the bjørnafjorden crossing · replacement within design life. complexity and costs related not...
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The Bjørnafjorden crossingFloating bridge – Concept development and selection process
Øyvind Kongsvik Nedrebø Anette Fjeld Svein Erik Jacobsen
E39 Stavanger – BergenNew highway
Stavanger
Bergen
Bjørnafjorden
Floating bridge, rev.: 2012
Subsea rock, Flua: -32 m
2016:
2016: NOT OK!
17.03.2017
1: Moved bridge east at north end (away from Flua)
Old, 2016
New, 2017
2: Changed from concrete to steel for pontoons
2017: New floating bridge design
K7
K8
End-anchored floating bridge
Side-anchored floating bridge
How to reach the required and convincing level clarity regarding which bridge candidate should be taken forward to FEED phase? Run additional conceptual design phase based onthe following:
a) Two teams work in parallel on four alternatives (K11…K14).
b) The two teams to be separated. No exchange of information between the teams are allowed.
c) The results reported to be based on extensive analysis work. The design documentation produced shall cover all major aspectsgoverning for the design.
d) Independant verification work to be carried out by DNV GL in parallel.
A challenging assignment! However, NPRA expectation:The two teams will be capable of reaching the same conclusionregarding which bridge alternative to select for FEED.
28.10.2019
Four alternatives nominated: K11, K12, K13, K14subject to assessment in new concept study phase (Nov. 2018 – Aug. 2019)
K7 →
Alternative K11: Arch-shaped floating bridge supported
only at each end, i.e. equivalent to K7.
Alternative K12: Arch-shaped floating bridge supported at
each end similar to K11, but in addition equipped with a mooring system.
Alternative K13: Straight side-anchored bridge similar to K8.
Alternative K14: Side-anchored bridge similar to K8.
However, straight part of bridge limited to the cable-stayed bridge. Floating bridge part to have curved geometry.
K8 →
1. The project setup of both teams
2. Proposed base cases from both teams
3. The different selection methods for both teams
4. Insight to one technical challenge; parametric exitation
5. Concluding remarks to our recommendation of K12
CONSULTANTS PART OF THE PRESENTATION
WORK COLLABORATIONNORCONSULT – OLAV OLSEN
HEYERDAHL ARKITEKTER AS
PROJECT ORGANISATION
COST AND UNCERTAINTY ANALYSES
K12
K13
K14
K11
PMCOMP. REPR.
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CAD/BIM
OTHER PLANNING
DISCIPLINES
SUPPORT
BASE CASES
K11: End-anchored K12: End-anchored with mooring
K13: Side-anchored K14: Side-anchored without
expansion joint
Base cases
QUANTITATIVE CONCEPT RANKING
COST ROBUSTNESS SUSTAINABILITY
+ AESTETHICS: Weighted value of monumental buildingadditional cost (1 billion)
CONCEPT DEVELOPMENT AND SELECTIONCOST MODEL
> Cost model connected to the concept definition model
> Bottom-up cost estimatecovering approx. 90% ofconstruction cost
> Consistant across thedifferent concepts
> Tool for working with themost important costelements
> Shows if proposed conceptalterations actually reducescosts and/or uncertainty
CONCEPT DEVELOPMENT AND SELECTIONROBUSTNESS CRITERION
> Over 100 events og risk elements were identified through workshops, interviews and a questionnaire. 21 of these where classified as concept specific and significant.
> Probability and consequence was estimated in a separate risk workshop (2 rounds) and the expected value of the risk element is calculated.
> Other risk elements (project general) was not evaluated and will be an addition to all concepts.
CONCEPT DEVELOPMENT AND SELECTIONRISK WORKSHOP INFLUENCE
12%
6%
Ship impact
Consequence cost distribution workshop 1:
Consequence cost distribution workshop 2:
Ship impact
VISUAL IMPACT
QUALITATIVE CONCEPT RANKING
K11 K12
Pros: - Known technology, built before (in a smaller scale)
- Simple system, easy to calculate response from loads, ductile behavior
- Known eigenperiods which are difficult to move
- Larger capacity for unknown overloading due to stronger bridge girder
- Installation of complete assembled floating bridge, less work in Bjørnafjorden
- Less maintenance, few “wearing parts”
- Redundant system with double horizontal load-carrying system.
- Largest potential for- and flexibility in designing a robust solution.
- Mooring reduces the response and increases design life compared to K11. Possible to increase design life further with small amount of
additional steel. - Fibre rope mooring gives favorable interaction
with bridge girder. - Linear behavior of mooring without risk of
successive mooring line failure for known load cases
- Installation of complete assembled floating bridge, less work in Bjørnafjorden, simple mooring hook-up
- Few and manageable anchor locations - No joints and bearings
Cons: - Lack of redundancy - Uncertain wind load as turbulence
spectra are normally not applied to structures with long eigenperiods
- Large, concentrated forces at landfalls
- Requires larger clearance between tower legs
- Mooring needs replacement within design life. Complexity and costs related to this operation not sufficiently reflected.
- Challenging soil conditions, risk of underwater slides
- Limited experience with taut mooring on these water depths
Rank: 2 1
Reason: Most simple Most robust
K13 K14
Pros: - Redundancy in mooring - Fibre rope mooring gives favorable
interaction with bridge girder. - Linear behavior of mooring without risk
of successive mooring line failure for known load cases.
- Simplest production. - Potential for moving landfall north onto
the bank outside Gulholmane and obtaining a shorter bridge.
- Redundancy in mooring - Fibre rope mooring gives favorable interaction with
bridge girder. - Linear behavior of mooring without risk of
successive mooring line failure for known load cases.
- No joints and bearings
Cons: - Mooring, part of main load-carrying system, needs replacement within design life. Complexity and costs related not sufficiently reflected.
- Challenging soil conditions, risk of underwater slides
- Many and some unfavorable anchor positions.
- Limited experience with taut mooring on these water depths
- Great number of work operations performed on the fjord.
- Monotonic driving experience - Maintenance of joints and bearings - Noise from joints
- Mooring, part of main load-carrying system, needs replacement within design life. Complexity and costs related not sufficiently reflected.
- Challenging soil conditions, risk of underwater slides - Some unfavorable anchor positions. - Limited experience with taut mooring on these
water depths - Great number of work operations performed on the
fjord.
Rank: 4 3
Reason: Most complex Compromise
K11 K12
Pros: - Known technology, built before (in a smaller scale)
- Simple system, easy to calculate response from loads, ductile behavior
- Known eigenperiods which are difficult to move
- Larger capacity for unknown overloading due to stronger bridge girder
- Installation of complete assembled floating bridge, less work in Bjørnafjorden
- Less maintenance, few “wearing parts”
- Redundant system with double horizontal load-carrying system.
- Largest potential for- and flexibility in designing a robust solution.
- Mooring reduces the response and increases design life compared to K11. Possible to increase design life further with small amount of
additional steel. - Fibre rope mooring gives favorable interaction
with bridge girder. - Linear behavior of mooring without risk of
successive mooring line failure for known load cases
- Installation of complete assembled floating bridge, less work in Bjørnafjorden, simple mooring hook-up
- Few and manageable anchor locations - No joints and bearings
Cons: - Lack of redundancy - Uncertain wind load as turbulence
spectra are normally not applied to structures with long eigenperiods
- Large, concentrated forces at landfalls
- Requires larger clearance between tower legs
- Mooring needs replacement within design life. Complexity and costs related to this operation not sufficiently reflected.
- Challenging soil conditions, risk of underwater slides
- Limited experience with taut mooring on these water depths
Rank: 2 1
Reason: Most simple Most robust
K13 K14
Pros: - Redundancy in mooring - Fibre rope mooring gives favorable
interaction with bridge girder. - Linear behavior of mooring without risk
of successive mooring line failure for known load cases.
- Simplest production. - Potential for moving landfall north onto
the bank outside Gulholmane and obtaining a shorter bridge.
- Redundancy in mooring - Fibre rope mooring gives favorable interaction with
bridge girder. - Linear behavior of mooring without risk of
successive mooring line failure for known load cases.
- No joints and bearings
Cons: - Mooring, part of main load-carrying system, needs replacement within design life. Complexity and costs related not sufficiently reflected.
- Challenging soil conditions, risk of underwater slides
- Many and some unfavorable anchor positions.
- Limited experience with taut mooring on these water depths
- Great number of work operations performed on the fjord.
- Monotonic driving experience - Maintenance of joints and bearings - Noise from joints
- Mooring, part of main load-carrying system, needs replacement within design life. Complexity and costs related not sufficiently reflected.
- Challenging soil conditions, risk of underwater slides - Some unfavorable anchor positions. - Limited experience with taut mooring on these
water depths - Great number of work operations performed on the
fjord.
Rank: 4 3
Reason: Most complex Compromise
K11 K12
Pros: - Known technology, built before (in a smaller scale)
- Simple system, easy to calculate response from loads, ductile behavior
- Known eigenperiods which are difficult to move
- Larger capacity for unknown overloading due to stronger bridge girder
- Installation of complete assembled floating bridge, less work in Bjørnafjorden
- Less maintenance, few “wearing parts”
- Redundant system with double horizontal load-carrying system.
- Largest potential for- and flexibility in designing a robust solution.
- Mooring reduces the response and increases design life compared to K11. Possible to increase design life further with small amount of
additional steel. - Fibre rope mooring gives favorable interaction
with bridge girder. - Linear behavior of mooring without risk of
successive mooring line failure for known load cases
- Installation of complete assembled floating bridge, less work in Bjørnafjorden, simple mooring hook-up
- Few and manageable anchor locations - No joints and bearings
Cons: - Lack of redundancy - Uncertain wind load as turbulence
spectra are normally not applied to structures with long eigenperiods
- Large, concentrated forces at landfalls
- Requires larger clearance between tower legs
- Mooring needs replacement within design life. Complexity and costs related to this operation not sufficiently reflected.
- Challenging soil conditions, risk of underwater slides
- Limited experience with taut mooring on these water depths
Rank: 2 1
Reason: Most simple Most robust
K13 K14
Pros: - Redundancy in mooring - Fibre rope mooring gives favorable
interaction with bridge girder. - Linear behavior of mooring without risk
of successive mooring line failure for known load cases.
- Simplest production. - Potential for moving landfall north onto
the bank outside Gulholmane and obtaining a shorter bridge.
- Redundancy in mooring - Fibre rope mooring gives favorable interaction with
bridge girder. - Linear behavior of mooring without risk of
successive mooring line failure for known load cases.
- No joints and bearings
Cons: - Mooring, part of main load-carrying system, needs replacement within design life. Complexity and costs related not sufficiently reflected.
- Challenging soil conditions, risk of underwater slides
- Many and some unfavorable anchor positions.
- Limited experience with taut mooring on these water depths
- Great number of work operations performed on the fjord.
- Monotonic driving experience - Maintenance of joints and bearings - Noise from joints
- Mooring, part of main load-carrying system, needs replacement within design life. Complexity and costs related not sufficiently reflected.
- Challenging soil conditions, risk of underwater slides - Some unfavorable anchor positions. - Limited experience with taut mooring on these
water depths - Great number of work operations performed on the
fjord.
Rank: 4 3
Reason: Most complex Compromise
• Milestones for development and selection- Initial phase: Establish base cases through:
▪ Experience form earlier phases▪ Initial analyses▪ Sensitivities▪ Possible showstoppers▪ Aestetic evaluation
- Development phase▪ Extensive analyses and design, including sensitivity analyses, ship impact, parametric excitation, comfort criterias, hydrodynamic effects etc.▪ Risk analyses▪ Cost estimates based on quantities
- Conclusive phase▪ Supplementary analyses▪ Conclusion on parametric excitation▪ Optimization▪ Risk reduction through continous risk analyses and risk mitigation▪ Updated cost estimated incl. Uncertainties▪ Aesthetics▪ Robustness
Conclusion: K12 is the preferred solution
Concept development and selection
Concept development and selectionAnalyses and special studies
Concept development and selectionAesthetics - Visual Impact
• Horizontal alignment• Landscape
• Vertical alignment• Pontoon, column, bridge deck, tower and cable stay shape/configuration• Walkway• Landscaping
Concept development and selectionCost estimates
Concept development and selectionRisk Analyses
Risk analyses are carried out as a work tool to:• Choose optimal bridge concept- Identification of risk elements- Comparisons of risk elements
between concepts- Comparisons of risk elements
to others• Outline areas/challenges for
further evaluation within theproject (mitigations)- Parametric excitation- Placing of anchors- Ship collosion
Concept development and selectionRanking –K12 superior tothe other alternatives
ChallangesParametric excitation and response
ChallangesParametric excitation and response
ChallangesParametric excitation and response
OON PROPOSAL: CONSERVATIVE DESIGN APPROACH
OON PROPOSAL: CONSERVATIVE DESIGN APPROACH
PARAMETRIC EXCITATIONCALCULATED RESPONSE
CALCULATED RESPONSE HAS A RETURN PERIOD OF APPROX. 700 MILL. YEARS
© Dr.techn.Olav Olsen AS
- End-anchored bridge; known structure without joints or bearings
- Aestethically the best alternative with good horizontal and vertical alignment
- Mooring reduces response and increases robustness and capacity for skew loading
- Quantities, a key cost driver, have «converged», but optimizations are still possible
- Significant development in construction and installation methods
CONCLUSION: K12 IS A ROBUST AND COST-EFFECTIVE SOLUTION
© Dr.techn.Olav Olsen AS
- Two completely independent assessments recommended the same floating bridge alternative, and DNV GL supports the conclusion.
- The recommendations are made on detailed information about the site conditions, given in the design basis prepared by NPRA.
- Uncertainties from previous phases, like parametric resonnance, has been adressed and handled in this project
CONCLUSION: K12 IS A ROBUST AND COST-EFFECTIVE SOLUTION
The NPRA has a solid basis for proceeding with the project
Summary on costs!Concepts considered for Bjørnafjorden
Illustration: Vianova/Baezeni/NPRA
Concept assessed 2015 - 2016: 42,8
Concept assessed 2015 - 2017: 22,9
2012: 14,5
2019: 15,8
Project cost: billions NOK (2019-kroner, incl. VAT)
Concept assessed 2015 - 2016: 27,6
Extra gain! ☺This lagoon saved from NPRA highway E39 ambition!
04.07.2017
Thank you!