Shearing Forces, Bending Moments and Torsional Moment Affecting Container Ship Hull Strength & Stability
Shearing forces, Bending moments and Torsional moment :
When considering the acceptability of a container cargo stowage plan, the following procedures/guidelines concerning hull strength & stability shall be taken into account:
Shearing forces, Bending moments, and Torsional moments - These three predominant types of hull stresses affect container ships and vary due to changes in the distribution of weights on board (cargo, ballast, and fuel).
Information on maximum allowable stresses at designated frames of the vessel is provided in the vessels loading manual, and these maximum values must never be exceeded.
Stresses are usually expressed in terms of percentage, with 100% being the ceiling limit. Hull stresses must be kept to the minimum as practicable and must never exceed 100%.
It is recommended that as far as possible, Hull stresses be maintained below 90% or thereabout.
This is especially applicable to container vessels having a larger length to breadth ratio (e.g., Panamax size container ships).
Such ships are prone to stress cracks in the hull structure. High stresses may be reduced by adjusting the vessels Ballast / Fuel condition.
If this does not result in bringing the stresses within required limits, the Terminal planner / Central planner must be informed and cargo stow plan appropriately modified.
Summarized below are some necessary procedures. These procedures are only indicative, not exhaustive, and must always be guided by practices of good seamanship.
Various container handling safety technics
The daily operations involved in a busy container terminal can be termed as one of the most complex environments within the transport sector. To improve productivity in cargo handling, most terminal operators employ equipment such as straddle carriers and gantries for moving containers into and
out of the terminal stack and positioning beneath a portainer crane for lifting onboard the ship. Read more...
Safe cargo stowage and planning When considering acceptability of a container cargo stowage plan, some basic check items, procedures / guidelines concerning cargo stowage shall be taken into account . Read
more...
On Arrival Port, Prior Commencing Cargo Operation
1) The composition of cargo watch personnel shall be decided, and duties well understood.
2) All personnel involved in the cargo watch shall be briefed regarding the expected operations and provided with a Cargo Discharge Plan
. Read more...
Guidelines and procedures concerning containership hull strength & stability When considering acceptability of a container cargo stowage plan, the following procedures/guidelines concerning hull strength & stability shall be taken into account:
a) Draft, Trim, and Heel Draft restrictions at berth, approaches, passage, and next port shall be taken into consideration, and vessels maximum draft must be maintained within the applicable restriction. Read more...
Procedures for reefer cargo handling
Reefer containers require special care after they are loaded on board ship. These containers need to be supplied with power, monitored closely for proper function and repaired as required in case of malfunction. Read more...
Containership operation: 2 in 1 (Two in One) Loading
The term 2 in 1 operation is typically used when two 20feet units are loaded in one 40feet bay underdeck. When such loading operation is being conducted, it must be ensured that the terminal staff is aware of the vessels lashing system. Read more...
Containership operation: Cargo lashing
Regular inspection and maintenance of ship cargo securing devices must be carried out. These would include a routine visual examination of components being utilized, lubrication of securing devices, repair of damaged securing devices and separating and rejecting damaged/unusable securing devices. Read more...
Containership Cargo securing When containers are carried on deck, the ship is required to be approved for that purpose and the containers themselves are secured with twistlocks and lashings. These usually consist of steel rods and turnbuckles. Read more...
Containership Cargo hold ventilation
Cargo holds of container ships are fitted with two basic types of ventilation systems, namely natural and mechanical. Mechanical ventilation could be of either the supply or the exhaust type.
Read more...
Safety navigation for container ships While planning the passage for intended voyage the safety of navigation should be accommodated in, where it is both reasonable and possible to do so, Read more...
Containership operation: Safety of personnel On board containerships there are several potential safety hazards in the cargo working area and these will have to be identified, made safe and monitored to ensure continued safety. Read more...
Containership operation: hull damage stevedores In case a third party including stevedores is responsible for an accident caused by work, such as Cargo handling, Bunkering, or Loading ships stores or the like, the Master shall handle the accident with appropriate steps to claim for damages. Read more...
Containership Navigation : Ships motion in a seaway Ships are affected by movement in six degrees of freedom; rolling, pitching, heaving, swaying, surging and yawing. Of these, rolling, pitching and heaving generate the highest forces during heavy weather.
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Container stacks being too heavy and too high overall, exposing the lower containers to excessive transverse racking and compressive forces due to the tipping effect. Read more...
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