Lesson Five

Bulkheads and Pillars

主讲内容主讲内容

BHDBHD

BHD BHD spacing spacing BHD BHD

constructionconstructiontypescargo ships

general

Passenger ships

stiffening

functions

• The walls of the ship serve a variety of functions. The main reason for the formation of bulkheads is to create compartments which can be used for storing cargos or creating accomodation spaces. It's believed that Chinese were the first people who started using bulkheads in their ships. Prior to that the whole hull of the ship used to be an open space.

• Not only that, bulkheads provide structural stability and rigidity to the ships. They also minimizes the violent sheer forces acting on the ship, that are generated due to waves. Moreover bulkheads are also useful from safety point of view. They prevent water from entering different parts of the ship in case there is flooding.

Language pointsLanguage points

• main bulkhead minor bulkhead

• heavy bulkhead light bulkhead

• watertight bulkhead non-watertight bulkhead

• transverse bulkhead longitudinal bulkhead

• collision bulkhead aft peak bulkhead

• corrugated bulkhead swedged bulkhead

Main bulkhead & minor bulkhead

• Main bulkheads are structurally important and must be watertight to contain flooding in a ship accident.

• Minor bulkheads are non watertight and not structurally important and designed to subdividing compartments into small units of accommodation or stores

Heavy bulkhead & light bulkhead

• Heavy bulkheads are made of thicker steel plates with larger dimensions and work as major strength members

• Light bulkheads are made of light steel plates with smaller scantlings and work as minor strength members

Watertight /non-watertight bulkhead

• Watertight bulkheads are used nowadays in all most all types of ships. They provide maximum safety in times of flooding or damage of hull. They divide the ship into watertight compartments which prevents seeping of water to other parts of the ship incase the hull is broken. The number of compartments that a particular ship has depends on the type and requirement of the vessel.

• They also facilitate storage of different types of cargo at the same time. Incase there is a fire, they prevent the source of fire or the flame to pass over to other compartment. They increase the overall strength of the ship by increasing the transverse strength. The number of bulkheads depends on the length of the ship and arrangement of machinery. It is imperative for all the ships to have a collision bulkhead

Transverse& longitudinal bulkhead

• The former extends from side to side

• The latter extends from bow to stern

Collision bulkhead& aft peak bulkhead

• The former fitted forward to protect the ship and its crew in case of collision.

• The latter fitted at the end of engine room to protect the heart of the ship without which the ship will lose power

Swedged&corrugated bulkhead

Both are characterized by not fitting stiffeners.

The use of corrugations or swedges in a plate instead of welded stiffeners produces as strong a structure with a reduction in weight. The troughs are vertical on transverse bulkheads but on longitudinal bulkheads they must be horizontal in order to add to the longitudinal strength of the ship. The corrugations or swedges are made in the plating strakes prior to fabrication of the complete bulkhead.

vertical stiffener

transverse bulkhead plating

vertical girder

side stringer

bottom plating

longitudinal bulkhead

longitudinal bulkhead

side framing

horizontal girder

horizontal bracket

bottom center girder

horizontal girder

corrugated bulkhead plating

section form of bulkhead plating

spacing

• Any bulkhead which separates any space allocated for the accommodation of passengers, other than as exercise space, from any space used as-

(a) a permanent coal bunker;(b) an oil fuel bunker;(c) a machinery space;(d) a lamp room or paint room;(e) a dry provision store room or any store room other than a linen locker, medicine locker or lifejacket locker;(f) a chain locker; or(g) a cofferdam,

shall be constructed of steel and shall be gastight and, where required, suitably insulated and, where necessary, watertight, to protect the passenger space.

Plain bulkhead

The plating strakes are horizontal and the stiffening is vertical. Since water pressure in a tank increases with

depth and the watertight bulkhead must withstand such loading, the bulkhead must have increasingly greater strength towards the base.This is achieved by increasing the thickness of the horizontal strakes of plating towards the bottom. The collision bulkhead must have plating some 12% thicker than other watertight bulkheads. Also, plating in the aft peak bulkhead around the stemtube must be doubled or increased in thickness to reduce vibration.

Assignment

• Memorize the language points

• Review the drawings with structure terms