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ship structure final
nk
217
Chemical Engineering
Undergraduate 1
12/18/2011

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Term
equation for stress
Definition
load/area
(tensile, compressive, shearing)
Term
ultimate tension for steel (tension & shear)
Definition
tension: 30 sq in shear: 22 sq in
Term
equation for bending moment (fixed beam)
Definition
distance x length
Term
equation for bending moment (concentrated load, unsupported ends)
Definition
mass x length / 4
Term
equation for bending moment (uniform load, unsupported ends)
Definition
mass x length / 8
Term
A _____ end beam will support _____ times the amount of load vs a _____ end beam
Definition
fixed; 2; free
Term
The deflection of a _____ ended rectangular beam is only _____ the deflection of a ____ ended beam
Definition
fixed; 1/4; free
Term
beam of equivalent size but made up of individual layers free to slip will only carry ____ the load of a solid beam
Definition
1/5
Term
Relative strength equation (beams)
Definition
(D_larger/D_smaller)squared x original
Term
comparing deflection equation
Definition
(S_long/S_short)cubed, result x original deflection
Term
relative strength of beams
Definition
original length/new length x original load
Term
torque equation
Definition
HP x 5252 / RPM
Term
LOA
Definition
Length Overall; Linear distance from bow to stern, measured parallel to baseline
Term
Sheer
Definition
Longitudinal curvature of vessel's deck
greater fwd than aft
increases buoyancy w/ air space
Term
Beam
Definition
Width of a Ship
Term
Extreme Beam
Definition
Width + projections (bridgewing, gangway, etc)
Term
Tumble Home
Definition
inward slope of the ships side
measured widest beam less narrowest beam
Term
Flare
Definition
opposite of tumblehome
outward slope of ships side
"dryer decks," throws waves from bow
creates space/lessens impact force of water
Term
Draft
Definition
vert distance from lowest part of hull to waterline
indicated fwd aft amidships
Term
air draft
Definition
distance from highest point to waterline
important re: bridge clearances
changes due to ballast
Term
Camber
Definition
Transverse slope of deck
directs water to drains at sides
not specifically for added strength
Term
Dead Rise
Definition
Rise or slant up athwartship from bottom keel to bilge aka rise of the bottom / rise of the floor
Term
Depth
Definition
vertical distance from the lowest point of the hull to the side of the deck to which it is referred
depth = draft + freeboard
Term
Molded Dims
Definition
Dimensions taken from inside plating of a ship
important for cargo stowage
Term
Freeboard
Definition
distance measured vertically downard, at the side of vessel amidships, from upper edge of deckline to waterline
Term
Divisions of Hull
Definition
Middle Body
Entrance
Run
Term
Middle Body
Definition
mid-ship part of vessel where constant cross-sectional shape is maintained thru length.
most merchant ships = parallel middle bodies, sides are vertical
Term
Entrance
Definition
immersed part of the hull fwd of middle body
expensive to build cuz it's curvy
Term
Run
Definition
immersed part of hull aft of middle body
where thrust is applied from prop
where torque is applied from rudder
Term
parallel mid bodies
Definition
cheapest to build, hold most cargo
Term
LC overlaid (symbol)
Definition
symbol for centerline plane
Term
Reference Planes
Definition
Used as an aid in locating points for design & building
Term
Baseline Plane
Definition
established near base of ship
runs thru upper edge of flat plate keel
vert dims measured from this ref point
Term
Centerline Plane
Definition
fore-aft (longitudinal)
at right angles to BL
hull shape essentially symmetrical on either side of CL
Term
Transverse Vertical Planes
Definition
at equal intervals along length of vessel
aka frame stations
may NOT be equal to actual frame locations
Term
Forward Perpendicular (FP)
Definition
line perpendicular to BL, intersecting the fwd edge of the stem at the design waterline
Term
After Perpendicular
Definition
perpendicular to the baseline, intersecting the after end of the rudder post at the design waterline
Term
Mid-Ship Perpendicular
Definition
center of ship (longitudinally), located at the midpoint between FP and AP
Term
LBP
Definition
Length Between Perpendiculars
measured parallel to BL
Term
Mean Draft
Definition
Average between fwd and aft drafts
Term
Determination of Hog/Sag
Definition
mean draft compared to midship draft
Term
Hogging
Definition
mean draft is > mid ship draft (which is actual draft of vsl)
Term
Sagging
Definition
mean draft < midship draft (which is actual draft of vsl)
Term
Static Hog/Sag
Definition
Hog/Sag caused by cargo load
Term
Dynamic Hog/Sag
Definition
Hog/Sag caused by crest & trough of wave under hull
Term
Reading Draft Marks
Definition
Bottom of number is even
top is + 6 inches
middway is + 3 inches
Term
2 primary types of tonnage
Definition
volume
weight
Term
volumetric tonnage
Definition
used to determine vsl earning capacity
from 13 cen "tun" - wine cask
equal to 100 cubic feet
Term
Volumetric tonnage determines...
Definition
port fees, dock fees, dry dock chgs
idea is to base fees on ability to earn
Term
Gross Tonnage
Definition
entire volume of the inside of the hull from main deck down to keel
Term
Net Tonnage
Definition
Remaining tonnage after non-earning spaces are removed from Gross
ex tanks, foc'sle, psgr above main deck
Term
Tonnage Openings
Definition
Nominally water tight; no gasket
secured via bolt hooks (old wood battens)
allows for space deduction from gross
Term
Non earning spaces
Definition
doublebottoms
fore/aft peak if water ballast only
poopdeck, bridge, foc'sle w/ tonnage openings
Term
tonnage % rule
Definition
design machinery space btwn 13 & 20% of total gross tonnage and 32% may be deducted
Term
cubic ft required per crewman
Definition
120 cu ft
16 sq ft
Term
weight tonnages
Definition
displacement tons
deadweight tons
lightship tonos
Term
Displacement tons
Definition
weight of water displaced by hull
exactly equal to ships weight
Term
deadweight tons
Definition
amount of water cargo fuel and stores a vessel can carry fully loaded
Term
lightship tons
Definition
weight of empty ship
displacement of vessel w/ no cargo crew stores fuel water or ballast
Term
Lightship tons + deadweight tons = ?
Definition
Displacement tons
Term
volumetric tonnage: 1 ton = ?
Definition
100 cubic feet
Term
weight tonnage:
long ton
short ton
metric ton
Definition
long = 2240 pounds
short = 2000 pounds
metric = 2204.6 pounds (1,000 kg)
Term
4 general categories of steel items used in shipbuilding
Definition
beams plates
columns shafts
Term
hull girder
Definition
coordinated functions of all 4 groups of steel used in shipbuilding
Term
trochoidal wave
Definition
length from crest to crest = length of vsl
height = 1/20 length of vessel
use of wave this size determines max load on hull girdle & scantling requirements
Term
Load
Definition
total force acting on structure, usually expressed in pounds or tons
Term
Stress
Definition
force per unit area, usually expressed in pounds/tons per square inch
Term
strain
Definition
distortion resulting from stress
Term
tensile stress
Definition
occurs between 2 parts of a body when each draws the other end toward itself
Term
equation for tensile stress
Definition
Tensile Stress = Pull / Area
Ts = P/A
Term
compressive stress
Definition
opposite of tensile stress
Cs = push/area
Term
shearing stress
Definition
tendency of one body to slide over another body
magnitude of this tendency at any point is termed shearing stress
Term
shear stresss equation
Definition
pull/area of rivet
Term
Mild steel:
ultimate tensile strength
ultimate shearing strength
Definition
ult ts = 28-32 tons per sq inch
ult ss = 22 tons per sq inch
Term
steel flattens when...
Definition
compressed at about 18 tons per sq inch
Term
limit of elasticity
Definition
point at which metal will no longer return to its original shape
Term
yield overcome
Definition
metal hardens, slight additional weight stretches it out of proportion until reaches ultimate strength, then fails
Term
standard factor of safety
Definition
4
Term
local strength
Definition
strength of individual parts of the ship
Term
hull girder strength
Definition
strength of ship as a whole
Term
Bending moment
Definition
A moment of a force about any line is the product of the force times the perpendicular distance to that line
Term
Bending moment: 100 lbs located 4' from end of board imbedded in a wall =
Definition
weight x distance
100 lbs x 4' = 400 ft-lbs
Term
Bending moment: 100 lbs located 8' from end of board imbedded in wall
Definition
BM = weight x distance
BM = 100 lbs x 8'
BM = 800 ft lbs
Term
Beams
Definition
Horizontal strength members loaded vertically
Term
Load applied to center of beam causes...
upper surface must be under...
lower surface must be under...
Definition
...deflection
...compression
...tension
Term
zero point
Definition
layer in deflected beam where compression & tension are neutral
located along center of gravity (centroid)
Term
beam made up of 5 individual layers (versus solid beam)
Definition
will only carry 1/5 load vs solid
top 2 will NOT be under compression
bottom 2 will NOT be tension
middle will NOT be nuetral
Term
depth of solid beam...
Definition
...determines resistance/strength.
AKA larger distance from neutral axis to edges = stronger beam
Term
5 factors determine size of beam
Definition
1 type & amount of load on beam
2 distance btwn supports
3 type and efficiency of end connects
4 number of supports
5 material beam is made of
Term
type & efficiency of end connections
Definition
A) fixed-ended rectangular beam supports twice as much concentrated load as free ended
B) deflection of fixed ended rect beam is 1/4th that of free ended
Term
effect of number of supports
Definition
greater # of supports in given distance equals shorter span. shorter span equals smaller bending moment.
Term
beam materials
Definition
most ship construction is mild grade steel
other materials: stainless steel
high tensile steel
aluminum
Term
columns
Definition
strut placed such that it is loaded vertically (also referred to as stanchion or pillar)
usually symmetrical (round)
Term
shafts subjected to twisting motion...
Definition
...said to be in torsion
twisting moment = torque
Term
Torque equation
Definition
horsepower x 5252 / RPM
Term
continuity of strength
Definition
vessels must be constructed so that stresses may be graduallly and continuously dissipated
no part over/undersized
discontinuity or change in shape = stresses = failure
Term
most common welding...
Definition
...fusion welding
6,000 degrees F
usually electric arc, gas less common
Term
In the 1930's welding...
Definition
...starts to replace other joining methods. By WWII it has replaced them almost completely.
Term
discontinuity
Definition
main cause of cracks aboard ships. ex hatches, port openings, faulty welds
Term
secondary causes of fractures
Definition
low temp, unusually high bending moments, heavy seas
Term
keel
Definition
backbone. ties together transverse bottom members. absorbs large portions of stresses from hull girder action.
Term
4 types of keels
Definition
bar keel. flat plate keel. box keel. bilge keel.
Term
bar keel (hanging keel)
Definition
olderships. protects when grounded. 1st pt contact. reduced rolling. disadvantages: increased draft no xtra cargo space.
Term
flat plate keel
Definition
utilizes increased shell plate thickness allowing it and components to better withstand dry docking /grounding loads. resembles i beam
Term
transverse bulkheads assist...
Definition
...in supporting keel and bottom by transforming long flexible girder into shorter length
Term
box (duct) keel
Definition
act as conduit for wires/cables. allows access into other areas of double bottom.
Term
bilge keels
Definition
fin like pieces of steel plate fitted to hull at turn of bilge along midship length . reduce rolling in heavy seas. NOT for stability.
Term
2 types of drydock
Definition
floating & graving
Term
Bottom structure acts as ________
Definition
lower flange
Term
______ along with ________ acts to resist longitudinal stresses from passing over highs and lows of waves.
Definition
Bottom structure; keel
Term
Bottom structure must be strong enough to withstand concentrated pressures due to _____, ____, and _____
Definition
dry docking, grounding, weight of cargo
Term
Floors
Definition
transverse vertical frames across bottom of hull; not equal to house floors
Term
5 features of ship floors
Definition
vertical
transverse
extend across ship
from bilge to bilge
usually at every frame (rib)
Term
strength ring
Definition
floors, deck beams, beam brackets, frames
Term
hull girder
Definition
structure formed by entire vessel (similar to duct keel)
Term
3 types of floors
Definition
closed, solid, open (bracket)
Term
4 features of closed floors
Definition
steel plating
tank end members
water/oil tight
pierced by piping then seal welded
Term
3 features of solid floors
Definition
lightening holes
air holes
limber holes
Term
3 features of lightening holes
Definition
allow access (maitnc/inspection)
reduce weight
cut across neutral access
Term
3 features of air holes
Definition
located at top of floor
allow air to escape/enter during filling/emptying
allow equalization of pressure
Term
limber holes purpose is...
Definition
drainage holes
Term
open floors (3 things)
Definition
constructed from plain angle
25% lighter vs solid floors
not allowed under mach spaces
or areas subjected to heavy pounding loading/discharging
Term
Double bottom
Definition
compartment at bottom of ship between inner bottom (tank top) and outer bottom; cellular like an ice cube tray
Term
advantages of double bottom vs single
Definition
stronger
tanks can be used to carry fuel & ballast
structure can withstand grounding and not flood holds/mach spaces as long as inner bottom remains intact
better resists pollution
Term
Frame
Definition
One of the ribs forming the skeleton of the ship
Term
intercostal
Definition
longitudinal version of floors (which are horizontal)
Term
Two primary types of framing
Definition
Transverse
Longitudinal
Term
Large vessels (greater than 120 m) may be framed...
Definition
longitudinally framed on the bottom shell and transversely framed on the side shell.
Term
2 features of transverse framing
Definition
Act as stiffeners holding the side shell plating against external water pressure

Furnish vertical support to the outboard ends of the beams supporting the decks
Term
Transverse framing leads to greater or lesser number of frames within the hull? Frame spacing?
Definition
greater; spaced 2-3 feet apart (less at bow and stern for strength)
Term
Transverse framing maximizes ____ ____ capacity.
Definition
bale cubic
Term
Advantages of Longitudinal Framing?
Definition
greater longitudinal strength, reduced vibration, weight savings, cost savings
Term
Disadvantages longitudinal framing?
Definition
loss of bale cubic due to depth of web frames
Term
longitudinals made from either _____ or ____ brackets welded to shell plating
Definition
bulb; L
Term
Panting Frame
Definition
Additional framing in bow area to distribute the panting stresses encountered in seaway
Term
Boss Frame
Definition
Curved frame designed to accomodate the prop shaft and housing
Term
Shell plating purpose
Definition
keep water out
tie together ship framework
resist longitudinal bending stresses
Term
strake
Definition
shell plating arranged longitudinally, one plate after another in a row
Term
3 types of shell plating
Definition
flat plate
rolled plate
furnaced plate
Term
rolled plates
Definition
curvature in only one direction
most often @ turn of bilge
Term
furnaced plates
Definition
curvature in two directions
must be heated and shaped over form
most expensive; avoided as much as possible
Term
shell plates girth greater or lesser at mid ship than at ends? results in?
Definition
greater; results in excess plating at ends
Term
drop strake
Definition
when 2 rows of shell come together,top strake is dropped (called dropped strake), lower row remains (called through strake)
Term
stealer plate
Definition
"new" single plate that butts up against drop strake and through strake
Term
Butt
Definition
transverse joint between plates
Term
seam
Definition
longitudinal joint between plates
Term
sheer strake
Definition
top strake that joins with deck plating
Term
garboard strake
Definition
first strake after keel plate
Term
thickened plates (where)?
Definition
sheer strake, keel plates, bottom forward plates, bottom & bilge plates, margin plates, deck stringer
Term
deck stringer
Definition
outboard most strake on deck
Term
on shell expansion plan, lettering runs from _____ and up, and numbering runs from _____ ______
Definition
keel strake; from aft forward
Term
Deck beams are...
Definition
athwart ship members located under deck plating
Term
Deck beams usually fitted....
Definition
...on every frame
Term
frames act as ______
Definition
pillars
Term
frames carry load _____ , where it is distributed over the bottom by the ______.
Definition
downward; floors
Term
3 primary functions of beams
Definition
act as beam to support vertical deck loads

acts as a tie to keep the sides of a shp in place

acts to keep the deck plating from wrinkling due to racking
Term
racking
Definition
twisting action on vessel as the ship sails at an angle to a heavy sea
Term
weather deck beams are of _____ scantling then would be used elsewhere
Definition
heavier
Term
beam size depends on these other structural members of the vessel...
Definition
pillars
girders
thickness of plating
height between deck
Term
Camber is measured...
Definition
...at the centerline
Term
standard camber?
Definition
1/50th of beam
Term
bow sheer
Definition
.2(length of ship)+20
Term
stern sheer
Definition
1/2 of bow sheer
Term
What are the purpose of cant frames in steel vessels?
Definition
provide strength to shell plating at stern
Term
what is a stanchion?
Definition
a vertical strength member
Term
what are the synonyms for pillar?
Definition
post
stanchion
column
Term
why should pillars always be fitted in a vertical line?
Definition
To transmit load directly down to the keel, and not onto beams and deck plates.
Term
why is a pillar fitted under the windlass?
Definition
to absorb the stress, vibration, and weight of the windlass
Term
what is a partial bulkhead
Definition
bulkhead that does not extend across a compartment; used to strengthen the structure
Term
what three things does the size of a pillar depend on?
Definition
load, location, and length
Term
How does acceleration affect the size of the pillar?
Definition
dynamic load can be double the static load
Term
what is the purpose of deck girders?
Definition
support deck beams by reducing span
Term
why should pillars be well protected when cargo is loaded/unloaded?
Definition
to prevent damage, bent pillars provide little to no vertical support
Term
what is the purpose of wood sheathing
Definition
insulates - wood has low heat transmission
absorbs damage and protects deck
keeps outer decks cool for passengers
prevents sweating due to rapid temp change under deck
add aesthetic value to appearance of ship
Term
what is the purpose of the stringer plate?
Definition
thicker outboard plating to prevent racking and provide support for cargo hatchess
Term
why should corners of all hulls cut into the strength deck be rounded, doubled, or both?
Definition
to prevent cracks and notches from forming due to stress
Term
differentiate between side stringer, girder, and longitudinal
Definition
side stringer: longitudinal strength member inside deck plating
longitudinal: fore and aft strength members in bottom structure
girder: fore and aft longitudinal strength members supporting decks
Term
functions of bulkheads?
Definition
provide additional vertical support & act as structural diaphragms to resist racking
create fire & flooding boundaries
Term
what is a 2 compartment ship?
Definition
A ship that can be flooded in 2 compartments and stay afloat
Term
max number of passengers a merchant ship can carry without being considered a passenger vessel?
Definition
12
Term
what is the maximum distance the collision bulkhead can be from the stem?
Definition
1/20th the vessel length at summer load line
Term
what are the functions of the stem?
Definition
vertical extension of the keel
gives strength and rigidity to hull along center-line
ties shell plating
gives rigidity to entire bow
Term
advantages of a clipper bow?
Definition
additional space and buoyancy
flare throws water away from bow when headed into heavy seas
Term
what is the function of the stern frame?
Definition
vertical extension of the keel
provides strength for rudder and single prop
ties shell plating together at stern
Term
pillars give vertical support to...
Definition
girders
deck beams
decks
heavy concentrated loads: ground tackle, anchor windlass, line handling winches, capstains
Term
why place pillar under deck beam or girder?
Definition
redices deflection by reducing span
relieves stress on beam brackets & transverse frames
Term
top/bottom of pillar (names)?
Definition
top: head
bottom: heel
Term
purpose of doubling plate at bottom of pillars?
Definition
to spread the load over larger portion of deck plating
Term
ideal depth of beam brackets
Definition
2.5 times depth of beam
Term
purpose of upper deck?
Definition
increases seaworthiness by forming watertight top of hull and contributes strength by acting as upper flange of hull girder
Term
purpose of lower deck?
Definition
working platforms for operation of machinery and loading of cargo
living spaces for passengers and crew
Term
Additional purpose of all decks
Definition
serve as horizontal diaphram, keeping the ship in shape longitudinally
Term
Girder stress concentration?
Definition
amidships and outboard
Term
2 methods of insulation on ships?
Definition
insulation bats fixed to underside of deck via wire studs
spray on insulation applied directly to steel deck
Term
purpose of insulation?
Definition
insulate space
prevent sweating
noise barrier in engine room decks and bulkheads on passenger vessels
Term
deck coverings
Definition
paint
cement composite that flexes with deck
carpet, tile or linoleum over top of cement composite
Term
bulkhead construction
Definition
flat plate steel
or
corrugated (adds strength, reduces need for additional framing)
Term
collision bulkhead
Definition
acts as auxiliary watertight bow in event actual bow is punctured in collision
Term
afterpeak bulkhead
Definition
encloses shaft in watertight compartment
required on all screw type vessels
prevents broken prop shaft from flooding aft section of vessel
Term
machinery space bulkheads
Definition
enclose machinery spaces - watertight
regulatory requirement due to large through-hulls in engine rooms
Term
3 bulkheads required by regulation
Definition
collision bulkhead
afterpeak bulkhead
machinery space bulkhead
Term
Bulkheads are usually plated...
Definition
horizontally
Term
plate thickness thicker towards the bottom of the ship..
Definition
due to increased water pressure
Term
Why are longitudinal bulkheads avoided
Definition
danger of capsizing due to collision and flooding of one side of the ship
but they are seen in tankers
Term
longitudinal bulkheads in tankers
Definition
single hull: port and starboard longitudinal bulkheads form boundaries between port, center, and stbd tanks
double hull: usually only centerline longitudinal bulkhead
Term
3 major types of bows?
Definition
plumb
clipper
spoon
Term
plumb bow
Definition
straight up and down
classic passenger ship, aided with riveted construction
Term
clipper bow
Definition
flared bow, extra space and buoyancy, throws water when headed into seas
Term
spoon bow
Definition
ice breaker, allows bow to ride up on ice and break it with the weight of the vessel
Term
forefoot
Definition
curved connection between stem and keel
sometimes cast
Term
solid stem bar
Definition
lower stem section joining forefoot to upper stem
Term
rolled plate
Definition
plate heated and rolled to form plating around upper stem
Term
breasthook
Definition
triangular plate that joins plating and reinforces the solid stem bar
Term
peak tank/forepeak tank
Definition
located forward of collision bulkhead
serves as forwardmost ballast tank
exerts greatest moment for trim changes, good for lessening sag
Term
components of forepeak tank
Definition
valves and piping
reach rods to open and close valves
swash bulkheads reduce wave motion, can be longitudinally or transverse (generally longitudinal)
Term
Bulbous bow - what vessel speed?
Definition
higher vessel speed - improves vessel flow through water, overcomes wave making resistance
acts to fill in trough of bow wave = less power needed to reach medium/high speed
Term
two primary types of sterns
Definition
cruiser: rounded, requires cant frames and beams to make curve. older construction
transom: flat, modern construction cuz its cheaper, and waterline is carried further aft
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