25 August 2011
Quakes Royal Commission Hearings Start 17
The Canterbury Earthquakes Royal Commission will begin hearings on 17
October 2011 at St Teresa Church Hall on the corner of Riccarton Road and
Puriri Street in Christchurch.
The Commission will hold hearings on the issue of seismicity. They are
expected to take about a week. Other hearings will be held about other topics
later in the year and in the New Year.
The Commission is not able to set out a full schedule of the hearings until
it receives the results of a separate investigation
being carried out by the Department of Building and Housing into the
failure of the CTV, PGC, Hotel Grand Chancellor and Forsyth Barr buildings. In
the meantime the Commission is continuing with its own investigation of the
failure of those buildings and many other buildings in the CBD, including those
in or near where lives were lost on 22 February 2011.
“Our terms of reference require us to
take the results of that investigation into account and determine the sequence
of our inquiry having regard to its availability. Until the results of the
departmental investigation are publicly available the Commission can not
schedule hearings dealing with those buildings,” says Chair Justice Mark
“Because the hearings in relation to the inspection of buildings and
the ‘stickering’ or ‘placarding’ of buildings should
logically follow consideration of the reasons for the failure of these
buildings, those hearings also cannot be scheduled at this stage.
“It is important that the departmental investigation is thorough as
that will assist the work of the Commission.”
On the issue of seismicity, the Commission has published a report on its
website prepared by GNS Science. It deals with the level of earthquake risk in
Christchurch, the nature and severity of the Canterbury earthquakes and the
implications for Christchurch and New Zealand’s national seismic hazard
Professor Ralph Archuleta of the University of California at Santa Barbara
and Professor Norman Ambrahamson of University of California at Berkeley are
carrying out separate peer reviews of the report to ensure that advice given to
the Commission reflects international understandings and best practice.
The Commission has called for submissions and evidence on the GNS Science
report to be provided to it (preferably in electronic form) by 30 September
The Commission has also published on its website a report by Professor
Emeritus Athol Carr of the University of Canterbury about Inelastic Response
Spectra. The report contains technical information for the use of structural
engineers to help them explain why observed damage has occurred to buildings as
a result of the earthquakes. It will also help in identifying what damage not
immediately apparent, may have occurred.
In coming weeks the Commission plans to publish further reports dealing with
some of the other subjects that will be considered in public hearings. These
include the characteristics of land in the Christchurch CBD, new building
construction methods and technologies, and the performance of unreinforced
masonry buildings in the earthquakes.
About the GNS Science Report
The GNS Science report is called ‘The Canterbury Earthquake sequence and implications
for Seismic Design Levels’.
GNS Science advise the report was largely compiled from existing
information, especially short-term projects to inform the rebuild of
Christchurch and associated scientific investigation that has been underway
since last September. There was also a lot of pre-existing background material.
However, it also contains material that is new to the general public.
- Comparisons between the four principal earthquakes, such as on pages 31 and
- The map plots (Figures 3.4, 3.7, 3.9, 3.14)
- Preliminary Alpine Fault rupture modelling. GNS notes more modelling work
needs to be undertaken.
About the Professor Emeritus Athol Carr
The Professor Emeritus Athol Carr report is called ‘Inelastic Response Spectra for the Christchurch Earthquake
Professor Carr advises the report resulted from observations that one of the
premises used by structural engineers, worldwide, did not appear to hold when
analyses were carried of buildings using the Christchurch earthquake
All design standards (or codes) assume, that for building with a longer
natural period of free-vibration (in NZS 1170.5; 2004 long is greater than 0.7
seconds, typically for buildings of four or five stories) that the
displacements of the building define to behave in a ductile manner, the
presumption for virtually all buildings built in New Zealand, the displacements
would be the same (or similar) to those of a building which behaved elastically
Ductile buildings with a short natural period would expect larger
displacements than those for the linear elastic building. The
observations from the spectra presented indicate that the displacements could
be considerably larger for buildings with natural periods up three seconds
(i.e. to about 18 stories).
This assumption by all design standards has had some criticism for several
decades but this criticism has largely been ignored, as of minor
consequence. However, it is a fundamental feature in the way the design
forces (actions) and displacements are computed for design.
Professor Carr advises the continued use of this assumption needs real
investigation. This could be particularly important for the new methods
of structural design which start off with a displacement spectra which is
obtained from the current acceleration design spectra using this equal
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