Deck Beams
• athwart ship member located under the deck plating
• usually fitted on every frame• more desirable to fit extra beams then to increase
thickness of deck plates• fastened to the frames by beam brackets
– frames act as pillars (vertical members) – carry load downward, where it is distributed over the
bottom by the floors
Three Primary Functions of Beams
• acts as a beam to support vertical deck loads
• acts as a tie to keep the sides of a ship in place – sagging (sides want to
move away from each other)
– hogging (sides want to move toward each other)
Three Primary Functions
• acts to keep the deck plating from wrinkling due to the twisting action on the vessel as the ship sails at an angle to a heavy sea– the twisting action is called racking
Racking
• concentration of stress occurs at the beam brackets (the upper corners of the ship)– beam brackets
– transverse bulkheads
– web frames• all help to resist
this stress
Racking
• concentration of stress also in bottom corners during racking– tank side brackets help
resist this stress
Beam Brackets
• fix end of beam to frames– uniformly distributed loads on a fixed-ended
beam• at ends: BM=WL/12
• in middle: BM=WL/24
• helps explain need for beam brackets
Beam Size
• depends on beam spacing– more beams translates to smaller beam size
• less depth of beams = more headroom
– fewer beams translates to larger beam size• more depth of beams = less headroom
Weather Deck Beams
• beams under the deck exposed to the weather (weather-deck) are of heavier scantling then would be used elsewhere– due to tremendous weights involved when the
vessel ships green water over the weather deck• tanker’s weather deck is the main-deck
Beam Size
• also depends on the number and size of other structural members of the vessel– pillars– girders– thickness of plating– height between deck
Camber
• water on deck will run toward the stringer strake (outboard) and into the scuppers (drains) and falls overboard
• measured at the centerline
• beams and plating are arched upward
Standard Camber
• standard camber is 1/50 of the beam– vessel with 150 foot beam will have 3 feet of
camber• camber is measured in inches per beam of ship
– 36 inches per 150 foot beam
» I will see only half of you if we each stand on the stringer strakes on opposite sides of a vessel whose beam is 150 feet!