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

Deck Beams beams act as tie (top) keeps deck plating from wrinkling (bottom)

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 Brackets a bracketed beam tends to check racking (twisting) of the hull

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!