Transcript Design, Construction and Dynamic Testing of a Post

Christchurch Town Hall
Briefing to Councillors
August 28, 2013
Introduction
• What happened
– Settlement
– Lateral Spread
– Measurements
• Analysis
– Current capacity
• Repair and strengthenign
– Foundation options and implications
– Superstructure strengthening
• Relevelling
• Peer Review
Damage sustained
Damage sustained
210mm
Level Survey
Verticality Survey
35 mm
Analysis
• Full 3D computer anlaysis model
developed
– Non-linear, ie models strength and then
determines outcomes
• Quake records run
– From major Canterbury earthquakes
– Scaled to reflect code demands
• Performance assessed
– Compared to current code, IL3
Computer Modelling
Computer Analysis – Canterbury earthquake
sequence
Computer Analysis – Code comparison
Current Seismic Status
45%NBS
45%NBS
27%NBS
63%NBS
14%NBS
Repair and Strengthening
• Repair
– Reinstate as nearly as practical to original
condition
• Accept or reinstate concrete damage where no
structural implications
• Strengthen
– Upgrade of foundations critical to prevent
future damage
• Option 1 – Piles
• Option 2 – Grouting
– CCC policy is to achieve 100%NBS
Option 1 - Piles
Option 2 - Grouting
Beneficial effect
• Movement under moderate earthquake
– Piles: 10mm lateral, 15mm vertical
– Grouting: 0mm lateral, 15mm vertical
• Movement under design level earthquake
– Piles: 150mm lateral, 30mm vertical
– Grouting: 50mm lateral, 75mm vertical
Conclusions:
• Jet Grouting selected as preferred option as:
– Less intrusive construction process
– Superior resistance to lateral spread
– Easier waterproofing detailing
Structural Work Summary
• Upgrade foundations
first
– Primary need before
any other work
– Jet grouting
• Re-level (Limes
Room)
• Strengthen
• Repair & refurbish
Strengthening
• Minimal strengthening required to
Auditorium, James Hay Theatre and
Kitchen
• Foyer
– Columns too flexible and under-strength:
rebuild
– Bracing excluded as too intrusive
– Steel frame alternative under consideration
• Limes Room/restaurant
– Columns too flexible and under-strength:
add bracing below level1
Peer Review
End