• Bulletin of the Society of Naval Architects of Korea
• /
• v.27 no.1
• /
• pp.17-23
• /
• 1990

When a thin walled member is subjected to compression in a condition such as collision, the energy is mainly absorbed by axial crumpling. In this case, dynamic crushing strength of the member is increased due to the effects of strain-rate compared with the static strength, even though the inertia effect is neglected. In this paper, the method of predicting the static crushing for tubular members is presented using the kinematic method of plasticity. Since, a predicted crushing load, taking account of the dynamic yield stress, usually overestimates the effects of strain-rate, the average plastic flow stress for the effects of strain-rate is used to obtain the dynamic crushing load for tubular members. The analytical results are compared with the experiments published in references, and a good correlation is observed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2010.05a
• /
• pp.165-166
• /
• 2010

Collision scenario was 12 cases considering gate location, water level and lateral location of collision etc. And then, analysis result of trunnion by collision loads (reservoir side gate). Compressive fracture may not occur because the maximum compressive stress of concrete is below the allowable compressive strength. but, it is possible to appear some local crack because the maximum tensile stress exceed the tensile strength.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.32 no.1
• /
• pp.50-54
• /
• 1995

선박의 구조설계단계에서 최종붕괴강도를 설계기준으로 삼는 경우는 거의 없으나 최근에 각국 선급에서 최종붕괴강도를 의무적인 설계기준으로 삼기 위해 자체적인 해석법과 설계식을 제시 하고 규정화하는 작업을 진행시키고 있다. [12, 17, 31, 32]. 1994년 ISSC [1]에서도 토론된바와 같이 특히 새로운 구조방식을 가진 선박의 합리적인 구조설계를 위하여는 해상플렛폼의 구조설 계시와 마찬가지로 삼아야 할 것이다. 본고에서는 선각거더의 최종붕괴강도에 대한 해석법과 간이계산식에 관한 연구동향을 문헌조사를 통하여 분석하였다. 그 결과 순수굽힘모멘트가 작용 하는 문제의 경우 최종붕괴강도 해석법은 어느정도 확립되었다고 판단되지만 최종붕괴강도의 간이계산식은 아직도 정도 등의 면에서 개선의 여지가 남아 있다고 생각된다. 앞으로 순수 굽 힘모멘트뿐만아니라 조합하중을 받는 경우와 피로균열을 비롯한 초기구조손상을 가진 노후화된 선박에 대한 최종붕괴강도를 보다 정밀하게 해석하기 위한 해석법의 개발과 간이계산식의 도 출이 필요하다고 사료된다. 또한, 충돌, 좌초, 폭발 등에 기인된 선각거더의 붕괴강도 평가를 위한 해석법의 개발도 앞으로 남은 과제중의 하나이다.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.4
• /
• pp.601-609
• /
• 2022

Jack-up drilling rigs are mobile offshore platforms widely used in the offshore oil and gas exploration industry. These are independent, three-legged, self-elevating units with a cantilevered drilling facility for drilling and production. A typical jack-up rig includes a triangular hull, a tower derrick, a cantilever, a jackcase, living quarters and legs which comprise three-chord, open-truss, X-braced structure with a spudcan. Generally, jack-up rigs can only operate in water depths ranging from 130m to 170m. Recently, there has been an increasing demand for jack-up rigs for operating at deeper water levels and harsher environmental conditions such as waves, currents and wind loads. All static and dynamic loads are supported through legs in the jack-up mode. The most important issue by society is to secure the safety of the leg structure against collision that causes large instantaneous impact energy. In this study, nonlinear FE -analysis and verification of the requirement against collision for 35MJ recommended by DNV was performed using LS-Dyna software. The colliding ship used a 7,500ton of shore supply vessel, and five scenarios of collisions were selected. From the results, all conditions do not satisfy the class requirement of 35MJ. The loading conditions associated with chord collision are reasonable collision energy of 15M and brace collisions are 6MJ. Therefore, it can be confirmed that the identical collision criteria by DNV need to be modified based on collision scenarios and colliding members.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.34 no.3
• /
• pp.137-149
• /
• 2021

Cable-stayed bridges are infrastructure facilities of a highly public nature; therefore, it is essential to ensure operational safety and prompt response in the event of a collapse or damage caused by natural and social disasters. Among social disasters, impact accidents can occur in bridges when a vehicle collides with a pier or when crashes occur due to aircraft defects. In the case of offshore bridges, ship collisions will occur at the bottom of the pylon. In this research, a procedure to evaluate the structural behavior of a cable-stayed bridge for aircraft impact is suggested based on a numerical analysis approach, and the feasibility of the procedure is demonstrated by performing an example assessment. The suggested procedure includes 1) setting up suitable aircraft impact hazard scenarios, 2) structural modeling considering the complex behavior mechanisms of cable-stayed bridges, and 3) structural behavior evaluation of cable-stayed bridges using numerical impact simulation. It was observed that the scenario set in this study did not significantly affect the target bridge. However, if impact analysis is performed through various scenarios in the future, the load position and critical load level to cause serious damage to the bridge could be identified. The scenario-based assessment process employed in this study is expected to facilitate the evaluation of bridge structures under aircraft impact in both existing bridges and future designs.

• Journal of the Korea Concrete Institute
• /
• v.26 no.4
• /
• pp.429-440
• /
• 2014

Since the World Trade Center and Pentagon attacks in 2001, terror, military attack, or man-made disaster caused impact, explosion, and fire accident have frequently occured on civil infrastructures. However, structural behavior researches on major Prestressed Concrete (PSC) infrastructures such as bridges, tunnels, Prestressed Concrete Containment Vessel (PCCVs), and LNG tanks under extreme loading are significantly lacking. Especially, researches on possible secondary fire scenarios after terror, bombing, collision of vehicles and vessels on concrete structures have not been performed domestically where most of the past researches related to extreme loadings on structures focused on an independent isolated extreme loading scenario. Due to the outcry of public concerns and anxiety of potential terrorist attacks on major infrastructures and structures, a study is urgently needed at this time. Therefore, in this study, the bi-directional prestressed concrete $1400{\times}1000{\times}300mm$ panels applied with 430 kN prestressing force using unbonded prestressing thread bars were experimentally evaluated under impact, fire, and impact-fire combined loadings. Due to test site restrictions, impact tests were performed with 14 kN impactor with drop heights of 10m and 3.5 m to evaluate impact resistance capacity. Also, fire and impact-fire combined loading were tested using RABT fire loading curve. The measured residual strength capacities of PSC and RC specimens applied with impact, fire, impact-fire combined loadings were compared with the residual strength capacity of undamaged PSC and RC specimens for evaluation. The study results can be used as basic research data for related research areas such as protective design and numerical simulation under extreme loading scenarios.

• Journal of Navigation and Port Research
• /
• v.29 no.8 s.104
• /
• pp.661-666
• /
• 2005

Recent warnings indicate that there is a potential risk of massive earthquake. These earthquakes could produce large-scale tsunamis. Consideration of the effect of Tsunami to the moored ship is very important bemuse it brings the loss of life and vast property damage in a viewpoint of ship operations within a harbor. If a tsunami occurs, a ship in a harbor may begin drifting in case of ship entering and departing harbor, and breakage of mooring rope and drifting of moored ship are happened. And extremely serious accident, such as stranding and collision to a quay, might occur. On the other hand, since the tsunami consists of approximately component waves of several minutes, there is a possibility of resonance with the long period motion of mooring vessel. As the speed of Tsunami is much faster than tidal current in a harbor, a strong resisting force might act on the moored ships. In this paper, the numerical simulation procedure in the matter of ship motions due to the attack of large-scale tsunamis are investigated and the effects on the ship motions and mooring loads are evaluated by numerical simulation.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.4
• /
• pp.489-494
• /
• 2015

This research focused on minimizing the response of fixed cylindrical offshore structures to a ship impact considering the seawater fluid part. A collision between a ship and offshore structure is generally a complex problem and it is often impractical to perform rigorous finite element analyses to include all the effects and sequences during the collision. The structural behavior of a fixed cylindrical type offshore substructure with a seawater fluid part has a simpler response and small deformation due to the dissipation of impact energy. Upon applying the impact force of a ship to the cylindrical structure, the maximum acceleration, internal energy, and plastic strain are calculated for each load cases using Ls-dyna finite element software. In the maximum cases 2.0 m/s velocity, the response result for the structure was carried out to compare between having a fluid region and no fluid region. Fluid-structure interaction analysis was performed using the ALE method, which make it possible to apply a fluid region on the impact problem. The case of a fixed cylindrical type offshore structure without a seawater fluid part can be a more conservative design.

• Journal of the Society of Naval Architects of Korea
• /
• v.49 no.3
• /
• pp.232-238
• /
• 2012

The effects of temperature on the structural behavior of polar class vessels have been experimentally and numerically investigated. Experiments were carried out on single frame structures made of steel material, DH36, which is used for outer shell of the vessels making transit through the polar region. A knife edge type striker was dropped down onto single frame structures. The temperatures of the single frames were set to $-30^{\circ}C$, $-50^{\circ}C$ and room temperature. The deflection around the mid-point of the single frame was measured and numerically simulated using finite element model. Strain rate effect on the structural behavior has been investigated and turned out that the strain rate effect can be neglected. From the results of the experiment and numerical analyses, it has been noticed that the permanent deflection at lower temperature was reduced due to a temperature hardening of material as expected.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2004.04a
• /
• pp.193-200
• /
• 2004

In this study, the impact load on bridge by vessel collision in consideration of fender system is evaluated by numerical method. The bow of object vessel(DWT5000) is standardized, and modeled by shell elements. The main body of objective vessel is modeled by beam elements that present mass distribution and stiffness of vessel. The buoyancy effect of vessel is considered as linear spring. The two types of fender systems, such as steel and rubber are analyzed in this study. In steel fender system, the steel plates that absorb collision energy by its collapse are modeled by shell element with stiffener. The steel is material modeled elastic-plastic material. In the rubber fender system, the rubber material is modeled hyper-elastic material and the main body of fender is modeled by solid elements. The global impact responses of vessel and fender system are evaluated by explicit dynamic scheme. The results show that the magnitude of vessel collision force are depended on the material behavior of fender system. Also the values of collision load are conservative compare to the those of design codes.