PROCESS CHART FOR GRILLAGE & SEAFASTENING DESIGN

FORCE CALCULATION

FORCE DISTRIBUTION

INPUT

SEAFASTENING DESIGN

GRILLAGE DESIGN

ACCESSORIES

INPUTS (from workpackage)

General Informationo Weight & c.o.g information.o Material information.o Allowable stresseso Computer program usedo Drawings (client drawing)

Appendiceso Weight & C.O.G of module.o Barge informationo Transportation layout.o Load distribution.o 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 following methods 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 transportation criteria, 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, roll in degrees.The full cycle period for roll, Troll in seconds.The single amplitude for pitch, pitch in degrees.The full cycle period for pitch, Tpitch in seconds.The single amplitude for heave, Aheave in meters.The full cycle period for heave, Theave in meters.

The spreadsheet will automatically detect the Noble Denton criteria ('General guidelines for 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 HeaveSmall barges

25 15 5 m

Larger barges

20 12.5 5 m

Small vessels

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, MoIx in Tm2.The mass moment of inertia about the pitch axis, MoIy 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, zCoG 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: zCoR = 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 dynamic forces 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 gravity of 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 to starboard, roll to portside and pitch are calculated in a similar fashion. Shown is the stern of a barge with cargo:

Roll

Static forces: kN kN

Dynamic forces: kN

kN

kNm

kN

Combined forces: kN kN

Pitch

Below the forces acting at a module, and exerted on the barge, are shown for pitch to bow:

Static forces: kN kN

Dynamic forces: kN

kN

kNm

kN

Combined forces: kN kN

 Transportation criteria                     Roll 20 deg single amplitude      10 s full cycle period                          Pitch 50 deg single amplitude      12.5 s full cycle period               Heave 5 m single amplitude      10 s full cycle period                          Cargo Specification                           = 24623.1 kNMass Moment of inertia about roll axis   MoIx = 226992.7 T-m^2Mass Moment of inertia about roll axis   MoIy = 578363.4 T-m^2X coordinate (from stern)     = 25.631 m

Y coordinate(from center line)     = 1.715 mZ coordinate (from bottom barge)     = 13.45 m                      Barge Information                     X coordinate from center of rotation     = 61 mMean draft of barge     = 3.8 m           

Example on Noble Denton Criteria:

INPUT

OUTPUT

CALCULATION OF FORCES AND ACCELARATIONS  Fv -22558.586 KN

roll to star board Fh -11686.965  KN  moment 31233.328  KN-M  heave(+-) 4855.4783  KN         Fv -23720.685  KNroll to port side Fh 11686.965  KN  moment -31233.328  KN-M  heave(+-) 4855.4783  KN       

  Fv -35008.848  KNPitch to Stern Fh -24086.526  KN  moment -127328.96  KN-M  heave (+-) 4855.4783  KN         Fv 3337.3147  KNPitch 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.

INPUT DATATransportation criteria

roll = 40 deg single amplitude10 s full cycle period

pitch = 12.5 deg single amplitude10 s full cycle period

heave = 5 m single amplitude10 s full cycle period

Cargo SpecificationWeight = 24623.1 kNMass Moment of inertia about roll axis MoIx = 226992.7 T-m^2Mass Moment of inertia about roll axis MoIy = 578363.4 T-m^2X coordinate (from stern) = 25.631 mY coordinate (from center line) = 1.715 mZ coordinate (from bottom barge) = 13.45 m

Barge Information

X coordinate from center of rotation = 61 mMean draft of barge = 3.8 m

EXAMPLE:-

OUTPUT

CALCULATION OF FORCES AND ACCELARATIONS

roll to star board Fv -21977.5 kNFh -22359.7 kN

moment 62466.66 kN-m

heave(+/-) 4855.478 kNkN

roll to port side Fv -24301.7 KnFh 22359.67 kN

moment -62466.7 kN-m

heave(+/-) 4855.478 kNkN

Pitch to Stern Fv -31529.5 KnFh -7370.17 kN

moment -49737.9 kN-m

heave(+/-) 4855.478 kNkN

Pitch to Bow Fv -16550.5 KnFh 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 forceo Due to weight of the module.

Dynamic forceo Due to heave.o Due to roll.o Due to pitch.

Distribution of roll force on roll braces. Distribution of pitch force on pitch 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 SEASAM2. 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 between supports).

Due to pure roll (Wave heading 90 0 /270 0 )

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 0 0 /180 0 )

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 45 0 /135 0 /225 0 /315 0 )

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 Braceso Tubular braceo Gusset plateo Additional strengthening plate

Roll Braceso Tubular braceo Gusset plateo 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 sectiono According to maximum bending moment & max. shear force.

Joint check b/w grillage & leg pot support as per AISC codeo Web local yieldingo Web cripplingo Web compression bucklingo Web sideways buckling.

Shear check in web. Local Check

o 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.