subject: MODELING FOR MARINE MOBILE FLOATING BERTHING PROTECTION FACILITIES [print this page] MODELING FOR MARINE MOBILE FLOATING BERTHING PROTECTION FACILITIES
1. INTRODUCTION
Worldwide seaborne traffic at major ports is continually growing. This bring along high demand for ships from shipbuilding companies and also jetty constructions. Port operators need to enhance the facilities in the ports so that they can compete with the other competitors. Due to the restriction of the capital to build the facilities that need a lot of money for example jetty, berth required in order reducing the heavy seaborne traffic which is a burden to the port owner. A cost effective way alleviate such burden for port owner is to acquire floating pier which act as loading and unloading floating pier. Floating piers are much less costly compare to building a jetty or berth. Marine fenders are crucial to a ship berth. A proper fender design should effectively absorb or dissipate the kinetic energy carried by a docking ship and thus mitigate the impact force to a sustainable level [1]. Fender design normally involves extensive trade-offs depending on the type, purpose, site, function, and operation concept of a berthing facility. Standard fender design practice to date uses a nominal berthing energy specified in terms of the displacement, approach speed, and attitude of docking ship. This paper describes the result of numerical model for a mobile berthing and mooring system. The study determines the safe berthing velocity, berthing energy and environmental loading for ships at various displacements [2].
2. Mehodology
2.1 Berthing facility structure and barge particulars
Platform which is originated as a barge is design because it is a moveable and floating structure which can be use anywhere and can be installed in anytime when needed. D-type fender and Tee bollard are selected to use as the protection equipments for the barge. General arrangement of the berthing facilities is drawn out by AutoCAD 2007 together with its relevant protection equipments.
2.2Berthing energy and berthing velocity
The berthing energy is used to determine the most suitable fender for the berthing facilities. The ships ranging from 1000-10000 tons in water displacement are choosing as models of ships that berth at the facilities. As the ship is stopped by the fender, the momentum of the entrained water continues to push against the ship and this effectively increases its overall mass. The mass of specified water is called Added Seawater Mass; the added seawater influence coefficient is called Cm [3].
The berthing velocity is obtained from actual measurements or relevant existing statistic information. When the actual measured speed velocity is not available, the BSI and PIANC etc. standard is adopted to determine the required velocity value [3]. 2.3 Environmental loads on berthing facilities
Winds, currents, and waves produce dynamic loads on moored vessels due to waves follows. Static loads due to wind and current are separated into longitudinal load, lateral load, and yaw moment. 2.3.1 Lateral wind load and longitudinal wind load
Loads on moored vessels due to wind result primarily from drag. 2.3.2 Lateral current load and longitudinal current load
Current loads developed on moored vessels result from form drag, friction drag, and propeller drag. Lateral forces are dominated by form drag. Form drag is dependent upon the ratio of vessel draft to water depth: as the water depth decreases, current flows around rather than underneath the vessel. Longitudinal forces due to current are caused by form drag, friction drag, and propeller drag[4].
3. RESULTS AND DISCUSSION
3.1 Structure selection
General arrangement of the berthing facilities is drawn by AutoCAD 2007 and it has the length of overall of 62.5m, breadth 14.5m, draft 3.5m. The wetted area of the berthing facilities is 1212.98m2. The underwater volume is 2198.24m3.
3.2 Berthing Energy
Results from the numerical model for the berthing velocity and berthing energy were is shown in Table 3 and Table 4.Value of the berthing velocity for the ships berthing at the berthing facilities varies from 1000 tons to 10000 tons of water displacement a. Easy berthing (sheltered) b.dificult berthing (berthing) c. easy berthing (exposed, d. Good berthing (exposed,) , Difficult berthing (exposed)
3.3 Environmental loadings on berthing facilities
From Table 3, the wind angle is taken from 30o to 175o with the average 30o as interval. The maximum lateral wind load occurs when the wind is extreme at 90o which has the value of 3109.75 pounds. The maximum longitudinal wind load occurs when the wind is extreme at 175o which has the value of 1500.52 pounds
the current angle is taken from 30o to 175o with the average 30o as interval. The maximum lateral current load occurs when the berthing facilities is in maximum draft and have the current angle of 90o which has the value of 112.34 pounds. The maximum longitudinal current load occurs when the berthing facilities is in minimum draft and have the current angle of 145o which has the value of 12.21 pounds 4. EQUIPMENTS SELECTION
Total Lateral load on berthing facilities is 3222.09 pounds, the total longitudinal load on berthing facilities is 1512.73 pounds and the horizontal hawser load, H is 3559.52 pounds.
Fender selection
According to the British standard, the ultimate fender capacity is 2 X berthing Energy. The maximum berthing energy occurs when the berthing facilities are in the maximum load and the berthing ship is at 1000 tons displacement which has the value of 89 ton.m. The fender capacity must be at least 2 x 89ton.m = 178 ton.m
Chain Selection
Approximate chain tension, T = 1.12 H (Horizontal Hawser Load) =
= 3986.66 pounds
Maximum allowable working load,Tbreak
Tdesign = 0.35 Tbreak
3986.66 pounds = 0.35 Tbreak
Tbreak = 11390.46 pounds
* 1-inch chain with a breaking strength of 14,500 pounds
Anchor Selection
Required holding capacity = 3559.52 pounds
Seafloor type is sand
Depth of sand = 30 feet
Anchor type is Stockless
safe efficiency =4
Holding capacity = efficiency x weight
3559.52 = (4)(weight)
Weight = 3559.52/4 =889.88pounds = 0.9 kips
Use 1,000-pound (1-kip) Stockless anchor
5. CONCLUSION
This paper presents numerical model for safe berthing and protection of mobile floating berthing protection facilities. The berthing facilities can help to decrease the heavy seaborne traffic and the cost of building an extra Jetty which may become a burden to ports operator. Mobile berthing facilities can be installed anytime and anywhere to help the port operator to save money and time. The model can be improved as a working platform by simulation and prototyping for experiment that can be used for further investigation.
REFERENCES
[1] You-Sheng Wu. (2001). Practical Design of Ships and Other Floating Structures. ELSEVIERAmsterdam.
[2] John H.Hansen (1978). Mobile Ship Loading and Unloading Facility. http://www.patentstorm.us/patents/4075860.pdf [Accessed 27 August 2009].
[3] J. P. Jones (2006).Fleet Moorings. Design of fleet mooring 110-135. Naval facilities Engineering
Command.
[4] Bert J. Warner. (1989). Stable Floating pier. United State Patent Publication
