CHEVRON AUSTRALIA PTY LTD
DESIGN BASIS FOR
SEA TRANSPORT ANALYSIS
For The
GORGON PROJECT
BARROW ISLAND LNG PLANT
Document No.: G1-TE-S-OOOO-PDB0003
Revision:
0
1
Prepared by:
P. Minchin
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Reviewed by:
P. McCarthy
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Approved by:
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D. Rowe
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Approved by:
J. Kelly
J. Kelly
Revision
Date:
060ct09
06Aug10
Issue
Purpose:
IFD
RFD
Kellogg Joint Venture Gorgon
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"Confidential Property of Chevron Australia Pty Ltd. May be reproduced and used only in
accordance with the express written permission of Chevron Australia Pty Ltd."
Gorgon Project, Barrow Island LNG Plant
Contract No: 68500019
Job No 6300
Design Basis For Sea Transport Analysis
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
SUMMARY OF DOCUMENT REVISIONS
Rev.
No.
Date
Revised
Section
Revised
A
31 Jul 09
-
Issued for Client Review (ICR)
0
06 Oct 09
-
Issued for Design (incorporating CVX comments)
1
06 Aug 10
1.3
4.4/ 4.5/ 4.6
4.7
5.2/ 5.3/ 5.4
5.5
7.1
-
Revision Description
References updated
Grillage & Sea Fastenings updated
Added
Accelerations updated
Wind speeds clarified
Combinations updated
Miscellaneous updates
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Gorgon Project, Barrow Island LNG Plant
Contract No: 68500019
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Design Basis For Sea Transport Analysis
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
TABLE OF CONTENTS
1.
GENERAL
5
1.1
1.2
1.3
Background
Scope of Document
Applicable Documents
1.3.1 Project Documents
1.3.2 Codes and Standards
Abbreviations
Definitions
5
5
5
5
6
6
7
DESIGN DATA AND ASSUMPTIONS
8
2.1
2.2
8
8
1.4
1.5
2.
3.
4.
OUTLINE PROCEDURE
9
3.1
3.2
9
9
11
4.1
4.2
4.3
4.4
4.5
11
11
11
12
13
13
15
17
17
17
17
17
18
19
20
21
22
22
22
4.7
Structural Model
Orientation on Transport Vessel
Transverse Location on Transport Vessel
Support Conditions
Modules
4.5.1 Grillages
4.5.2 Sea-fastenings
4.5.3 Uplift Restraints
PARs
4.6.1 General
4.6.2 Elevated PARs
4.6.3 3 m PARs
4.6.4 6 m PARs
4.6.5 PARs < 12 m wide
4.6.6 PARs ≥ 12 m wide
4.6.7 Stacked PARs
PAUs
4.7.1 PAUs 9 m or Wider
4.7.2 PAUs Less Than 9 m Wide
LOADS
5.1
5.2
5.3
5.4
5.5
5.6
6.
Description
Application in StaadPro
COMPUTER MODEL
4.6
5.
Criteria & Assumptions
Steel
24
Weight
Vessel Motions - Modules
Vessel Motions - PARs
Vessel Motions – PAUs
Wind Loads
Vessel Deflection
24
24
25
25
26
26
BASIC LOAD CASES
28
6.1
28
28
28
28
6.2
Stage 1 – Static Loads Analysis
6.1.1 Static Loads
6.1.2 CG Envelope
Stage 2 – Inertia Loads Analysis
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Contract No: 68500019
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Design Basis For Sea Transport Analysis
7.
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
DESIGN VERIFICATION
30
7.1
7.2
30
32
Load Combinations
Code Checks
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Design Basis For Sea Transport Analysis
1.
GENERAL
1.1
Background
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
The Modules, PARs and PAUs for the Gorgon LNG Plant will be transported by sea
from the fabrication yards in North-East or South-East Asia to Barrow Island, Australia.
The modularised structures addressed in this Design Basis will be loaded out at the
fabrication yard onto the transport vessel using self-propelled modular transporters
(SPMT) or by lifting. On reaching Barrow Island, the structures will be moved to their
design locations in the facility using SPMT.
The transport vessels will be self-propelled and capable of weather routing to avoid the
most severe cyclone conditions en route to Australia. If any structures are to be carried
by barge, additional Sea Transport criteria will be developed.
1.2
Scope of Document
This Design Basis describes the procedure to be used during Phase 4 (Detail Design)
for the structural strength analysis of modularised structures for Sea Transport
operations.
The purpose of the analysis is to obtain forces and deflections in the structure for input
to primary member and joint design. The Design Basis gives the principles and
methods for determining forces on the structure, the modelling and analysis method,
and defines the load combinations for code checking.
Sea Transport is one of several design conditions for the structure. Other design
conditions are covered in Reference [2] and referenced documents.
9
Any re-sizing of members and joints arising from the Sea Transport analysis must be
done in conjunction with results from these other design conditions.
Fatigue design, including the Sea Transport condition, is addressed in Reference [19];
the fatigue methodology for Sea Transport is described in Ref. [22].
9
1
1.3
Applicable Documents
The applicable CVX, KJVG documents, Codes, Industry Standards and Government
Regulations are referenced below.
1.3.1
Project Documents
The following are referenced or associated Project Documents:
1.
G1-TE-S-0000-SPC0001
Design Requirements for Wind Loads
2.
G1-TE-S-0000-SPC2001
Structural Steel Design Criteria
3.
G1-TE-S-0000-SPC2002
Modularised Structural Steel Fabrication and Welding
4.
G1-TE-S-0000-SPC2060
Structural Steel Fabrication and Welding
5.
G1-TE-T-0000-SPC0002
Loadout and Seafastening Specification
6.
G1-TE-Z-0000-REP1006
Module Weight Report
7.
G1-TE-Z-0000-REP1014
PARs and PAUs Weight Report
8.
G1-TE-S-0000-PDB0001
Design Basis for Structural Analysis Computer Model
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Design Basis For Sea Transport Analysis
1.3.2
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
9.
G1-TE-S-0000-PDB0002
Design Basis for Land Transport Analysis
10.
G1-TE-S-0000-PDB0005
Design Basis for Primary Joints
11.
G1-TE-T-0000-REP0005
Module Transportation Phase 4 Design Accelerations
12.
G1-TE-T-0000-REP0007
PAR Transportation Phase 4 Design Accelerations
13.
G1-TE-T-0000-REP0008
PAU Transportation Phase 4 Design Accelerations
14.
G1-TE-T-0000-TCN0001
Design of Transportation Grillages and Seafastening Steelwork
15.
G1-TE-T-0000-TCN0002
Module Transportation - Vessel Deflections
16.
G1-TE-T-0000-TCN0003
PAR Transportation - Vessel Deflections
17.
G1-TE-T-0000-TCN0004
PAU Transportation - Vessel Deflections
18.
G1-TE-S-0000-PDB0004
Design Basis for In-Service Analysis
19.
G1-TE-S-0000-PDB0008
Design Basis for Fatigue Analysis
20.
G1-PP-DWN-WIN-KS200009
StaadPro Guidance Notes
21.
G1-PP-DWN-WIN-KS200013
Structural Analysis Load Combinations
22.
G1-PP-DWN-WIN-KS200019
Sea Transport Fatigue Methodology
23.
G1-NT-REPKZ900002
Modules Sea Transport Schedule
Codes and Standards
Structural design shall be carried out in accordance with the following codes and
standards:
1.4
24.
AISC 360-05
Specification for Structural Steel Buildings [Allowable Stress Design]
25.
API RP 2A-WSD
Recommended Practice for Planning, Designing and Constructing Fixed
Offshore Platforms – Working Stress Design – 21st Edition
Abbreviations
ASD
Allowable Stress Design
ASF
Allowable Stress Factor
CG
Centre of Gravity
COR
Centre of Rotation
MOD
Module
PAR
Pre-Assembled Rack/ Pipe Track
PAU
Pre-Assembled Unit
SHLV
Semi-Submersible Heavy Lift Vessel
SPMT
Self-Propelled Modular Transporter
WSD
Working Stress Design
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1.5
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
Definitions
Definitions of Primary/ Major/ Secondary and Tertiary Steel are given in Table 1 of
Reference [2].
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Document No: G1-TE-S-0000-PDB0003
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2.
DESIGN DATA AND ASSUMPTIONS
2.1
Criteria & Assumptions
The accelerations for Structural Design of MODs, PARs and PAUs are obtained from
References [11], [12] and [13]. They are an envelope of the various acceleration
components for all the cargo and vessel cases considered.
1
1
1
The corresponding stowage plans and deflected shapes for the transport vessels are
given in [15], [16] and [17]. Proposed stowage plans are collated in Reference [23].
1
1
1
1
In determining structure orientation on the transport vessel, it is assumed that load-out
and load-in are over the stern of the vessel.
Unless specified otherwise, the transport vessel in harbour will be assumed to be on
level keel, i.e. the structural supports lie in the same horizontal plane.
2.2
Steel
Steel material properties for analysis and design shall be as given in Reference [2].
1
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Design Basis For Sea Transport Analysis
3.
OUTLINE PROCEDURE
3.1
Description
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
The structural strength model will have supports corresponding to the grillage positions
on the transport vessel. In general, the support locations will be arranged so that
transfer of longitudinal hogging and sagging deflections of the vessel to the structure will
be minimised.
Where there are multiple support positions along the axis of the vessel, such that
deflections are imposed on the structure, the vessel deflection will be modelled by
imposing support deflections on the structural model.
The sea transport loading conditions are complex combinations of hydrodynamic loads
applied to the transport vessel and inertial gravitational loads associated with the
resulting motions. For the motion-induced loads, the analysis will assume that the most
onerous combination of displacement and acceleration may occur simultaneously.
Mass moment of inertia effects are considered in the derivation of inertial forces.
STATIC CONDITION
The structure is supported on the transport vessel in the harbour, immediately after setdown on the seafastening grillage, and before weld-out of seafastenings. The structure
is analysed for gravity load only and is free to deflect in the horizontal plane.
STATIC AND INERTIA FORCES
The structure is supported on the transport vessel in the sea-going state, with the
seafastening restraints applied. The structure is subject to combinations of inertia
forces caused by the vessel accelerations, and the varying effects of gravity forces
corresponding to the pitch and roll angles of rotation.
Although the forces are dynamic, the wave periods (typically 10 to 15 sec) are much
longer than the natural periods of the structure, so that the motions can be analysed as
quasi-static forces.
The static loads, together with loads to balance any spurious restraints, are combined
with the inertial loads.
Support displacements, due to flexibility of the vessel, are modelled.
3.2
Application in StaadPro
The application in StaadPro of the Staged analysis method (above) is described in
Section 6.3 of [8].
1
Where the support condition is geometrically non-linear, e.g. “compression-only”
supports, all loads need to be included in a single analysis step to ensure convergence
to the correct result.
Static loads are analysed in isolation (as described in 3.1) to determine the restraint
forces generated in roll- or pitch-restraints if they were present.
These forces, or equivalent deflections, are introduced into the inertial analysis as an
additional loadcase, ensuring that spurious forces are removed from the model and the
correct member forces induced.
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Design Basis For Sea Transport Analysis
Document No: G1-TE-S-0000-PDB0003
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The detailed procedure in Reference [20] has been developed to allow the application of
vessel hog and sag deflections together with the gravity and inertial forces.
1
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4.
COMPUTER MODEL
4.1
Structural Model
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
The computer model for Sea Transport will include all significant items of equipment
present during the Sea Transport. Items such as tall vessels, large skids, etc. are
modelled explicitly using nodes and dummy elements to give the correct mass
properties, particularly the vertical CG.
The sea transport analysis model will include sets of supports for the static loads and for
the inertia loads.
•
Vertical supports representing the dead-weight supports on the vessel grillages
•
Lateral restraints, which are different for the static and inertia analyses
•
Any loads or parts of the structure not present during sea transport will be excluded
•
Displacement load cases to represent vessel deflection. This is applicable where
the structure is supported at more than two locations along the length of the vessel
•
Dead load cases to represent the weight of any temporary items present during sea
transport
•
Six unit load cases to represent the individual acceleration components, referenced
to the appropriate centre of rotation
•
Load combinations of static, inertia loads and vessel displaced shape.
It should be noted in particular that, because on the “legs down” philosophy adopted for
module construction and installation, the main grillage lines are eccentric to the main
structural framing lines. The analysis model must reflect the true proposed support and
load transfer arrangement.
4.2
Orientation on Transport Vessel
The orientation of the structure on the transport vessel is influenced by:
•
SPMT alignment with respect to the transport vessel. The analyses assume that
load-out and load-in are over the stern of the vessel, so that the SPMT are aligned
bow-stern.
•
SPMT alignment with respect to the structure. The alignment of the SPMT with
respect to the structure is determined by the direction in which the structure is to
approach its final location at the Gorgon LNG Plant. This is dictated by the
construction philosophy.
The orientation of each structure with respect to the vessel must be confirmed explicitly
on a case-by-case basis. In particular, smaller structures may have to be analysed for
more than one orientation and position on the vessel.
In each case, reference will be made to the stowage plans.
4.3
Transverse Location on Transport Vessel
In general, wider or heavier structures will be centred on the longitudinal centreline of
the transport vessel at an extreme bow or stern location. Smaller structures will be
assumed to be in an extreme port or starboard quarter location.
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Document No: G1-TE-S-0000-PDB0003
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The different positions will be considered in the transport motions analysis; the
accelerations generated by the Naval Architect [11] [12] [13] reflect the selected
location.
1
4.4
1
1
Support Conditions
Supports will be modelled as fixed joint restraints in the global X, Y or Z directions.
Longitudinal (hog or sag) bending of the vessel will be modelled by applying imposed
deflections to the model restraints.
In the static loads analysis, the model will be supported vertically at the points
corresponding to the dead weight supports on the transport vessel. In practice, the
structure is free to translate horizontally, being restrained only by friction. Therefore,
‘dummy’ lateral restraint forces will be induced in the static model. An example of a
suitable configuration is shown in [8].
1
In the inertia loads analysis, horizontal restraints will be applied that replicate the
proposed pitch and roll restraints, as outlined in Section 4.5.2. Deflections will be
applied to the roll and pitch braces to balance/ eliminate the unintended static restraints
included in the preliminary static analysis.
1
The supports system in Figure 4-1 is to be used for the final verification analysis.
1
The pitch restraints will be at or close to the centre of the Module and all the vertical
restraints along this transverse frame will be acting both in tension and compression. All
other vertical restraints will be modelled as compression only members.
Roll braces will be modelled at each transverse frame.
Horizontal restraints will be applied at the underside of the lower deck girders. If
seafastening braces need to be introduced at a higher elevation (for example to reduce
stresses in a slender or tall structure), these bracing members will be modelled in the
analysis.
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Figure 4-1 Grillage Arrangement
Typical Grillage
Support Beams
Forward
Vessel
Unless noted otherwise all the
Vertical Supports at the Grillage
Beam positions are to be
Compression Only Supports
1) Pitch Restraints to be in or near the
middle of the module centreline
2) All Vertical supports at the grillage points
at or near the middle of the module are to
be both tension and compression supports.
3 Different positions of internal Roll Braces have been shown. Any one which
suits the module should be selected.
4.5
Modules
4.5.1
Grillages
A typical Module grillage layout is shown in Figure 4-2. The main load is taken by the
two 1300 mm deep plate girders (nominally 400 mm wide) under the transverse beams
on either side of the main columns. These plate girders then distribute the loads to four
1100 mm deep plate girders which then transfer the load to the SHLV web frames at
eight points. The dimensions are “typical” and may need to be varied in specific cases.
1
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Figure 4-2: Typical Grillage Arrangement
Longitudinal Beam
SHLV Web Frames
B
Transverse Beam
B
A
A
Plan View
SHLV Deck
View B -- B
SHLV Web Frames
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4.5.2
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
Sea-fastenings
The Module roll and pitch braces will frame to the underside of the primary steel to
ensure they are easy to install and remove.
For 36 m-wide modules, the roll braces will be within the structure footprint. For
structures of other widths, depending on the location on the transport vessel, some of
the roll braces may need to be outside the footprint.
Additional members, from the centreline of the primary member to the top of the grillage,
will be introduced to model the eccentricities to top of grillage supports. Vertical
restraints will be modelled at these ends, nodes N2, N6, N9 and N13. Roll braces will
be modelled from centreline of the primary members and roll restraints will be applied at
the bottom ends of the roll braces, node N7 (Figure 4-3). The most appropriate position
of the roll braces along transverse frames will be decided by the engineer to minimise
the support reactions and will be one of the three options shown in Figure 4-1.
1
1
In the case of external roll braces, additional members will be modelled for the roll
braces and to represent the eccentricity of the connection to the primary steel member
centreline and also to top of the grillages. Roll restraints will be applied at the bottom
end of the roll braces, node N1; vertical restraints will be applied at nodes N4 and N8,
ref. Figure 4-4.
1
In Figure 4-3 and Figure 4-4, uplift restraints are shown connecting the grillage to the
underside of the module. Uplift restraints are discussed further in Section 4.5.3.
1
1
1
Figure 4-3: Typical Internal Roll Brace Arrangement
N1
N3
N2
N5
N8
N6
N9
N4
Vertical Restraints at N2, N6, N9 & N13
Roll Restraints at N7
N10
N12
N13
N11
N7
Internal Roll Braces
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Figure 4-4: Typical External Roll Brace Arrangement
Pitch braces will be modelled at or near the middle of the Module (Figure 4-1) and will
be connected to one transverse frame only, to avoid load being induced into the module
as the transport vessel deflects under wave loads; they will be in line with the
longitudinal frames. Typical arrangements are shown in Figure 4-5 and Figure 4-6.
Pitch restraints will be applied at node N4.
1
1
1
The preferred arrangement is shown in Figure 4-5, where the pitch braces are
connected to an intermediate transverse frame. In this case, the pitch braces will be
connected to nodes N1 and N4 and pitch restraint will be applied at node N4. Figure
4-6 may be adopted if Figure 4-5 cannot be used in a particular case.
1
1
1
Figure 4-5: Preferred Pitch Brace
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Figure 4-6: Pitch Stop Arrangement
4.5.3
Uplift Restraints
Uplift forces will be taken by grillage supports on transverse frames at or close to the
centre of the Module (Figure 4-1), or elsewhere as optimised. Other grillage supports
are to be designed to take compressive forces only.
1
4.6
PARs
4.6.1
General
PARs will be transported from the fabrication yard to Barrow Island on board SHLV type
vessels. A number of PARs will be transported on each vessel, where they are close to
each other. This leaves restricted space for installing roll or pitch braces.
The pitch restraints will be located at a single transverse frame close to or at the centre
of the PAR.
Roll restraints will be located at each transverse frame.
4.6.2
Elevated PARs
Elevated PARs will be transported from the fabrication yard to Barrow Island on board
SHLV type vessels. A number of these PARs are being transported on each vessel,
where they are fairly close to each other. This leaves restricted space for installing roll
or pitch braces.
4.6.3
3 m PARs
The 3 m wide PARs require only one row of SPMT for load-on and load-off from the
SHLV. Due to column spacing and the base plates which will be required for fixing to
the main columns on site, there is not sufficient space for the single row of trailers.
Hence for load-on and load-off from the SHLV temporary spreader beams will be
required under the main columns. These spreader beams will also be used for sea
transportation such that grillages will be set apart at 3500 mm, Figure 4-7.
1
The computer analysis model for the 3 m wide PARs will be as shown in Figure 4-7,
where the eccentricities will be modelled to represent grillage supports under the
spreader beams relative to the main columns. Vertical and roll restraints will be applied
1
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at nodes N5 and N10 and on one transverse frame the pitch restraints will be applied at
nodes N3 and N8. Alternatively, pitch restraints could be considered at N1 and N6, to
reduce minor-axis bending of the columns.
Figure 4-7: 3m Interconnecting PARs
4.6.4
6 m PARs
The 6 m wide PARs will be loaded using a temporary frame and the grillage will be
supported off the stubs connected to the main columns, Figure 4-8. The grillage beams
will then distribute the loads to the SHLV web frames at four points adjacent to each
column.
1
The computer analysis model will as shown in Figure 4-8; eccentricities will be modelled
to represent the intersection of the braces with the columns and the grillage supports.
Vertical and roll restraints will be applied at node N5 and on one transverse frame the
pitch restraints will be applied at node N3.
1
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Figure 4-8
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
Support for 6 m PAR
N1
N4
~420
N2
~420
N5
~510
N3
~510
~800
~800
4.6.5
PARs < 12 m wide
For PARs below 12 m width, the preferred option is to use a permanent load-out beam,
the underside of which will be set 2900 mm above the underside of the column base
plate level and the grillage will be under the stubs connected to the main columns,
Figure 4-9. The grillage beams will then distribute the loads to the SHLV web frames at
two points adjacent to each column. If this option is unsuitable then a temporary loadout beam will be used [Figure 4-10] but with grillage arrangement similar to that for the
preferred option.
1
1
For the preferred option, the computer analysis model will as shown in Figure 4-9, with
eccentricities modelled to represent the actual points of intersection of the braces with
the columns and also where the grillage supports will be. Vertical and roll restraints will
be applied at node N5 and on one transverse frame the pitch restraints will be applied at
node N3.
1
The computer analysis model for the second option will as shown in Figure 4-10, with
eccentricities modelled to represent the intersection of the braces with the columns and
also where the grillage supports will be. Vertical and roll restraints will be applied at
node N5 and on one transverse frame the pitch restraints will be applied at node N3.
1
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Figure 4-9
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
PARs up to 12m Wide – Preferred
BEAM FOR TRANSPORTATION IS APPROX 3m ABOVE GRADE,
WILL ALLOW SMALL VEHICLE ACESS AND ENCE NEED NOT
BEAM FOR TRANSPORTATION IS APPROX 3m ABOVE GRADE,
WILL ALLOW SMALL VEHICLE ACESS AND ENCE NEED NOT
~2900
~2900
N1
150
N4
~750
N2
N5
~950
N3
~750
300
~900
~950
300
~900
Figure 4-10 PARs up to 12m Wide – Alternative
4.6.6
PARs ≥ 12 m wide
For PARs with width of 12 m or more, the load-out will use a temporary frame and the
grillage will be under the stubs connected to the main columns, Figure 4-11. The
grillage beams will then distribute the loads to the SHLV web frames at four points
adjacent to each column.
1
For the 12 m and wider PARs the computer analysis model will as shown in Figure 4-11,
where the eccentricities will be modelled to represent the actual points of intersection of
the braces with the columns and also where the grillage supports will be. Vertical and
1
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roll restraints will be applied at nodes N5 and N7 and on one transverse frame the pitch
restraints will be applied at node N3.
Figure 4-11: PARs ≥ 12 m Wide
N1
N4
N6
N2
N5
N7
1050
N3
1050
~1250
1000
~300
1000
~1250
~300
~1250
4.6.7
1000
1000
~1250
Stacked PARs
Stacked PARs are to be transported using spreader beams over the SPMTs - Figure
4-12. The analysis scheme follows that of Figure 4-7.
1
1
Figure 4-12: Stacked PARs
The spreader beams will be transported with the PARs to Barrow Island where they will
be re-used to off-load the PARs before being separated for transport and installation.
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4.7
PAUs
4.7.1
PAUs 9 m or Wider
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
For PAUs with width of 9 m or more, grillage beams will be located on one side of the
main column only and external roll braces will be used, see Figure 4-13. The grillage
beams will then distribute the loads to the SHLV web frames at four points adjacent to
each column, typical side elevation will be similar to Figure 4-2 View B – B.
1
1
The computer analysis model for these PAUs will be as shown in Figure 4-13.
Eccentricities will be modelled to represent the grillage supports points. Vertical
restraints will be applied at nodes N4 and N9. The external roll braces will be modelled
as in Figure 4-13 and roll restraints will be applied at nodes N5 and N10.
1
1
Pitch braces will be modelled on one transverse frame near the middle of the PAU.
Modelling of these braces will be similar to those shown in Figure 4-5 for the Modules.
1
Figure 4-13: PAU 9m or Wider
4100
400
400
400
1205
1205
N8
N3
N1
N4
N6
N
4100
N5
N2
N1
0
N7
400
400
1205
4.7.2
400
1205
PAUs Less Than 9 m Wide
For PAUs less than 9 m wide, the grillage beams will be located below the permanent
cantilever steelwork on the external side of the main columns - Figure 4-14. External
roll braces will be used and will be connected to the cantilever steelwork, Figure 4-14.
The grillage beams will then distribute the loads to the SHLV web frames at four points
adjacent to each column, typical side elevation will be similar to that in Figure 4-2 View
B – B.
1
1
1
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For these PAUs, the computer analysis model will as shown in Figure 4-14 where the
eccentricities will be modelled to represent the actual points of intersection of the braces
with the columns and also where the grillage supports will be. Vertical restraints will be
applied at nodes N4 and N11 and roll restraints will be applied at nodes N5 and N10.
1
Pitch braces will be modelled on one transverse frame near the middle of the PAU.
Modelling of these braces will be similar to those shown in Figure 4-5 for the Modules.
1
Figure 4-14: PAUs less than 9m Wide
4100
400
400
400
1205
1205
150
150
N1
N3
N8
N6
N4
N9
N1
N1
4100
N2
N7
400
N5
400
400
1205
N10
1205
Dimensions are “typical” and may need to be varied in specific cases.
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5.
LOADS
5.1
Weight
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
The Sea Transport analysis will use the latest transport weight derived from the Weight
Report [6] [7].
1
1
Load cases will be adjusted to ensure that the weight and CG (including the vertical CG)
from the analysis match the Weight Report values, taking into account demonstrable
weight changes.
5.2
Vessel Motions - Modules
Module Transport design accelerations are given in Table 5-1 (from [11]).
components are defined in Figure 5-1.
1
1
The
1
Table 5-1: Design Accelerations
In applying rotational accelerations to the structural model, it is necessary to define the
centre of rotation (COR) to which the acceleration sets are referenced.
Figure 5-1 shows the directions of positive inertia forces and moments.
1
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The horizontal linear accelerations include the variations in gravity forces caused by the
pitch and roll rotations of the vessel.
The acceleration components are ‘single-amplitude’. The components are equal in
magnitude in the positive and negative directions. Thus, for example, roll accelerations
to port and to starboard are of the same magnitude, but in the opposite direction. The
values in the table correspond to positive roll and pitch displacements; the full list of load
conditions will consider all possible combinations of motion couplings (positive and
negative).
5.3
Vessel Motions - PARs
PAR Transport design accelerations are given in Table 5-2 (from [12]).
1
1
These apply to PARs generally except Jetty PARs.
Table 5-2: PAR Design Accelerations
5.4
Vessel Motions – PAUs
Design accelerations for PAUs are given in Reference [13].
1
Table 5-3: PAU Design Accelerations
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Figure 5-1: Inertia Force Components
5.5
Wind Loads
Wind loads are included in the Naval Architect’s inertia analysis, applied in the same
direction as the horizontal forces caused by the vessel motion.
Wind speed (1-min mean at 10 m above sea level) [2] is 25 m/s (non-cyclonic) for units
transported on SHLV.
1
Local wind loads on the structural elements may be generated using the Ultimate Limit
State wind loads from the In-Service analysis, and scaled down for the correct wind
speed using the REPEAT LOAD facility in STAAD.Pro.
5.6
Vessel Deflection
The transport vessel will deflect longitudinally into hogging and sagging shapes during
sea transit. These deflections can affect the structural integrity, depending on the
configuration of the seafastenings provided.
If the structure is restrained longitudinally at two or more locations, it will act compositely
with the vessel. Hogging and sagging deflections in the vessel will then produce
longitudinal shear forces between barge and structure that could exceed the structural
capacity. This effect is avoided if longitudinal (pitch) restraint is provided at only one
longitudinal position, with the structure free to displace longitudinally elsewhere.
Therefore, where practical, pitch restraints will be provided at only one longitudinal
location.
Depending on the number of vertical support positions, sagging and hogging
displacements of the vessel could impose vertical displacements and curvatures on the
structure. For structures with more than two lines of support on the vessel the hogging
and sagging of the vessel will impose vertical displacements on the structure supports.
These displacements will be included in the analysis using forced-displacement load
cases.
The vessel deflected shapes for the various transportation voyages are defined in [15],
[16] and [17]. It is assumed that the grillage supports are shimmed so that the structure
is level in the Stillwater condition. The effective vessel hog and sag will be relative to
the Stillwater condition, as demonstrated in Figure 5-2.
1
1
1
1
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Figure 5-2: Effective Hog and Sag
Effective Vessel Hog
(90m from stern)
Effective Vessel Sag
(90m from stern)
The effective vessel hog and sag deflection will be calculated at each support, taking
into account the support location along the length of the vessel and using the curve for
the applicable voyage.
Forced displacements will be applied in STAAD to the supports located within the length
of the structure (rows 2, 3 and 4 in Figure 5-3), and will be calculated relative to the
displacements at the end supports (rows 1 and 5 in Figure 5-3). Zero displacement will
be applied in STAAD to the end supports.
1
1
Figure 5-3: Longitudinal Section of Example Structure on Vessel
Vessel Deck
Support Row: 1
2
3
4
5
Hog and sag of the transport vessel will be combined with the surge, pitch and heave
accelerations.
Transverse and torsional deflections of the transport vessel will be assumed to be
negligible.
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6.
BASIC LOAD CASES
6.1
Stage 1 – Static Loads Analysis
6.1.1
Static Loads
Basic load cases that define the total transport weight in the static analysis are outlined
in Table 6-1 (this is an indicative list). These will be analysed in the static loads
analysis, for later combination with results of the inertia loads analysis.
1
Table 6-1: BASIC LOAD CASES FOR STATIC ANALYSIS
Load
Case
Description
Load cases developed as
required
Dead: Self Generated Dead Weight
Dead: Non-generated Structural Dead Loads
Dead: Architectural Dead Loads
Dead: Mechanical and HVAC Equipment - Dry
Dead: Electrical Equipment
Dead: Instrumentation
Dead: Loss Prevention
Dead: Piping - Dry
Temporary items (slings, rigging, or equipment in temporary location)
Temporary: HUC Equipment transported with structure
6.1.2
CG Envelope
Uncertainty in the Centre of Gravity is accounted for as described in Reference [9].
1
The dimensions of the CG envelope are the same for Land Transport and Sea
Transport analyses. Two load cases, simulating moments about the Global X and Z
axes, are used to shift the static load CG to the four corners of the CG envelope. The
load combinations will incorporate each location for the static load CG.
6.2
Stage 2 – Inertia Loads Analysis
Unit inertia load cases lists are given in Table 6-2. These load cases will be suitably
factored in Stage 3 to give the appropriate total inertia loads on the structure.
1
The basic unit acceleration load cases (701 – 706) will be generated using the weight
load cases in Table 6-1 to define the total mass of the model.
1
Rotational accelerations are defined using the angular acceleration and the reference
centre of rotation. The latter describes the cargo location relative to the transport
vessel, according to the Naval Architect data. The height of the seafastening grillage
and the depth of the structure framing need to be taken into account in when defining
the coordinates of the location of the cargo in the Naval Architectural model.
Where “compression only” supports are to be used, Stage 1 and Stage 2 loads are
combined directly in a single analysis, as the gravity loads are required for convergence
to the correct results. The restraint forces derived from the Stage 1 analysis are
balanced out in the combined analysis.
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Table 6-2: BASIC LOAD CASES FOR INERTIA ANALYSIS
Load
Case
431
Sea Transport Wind: towards bow (10 yr return, 1min. mean), Structure +X direction
432
Sea Transport Wind: towards stern (10 yr return, 1min. mean), Structure -X direction
433
Sea Transport Wind: towards starboard (10 yr return, 1min. mean), Structure +Z direction
434
Sea Transport Wind: towards port (10 yr return, 1min. mean), Structure -Z direction
701
Unit 1.0 m/s² surge force towards bow (Structure +DX)
702
Unit 1.0 m/s² heave force upwards (Structure +DY)
703
Unit 1.0 m/s² sway force towards starboard (Structure +DZ)
704
Unit Rotational Accn. 1.0 deg/s² about longitudinal axis (Structure +RX)
705
Unit Rotational Accn. 1.0 deg/s² about vertical axis (Structure +RY)
706
Unit Rotational Accn. 1.0 deg/s² about transverse axis (Structure +RZ)
751
Vessel sagging deflection
752
Vessel hogging deflection
Description
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7.
DESIGN VERIFICATION
7.1
Load Combinations
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
The static and inertia loads are assembled into combinations (Table 7-1) for code
checking. The combination factors are derived from the acceleration values (m/s²,
deg/s²) calculated by the Naval Architects. Gravity loads (Case 1800), Centre of Gravity
Shift, vessel deflections and wind loads (in appropriate directions) are included in the
combinations.
1
The engineer shall check manually the total loads output for these combinations.
The load combinations derive from the specified sets of unit accelerations, using the
accelerations as the combination factors (in all permutations of positive and negative
senses). Ensure that gravity (in the vertical direction) is not double-counted.
Where the analysis requires ‘compression-only’ (or ‘tension-only’) supports, a singlestage (combined) analysis must be used, so that it converges to the correct solution.
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Table 7-1: COMBINATIONS OF MOTION FORCES
Sea Transport Wind Factored from Operating ULS Wind
Create REPEAT loads by factoring ULS wind cases by (Vsea/VULS)
2
-2
Positive Inertia Loadcases (1ms unit in STAADOffshore)
Module +X axis parallel to Vessel
702
703
704
705
Module +X axis parallel to Vessel
1800
Load
comb
No.
431
Wind to Bow
REPEAT (REPEAT
load: All 401 x
Transport
(V /V )2
dead loads sea ULS
x diagonal)
Load Combination Description
432
Wind to
Stern
(REPEAT
402 x
(Vsea/VULS)2
x diagonal)
433
Wind to
Starb'd
(REPEAT
403 x
(Vsea/VULS)2
x diagonal)
434
621
Wind to Port
(REPEAT
404 x
(Vsea/VULS)2
x diagonal)
CG
Correction,
unit ΣMX =
1000kNm
622
CG
Correction,
unit ΣMZ =
1000kNm
701
DX
DY
DZ
RX
RY
706
RZ
751
Sag
752
Hog
Adjustment factor = 0.114
Sea Transport (AISC - WSD)
1.0
Stillwater
1802
Surge/Pitch to Bow
Sway/Roll to Stbd
+Yaw
Surge/Pitch to Stern
Sway/Roll to Stbd
-Yaw
Surge/Pitch to Bow
Sway/Roll to Port
-Yaw
Surge/Pitch to Stern
Sway/Roll to Port
+Yaw
Surge/Pitch to Bow
Sway/Roll to Stbd
+Yaw
Surge/Pitch to Stern
Sway/Roll to Stbd
-Yaw
Surge/Pitch to Bow
Sway/Roll to Port
-Yaw
Surge/Pitch to Stern
Sway/Roll to Port
+Yaw
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
Min Heave
1804
Min
Max
Min
Max
Heave Heave Heave Heave
1803
Max Heave
1801
Surge/Pitch to Bow
Sagging
Surge/Pitch to Stern
Sagging
Surge/Pitch to Bow
Sagging
Surge/Pitch to Stern
Sagging
Surge/Pitch to Bow
Hogging
Surge/Pitch to Stern
Hogging
Surge/Pitch to Bow
Hogging
Surge/Pitch to Stern
Hogging
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
+
1.0
1.0
1.0
1.0
+
1.0
1.0
1.0
1.0
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
-
+
+
+
+
+
+
+
+
-
+
+
+
+
-
+
+
+
+
+
+
+
+
-
+
+
+
+
-
+
+
+
+
-
+
+
+
+
-
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Notes: The load combinations in Table 7-1 are suitable for where the structure longitudinal (X) axis is parallel to the vessel and pointing towards the bow.
1
Further information on load combinations is contained in Ref [21].
1
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7.2
Document No: G1-TE-S-0000-PDB0003
Revision: 1
Issue Purpose: RFD
Code Checks
The structure will be checked to the provisions of AISC-ASD [24].
1
The Allowable Stress Factor (ASF) shall be in accordance with Table 7-2, based on
Reference [2].
1
1
Table 7-2: Sea Transport - Allowable Stress Factors
Design Condition
Allowable Stress Factor
(ASF)
Sea Transport – Harbour or Still-water Case
1.0
Sea Transport – Inertial Cases: all members, including Tie-downs
1.33
Sea Transport – Inertial Cases: Tie-down connections to SHLV
1.0
The target normalised member utilisation ratio shall be in the range 0.80 to 0.90.
Where members need to be re-sized to the target utilisation range, this will be done in
conjunction with results from In-Service and Land Transport analyses.
‘Dummy’ members – included in the model to represent loading mechanisms – are
excluded from all code checks.
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