sea fastening desig mannual
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7/16/2019 Sea Fastening Desig Mannual
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PROCESS CHART FOR GRILLAGE & SEAFASTENING DESIGN
FORCE CALCULATION
FORCE DISTRIBUTION
INPUT
SEAFASTENING DESIGN
GRILLAGE DESIGN
ACCESSORIES
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INPUTS (from workpackage)
General Information
Weight & c.o.g information.
Material information.
Allowable stresses
Computer program used
Drawings (client drawing)
AppendicesWeight & C.O.G of module.
Barge information
Transportation layout.
Load distribution.
Cargo on barge.
References & literatureo Seakeeping analysiso Structural analysis report.
o Weight control report.
o AISC “ASD manual of steel Construction”
o ANSI/AWS D1.1 “Structural Welding Code”
o API RP 2A-WSD “Working Stress Design”
o BLODGELT,OW “Design of Welded Structure”
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FORCE CALCULATION
Depending upon the client requirements any of the followingmethods can be used.
Noble Denton crirteria John Brown method.
Sea keeping analysis.(etc)
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NOBLE DENTON CRITERIA
It is used for smaller cargo transported on barge. No complicated structure is
used in this criteria.
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TRANSPORTATION FORCESThe spreadsheet 'TRANSPORTATION FORCES' calculates the static and dynamic
transportation forces and accelerations. Parameters to be entered are transportationcriteria, cargo specifications and barge or ship information. Input and output of the
spreadsheet are consistent with the Bartran axis system. Angles and moments,
however, are according to the Right Hand Rule!
Transportation criteria
Input:
The single amplitude angle for roll, θ roll
in degrees.
The full cycle period for roll, T roll
in seconds.
The single amplitude for pitch, θ pitch
in degrees.
The full cycle period for pitch, T pitch
in seconds.
The single amplitude for heave, Aheave in meters.
The full cycle period for heave, T heave
in meters.
The spreadsheet will automatically detect the Noble Denton criteria ('General guidelinesfor marine transportations' 0014/NDI/JR - dec. 1986, section 5.2.1) and will prompt so on
the sheet.
Noble Denton Criteria are:
Single amplitude(10 sec full cycle period)
Type Roll Pitch Heave
Smallbarges 25°
15°
5 m
Larger barges
20° 12.5° 5 m
Smallvessels
30° 15° 5 m
Note that the 5 m heave at a 10 sec. cycle period accounts for a vertical accelerations of 0.2 g.
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Cargo specifications
A suitable name for the cargo can be entered for reference purposes.
Input:
The weight of the cargo, W in kN.The mass moment of inertia about the roll axis, M
o I x
in Tm2.
The mass moment of inertia about the pitch axis, M o I y
in Tm2.
The x - co-ordinate of the cargo centre of gravity, xCoG
in m.
The y - co-ordinate of the cargo centre of gravity, yCoG
in m.
The z - co-ordinate of the cargo centre of gravity, z CoG
in m.
Barge / ship information
The name or description of the barge / ship can be entered for reference purposes.
Input:
The x - co-ordinate of the centre of rotation, xCoR
in m. (Usually xCoR
is a few meter
shorter than half the barge length)
The centre of rotation is on the waterlevel: z CoR
= meandraft in m.
Note that by default the centre of rotation in y - direction is at half breadth of the
barge.
Transportation forces and accelerations
The calculated transportation forces and accelerations are a combination of dynamicforces and static forces on the centre of gravity of the cargo. The spreadsheet calculates
the vertical force, the horizontal force, the moments and the heave in the centre of gravityof the cargo. These forces and moment are calculated for roll to starboard and portside,
and pitch to stern and bow. Note: the output forces are exerted by the module on the
barge, their workpoint is the module C.o.G. An example is given below for roll tostarboard, roll to portside and pitch are calculated in a similar fashion. Shown is the stern
of a barge with cargo:
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Roll
Static forces: )cos(*, roll static
W F θ ν
−= kN)sin(*
, roll statichW F θ −= kN
Dynamic forces:
=
2
, 2***81.9 roll
roll CoGdynamicvT
yW F π
θ kN
−−=
2
,
2**)(*
81.9 roll
roll CoRCoGdynamichT
z z W
F π
θ kN
=
2
2**
roll
roll xoroll T
I M M π
θ kNm
=
2
2**
81.9 heave
heaveroll T
AW
H π
kN
Combined forces: dynamicv staticvSBv F F F ,,, += kN
dynamich statichSBh F F F ,,, += kN
Pitch
Below the forces acting at a module, and exerted on the barge, are shown for pitch to
bow:
Static forces: )cos(*, pitch staticv W F θ −= kN
)sin(*, pitch statich
W F θ = kN
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Dynamic forces:
−−=
2
,
2**)(*
81.9 pitch
pitchCoRCoGdynamicvT
x xW
F π
θ kN
−=
2
,2**)(*
81.9 pitch
pitchCoRCoGdynamichT
z z W F π θ kN
=
2
2**
pitch
pitch yo pitchT
I M M π
θ kNm
=
2
2**
81.9 heave
heave pitchT
AW
H π
kN
Combined forces: dynamicv staticv sternv F F F ,,, += kN
dynamich statich sternh F F F ,,, += kN
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Example on Noble Denton Criteria:
INPUT
Transportation criteria
Roll 20 deg single amplitude
10 s full cycle period
Pitch 50 deg single amplitude12.5 s full cycle period
Heave 5 m single amplitude
10 s full cycle period
Cargo Specification
= 24623.1 kN
Mass Moment of inertia about rollaxis MoIx = 226992.7 T-m^2
Mass Moment of inertia about rollaxis MoIy = 578363.4 T-m^2
X coordinate (from stern) = 25.631 m
Y coordinate(from center line) = 1.715 m
Z coordinate (from bottom barge) = 13.45 m
Barge Information
X coordinate from center of rotation = 61 m
Mean draft of barge = 3.8 m
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OUTPUT
CALCULATION OF FORCES ANDACCELARATIONS
Fv -22558.586 KN
roll to star board Fh -11686.965 KN
moment 31233.328 KN-M
heave(+-) 4855.4783 KN
Fv -23720.685 KN
roll to port side Fh 11686.965 KN
moment -31233.328 KN-Mheave(+-) 4855.4783 KN
Fv -35008.848 KN
Pitch to Stern Fh -24086.526 KN
moment -127328.96 KN-M
heave (+-) 4855.4783 KN
Fv 3337.3147 KN
Pitch to Bow Fh 24086.526 KN
moment 127328.96 KN-M
Heave(+-) 4855.4783 KN
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JOHN BROWN METHOD
This is the preliminary method to calculate accelerations and forces when
the time period and angular displacements are given.
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EXAMPLE:-
INPUT DATATransportation criteria
roll = 40 deg single amplitude
10 s full cycle period
pitch = 12.5 deg single amplitude
10 s full cycle period
heave = 5 m single amplitude
10 s full cycle period
Cargo SpecificationWeight = 24623.1 kN
Mass Moment of inertia about roll axis MoIx = 226992.7 T-m^2
Mass Moment of inertia about roll axis MoIy = 578363.4 T-m^2
X coordinate (from stern) = 25.631 m
Y coordinate (from center line) = 1.715 m
Z coordinate (from bottom barge) = 13.45 m
Barge Information
X coordinate from center of rotation = 61 m
Mean draft of barge = 3.8 m
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OUTPUT
CALCULATION OF FORCES AND ACCELARATIONS
roll to star board Fv -21977.5 kN
Fh -22359.7 kN
moment 62466.66 kN-m
heave(+/-) 4855.478 kN
kN
roll to port side Fv -24301.7 Kn
Fh 22359.67 kN
moment -62466.7 kN-m
heave(+/-) 4855.478 kN
kN
Pitch to Stern Fv -31529.5 KnFh -7370.17 kN
moment -49737.9 kN-m
heave(+/-) 4855.478 kN
kN
Pitch to Bow Fv -16550.5 Kn
Fh 7370.17 kN
moment 49737.88 kN-m
heave(+/-) 4855.478 kN
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SEAKEEPING ANALYSIS
It is used when contractually required and/or for more complicated structure.
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Output from seakeeping analysis:-
1. HYDROSTATIC ANALYSIS- in this c.o.g information of barge and
module will come with their stability criteria.
2. DYNAMIC ANALYSIS – in this motion and accelerations will come.
This will give the input for force calculation.
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Coordinate system for seakeeping analysis
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C.O.G INFORMATION :-
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FORCE DISTRIBUTION
Static force
o Due to weight of the module.
Dynamic force
o Due to heave.
o Due to roll.o Due to pitch.
Distribution of roll force on roll
braces.
Distribution of pitch force on pit
braces.
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In case of force distribution following points will be followed:-
1. First we find the percentage distribution of forces on supports by
using either of following softwares-
• SACS
•MOSES
• SEASAM
2. Then we distribute the static & dynamic forces on supports.
3. We design grillage & sea fasteners according to maximum reaction
and maximum Bending moment.
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Example of weight distribution by using SACS software-
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SACS Model output file-
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Position of GU pile on Barge for SACS Model (drawing-1)-
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According to the weight percentage we distribute the forces on support:-
Distribution of vertical forces:-
1. Vertical support reaction=(Percentage distribution of
forces at support* weight of module)
2. Heave forces=(Percentage distribution of forces at support* weight
of module)
3. Vertical force due to roll moment=(Percentage sharing of support
roll moment * Total moment *
Distance from center of support
in)/(second moment of area of
support)
4. Vertical force due to pitch moment=( percentage sharing of support in
pitch moment)*(total
moment)/(distance betweensupports).
Due to pure roll (Wave heading 900/2700)
Summary of total support reactions
• Maximum vertical force = vertical force +heave force + roll
couple.
• Minimum vertical force=vertical force – heave force - roll
couple.
Due to pure pitch (Wave heading 00/1800)
Summary of total support reaction
• Maximum vertical force = vertical force + heave force + pitch
couple
• Minimum vertical force = vertical force- heave force - pitch couple
Due to Quartering sea (Wave heading 450/1350/2250/3150)
Summary of total support reaction
• Maximum vertical force = vertical force + heave force + pitch
couple + roll couple
• Minimum vertical force = vertical force- heave force - pitch
couple - roll coupl
Distribution of horizontal forces:-
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To prevent the horizontal movement we use roll braces and pitch braces.
1. when the number of rows of supports are two:
Brace force = (max horizontal force * distance from c.o.g)/ (distance between row* number of braces in that row)
For Ex:-
kN
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2. when the number of rows of supports are more than two:
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For more than two rows we use BOUTEN STELLING formulae.
Brace force = ((Total moment * distance of row from c.o.s)/ (second moment of area of support)) + (Maximum horizontal force/number of rows)
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SEAFASTENING DESIGN
Pitch Braces
o Tubular brace
o Gusset plate
o Additional strengthening plate
Roll Braces
o Tubular brace
o Gusset plate
o Additional strengthening plate
CHECK WELD B/W:
o Brace & Gusset plate.
o Gusset plate &Barge deck.
o Under deck weld
GRILLAGE DESIGN
Design of Grillage arrangement.
o According to hard points on barge & their capacities.
Design of Grillage cross section
According to maximum bending moment & max. shear force.
Joint check b/w grillage & leg pot support as per AISC code
o Web local yielding
o Web crippling
o Web compression buckling
o Web sideways buckling.
Shear check in web.
Local Check
Flange bending
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ACCESSORIES
Depending on design requirement.
Wing plate
Shear plate
Saddle
Shim plate
Uplift bracket
Setup cans
Skid shoes
Wood skid beams
Load spreader beams Stoppers
Barge capacity check
Trailors arrangement etc.
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