design of fixed offshore platforms

7/25/2019 Design of Fixed Offshore Platforms

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MP 02-P-01 Design of Fixed Offshore Platforms in Moderate Environ. July 1!

%a&le of 'ontents

"#o$e...................................................................................................................................... 1

1. (eferen#es......................................................................................................................)

1.1. Master PracticesExxonMobil Engineering Practices...........................................5

1.2. ExxonMobil Data Sheets.......................................................................................5

1.3. ExxonMobil Practice Tutorials...............................................................................6

1.4. AS!A"erican nstitute o# Steel !onstruction....................................................6

1.5. APA"erican Petroleu" nstitute........................................................................6

1.6. A$SA"erican $el%ing Societ&..........................................................................'

2. *eneral............................................................................................................................+

,. Design 'riteria................................................................................................................+

. Design oads..................................................................................................................!

4.1. Dea% (oa%s...........................................................................................................)

4.2. (i*e (oa%s.............................................................................................................)

4.3. +o"inal Dec, (oa%s.............................................................................................-

4.4. En*iron"ental (oa%s.............................................................................................-

4.5. !onstruction (oa%s..............................................................................................1

4.6. A//urtenance (oa%s............................................................................................11

4.'. E0ui/"ent Test (oa%s.........................................................................................12

). Design of Ja#/ets and $$urtenan#es......................................................................12

5.1. eneral e0uire"ents........................................................................................12

5.2. nPlace Anal&sis.................................................................................................13

5.3. atigue Anal&sis..................................................................................................13

5.4. D&na"ic Anal&sis................................................................................................14

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5.5. (oa%out Anal&sis.................................................................................................14

5.6. Trans/ortation Anal&sis.......................................................................................15

5.'. (aunch(i#t Anal&sis.............................................................................................1'

5.). lotation Anal&sis.................................................................................................1-

5.-. /en%ing Anal&sis...............................................................................................2

5.1. 7n8otto" Stabilit& Anal&sis...............................................................................22

5.11. 8oat (an%ing Design...........................................................................................23

5.12. 8arge 8u"/er Design.........................................................................................24

5.13. Mu%"ats..............................................................................................................24

5.14. !orrosion.............................................................................................................25

5.15. 7ther e0uire"ents............................................................................................25

. Design of Piles..............................................................................................................2+

6.1. se o# rout........................................................................................................2'

6.2. n%er%ri*e Allo9ances........................................................................................2'

6.3. Preli"inar& Plans.................................................................................................2)

6.4. inal Plan.............................................................................................................2)

+. Design of De#/s...........................................................................................................2!

'.1. eneral e0uire"ents........................................................................................2)

'.2. nPlace Anal&sis.................................................................................................2-

'.3. (oa%out Anal&sis.................................................................................................2-

'.4. Trans/ortation Anal&sis.......................................................................................3

'.5. (i#t Anal&sis..........................................................................................................32

'.6. Dec, !learance...................................................................................................33

'.'. 7ther e0uire"ents............................................................................................33

!. Design of ridges3 4al/5ays3 ##ess Platforms and "tairs..................................,

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).1. 8ri%ges.................................................................................................................34

).2. $al,9a&s: Access Plat#or"s an% Stairs.............................................................34

. Design *eneral.............................................................................................................,)

-.1. Allo9able Stresses..............................................................................................35

-.2. $el%e% !onnections...........................................................................................35

-.3. se o# Tubular Me"bers.....................................................................................35

10. Material "ele#tion.........................................................................................................,

11. Do#umentation.............................................................................................................,

11.1. Design !alculation +oteboo,s............................................................................36

11.2. Design Dra9ings.................................................................................................3'

11.3. !o"/uter Anal&sis 7ut/ut...................................................................................3'

11.4. !o"/uter Mo%els................................................................................................3)

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1. (eferen#es

The follo*ing publications form a part of this Master Practice. +nless other*ise specified herein, usethe latest edition.

1.1. Master Pra#ti#es6ExxonMo&il Engineering Pra#ti#es

MP &P Transportation - oadout of /ffshore #tructures

MP '0P1 Painting 2eneral 3equirements

MP 1P& Pedestal Mounted 3evolving %ranes

MP 04P1 %athodic Protection for /ffshore #teel #tructures

MP 0P1 3equirements for Matl. - 5elding/ffshore #tructures in a Moderate

%limate

1.2. ExxonMo&il Data "heets

ExxonMobil 6ata

#heets

ExxonMobil 6ata #heet 7ome Page

T&1%1 6esign of 8ixed /ffshore Platforms in Mod Environments oadout

%ontractor 3esponsibilit9 %ustomar9 +nitsT&1%& 6esign of 8ixed /ffshore Platforms in Mod Environ #eafastening

Transport %ontractor 3esponsibilit9 %ustomar9 +nits

T&1%' 6esign of 8ixed /ffshore Platforms in Mod Environ :nstallation

%ontractor 3esponsibilit9 %ustomar9 +nits

T&1% 6esign of 8ixed /ffshore Platforms in Mod Environ 6esign %ustomar9

+nits

T&1M 6esign of 8ixed /ffshore Platforms in Mod Environ 6esign Metric

+nits

T&'%1 8abrication - oadout of /ffshore #tructures oadout %ontractor

3esponsibilit9 %ustomar9 +nits

T&'M1 8abrication - oadout of /ffshore #tructures oadout %ontractor

3esponsibilit9 Metric +nits

T&'%& 8abrication - oadout of /ffshore #tructures #eafastening Transport %ontractor 3esponsibilit9 %ustomar9 +nits

T&'M& 8abrication - oadout of /ffshore #tructures #eafastening Transport

%ontractor 3esponsibilit9 Metric +nits

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T&'%' 8abrication - oadout of /ffshore #tructures :nstallation %ontractor

3esponsponsibilit9 %ustomar9 +nits

T&'M' 8abrication - oadout of /ffshore #tructures :nstallation %ontractor

3espons Metric +nits

6&'%1 8abrication - oadout of /ffshore #tructures 6ocumentation

3equirements #heet

:&'%1 8abrication - oadout of /ffshore #tructures :nspection - Testing

3equirements #heet

T&%1 Transportation - oadout of /ffshore #tructures oadout %ontractor


T&%& Transportation - oadout of /ffshore #tructures #eafastening Transport

%ontractor 3esponsibilit9 %ustomar9 +nits

T&%' Transportation - oadout of /ffshore #tructures :nstallation %ontractor


1.,. ExxonMo&il Pra#ti#e %utorials

EPT 1T1 /ffshore 8acilit9 a9out

1.. 7"'6meri#an 7nstitute of "teel 'onstru#tion

!:#% #''0 #pecification for #tructural #teel "uildings !llo*able #tress 6esignand Plastic 6esign *ith %ommentar9

1.). P76meri#an Petroleum 7nstitute

!P: 3P &!5#6 3ecommended Practice for Planning, 6esigning and %onstructing 8ixed

/ffshore Platforms 5or;ing #tress 6esign T*entieth Edition< #upplement

11==4

1.. 4"6meri#an 4elding "o#iety

!5# 61.1 #tructural 5elding %ode #teel 8ifteenth Edition



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2. *eneral

The requirements for the structural design of fixed offshore steel platforms, modifications to existing

platforms and bridges, and bridge supports for offshore facilities in moderate environments shall be inaccordance *ith requirements of this Master Practice, unless superceded b9 more stringent local

regulations.

The English dimensional s9stem shall be used in all design calculations, computer anal9ses,

dra*ings and documentation, unless other*ise required.

Elevations on dra*ings, s;etches, etc. shall be referenced to mean lo* *ater (M5) level.

M5 shall appear as elevation . ft. /ther elevations shall appear as either elevation > (plus) or

(minus), above or belo* M5, respectivel9, unless other*ise required.

!ll computer programs used for structural design and anal9sis require prior %ompan9

approval.

,. Design 'riteria

The design shall incorporate all requirements for the platform as specified on applicable ExxonMobil

6ata #heetsfor this Master Practice.

The environmental criteria (oceanographic?meteorological data) shall be provided on the

appropriate ExxonMobil 6ata #heets.

2eotechnical data shall be obtained from a geotechnical investigation of the platform site b9

means of borings, field tests, laborator9 tests and engineering calculations. !s a minimum, the

follo*ing shall be obtained from the investigation and used in the foundation design@

+ndrained pile capacit9 versus depth curves

+ltimate pile capacit9 versus depth curves

ateral soil resistanceApile deflection (p9) data

oad transfer in s;in friction for tension and compressionAaxial pile segment

displacement (tB) data

Tip resistance in end bearingApile tip movement (qB) data

Mudline bearing capacit9

The contractor shall *or; *ith the fabrication contractor and the installation contractor to

ensure consistenc9 *ith the design assumptions. :dentification of the contractorCs responsibilities

is sho*n in the appropriate ExxonMobil 6ata #heets.



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. Design oads

.1. Dead oads

6ead loads *ill not change during the normal design life of a platform. The9 include the

follo*ing, as a minimum@

1. 5eight of platform structural components, including dec;s, Dac;ets and piling *here

appropriate

&. 5eight of platform appurtenances such as boat landings, barge bumpers, sumps,

risers, anodes, etc.

'. 5eight of equipment, flare to*ers, piping, cables, cable tra9s, etc. that are

permanentl9 mounted on platform dec;s

. 5eight of an9 bridgeCs connecting platforms

0. 79drostatic forces acting on platform members belo* the *aterline (including

external pressure and buo9anc9)

.2. ive oads

ive loads ma9 change in magnitude, position and?or direction during the normal design

life of a platform. The9 include the follo*ing, as a minimum@

1. 5eight of equipment that can be added to or removed from the platform.

&. 5eight of variable supplies and liquids (including extreme conditions).

'. 7elicopter design landing loads.

. The forces exerted on a platform b9 dec; cranes. These forces shall be determined as

specified in MP 1P&.

0. Vessel impact loads based on local marine operations, as specified in the appropriate

ExxonMobil 6ata #heets.

4. 6rill rig pull load of = metric tons (1 short tons) at an9 *ell location, if the

platform is designed to support a platform drilling rig (unless other*ise required).

. +niforml9 distributed area loads.

.,. 8ominal De#/ oads

:n the absence of specific loads, nominal dec; loads shall be used as specified in Table 1.

:f actual loads differ, appropriate chec;s shall be made.



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"a#le 1$ %ominal De&' (oads

Platform De&' %ominal )rea (oad

'g*m2+l#*ft2,

%ote

6rilling? Production 6rill (except *ellba9)

(1) Ma9 be adDusted ifactual data ;no*n

5ell "a9 140 (') Ma9 be adDusted if

actual data ;no*n

/ther 1=0' () Ma9 be adDusted if

actual data ;no*n

Production Main 1=0' () Ma9 be adDusted if

actual data ;no*n

%ellar 1= ('0) Ma9 be adDusted if

actual data ;no*n

"ridges (1) Ma9 be adDusted if

actual data ;no*n

The nominal dec; loads shall be applied as follo*s@

#tructural %omponent !rea oad Percentage

6ec;ing (plate and dec; beams) 1F

2irders, trusses, dec; legs, piles 0F

.. Environmental oads

Environmental data, including meteorological and oceanographic data, is provided in the

appropriate ExxonMobil 6ata #heets. The criteria for determining environmental loads

follo*s@

1. 5ave ;inematics shall be determined b9 using the 1th /rder #tream 8unction

formulation. /ther formulations are subDect to %ompan9 approval.

&. The MorisonCs equation shall be used to calculate *ave loads, using the follo*ing

coefficients, unless other*ise required in the appropriate ExxonMobil 6ata #heets.

a) 6rag %oefficient .

b) :nertia %oefficient 1.

'. 5ave loads shall be maximiBed over the specified *ave period range.

. 3eduction of *ave loads due to conductor shielding is generall9 not allo*ed.

Exceptions require %ompan9 approval.

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submit to The %ompan9 for approval prior to beginning transportation

anal9ses.

The contractor shall also provide the environmental criteria, bargecharacteristics and barge motions used to develop the transportation loads.

! preliminar9 transportation load shall be developed to form the basis of theengineering anal9sis and design.

.).,. Offshore ift oads

The contractor shall develop offshore lift loads on dec;s, Dac;ets and piling

for each unique offshore lift, as specified b9 !P: 3P &!5#6and MP &P

, and submit to The %ompan9 for approval prior to beginning lift anal9ses.

.. $$urtenan#e oads

The exposed *ave loading area of the appurtenances (boat landings, barge bumpers,

conductors, risers, caissons, sumps, etc.) shall be simulated in the structural anal9sismodel to calculate the additional *ave loads applied to the Dac;et. The model shall

neglect the stiffness contribution of the boat landing to the total Dac;et stiffness.

The exposed *ave loading area of sacrificial anodes does not need to be explicitl9

simulated but shall be considered b9 increasing the total *ave load, increasing member

*ave diameters or some other acceptable rational approximation.

.+. E9ui$ment %est oads

6ec; structures supporting equipment subDect to test loading shall be designed to carr9 the

additional loads. /nl9 one equipment item shall be tested at a time. The loads shall onl9

be used for siBing structural members local to the equipment and shall not be included inoverall dec; or Dac;et structure anal9sis.

). Design of Ja#/ets and $$urtenan#es

).1. *eneral (e9uirements

Preliminar9 anal9ses of the Dac;et, piles and appurtenances ma9 be performed

independentl9 of the dec; *ith onl9 global dec; loads being imposed on the Dac;et. The

final inplace anal9ses shall be conducted on a combined dec; and Dac;et, *hich also

account for significant dec; loading variations such as drill rig location, rig hoo; loads

and rig setbac; loads.



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).1.1. 'om$uter nalyses

%omputer anal9ses shall be provided for the design of the follo*ingconditions@

1. :nplace conditions, including coupled nonlinear interaction of soilpile

s9stem *ith Dac;et

&. 8atigue anal9sis for inplace conditions

'. 69namic anal9sis (if required b9 #ection 0.)

. 8abrication conditions

0. oadout conditions

4. Transportation conditions

. Gac;et launch?lift conditions

. /nbottom stabilit9 anal9sis

).1.2. Manual nalyses

Manual anal9ses are acceptable for design of the follo*ing items, but do not

preclude computer anal9ses@

1. "oat landings

&. "arge bumpers

'. Mud mats

. !node attachments

0. Pad e9es

4. 3igging

).2. 7n-Pla#e nalysis

! static threedimensional inplace anal9sis of the platform shall be performed as

specified b9 !P: 3P &!5#6. The computer model shall include Dac;et, piles and an

appropriate simulation of the dec;. Honlinear pile?soil interaction shall be included in

the model.

Each platform shall be designed for all realistic combinations of design loads, as defined

in #ection 0, and consistent *ith !P: 3P &!5#6. oad combinations shall include but

not be limited to the follo*ing@

1. 19ear return period *ave and associated *ind and current

&. /perating *ave, *ind and current

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'. 6ead loads

. ive loads

0. 79drostatic loads

The maximum *ind, *ave and current loads shall be applied concurrentl9 and in the same

direction on the platform. 6irectional variations shall be used in platform design. 6esignmagnitudes and directions (if applicable) are provided in T&1% and T&1M.

).,. Fatigue nalysis

8atigue life of all platforms shall be t*ice the expected service life, *ith a minimum

fatigue life of 9ears. 7igher fatigue lives ma9 need to be specified for critical Doints or

Doints in areas difficult to inspect.

).,.1. "im$lified nalysis

! simplified fatigue anal9sis shall be performed in less than 1&& m ( ft)

of *ater for each platform constructed of ductile steels *ith redundantstructural framing and *ith natural periods less than three seconds for the in

place condition, as specified b9 !P: 3P &!5#6. This procedure *ill

determine the maximum allo*able hot spot stresses resulting from the

application of the fatigue design *ave.

The IPrime #H curve shall be assumed in calculation of allo*able pea;

hot spot stresses. The procedure described in !P: 3P &!5#6is calibrated

for the t9pical 2ulf of Mexico *ave climate, but it can be adapted to other

regions *ith different long term distribution of c9clic loads.

).,.2. %hree-Dimensional nalysis

! detailed threedimensional d9namic spectral fatigue anal9sis shall be

performed for platforms *ith natural periods greater than three seconds. The

anal9sis shall consider the uncertainties inherent in calculating the natural

period of the platform. Therefore, c9clic stresses used in the fatigue anal9sis

shall be maximiBed for design b9 considering a 1 percent variation in

natural period. The contractor shall submit the fatigue anal9sis procedure toThe %ompan9 for approval.

The stress concentration factor parametric equations to be used shall

be approved b9 The %ompan9 in *riting.

The *ave regime or spectra to be used for the fatigue anal9sis, if

required, is provided in the appropriate ExxonMobil 6ata #heets.

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).. Dynami# nalysis

! d9namic anal9sis is required for platforms *ith natural periods greater than three

seconds.

! 6!8 approach shall be used to determine the increased loads resulting from thed9namic behavior of the platform. The d9namic anal9sis shall not decrease the total

environmental loading on a fixed platform belo* the level determined b9 the static

application of the design *ave.

The methodolog9 used to determine the 6!8 shall be approved b9 The %ompan9.

!lternate methods ma9 be used *ith %ompan9 approval.

).). oadout nalysis

! threedimensional anal9sis is required for an9 Dac;et that is s;idded onto a

transportation barge. The anal9sis shall include a sufficient number of positions duringthe s;idding operation to maximiBe member stresses. The anal9sis shall also compl9 *ith

an9 further requirements in MP &P.

Member stresses and punching shear in all permanent and temporar9 members and Doints

shall be determined. ocaliBed bearings at structure support points shall also be chec;ed.

#tresses in the structure shall not exceed the requirements of !P: 3P &!5#6for tubularand tubular Doints and !:#% #''0for structural shapes and builtup members. #tresses

shall be limited to basic allo*ables.

).).1. oad 'onditions

The structure shall be anal9Bed for the forces imposed during the loadout. :n

defining the load conditions, consideration shall be given to the operational

restraints of the loadout s9stem. !mong the conditions to be considered are

the follo*ing@

1. :ncorrect trim or draft due to tidal fluctuation or *ind

&. "arge movement due to nearb9 marine traffic

'. ocation, slope or settlement of s;id*a9s

).).2. Final 'riteria "ased on the anal9sis, deflection criteria shall be established that

give the allo*able deflection tolerance for the structure as it moves along

the s;id*a9.

3eanal9ses ma9 be required as a result of the final loadout plan

prepared b9 the fabrication contractor.



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! revie* of the selected barge shall be performed to ensure that the

barge has the structural strength to *ithstand the expected static and

d9namic loadings from the loadout operation.

).. %rans$ortation nalysis

! detailed transportation anal9sis shall be performed for each Dac;et as specified b9 !P:

3P &!5#6and MP &P. Motions of the bargeDac;et s9stem shall be determined

and subsequentl9 used to calculate the Dac;et member stresses.

)..1. 'riteria (e9uirements

The selection of comprehensive or reduced design criteria is indicated in the

#cope of 5or;@

)..1.1. 'om$rehensive 'riteria

!n environmental report shall be obtained detailing the characteristics

(significant *ave height and period, and applicable *ave spectrum) of a 1

9ear recurrence internal maximum storm for the specific route and time of

9ear.

)..1.2. (edu#ed 'riteria

#implified criteria shall be established and revie*ed b9 The %ompan9.

)..2. Positioning

The selection of the structureCs position on the barge shall be based on both

engineering and operational considerations. !mong these considerations are

the follo*ing@

1. MinimiBe transportationinduced forces on the cargo

&. ocate structure over JstrongJ points

'. MinimiBe overhang

. MinimiBe bloc;age of access *a9s

0. ocate a*a9 from barge fitting and tan; vents

)..,. oad 'onditions

The structure shall be anal9Bed, using the transportation ballast

configuration, for forces resulting from the application of the appropriate

forces to the barge?cargo s9stem.



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Maximum loadings shall be applied in appropriate

combinations to determine the structural integrit9 of the cargo and

seafastening.

! variet9 of storm approach directions relative to the barge

axes shall be ta;en into account. oad conditions shall consider the

effects of roll, pitch, heave, s*a9, surge, 9a*, *ind and *ave slam.

#tructure stress anal9sis for the structure, including seafastening,

shall be performed using the loads, and the seafastening and support

locations defined above.

)... llo5a&le "tresses

#tructure member stresses shall not exceed the !P: 3P &!5#6

requirements for tubular and tubular Doints, and !:#% #''0requirements for

structural shapes and builtup members. !llo*able stresses shall include a

onethird increase over !:#% #''0allo*ables.

)..). "hear:Other nalyses

Punching shear at the structure and tiedo*n tubular Doints shall be

chec;ed for the load condition forces and stresses.

#tructure fatigue anal9sis for the transportation period shall be

provided. The fatigue anal9sis shall be based on the environmental

conditions expected along the to* route. The fatigue lives shall be

established using appropriate stress concentration factors.

! vortex shedding anal9sis shall be provided for the structure, based

on the environmental conditions expected along the to* route.

)... "eafastening and (einfor#ement

#tructural members that do not meet the requirements of the

allo*able stresses and that have fatigue lives usation factor of .0 or

greater, shall be reinforced.

#eafastenings shall be designed according to the transportation

anal9ses. #eafastenings shall be located at hard points on the Dac;et and

framed barge dec; areas and shall be designed to restrain the structure

*hen subDected to the design to*ing conditions. %onsideration shall also

be given for the efficient removal of the seafastening *hen selecting theirlocation and design.

2usset plates to alleviate a punching shear overstress condition at a

structure tubular Doint shall be avoided. 2usset plates are acceptable to

spread load in the barge dec; or at an intersection *ith structural shapes.



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#eafastening and reinforcement shall be detailed to provide good

fatigue characteristics under c9clic loading. #harp corners,

discontinuities and other stress concentrations are not permitted.

! limiting *eather condition shall be determined that reflects the

criteria used for the stress anal9sis of the structure and seafastenings.

)..+. Final (evie5

3eanal9ses and design ma9 be required as a result of the final

transportation plan prepared b9 the installation contractor.



d9namic loadings from the to* operations.

).+. aun#h:ift nalysis

! threedimensional launch?lift anal9sis shall be performed for each Dac;et, as specified b9

!P: 3P &!5#6.

).+.1. Preliminary Plan

! preliminar9 launch?lift plan shall be developed that *ill include prelaunch?lift, launch?lift and postlaunch?lift operations. The preliminar9

launch?lift plan shall include the follo*ing@

1. 3igging plan

&. Marine equipment position and site la9out dra*ings for launch?liftoperations

'. #equence for all operations

. "arge ballasting plan for launch

0. imiting environmental conditions

).+.2. aun#h %ra;e#tory nalysis

8or launched Dac;ets, a launch traDector9 anal9sis shall be performed. The

anal9sis shall provide the follo*ing@

1. Time histories of Dac;et position, including depth and profile of dive

&. aunch velocities of Dac;et members

'. !ccelerations of Dac;et members

. "argetoDac;et clearances

0. ! determination of the need for auxiliar9 flotation tan;s



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4. !n optimiBation of the initial barge parameters, such as trim and ballast

conditions

).+.2.1. 'onsiderations

The launch traDector9 anal9sis shall consider the follo*ing@

1. :nitial trim angle of barge

&. "allast condition of barge

'. +se of auxiliar9 buo9anc9

. 3ange of coefficients of friction

0. Expected environmental conditions

4. Threedimensional bargetoDac;et interaction

. "arge motions caused b9 the launch

The final launch traDector9 shall consider the limitations of barge

submergence, provide a bottom clearance of ft and preclude the possibilit9

of Dac;ettobarge impact.

8or launched Dac;ets, the structural integrit9 of the Dac;et, launch runner and

launch truss framing during launch shall be verified b9 a launch stress

anal9sis.

).+.,. aun#h "tress nalysis

The launch stress anal9sis shall consider Dac;et and appurtenances *eight

(including contingenc9 factor), buo9anc9, inertial loads and roc;er armreactions. :t shall be based on the results of the launch traDector9 anal9sis.

The contingenc9 factor for preliminar9 design shall include an allo*ance for

additional *eight as the Dac;et design progresses. The support simulation

shall consider the flexibilit9 of the roc;er arm.

Gac;et members shall be chec;ed for h9drostatic collapse if the dive depth or

upending condition and depth for a given member is greater than the installed

condition.

).+.,.1. (e9uired 'al#ulations

The follo*ing calculations are required@

1. #tress anal9sis for Dac;et members, launch truss and launch runners

&. Gac;et Doint punching shear anal9sis

'. aunch leg stress anal9sis

. 5ave slam anal9sis



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).+.,.2. llo5a&le "tresses

Gac;et member stresses shall not exceed the !P: 3P &!5#6requirements

for tubular and tubular Doints, and !:#% #''0requirements for structural

shapes and builtup members. !llo*able stresses shall include a onethird

increase over basic allo*ables.

!n9 Dac;et leg section or Doint not meeting allo*able stresses shall have ring

stiffeners added as reinforcements.

).+.. Final (evie5

3eanal9ses ma9 be required as a result of the final launch?lift plan

prepared b9 the installation contractor.



d9namic loadings from the launch operations.

).!. Flotation nalysis

8or Dac;ets to be floated, a flotation anal9sis shall be performed for the Dac;et to determine

its final equilibrium floating position.

"uo9anc9?*eight distribution shall allo* the Dac;et to be near horiBontal in

its final floating position, *ith the top end of the Dac;et above the *aterline so that

slings, upending controls or other upending equipment are accessible to personnel.

! final equilibrium floating position that is not horiBontal ma9 be

recommended to The %ompan9, for approval, if proved to be technicall9 acceptableand economicall9 advantageous.

).!.1.


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).!.2. Damaged Ja#/et 'ases

8lotation anal9sis and stabilit9 chec;s shall be performed for damaged Dac;etcases, assuming that buo9anc9 is lost at selected locations on the Dac;et.

The %ompan9 shall approve selection of damaged cases.

).!.,. uxiliary uoyan#y

5hen Dac;et *eight or buo9anc9 distributions require the use of auxiliar9

buo9anc9 to satisf9 launch or upending requirements, closure plates,

diaphragms and flotation tan;s shall be considered.

%losure plates and diaphragms shall be used in freeflooding members of the

Dac;et to maintain complete or partial buo9anc9. These members include

Dac;et legs, s;irt pile sleeves, preinstalled s;irt piles and conductors.

!dditional flotation tan;s shall be considered onl9 after the use of free

flooding members has been exhausted or deemed impractical. 5hen

flotation tan;s are required, the9 shall be designed in accordance *ith !P:3P &!5#6and use ring stiffeners or another method to provide the most

costeffective design. The maximum h9drostatic head to *hich the flotation

tan;s are expected to be exposed during the installation process, shall

determine design pressure. The design of flotation tan; connections shall

minimiBe offshore removal time and effort.

).. =$ending nalysis

8or Dac;ets to be floated, a stepb9step procedure shall be established for upending the

Dac;et from its final equilibrium floating position to its upright floating position. The

combination of lifting *ith crane vessel and?or sequential ballasting of Dac;et and flotation

tan; components shall be anal9Bed.

)..1. Preliminary Plan

! preliminar9 Dac;et upending and placement plan shall be developed during

the engineering and planning phase of the proDect. This plan shall form the

basis for all offshore operations concerning the upending and placement of

the Dac;et. The plan shall include the follo*ing@

1. +pending procedure, including Dac;et ballasting plan

&. +pending and placement sequence

'. Marine equipment position and site la9out dra*ings for upending and

placement operations

. 3igging plan

0. %ontingenc9 plans



21/37


)..2. =$ending O$eration

The Dac;et shall maintain stabilit9 during the upending operation. #ufficientrighting moment shall be displa9ed during all stages of the upending

operation to prevent the occurrence of an9 rolling or heeling of the structure.

!dditionall9, the Dac;et shall have at least a .0 m (10 ft) bottom clearance at

all times during the upending operation.

)..,. 'ontingen#y Pro#edures

%ontingenc9 upending procedures shall be established assuming failure of

an9 part of the upending s9stem. #uch failures shall include loss of

buo9anc9 or inoperative ballast valves. The %ompan9 shall approve

contingenc9 upending procedures.

)... Padeyes

Pade9es that carr9 the upending loads shall be chec;ed at multiple stages ofthe intended operation, considering the hoo;load variation and differentslingtopade9e angles. Pade9es shall be chec;ed for the Dac;et vertical

position and the maximum hoo;load experienced before Dac;et set do*n.

)..). Ja#/et Pla#ement

The s9stem for the upending and placement of the Dac;et shall be designed to

be compatible *ith and fulfill the requirements of the upending procedure.

)... (ea#h (ods

3each rods are the preferred s9stem for operating ballast valves *here thelength of the reach rod length is less than =1 m (' ft). 5hen the intended

reach rod length exceeds '.0 m (1 ft), the follo*ing special precautions

shall be considered@

1. +se of gearbox operators to minimiBe torque requirements of valves

&. +se of lo*friction reach rod guides

'. :ncreased reach rod section modulus to limit *indup

. :ncreased number of guides to offset launch induced forces

0. 3each rod support method to prevent full *eight of reach rod acting onvalve

4. !lignment tolerance for reach rod guides and reach rods

)..+. lternatives to (ea#h (ods

!s an alternative to reach rods (*here environmental conditions pose no

danger to umbilical hose heading from Dac;et to the crane vessel), a s9stem

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of metered pumping of sea*ater into Dac;et legs, through manifold piping

from cranevesselmounted pumps, is acceptable.

8or cases *here the use of reach rods is prohibited b9 length, for harshenvironmental conditions, or *here controlled pile sleeve ballasting is

required, remotel9 actuated (h9draulic) ball valves for ballasting are

preferred. 8or po*er and control of the h9draulicall9 actuated valves, acentral control console is required. The control console can be barge

mounted *ith an umbilical leading to the Dac;et. /ther*ise, the console

shall be Dac;etmounted (above *aterline in the Dac;etCs final equilibrium

floating position) and subDect to launch forces and submersion during launch.

6etail design of the console shall include description of components,

specifications, operational requirements, arrangement dra*ings, schematics

and other information relevant to procurement, fabrication, testing,

commissioning and operation.

)..!. Final (evie5

! complete description of equipment necessar9 to fulfill the requirements ofthe contingenc9 upending procedures shall be provided.

3eanal9ses ma9 be required as a result of the final upending and

replacement plan prepared b9 the installation contractor.

).10. On-ottom "ta&ility nalysis

! static onbottom stabilit9 anal9sis shall be performed for each Dac;et to ensure stabilit9

before and during pile driving. :nstallation aids, such as mud mats, shall be designed

using these results.

/verturning stabilit9 of the Dac;et *hile in the most critical position shall be

chec;ed using the /perating 5ave %riteria, as specified on ExxonMobil 6ata #heets.

The criteria to be used for the stabilit9 anal9sis shall be as specified on

T&1% and T&1M.

!n onbottom stabilit9 anal9sis shall be performed to determine the limiting sea states in

*hich the unpiled Dac;et shall maintain a stable, free standing and level condition. #uch

condition shall be maintained *ith or *ithout pile sections in the Dac;et legs, *hichever is

more critical. The limiting sea state shall be used as *eather criteria for decisions to lift orlaunch the Dac;et from the barge.

).10.1. 'onsiderations

The onbottom stabilit9 anal9sis shall consider the follo*ing@

1. 6etermination of limiting sea state for Dac;et *ith or *ithout pile

sections in the Dac;et legs, *hichever is more critical

&. 6etermination of stabilit9 for one9ear storm conditions

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'. %hec; of soil bearing capacities

. %hec; of mud mat and Dac;et structure strength

0. 6etermination of Dac;et instabilit9 point

).11. oat anding Design

T*o boat landings shall be installed on opposite sides of the Dac;et or as

specified on T&1% and T&1M.

Each boat landing shall have t*o levels *ith tops of the upper landing at

elevation >&. m (>=. ft) and the lo*er boat landing at elevation >& m (>4.0 ft).

The bottom elevation of the boat landing shall be at elevation 1.& m ( ft),

to preclude boats in the *ave trough from contacting the underside of the boat

landing.

The boat landing design shall consider provision for field adDustment fromthe design elevation.

The boat landing shall be designed for a load of 11',4 ;g (&0, lb)

normal to the face of the landing plus &&, ;g (0, lb) tangential to the face.

Each single horiBontal truss shall be designed for t*othirds of this load. The supports

shall be designed for the maximum support reaction, determined b9 appl9ing the load

at end of truss.

T*o s*ing ropes shall accompan9 each level of landings. Each boat landing

shall be equipped *ith an emergenc9 ladder penetrating a minimum of 1.0 m (0 ft)

into the *ater.

).12. arge um$er Design

"arge bumpers using shoc;cells shall be designed to meet the follo*ing requirements@

(The shoc;cell vendor shall provide calculations demonstrating that the requirements are

met.)

1. Energ9 absorption shall be ', ;gm (11 fttons), minimum. Maximum reaction

at a post support shall not exceed 1, ;g ('&0, lbs).

&. "arge bumpers shall extend from elevation &. m (= ft) to elevation >.4 m (>10 ft).

'. %ontact surface height of the bumper post shall be m (&' ft), minimum.

. oad shall be applied half*a9 bet*een the post supports for siBing the supporting

shoc; cells.

0. oad shall be applied at onethird points for siBing the supporting shoc; cells.

4. !llo*able steel stresses shall not be increased onethird *hen siBing steel

components.

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. #hoc; cells shall be chec;ed assuming that the applied load is applied in the plane of

the barge bumper and at an angle of & degrees to the plane of the barge bumper.

. The energ9 absorbing units and flanged connections to the stubs on the Dac;et shall be

designed to fail at 1.0 times the forces induced b9 the impact requirements specified.

The9 shall be designed to fail in such a fashion that the Dac;et and the impacting

vessel are not subDect to haBard caused b9 s9stem element collapse or detachment.

=. "arge bumper assemblies shall be designed such that the bumper face is at theminimum practical distance from the Dac;et leg.

1. !ll internal and external surfaces, other than those coated *ith rubber, shall be painted

as specified b9 MP '0P1.

11. 6esign of barge bumpers shall provide for a field elevation adDustment of .= m (' ft).

).1,. Mudmats

Mudmats shall be located such that their bottom is flush *ith or slightl9 belo* the bottomof the Dac;et horiBontal braces at that level.

).1,.1. "i>ing

Mudmat areas shall be siBed for the follo*ing conditions@

Maximum unpiled Dac;et onbottom *eight

!llo*able soil bearing pressure on all mudmats and horiBontal

braces at the mudline

"asic allo*able stresses

).1,.2. 'onditions

"ased on the mudmat areas, the members shall be chec;ed for the follo*ing

conditions@

Maximum unpiled Dac;et onbottom *eight

+ltimate soil bearing pressure on half the mudmats and horiBontal

braces at the mudline

"asic allo*able stresses increased b9 onethird

).1. 'orrosion

%orrosion protection for all steel surfaces belo* elevation >&. m (> ft)

M5 shall be provided b9 anodes, as specified b9 MP 04P1.



25/37


%orrosion protection for all steel surfaces above elevation &. m ( ft)

(including the dec;) shall be provided as specified b9 MP '0P1.

!n additional *all thic;ness of 1&. mm (1?&in) shall be provided for all

main Dac;et members in the splash Bone from elevation &. m to >&. m ( ft to >

ft).

This additional thic;ness cannot be used to provide strength or stabilit9 to the

member in structural anal9ses.

The *eight of this additional steel shall be considered in the buo9anc9

calculations, launch?lift anal9sis and mud mat design.

).1). Other (e9uirements

).1).1. oat 'leats

5here boat cleats, etc. are required, consideration shall be given to theirdesign.

).1).2. nnulus &et5een Ja#/et eg and Pile

The annulus bet*een the Dac;et leg and pile shall be &0 mm (1 in)

and ungrouted, unless other*ise specified b9 The %ompan9.

Gac;et to main pile connections shall be shimmed and *elded.

).1).,. Pile "$a#ers

Pile spacers shall be emplo9ed at all hard points and at an elevation from .4m (& ft) above the mudline and continuous to the bottom of the Dac;et.

Pile spacers shall net a 1&. mm (1?&in) clearance for the pile and shall be

spaced at no more than 0 mm (1 in) centers around inside of the Dac;et

leg at the upper hard points and at no more than &' mm ( in) centers at the

lo*er hard point to the bottom of the Dac;et.

).1).. 'ondu#tor *uides

%onductor guides shall be provided as required for conductor pipe supports.

The inside diameter of guides shall be 0 mm (& in) greater than the outside

diameter of the *ell conductor. #ubmerged conductor guides shall be

designed to minimiBe fatigue.

).1).). Marine *ro5th

Marine gro*th shall be accounted for b9 adding &0 mm (1 in) to the

radius of Dac;et members, conductors, caissons and risers bet*een

elevation M5 and 0. m (10 ft).



26/37


8or members from elevation 0. m (10 ft) to the mudline, 1&.

mm (1?&in) shall be added to the radius.

3equirements for local conditions ma9 be different.

).1).. "#our

! minimum of 1.0 m (0 ft) of scour shall be allo*ed for in the design, unless

a greater amount is specified in T&1% and T&1M of the

ExxonMobil 6ata #heetsfor this Master Practice.

).1).+. Ja#/et-eg Penetrations

Gac;et leg mudline penetrations shall be governed b9 local soil conditions.

2enerall9, Dac;et legs shall penetrate ' m (1 ft) for softer soil and 1.0 m (0

ft) for stiffer soils. The Dac;et leg shall be designed to share in resisting

bending moment of the pile in the extension area.

).1).!. "ea Floor Movement For#es

The platform shall be designed to resist the lateral and vertical forces

imposed b9 seafloor movements, if specified in T&1% and T&1M

of the ExxonMobil 6ata #heetsfor this Master Practice.

. Design of Piles

The contractor shall design the piles (that is, specif9 the outer diameter), *all thic;ness, steel qualit9,pile segments and final penetration based on pile loads determined b9 the platform structural anal9sis,

the axial pile capacit9 data included in T&1% and T&1M of the ExxonMobil 6ata #heetsfor

this Master Practice and geotechnical data.

#tresses during pile installation, due to *eight of the hammer on the pile, shall be chec;ed.

! pile driveabilit9 anal9sis shall be performed to determine that piles can be driven to design

penetrations and to select the appropriate pile hammers.

.1. =se of *rout

T9picall9, piles *ill not be grouted. 7o*ever, if the piles are grouted, ever9 effort shall be

made to protect the grouting and control lines during transportation, launching?lifting, and

installation. "ac;up s9stems shall also be designed and installed in case of accidentaldamage.



27/37


.2. =nderdrive llo5an#es

!llo*ance for underdrive shall be considered for piles having variable *all thic;ness.

Provisions shall be made for extra length of heav9 *all material so the pile *ill not be

overstressed at the *all transitions if the design penetration cannot be reached. The

amount of underdrive allo*ance permitted *ill depend on the degree of uncertaint9regarding the penetration that can be attained.

.,. Preliminary Plans

! preliminar9 loadout plan shall be developed to form the basis of

engineering anal9sis and design. The preliminar9 loadout plan shall include

attachment points. #tresses shall be limited to basic allo*ables.

! preliminar9 transportation plan shall be developed to form the basis of

engineering anal9sis and design. The preliminar9 loadout plan shall include

attachment points. #tresses in the piles shall not exceed the requirements of !P: 3P&!5#6. #tresses shall include a onethird increase over basic allo*ables.

#ea fastenings shall be designed according to the transportation anal9ses.

#ea fastenings shall be located on framed barge dec; areas and shall be designed to

restrain the piles *hen subDected to the design to*ing conditions. %onsiderations

shall also be given for the efficient removal of the seafastening *hen selecting their

location and design.

! preliminar9 lift plan shall be developed to form the basis of engineering

anal9sis and design. The preliminar9 lift plan shall include attachment points.

#tresses in the piles shall not exceed the requirements of !P: 3P &!5#6. #tresses


.. Final Plan

3eanal9ses ma9 be required as a result of the final loadout plan prepared b9 the

fabrication contractor and?or the final transportation and installation plan prepared b9 theinstallation contractor.

+. Design of De#/s

+.1. *eneral (e9uirements

The structural design shall consider an9 maDor or unique topside facilities and, as a

minimum, include the follo*ing@



28/37


1. Preliminar9 anal9ses of the Dac;ets, piles and appurtenances ma9 be performed

independentl9 of the dec; *ith onl9 global dec; loads being imposed on the Dac;et.

The final inplace anal9ses shall be conducted on a combined dec; and Dac;et (*ith

nonlinear coupled piles), *hich shall also account for significant dec; loading

variation such as drill rig location, rig hoo; loads and rig setbac; loads.

&. %omputer anal9ses are required to design for each of the follo*ing conditions@

a) :nplace conditions

b) oadout conditions

c) Transportation conditions

d) 6ec;lift conditions

+.2. 7n-Pla#e nalysis

! static threedimensional anal9sis shall be performed for each complete platform dec;, inaccordance *ith the provisions of !P: 3P &!5#6and !:#% #''0. The computer

model shall include all the main members of the dec;.

Each dec; shall be designed for all realistic combinations of the follo*ing load

conditions, as defined in #ection 4. and !P: 3P &!5#6. The combinations shallinclude but not be limited to the follo*ing@

1. 19ear return period *ind

&. /perating *ind

'. 6ead loads

. ive loads, including multiple positions of moveable equipment such as drilling rigs

0. Equipment test loads

+.2.1.


29/37


+.,. oadout nalysis

! threedimensional anal9sis shall be required for an9 dec; section that is s;idded onto

the transportation barge. The anal9sis shall include a sufficient number of positions

during the s;idding operation, so as to maximiBe member stresses. The anal9sis shall also

compl9 *ith an9 further requirements of MP &Pand the ExxonMobil 6ata #heets.

Member stresses and punching shear shall be determined in all permanent and temporar9

members and Doints.

#tresses in the structure shall not exceed the requirements of !P: 3P &!5#6for tubular

and tubular Doints, and !:#% #''0for structural shapes and builtup members. #tresses


+.,.1. oad 'onditions

The structure shall be anal9Bed for the forces imposed during the loadout. :n

defining the load conditions, consideration shall be given to the operationalrestraints of the loadout s9stem. The follo*ing are among the conditions to

be considered@

1. :ncorrect trim of draft due to tidal fluctuation or *ind

&. "arge movement due to nearb9 marine traffic

'. ocation, slope or settlement of s;id*a9s

. "ased on the anal9sis, deflection criteria shall be established that give theallo*able deflection tolerance for the structure as it moves along the

s;id*a9

+.,.2. Final (evie5

3eanal9ses ma9 be required as a result of the final loadout plan prepared b9

the fabrication contractor.

! revie* of the selected barge shall be performed to ensure that the barge has

the structural strength to *ithstand the expected static and d9namic loadings

from the loadout operations.

+.. %rans$ortation nalysis

! detailed transportation anal9sis shall be performed for each dec; in accordance *ith

!P: 3P &!5#6and MP &P. Motions of the bargedec; s9stem shall be determined

and subsequentl9 used to calculate the dec; member stresses.

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+..1. 'riteria (e9uirements

The selection of comprehensive or reduced design criteria is indicated in theDob specifications.

+..1.1. 'om$rehensive 'riteria

!n environmental report shall be obtained detailing the characteristics

(significant *ave height, period and applicable *ave spectrum) of a 19ear

recurrence, internal maximum storm for the specific route and time of 9ear.

+..1.2. (edu#ed 'riteria

#implified criteria shall be established, *ith revie* b9 The %ompan9.

+..2. Positioning

The selection of the structureCs position on the barge shall be based on both

engineering and operational considerations. !mong these considerations arethe follo*ing@

1. MinimiBe transportation induced forces on the cargo.

&. ocate structure over JstrongJ points.

'. MinimiBe overhang.

. MinimiBe bloc;age of access *a9s.

0. ocate a*a9 from barge fitting and tan; vents.

+..,. oad 'onditions

The structure shall be anal9Bed, using the transportation ballast

configuration, for forces resulting from the application of the appropriate

forces to the barge?cargo s9stem.

Maximum loadings shall be applied in appropriate

combinations to determine the structural integrit9 of the cargo and

seafastening.

! variet9 of storm approach directions relative to the barge

axes shall be ta;en into account.

oad conditions shall consider the effects of roll, pitch,

heave, s*a9, surge, 9a*, *ind and *ave slam.

#tructure stress anal9sis for the structure, including seafastening,

shall be performed using the loads and the seafastening and support

locations defined above.



31/37


+... llo5a&le "tresses:"hear

#tructure member stresses shall not exceed the !P: 3P &!5#6requirements for tubular and tubular Doints, and !:#% #''0requirements for

structural shapes and builtup members. !llo*able stresses shall include a

onethird increase over basic allo*ables.

+..). Other nalyses

Punching shear at the structure and tiedo*n tubular Doints shall be

chec;ed for the load condition forces and stresses.

#tructure fatigue anal9sis for the transportation period shall be

provided. The fatigue anal9sis shall be based on the environmental

conditions expected along the to* route. The fatigue lives shall be

established using appropriate stress concentration factors.

! vortex shedding anal9sis shall be provided for the structure, based

on the environmental conditions expected along the to* route.

+... (einfor#ement and "eafastenings

#tructural members that do not meet the requirements of the

allo*able stresses and that have a fatigue life usation factor of .0 or

greater shall be reinforced.

#eafastenings shall be designed according to the transportation

anal9ses. #eafastenings shall be located at hard points on the dec; and

framed barge dec; areas, and the9 shall be designed to restrain the

structure *hen subDected to the design to*ing conditions. %onsideration

shall also be given for the efficient removal of the seafastening *henselecting their location and design.

2usset plates shall be avoided to alleviate a punching shear

overstress condition at a structure tubular Doint. 2usset plates areacceptable to spread load in the barge dec; or at an intersection *ith

structural shapes.

#eafastening and reinforcement shall be detailed to provide good

fatigue characteristic under c9clic loading. #harp corners, discontinuities

and other stress concentrations are not permitted.

! limiting *eather condition shall be determined that reflects the

criteria used for the stress anal9sis of the structure and seafastenings.

+..+. Final (evie5

3eanal9ses and design ma9 be required as a result of the final transportation

plan prepared b9 the installation contractor.

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! revie* of the selected barge shall be performed to ensure that the barge has

the structural strength to *ithstand the expected static and d9namic loadings

from the to* operations.

+.). ift nalysis

! threedimensional lift anal9sis shall be performed for each dec; section in accordance

*ith !P: 3P &!5#6and MP &P. /ne anal9sis ma9 serve for several dec; sections

of similar siBe and *eight.

ifting pade9es, spreader bar(s), sling and shac;le designs shall be governed b9 the lift

anal9ses, !P: 3P &!5#6and MP &P.

+.).1. Preliminary Plan

! preliminar9 lift plan shall be developed that *ill include prelift, lift and

postlift operations. The preliminar9 lift plan shall include the follo*ing@

1. 3igging plan

&. Marine equipment position and site la9out dra*ings for lift operations

'. #equence for all operations

. imiting environmental conditions

+.).2. llo5a&le "tresses

6ec; member stresses shall not exceed the !P: 3P &!5#6requirements

for tubular and tubular Doints, and !:#% #''0requirements for structuralshapes and builtup members. !llo*able stresses shall include a onethirdincrease over basic allo*ables.

+.).,. Final Plan

3eanal9ses ma9 be required as a result of the final lift plan prepared b9 the

installation contractors.

+.. De#/ 'learan#e

The bottomofsteel of the cellar dec; shall be at an elevation above M5 that is obtainedas described on the appropriate ExxonMobil 6ata #heets.

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+.+. Other (e9uirements

+.+.1. Flooring

6ec; flooring shall be a minimum of mm (0?14in) s;id resistant steel plate

or &0 mm (1 in) depth steel serrated bar grating (hot dipped galvaniBed after

fabrication) for closed and open dec; areas, respectivel9.

+.+.2. Drainage

Trought9pe dec; drains shall be provided on closed dec;s.

5henever possible, an open trough shall be used for gathering alldrainage to a central opening into an & mm ( in) /.6. pipe

do*ncomer to the sump. 6o*ncomer pipes shall have a minimum 1

degree slope. 6o*ncomer pipes from drilling areas shall have a

minimum ' degree slope. ! screen t9pe drain cleanout shall be

provided at the entrance into the do*ncomer. !lso a trash stopper shallbe provided at ends of each lateral trough into the main trough.

6rain troughs and other drainage inlets shall be covered *ith

galvaniBed bar grating. (8iberglass grating ma9 be used, subDect to

%ompan9 approval.)

+.+.,. 'ranes

/n drilling platforms, consideration shall be given to a crane

la9do*n area extending outside the top dec; to accommodate placing

crane loads in the cellar dec; during drilling and producing operation.

:f facilities la9out allo*s, access hatches in upper dec; levels shall

be provided for crane access to lo*er dec; levels.

+.+.. "u$$ort Pads

#upport pads shall be provided for aidstonavigation, as required.

Equipment shall be readil9 accessible for maintenance purposes.

!. Design of ridges3 4al/5ays3 ##ess Platforms and"tairs

!.1. ridges

Threedimensional computer anal9ses are required for inplace and lift

conditions.

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6eflection of bridges shall be limited to 1?'of the span under dead load plus

live load.

ongspan bridges shall be cambered to compensate for dead load plus live

loads. #hortspan bridges ma9 not require camber.

!.2. 4al/5ays3 ##ess Platforms and "tairs

5al;*a9s, access platforms and stairs shall be designed for ;g?m&(1

psf) live loading and have a minimum *idth of .= m (' ft).

Primar9 access to main operating levels, main service levels and roofs of

buildings supporting maDor equipment shall be b9 stair*a9s. Main operating and

service levels shall be those serving grouped equipment that requires frequent

attention of operating and maintenance personnel. Primar9 access to platforms

attached to vessels and to auxiliar9 service platforms shall be b9 ladders.

7andrails shall enclose all platforms and stair*a9s. 7andrails shall be fixedor removable, as specified in the Dob specification.

Toe plates shall be provided at the perimeter of all platforms and stair

landings, and around floor openings for permanent equipment. The latest /#7!

standards shall be follo*ed. Except for areas *here collection of surface drainage

is required, the bottom edge of all toe plates shall be 4.' mm (1?in) above the

floor level.

#afet9 gates or chain shall be provided across ladder openings at all landings.

%ages shall be provided for ladders extending over '. m (1& ft) above dec; or

landing and shall start &. m ( ft) above dec;.

!ccess shall be provided to change out s*ing ropes and other high

maintenance items located under the cellar dec;.

. Design *eneral

.1. llo5a&le "tresses

!ll platform members shall be designed according to the basic allo*able stressesspecified b9 !:#% #''0or !P: 3P &!5#6.

5here stresses are due in part to the lateral and vertical forces imposed b9 design

environmental conditions, the basic !:#% #''0allo*able stresses ma9 be increased b9

onethird. The required section properties computed on this basis shall not be less than

required for design dead and live loads computed *ithout the onethird increase.



35/37


.2. 4elded 'onne#tions

!ll *elded connections shall be designed as specified b9 !5# 61.1.

.,. =se of %u&ular Mem&ers

!ll structural members, braces, supports, etc. belo* the cellar dec; elevation shall be

designed using tubular materials.

10. Material "ele#tion

#teel t9pes specified in Table & are recommended for use in platform fabrication. #ubstitutions shall

not be allo*ed *ithout prior *ritten approval b9 The %ompan9. :n addition, reference shall be madeto MP 0P1.

"a#le 2$ e&ommended tru&tural Materials

Material Designation )reas of /sation

!#TM !'4 Mild steel for general purpose, including rolled

tubulars, beams, girders, trusses, plates, bar

grating, stiffeners, pade9es, braces, dec; legs,

Dac;et legs, Dac;et braces, crane pedestals, piles,

conductors, follo*ers, conductor guides

!#TM !4'' 2rades !, ", %, 6 Pad e9es, Dac;et legs, piles

!#TM !0' 2rade " Tubulars (*elded or seamless), handrails,

conductor guides

!#TM !14 2rade " (Horm) Tubular (seamless for high temperature use), ventboom

!#TM !' 2rade ! or " #tandard bolts and nuts

!#TM !'&0 7igh strength bolts

!#TM !44 2rade 8 or 2 Vent boom pins

!P: 0 2rade " Tubulars (line pipe), dec; trusses, Dac;et braces!P: &7 2rade & or 0 6ec; leg Doint cans, crane pedestal Doint cans,

Dac;et braces, Dac;et Doint cans, pade9es

!P: 0I 2rade I0& Tubulars, Dac;et braces, Gtubes

!P: !0& 2rade &, 0 %aissons, piling, crane pedestal, dec; leg

ocal national requirements and designations shall be addressed *hen appropriate.



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11. Do#umentation

11.1. Design 'al#ulation 8ote&oo/s

! complete set of design calculations shall be suitabl9 bound in &14 x & mm ( 1?&x 11

in) format.

The information shall be indexed and sorted according to maDor platform

components and anal9ses. :t shall contain the design criteria, summaries of storm and

operating loading, pile loading summaries, critical member and Doint loads, as *ell as

summaries of member stresses encountered during loadout, lifting, launching and

transportation.

#;etches sho*ing unit9 chec; ratios, *ith the controlling condition *here

applicable, for all members of the dec;, Dac;et and piling shall be prepared andincluded in the design notes.

The documentation shall include area ta;eoffs for cathodic protection, from

mudline to the M5 line, and from belo* the mudline to the bottom of the piles.

The contractor shall perform detailed *eight calculations for the various

components of the structure and furnish them in an itemiBed format as part of the

calculation noteboo; design.

! registered professional engineer or equivalent, according to local practice

shall certif9 all documentation.

11.2. Design Dra5ings

6ra*ings shall be drafted on standard J6J siBe, 00= x ' mm (&& x ' in) sheets. !lso,

& x 1 mm (11 x 1 in) halfsiBe reproductions of all dra*ings shall be furnished.

6eviations in dra*ing siBe according to local customs shall be provided b9 The %ompan9

*hen necessar9.

%onductor slots (for ne* platforms *hen applicable) shall be numbered

numericall9 (1, &, ', ...) beginning in the north*est corner and progressing left to

right, unless the Dob specifications indicate other*ise.

Each dra*ing shall use the standard title bloc; of the operating %ompan9

affiliate and shall be identified as the propert9 of said %ompan9 affiliate.

Platform north shall be oriented to the top or to the left of the page of each

dra*ing. 6ec; la9outs shall sho* the longitudinal dec; trusses lettered alphabeticall9

as 3o* !, etc. from *est to east and transverse trusses numericall9 as "ent 1, etc.

from north to south.



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Each dec; plan dra*ing shall contain a ;e9 dra*ing reflecting the design

load for each area.

! registered professional engineer or equivalent, according to local practice,

shall certif9 all dra*ings.

11.,. 'om$uter nalysis Out$ut

%opies of all final computer anal9ses shall be provided.

11.. 'om$uter Models

! cop9 of the final dec;, Dac;et and piling (including appurtenances) computer models

used for the design anal9ses shall be provided to The %ompan9 in !#%:: format on 1

mm (01?&in) or = mm ('1?&in) magnetic dis;ette.

design of fixed offshore platforms

Documents