A project undertaken by TRANSIT NEW ZEALAND in conjunction with
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Transcript of A project undertaken by TRANSIT NEW ZEALAND in conjunction with
![Page 1: A project undertaken by TRANSIT NEW ZEALAND in conjunction with](https://reader036.fdocuments.in/reader036/viewer/2022081603/568137ed550346895d9fa7f0/html5/thumbnails/1.jpg)
A project undertaken by
TRANSIT NEW ZEALAND
in conjunction with OPUS INTERNATIONAL CONSULTANTS LIMITED
APEX PROJECT MANAGEMENT LIMITED
and
REGIONAL BRIDGE CONSULTANTS
S E I S M I C S E C U R I T Y O F S T A T E
H I G H W AY B R I D G E S I N
N E W Z E A L A N D
SCREENING & RETROFIT – PROGRESS SUMMARY
S E I S M I C S E C U R I T Y O F S T A T E
H I G H W AY B R I D G E S I N
N E W Z E A L A N D
SCREENING & RETROFIT – PROGRESS SUMMARY
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OBJECTIVE & STATUS
• To identify bridges that justify a more detailed seismic assessment and, possibly, retrofitting
• Seismic screening completed
• Retrofitting underway
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BACKGROUND
Project drivers:
• Experience from earthquakes – integrity of the roading network is vital
• Dramatic improvement in performance often achievable from simple measures, e.g. linkages
• Past practice - since 1933, bridges either monolithic or have spans interlinked
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BACKGROUND
• Past retrofit policy – low cost seismic improvements in conjunction with work to raise service standards
• In early 1990s, 8 bridges in regions of higher seismicity retrofitted for linkages
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BACKGROUND
• Wellington’s Thorndon Overbridge and the Auckland Harbour Bridge retrofitted
• A screening procedure was developed Refer 12th World Earthquake Conference (Chapman et al)
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RISK ASSESSMENT
• Identification of structure vulnerabilities
• Classification of risk level for each risk event - likelihood & consequences
• likelihood derived from:
• peak ground acceleration causing risk event• seismicity of site
• consequences derived from:
• effect on safety• extent of traffic disruption
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ECONOMIC RANKING INDICATOR (ERI)• For “high” and “significant” risks, an
“Economic Ranking Indicator” determined
• “ERI” was based on factors such as:• traffic volume
• duration & probability of disruption
• cost of traffic disruption
• cost of bridge damage (if significant)
• discounted cost (ROC) of retrofit
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RANKING
• Ranking was based on factors such as:• Route priority
• Risk to Life
• ERI value
• Number of risk events
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OUTCOME
• 3813 bridges & culverts screened• 2842 (75%) eliminated• 971 (25%) subjected to risk assessment• 381 (10%) “high” or “significant” risk level• 188 (5%) separately identified as having
linkage deficiencies• $850 per bridge for 2322 bridges
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ASSESSING & RETROFITTING STRUCTURES• Top 50 ranked structures will be assessed
• Available specialist resources likely to constrain the timeframe for assessments
• Expenditure ~ $5M to ~$6M per annum
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Bridge Seismic ScreeningStage 2
• Progress to date
– Linkage Retrofit
– Detailed Assessments
– Detail Design & Construction
• Programme Management
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Progress to date• Linkage Retrofit
– P1 & P2 routes (130 comepleted)
• Detailed Assessments
– Re-prioritised 50 completed detail assessments
– On hold till first 25 bridges addressed
• Detail Design & Construction
– Retrofits complete 10
– Retrofits under construction 5
– Designs in progress 6
– Recommended for replacement 2
Programme Total P1 P2 P3
Detail Assessments 335 192 72 71
Linkages 173 92 45 36
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Programme Management
• Delegated authority
• Project Team
– Rudolph/Gavin/John Wood/Howard Chapman
• Project Management Framework
– Basis of seismic design for existing bridges.
– Remaining life of structure & condition
– Mode of failure
– Performance indicators & risk profile
– Retrofit vs. replacement cost
– Route importance
– Bridge Design Statement