This document summarizes the performance of masonry buildings in Christchurch during the 2010-2011 earthquake swarm. It provides an overview of the history of masonry construction in New Zealand and Christchurch. It describes the characteristics of the 2010 and 2011 earthquakes and compares the damage to different building types such as unreinforced masonry, reinforced concrete, and timber buildings. It discusses the factors that influenced building performance such as short ground shaking duration. It also summarizes the lessons learned about retrofitting technologies and the seismic vulnerability of unreinforced masonry buildings.
6. Early Christchurch
Both stone and clay brick masonry
Victorian Christchurch in 1885 (Coxhead 1885) Christchurch’s first ‘skyscraper’, photo
circa 1910 (Brittenden Collection 1910)
7. 1931 Hawke’s Bay earthquake
(256 deaths, 525 aftershocks in 14 days, M7.8)
Hastings Street, Napier, circa 1914 (Alexander View down Hastings Street, Napier after the
Turnbull Library). 1931 earthquake (Alexander Turnbull Library).
8. 1931 Hawke’s Bay earthquake
(earthquake followed by fire)
Looking over Napier at the buildings ruined by Ruins of the Napier Anglican Cathedral
the 1931 earthquake and the fires (Alexander after the 1931 Napier earthquake
Turnbull Library). (Alexander Turnbull Library).
9. Slow steady loss of heritage unreinforced
masonry buildings, post-1930
Alexander Turnbull Library Alexander Turnbull Library
Wellington, 1950
19. Earthquake statistics
• Date: 04.09.2010 4:35 am (NZ Standard
time)
• Magnitude: Mw 7.1
• Focal depth: 10 km
• Maximum Intensity: MMI 8
• No direct fatalities (one heart attack)
• 1 major casualty due to falling chimney
• Largest earthquake on record to occur
within 40 km of major city and cause no
fatalities
Credit: GeoNet
20. Fault trace
• Numerous places where offset could be
measured – right lateral up to about 3 m,
with variable vertical throw (mostly < 1 m).
Credit: GNS
24. 22 February 2011
• David Biggs overnighted in Grand Chancellor
hotel
• Jason flew from Nelson arriving 7.30 am, bags
checked on to Wellington
• Interviewed by Canterbury TV at 11.00 am
• Ken Elwood (Vancouver) in audience
• 84 attendees at afternoon seminar
• Earthquake struck at 12.51 pm
144. Transect
• Designed to sample on a pre-determined
route
• Used for sampling biological species
• Deficiencies
– Dependent on route, and route was intentionally
selected to survey large stock of URM buildings
– Level 1 sampling, building condition judged
exclusively by appearance of street frontage
– Data is subjective
145. URM = 52%
Of URM, 48% red
Red URM = 24.8%
Some buildings worse
than appear from street
front
Say about 1 in 3 red
overall
Thanks to Quincy Ma,
Liam Wotherspoon,
Rick Henry
146. Benefits
• Immediately of interest to Christchurch City
Council
• Requested by the Historic Places Trust
• Used to provide accurate information to
media
• Used in response to a request to identify a
suite of ‘indicator buildings’
148. Indicator buildings
• If these buildings exhibit damage then others
of this class need to be inspected also
• URM: Soft enough (damaged) so that it did
not take shock of comparable intensity to
cause further damage
• Other forms: Exhibiting measurable damage
that can be easily monitored
163. David was one of the last paying customers!
Grand Chancellor Hotel
• 1980s construction
• Constructed in 2 stages
• Core wall up to 7th storey
• Perimeter moment frame
above
• South face dropped 600mm
to 900mm due to failure of
wall at ground level and
columns at 7th storey
164. RC Structural Wall Buildings
Overall differential settlement of
around 300 mm
Lightly confined boundary zones
168. Other locations being inspected
1000+ clay brick masonry
500+ concrete masonry
100+ stone masonry
250+ churches
Perhaps 25% of all
heritage masonry
buildings in New Zealand
169. Is this what we should expect for
an earthquake this intense?
(1:10,000 years or 1:3.65 million days!)
CENTRAL CITY AND NZS1170 SPECTRA
CLASS D DEEP OR SOFT SOIL
Larger Horizontal Components
1.8
1.6
NZS1170 2500-yr Class D
1.4
Demand 1.2
NZS1170 500-yr Class D Deep or
Soft Soil
CHHC_MaxH_FEB
1
SA(T) (g)
0.8 CCCC_MaxH_FEB
0.6
CBGS_MaxH_FEB
0.4
Capacity REHS_MaxH_FEB
0.2
GM_Larger_FEB
0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Period T(s)
170. Is this what we should expect?
• Yes. URM buildings consistently collapse in
large earthquakes
• The NZ URM building stock is analogous to
that of other European colonies. Past failures
elsewhere have relevance to NZ
• Unretrofitted URM buildings loaded to about
6 times their calculated capacity
• Why did they not all completely collapse?
171. Short duration of ground shaking
(Less than 10 seconds of string ground shaking on both occasions)
0.30
Acceleration(g)
N64E
0.15
0
-0.15 4 Sept 2010
-0.30
0 10 20 30 40 50 60
Time(s)
22 Feb 2011
173. Implications for elsewhere in NZ?
• The URM building stock throughout NZ is
remarkably homogeneous
• The same outcome can be expected
anywhere in NZ after a large earthquake
1. Do nothing
2. Seismic improvement
3. Demolition
174. Von Sierakowski and Co. Building
[1906] [2010]
The Von Sierakowski Building, Corner Tuam and Columbo Street (1906). The factory
was erected in 1906 and was the largest wireworks factory in the Colonies.
175. Von Sierakowski and Co. Building
[1906] [September 2010]
The September Darfield earthquake of 2010 caused out-of-plane wall failure and loss
of the parapet.
176. Von Sierakowski and Co. Building
[1906] [February 2011]
The September Darfield earthquake of 2010 caused out-of-plane wall failure and loss
of the parapet.
177. The Christchurch Cathedral
[1888] [February 2011]
The Cathedral was designed by the Englishman G.G. Scott and work began on it in
1863. The tower and spire, paid for by the Rhodes family, are complete in the
photograph but were damaged multiple times by earthquakes in 1881, 1888 which
brought down part of the top section, and again in 1901.
178. Poor quality of mortar
Many tested samples 1.0-1.5 MPa
Τ=C+µN compression strength
181. Diaphragm Extraction and Testing
Establish the properties of actual heritage diaphragms with true timber species and aged
nail connections. Test both roof and floor diaphragms
191. Vulnerability of cavity construction
Documenting damage
Identifying prevalence of failure modes
Fragility functions
Performance of retrofit technologies
Repair vs demolish scenarios
203. Timber frame with
masonry veneer
(18) Reinforced concrete
Timber construction
or steel structure
(16)
(20)
URM stone
(22)
URM brick Approximately 250
(24) churches
204. Damage to rubble masonry Damage to brick masonry Damage to a gable in St
construction in Holy Trinity in St Luke’s church (1859), James church (1926),
church (1872), Avonside Christchurch Riccarton
Plaster Brick Unrein. (?) concrete Stone
10 220 170 230
St James Church (1926), Riccarton; wall composition
226. Conclusions
• URM – why was there not more collapses (because of low
duration)?
• Massive loss of architectural heritage “Christchurch now
has no earthquake-prone buildings”
• Clear lesson for all of NZ regarding earthquake prone
buildings. Improve or remove
• Better knowledge of URM and diaphragm materials
• Proven success of a number of retrofit technologies
• Good data on seismic performance macros URM building
stock and of churches
• RCM failures mostly attributable to poor grouting and
rebar detailing
227. As the recovery begins ...
• Futility is appearing, public lack of confidence
• Insurance companies saying that they will not
insure a strengthened URM building
• Used to be 1/3rd of 0.22. Now 2/3rd of 0.30
(strengthening requirement is now 3 times what
it was a year ago)
• “Knock them all down – its too hard to make
them safe”
228. “Is it acceptable that 2 New Zealand cities have been destroyed
by earthquakes in the past 80 years?”
Nigel Priestley at the PCEE conference