further examines the brittle behavior of them when crushed against a flat steel plate. The influences of ice temperature, cone geometry and ice type, resulting from various production techniques, is examined.

ABSTRACT: The impacts of ships with a cross sea bridge are studied numerically. Firstly, finite element models of the ships and the bridge are built. And then, the collisions are simulated using finite element software, assuming the ship moves to the bridge at different speeds. The stresses and deformations of both the bridge and the ships are calculated. And then, the effect of the ship's mass is also evaluated, when the displacement of the ship varies from 3000t to 30000t. The relationships of the impact speed, impact period and damage extent are discussed. At last, the stresses of the bridge pier are analyzed. The results show that the damage extent of the bridge is related with the speed and the mass of the ship besides the strength of the bridge and the ship. The results can be referenced in the evaluation of damaged bridges. INTRODUCTION More and more cross sea bridges are being built at the coastal area in the east the China. And also shipping transportation are quickly developing at the same region. Occasionally, collisions occur between ships and cross sea bridges. They cost great losses with lives and treasures, both to the ships and the bridge structures. Some researchers discussed the probability, kinetic energy and impact force of collision between ship and bridge structure. Many researchers focus on the discussion of the structure damage of the ships. Kitamura(1997), Sano, Muragish(1996), Kusuba(1995) and Wang, Gu(2001) studied the performance of broadside when collision occurs. Here, both the damage of the ship and the bridge are discussed. By means of nonlinear finite element simulation method, the dynamic process of the collisions between ship and bridge pier are calculated for four different ships with displacements of 3000t, 8000t, 10000t and 30000t at different initial velocities, respectively.

Recently, the risk based engineering activities for offshore projects in the shipyard are gaining tremendous attention because of many catastrophic failure occurrences in past. There is a need for having a well established procedure for risk assessment in the shipyard. Results from the risk assessment will have an unexpected and direct impact on the design, the associated procurement and the construction in EPC (Engineering, Procurement and Construction) projects. This paper introduces a sort of procedure for the risk assessment from the classification of the vulnerable areas to the consequence analysis which is established by DSME, and the actual applications to FPSO projects for ship collision, dropped objects and explosive blast. INTRODUCTION Worldwide, there have been several major offshore accidents such as collision between ships and gas installations, impacts arising from dropped objects and swinging load incidents involving cranes and explosive blast from hydrocarbon leakage. In particular, in the offshore industry, an increased focus was placed on the risk-based design after the Piper Alpha accident in 1988. The accidental loads may have results in the total loss of the offshore units and/or marine environment and hearth threats. In this reason, the owners usually request the risk-based engineering for structural integrity against the accidental loads, so that it is of high significance for the shipyard to successfully complete offshore projects. In spite of this importance and a great many past offshore projects, a few reference papers and handbooks which are described the systematic process and/or procedure may be in existence for the shipyard. Project reports and analysis results are occasionally made to introduction, but it is difficult to share the information because of the security. In addition, the descriptions for the problems between the owner and the shipyard may be lack to understand fully during the going on project.

A crew in operation suffers danger of ship collision impact. The transient behavior of seated passenger has been studied. This paper describes a simple three dimensional human body model for a numerical simulation of an upright crew at ship collision. The human model consists from only 200 elements, which enable numerous simulations within a very short time. We carried out a series of numerical simulation to estimate the transient behavior of the upright crew, using 3 different operation conditions, the flat floor, the flat floor with a step and the flat floor with an operation panel, considering the effects of handrail in each case. The direction of the collision is considered too. The results show that the flat floor with a step generates large movement on the body of the upright crew. It also generates large head velocity according to the direction of the collision. We can not expect the effects of the handrail in case of ship collision considered here. The handrail may help us at the accident with very small impact. The existence of a small step on the flat floor may increase the amount of injuries. INTRODUCTION Not a few accidents of ship collision against a quay or a ship or a floating wood, have been reported. Some numbers of passengers and crews are injured by the collision against a floor and a wall with these accidents. In April 2006, an accidental collision of a high speed hydrofoil boat with a velocity of about 80km/h (about 22knots) against a floating wood occurred in the southern sea of Japan. All of the passengers and crews injured by the accident. Even some seated passengers with equipped seat belts severely injured to brake their hipbones. The safety of passengers and crews at ship collision is very important especially in case that the ship goes very fast.

ABSTRACT This paper describes a simple two dimensional model for a numerical simulation. The model consists from a human body, a seat and a seat belt. The model is made for the estimation of the neck stress and the head acceleration caused by a collision of a ship. The effect of the elasticity of both a human body and a seat cushion is considered to reduce head acceleration value, which is caused by the contact between a human body and a seat. This effect is taken into consideration for this model. Based on this model, a seat condition which gives less trouble to passengers is considered. INTRODUCTION Effects of the shock at a high speed ship collision on the transient behavior of a passenger's head and neck are estimated by a finite element method using a two dimensional multi-body model. An explicit finite element method code ‘LS-DYNA’ is used for the simulation tool in this paper. Situations of the ship collision are as follows. A passenger is seated facing backwards. A ship collides with a pier from its bow. The ship stops suddenly collapsing its bow structures. The change of velocity of the passenger and the seat caused by the ship collision is 5m/s. The seatbelts are fixed to the ship structure. The feet of the seat are supported on the floor of the ship. The seat is allowed to move forward and backward, against the resistance of the fastening parts. One of the authors had studied the effects of the seat direction on the behavior of a human body at the ship collision by the numerical simulation using implicit finite element code ‘ABAQUS’. He showed the possibility to decrease the head acceleration by the control of the connecting stiffness between the seat and the ship structure by this study.

ABSTRACT Owing to the increase of bridges and offshore structures near ship's waterways as well as marine traffic, ship collision accidents with these structures have been increasing. To keep safety from ship collision accidents with these structures, various kinds of protective device are planed. The new material protective device is used for these purposes. In order to design this protective device for ship collision, it is necessary to be investigated the strength of ship as well as the strength of protective device. In this study, authors investigated on the strength of this ship bow. From this research, simplified were formula introduced for calculation of ship bow strength related to ship's length based on relation about various dimensions of ship bow structures, which are depth of ship, thickness of plate, entrance angle of bow, frame space and so on. On the strength of protective device, experimental formulas were introduced for calculation of reaction force of protective device related to indentation of ship bow from the various parameters, which are form factor, depth of unit piece, bending elastic modulus of material and so on. The scale effect was also considered from scale model experimented results. Using these formulas case studies were executed which considered standard allowance of collapse of ship bow on the design of protection device of Honshu-Shikoku Connecting Bridge. In this paper the design procedure of 2 different size ships was introduced. In this procedure the minimum depth of the protection device which can avoid the collision between ship and bridge pier can be designed. INTRODUCTION In these years, many bridges and offshore structures have been constructed near ship's waterways. After 1980, serious accidents have not happened but the number of accidents does not decrease yet. The record indicates an average of ten collision accidents per a year.

ABSTRACT Risk analysis of planned jacket installations has shown that collision with passing vessels, with a kinetic energy in the range of 40–50 MJ, is a potential hazard. This implies a vessel of 2–3000 tons displacement at a speed of 6–7 m/s. Bow collisions with passing vessels are normally not designed for, and no relevant information of bow strength for leg impacts is available. The objective of the present work is to establish similar design curves for bow impacts against jacket legs by means of non-linear finite element analysis. The penetration of a bow structure by a rigid cylinder representing a jacket leg is simulated. The curves, which are proposed being implemented in the NORSOK N-004 code, can be used for strength design of the platform. The use of the proposed design curves is illustrated in a case study of an actual platform subjected to ship collision on legs. INTRODUCTION A major hazard to offshore structures is ship collision. The largest damage potential is associated with collision with large merchant vessels. Their kinetic energy is, however, so large that it is virtually impossible to design jackets for this event. The risk should instead be controlled by keeping the probability of occurrence acceptably low. Encounters with attendant vessels, on the other hand, have a rather high probability of occurrence, approximately 0.15 per platform year (Wicks et. al. 1992). The concern for ship collision is reflected in various design codes. Since 1980 the Norwegian Petroleum Directorate (NPD 1984) requires that platforms normally be designed for impacts from supply vessels of 5000 tons displacement with a speed of 2 m/s, yielding a kinetic energy of 14 MJ for beam impact and 11 MJ for bow or stem impact, when specified values for hydrodynamic added mass (NPD 1984) are taken into account.

ABSTRACT As concerns vessel and bridge collision, serious accidents do not happen in these days but accidents do not decrease yet. The record indicates an average of ten collision accidents per year at least. To these circumstances various kinds of protection system of bridge pier are planned. The protection system should be designed not only to protect the bridge structure but also to protect the vessel against serious damage. Pelprene protective device reported here is one of the new material protective devices contacted with bridge and absorbed colliding energy by elastic deformation of the protection. In this paper authors studied on the effect of this protection system by model experiment dynamically. To study the characteristics calculation of this model is also executed and compared to the experimented result. These result shows good agreement. From this study the characteristics of this protective device and effectiveness for actual ship collision were considered. INTRODUCTION In these years, many bridges and offshore structures near ship's waterways are constructed. For example, Seto Bridge which is one route of Honshu-Shikoku Connecting Bridges was opened in 1988, Tokyo Bay Crossing Bridge-Tunnel was opened in December 1997 and Akashi Kaikyo Bridge of Honshu-Shikoku Connecting Bridges was opened in April 1998. In Denmark, Great Belt Bridge-Tunnel was also constructed. Owing to the increase of bridge and offshore structure as well as marine traffic, ship collision accidents with these structures have been increasing. The accidents of the Tasman Bridge of Australia in 1975, the Tj0m Bridge of Sweden in 1980 and the Sunshine Skyway Bridge of U.S.A. in 1980 were brought about by ship collision. After 1980 serious accidents have not happened but the number of accident does not decrease yet. The record indicates an average of ten collision accidents per a year at least.

ABSTRACT An analytical model for predicting the mean crushing strength of stiffened plated structures under quasi-static crushing loads is developed. Dynamic effects are included into the model by considering the strain-rate sensitivity of material. Verification examples are shown to validate the accuracy and applicability of the proposed method. As an illustrative example, the model is applied to assessment for collision strength performance of bow structure for an actual chemical product carrier colliding with a fixed object. INTRODUCTION Ship collision and grounding can result in structural damage, marine pollution dependent on cargo type, and hull girder collapse after the accident. The task of protecting against such environmental disaters or vessel loss due to potential accidents is complex, but can generally be divided into two major groups, namely active and passive safety methods (Pedersen 1995). The active method is aimed at preventing an accident to occur. This approach includes auto-pilot system of the vessels, crew-training program for instance with realistic simulators for ship operations, and traffic control systems. The passive safety method works after an accident has occurred. It is designed to mitigate the risk of serious consequences, such as ingress of sea water, outflow of hazadous cargo, and hull girder collapse. The latter is related to the improvements of structural crashworthiness, and rapid salvage and rescue operations. The present study is concerned with application of the passive method on the improvements of structural crashworthiness in ship's bow collision. For that purpose, it is necessary to better understand the mechanics of ship collision such that the structural safety of vessels against accidental loading can be improved. During ship collision, typical failure modes include crushing of structural elements. Much research have been focused on investigating the behavior of structural components under crushing loads.

ABSTRACT First of all, ship collisions with bridges in Japan are surveyed and their causes are analyzed. The results obtained by hydraulic model tests conducted on ship's impact force during collisions with the fender systems of bridge piers are discussed. The parameters in these hydraulic model tests are mainly the load-deflection characteristics and spring constants of the fenders. A numerical simulation to evaluate ship motions and fender deflections during ship collision are also presented and evaluated. INTRODUCTION Bridges spanning straights, canals, rivers have to be designed for safety against ship collision. To protect the piers of bridges against ship collision, fender systems are installed at the fronts of the piers of bridges. In the design of large ships, the impact energy by ship collision is considered to be absorbed both by deflection of the fender systems and deformation of the ship's bow or hull. For small ships, safety against deformation shall be preserved both by the piers of the bridge and the hull of the ships. Therefore, the impact energy by ship collision is considered to be absorbed only by deflection of the fender system. In this paper, the results of both hydraulic model tests and computations for ship's impact force on fender systems which protect bridge piers against ship collisions are presented. The hydraulic model tests are carried out varying fender system characteristics such as, for example, linear-type, reaction increment-type, buckling-type and large hysteresis-type. Fender system spring constants are also changed in the hydraulic model tests. The reaction force and deflection of fenders, as well as shear forces are measured in the hydraulic model tests. Numerical simulations to evaluate ship motions and fender deflections against ship collisions are also presented and evaluated.