api rp 2gen - 7 structures verret wisch[1]

1 2014 BSEE Standards Forum - API 2GEN Presentation - January 28, 2014

API 2GEN Presentation

Sean Verret/Dave Wisch

2014 BSEE Standards Forum

New Orleans, Louisiana


Status

• Group Formed December 1, 2010 • Developed Fundamental TG Objectives • Discussions on what 2GEN should contain • Assessing present API Practice (review/audits) • Practices are similar in intent but different in

application (nomenclature) • Understanding differences between 2GEN and

ISO 19900


Objectives

• Develop 2 Gen – API/ISO Alignment – General Requirements for Offshore

Structures • Fixed • Floating • TLP • Drilling • Marine

• Comment on ISO


2GEN Fundamental Objectives

• Create a framework for the functional documents to address – Create consistency among all functional documents residing below 2GEN – Clarify Categorization and Design Criteria of Facilities

• Manned / Unmanned • Operational / Shut In • Restricted / Unrestricted • Economic

– Clarify expectations on performance – Ensure consistency between floating and fixed structures

• Point to same type of checks (i.e. life safety, robustness, etc) • Logic needs to work on both • Performance Levels / Limit States • Provide guidance and discussion around design


Current Issues

• Categorization of facilities – Life safety – Hydrocarbon Operations – Economic Consequence

• High • Medium? • Low

– Restrictions • Evacuated and shut-in • Change in platform configuration (e.g. disconnectable FPSO’s) • Pre-service conditions (i.e. tow metocean, mating, etc)

• Determination of Exposure Levels • Structural Performance Levels • Acceptance Criteria • Review of current design criteria and loading conditions

(e.g. return periods) • Difference between assessment and new build


Categorization of Facilities based on Characteristics

Facility Category

Characteristics

Categorization Life Safety Hydrocarbon Operations Economic Restrictions**

Dri l ling and/or Production Faci lity with no Restrictions

Manned Operational High / Medium / Low None UNR-1 & EQU-1

Dri l ling and/or Production High Economic Facility with Restrictions

Manned* Operational High None UNR-1 & EQU-1

Unmanned Shut In High Evacuate & Shut-in prior to forecasted

event RES-1

Dri l ling and/or Production Medium Economic Facility with Restrictions

Manned* Operational Medium None UNR-1 & EQU-1

Unmanned Shut In Medium Evacuate & Shut-in prior to forecasted

event RES-2

Not Normally Manned Drilling and/or Production Low Economic Facility with Restrictions

Manned* Operational Low less than 24hrs per

visit & total 4 weeks per year

UNR-1

Unmanned Shut In Low Evacuate & Shut-in prior to forecasted

event RES-3 & EQU-3

Accidental Limit States*** Manned Operational High None ACC-1

Pre-Service*** Unmanned Shut In High / Medium / Low

Unrestricted Operations CON-NR

Restricted Operations CON-R

* - While Manned ** - Other Restrictions may apply *** - Applicable to all Facility Categories


2GEN Structural Performance Level

Fu/Breaking Strength

SLS = Operational – limit deflections and vibrations, defined elastic margins

ULS = “Extreme Storm” – No Primary damage, defined elastic margins

ULS/AbLS/AcLS ~ impending collapse, rupture

ULS/AcLS – minor repairable damage, defined to yield

A

B

C

D Fy/Factored Stress


Structural Performance Level’s by RP

Fu/Breaking Strength

SLS = “Operational” – All RP’s 2A, 2FPS, 2N, 2SM, 2T…. - limit deflections and vibrations, defined elastic margins

ULS = “Extreme Storm” – All RP’s Except 2EQ - No Primary damage, defined elastic margins

ULS/AbLS/AcLS – 2A, 2EQ, 2SIM, 2T ~ impending collapse, rupture

ULS/AcLS – 2A, 2EQ, 2FB, 2T - minor repairable damage, defined to yield

A

B

C

D Fy/Factored Stress


Acceptance Criteria - WSD

Component Criterion A B C DWelding ultimate 1/3 fu 1/3 fu*1.333 - <fuMooring breaking - 1/1.6fu 1/1.25fu fuJackets yield 2/3 fy 2/3 fy*1.333 fy fu

TLP yield 2/3 fy 2/3 fy*1.333 fy fuFloating Hulls yeild 2/3 fy 2/3 fy*1.333 fy fu

Soils ultimate - 1/2fu 1/1.5fu -Shackles ultimate 1/6fu 1/6fu - -

Slings ultimate 1/4fu 1/4fu - -

Parallels with Load and Resistance Factor Design (LRFD)


Structural Performance

Level Including Restrictions

(Load) (Resistance)Exposure

LevelPerformance

LevelSLS - Storm A

ULS - Storm B

ALS - Storm (Abnormal ) D

ALS (Accidenta l ) ACC-1 C & D

ULS - Earthquake Extreme (ELE) C

ALS - Earthquake Abnormal (ALE) D

Pre Service CON ASLS - Storm A

ULS - Storm B

ALS - Storm (Abnormal ) D




ULS - Storm B

ALS - Storm (Abnormal ) C

Pre Service CON ASLS - Storm A

ULS - Storm BALS - Storm(Abnormal )

D




ULS - Storm B

ALS - Storm (Abnormal )C Jackets - Robust

ConfigurationPre Service CON ASLS - Storm UNR-1 A

ULS - Storm RES-3 B

ULS - Extreme (ELE) C


Pre Service CON A

Drilling and/or Production Facilitywithout Restrictions

UNR-1

EQU-1

Design Loading Conditions / Design Situations

Limit StateFacility Category

Drilling and/or Production High Economic Facilitywith Restrictions

UNR-1

EQU-1

RES-1

EQU-3

UNR-1

RES-2

EQU-1Drilling and/or Production Medium Economic Facilitywith Restrictions

Not Normally Manned Drilling and/or Production Low Economic

Facility with Restrictions


Present GOM Practice

Note: RP2A 22nd uses 5 Design Conditions •LC1 ~ A •LC2 ~ A •LC3 ~ B •LC4 ~ B •Dk Ht ~ C

Structural Performance Level

Limit State

Recommended PracticeReturn Period

Restricted/ Unrestricted

A SLSAll RP's:

2A, 2FPS, 2N, 2SM, 2T…. 1-10 yrs URB ULS All Except 2EQ 100 yrs UR or R

C ULS/ALS2A, 2EQ, 2FB, 2T

200-1000 yrs UR or R

D ALS 2A, 2EQ, 2SIM, 2T >1000 yrs UR or R

AB

CD


Review of Current Design Criteria

• Fixed GOM Jacket (High Consequence) – A : 1 yr wave with basic allowables – B : 100 yr wave with 1/3 increase – C : 1000 yr deck clearance

• D: good “by inspection” for Ultimate (life safety)

Design for Performance Level B yields performance greater than 10,000 yr life

safety (Winter/Sudden)

Deck Elevation

Strength

AB

CD

A B

C

D


Summary

• Multiple Design Objectives – many “hidden” in design practice • Consequence Based Criteria (CBC) – “simple” in 1992, broad moving forward • Need to Partition Design Conditions

– Life Safety, Environmental, Economics/Headline – Not Lumping Into Single H, M, L

• Explicit consideration – Load Recurrence – Acceptance conditions

• Express as Return Period and Acceptance • High Level Consistency • Implementation in Specific Documents • Address Design and Assessment • Simpler Assessment In the Future