sea fastening desig mannual

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PROCESS CHART FOR GRILLAGE & SEAFASTENING DESIGN

FORCE CALCULATION

FORCE DISTRIBUTION

INPUT

SEAFASTENING DESIGN

GRILLAGE DESIGN

ACCESSORIES



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”



FORCE CALCULATION

Depending upon the client requirements any of the followingmethods can be used.

Noble Denton crirteria John Brown method.

Sea keeping analysis.(etc)



NOBLE DENTON CRITERIA

It is used for smaller cargo transported on barge. No complicated structure is

used in this criteria.



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.



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:



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



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



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


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



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



JOHN BROWN METHOD

This is the preliminary method to calculate accelerations and forces when

the time period and angular displacements are given.



EXAMPLE:-

INPUT DATATransportation criteria

roll = 40 deg single amplitude


pitch = 12.5 deg single amplitude


heave = 5 m single amplitude


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



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



SEAKEEPING ANALYSIS

It is used when contractually required and/or for more complicated structure.



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.



Coordinate system for seakeeping analysis



C.O.G INFORMATION :-



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.



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.



Example of weight distribution by using SACS software-



SACS Model output file-



Position of GU pile on Barge for SACS Model (drawing-1)-



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:-



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



2. when the number of rows of supports are more than two:



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)



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



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.

sea fastening desig mannual

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