4.3 Observations from the Canterbury Earthquakes II
The Canterbury Earthquake: A Consultant’s Response
S. Robertson, W. Parker & S. Keenan
ABSTRACT: In the initial hours, days and weeks following the Canterbury Earthquake, Opus staff worked long hours to establish the safety of buildings and other infrastructure for clients, staff and the general public including key support for Civil Defence and Urban Search and Rescue. Within a short period, Opus Engineers were mobilised globally to support local capability and the overall recovery effort.
While many of the actions taken during this time broadly followed existing emergency response procedures and business continuity plans, new systems had to be rapidly developed and existing communication and business continuity plans revised.
This was a true test of preparedness and the need for empowered decisions to be made in the rapidly changing and challenging environment. The response presented a number of key challenges and many valuable lessons were learnt throughout the response period, particularly in the areas of staff care, resource preparedness and response delivery. This paper focuses on the lessons learnt, that can be drawn from this experience, which will greatly assist both Opus and other organisations in the improvement of the preparedness for future events and subsequent response.
Lessons Learnt from the Darfield Earthquake – A Bridge Consultants Perspective
A.G. Rooke & M.J. Cowan
ABSTRACT: As the New Zealand Transport Agency’s (NZTA) Regional Bridge Consultant in Canterbury and the West Coast, Opus International Consultants Ltd were required to respond to the MW7.1 earthquake that struck 40km west of Christchurch on September 4th. This involved the coordination and execution of inspections to confirm the serviceability of bridges in the immediate aftermath of the earthquake along with follow up inspections to record the extent and severity of damage suffered during the event. In addition, Opus also undertook the inspection of some 500 local authority bridges in Christchurch and the Banks Peninsula. All NZTA inspections were completed and a report on damage sustained issued within five days. Christchurch City Council inspections were completed and reported within two weeks of the event.
This paper explores Opus’ response to the earthquake as bridge consultant for two different clients. It reviews the procedures implemented by Opus in responding to the earthquake and identifies some of the lessons learnt both during the immediate response and subsequent inspections in the following days and weeks.
Damage observed from a range of bridge sites is presented and the benefits of having a comprehensive well maintained bridge information system to assist in the response to emergency events is highlighted.
Performance of Masonry Buildings in the Christchurch Earthquakes
Jason M. Ingham, Lisa Moon, Jocelyn Dickie & Dmytro Dizhur
ABSTRACT: Christchurch has a large stock of masonry buildings, including natural stone unreinforced masonry (URM), clay brick unreinforced masonry, and reinforced concrete masonry buildings. All of these buildings types have been subjected to extensive damage during the recent earthquakes. It is unfortunate to see such widespread damage to the clay brick unreinforced masonry buildings in the heritage precinct of Christchurch’s CBD as the poor seismic performance of this class of building has been known for decades. However, two principal lessons pertaining to URM buildings can be taken from this event: (1) that all of New Zealand must be reminded of the vulnerability of this class of building and act accordingly to strengthen or demolish dangerous buildings to remove such a hazard, and (2) that we now have unique data on seismic retrofit details that have succeeded (and that have also failed) for different levels of peak ground acceleration associated with the different events. This information will be extremely useful when making recommendations for recovery in Christchurch and for seismic improvement to URM buildings nationwide.
Although less seismically vulnerable, reinforced concrete masonry buildings have also been damaged in the earthquake. These damage observations can be used to indicate deficiencies in design, detailing and construction of reinforced concrete masonry buildings, and will be important for future masonry design standards.
The presentation will review the primary damage modes for masonry buildings, and the implications for future retrofit and design of masonry buildings.
Presentation 163
Response of Multi-Storey Buildings to the Darfield Earthquake
B.D. Galloway, H.J. Hare & D.K. Bull
ABSTRACT: The recent Darfield Earthquake produced particularly strong ground motions in the long period range, inducing strong responses from the multi-storey buildings in the Christchurch CBD.
Christchurch’s taller buildings are likely to have experienced shaking intensities in excess of their design spectra, although of a shorter duration than might be expected of a full code level earthquake. This paper focuses on the majority of these buildings which were of reinforced concrete construction, designed to the relatively modern seismic design codes of the 1980’s and incorporated the principles of capacity design.
Plastic hinge formation of ductile concrete moment resisting frame structures was observed, with frame elongation effects causing tearing of precast floor diaphragms reinforced with cold drawn wire mesh. Concrete wall structures were generally found to perform adequately, with minor shear and flexural cracking observed. Deformation compatibility issues were observed between the primary seismic and secondary gravity structures.
This paper seeks to contrast some of the observed performance of these buildings with what might be expected from current analysis and design practices, as well as to consider the implications of significantly higher long-period response that has been observed for much of central Christchurch. Implications for future design practice and research needs are also discussed.
Considerations on the Seismic Performance of Pre-1970S RC Buildings in the Christchurch CBD during the 4th Sept 2010 Canterbury Earthquake: Was That Really a Big One?
S. Pampanin, W.Y. Kam, A.S. Tasligedik, P.Quintana Gallo & U. Akgüzel
ABSTRACT: The 4th of September 2010 Mw 7.1 Darfield (Canterbury) earthquake had generated significant ground shaking within the Christchurch Central Business District (CBD). Despite the apparently significant shaking, the observed structural damage for pre-1970s reinforced concrete (RC) buildings was indeed Ltd and lower than what was expected for such typology of buildings. This paper explores analytically and qualitatively the different aspects of the ‘apparent’ good seismic performance of the pre-1970s RC buildings in the Christchurch CBD, following the earthquake reconnaissance survey by the authors. Damage and building parameters survey result, based on a previously established inventory of building stock of these non-ductile RC buildings, is briefly reported. From an inventory of 75 buildings, one building was selected as a numerical case-study to correlate the observed damage with the non-linear analyses. The result shows that the pre-1970s RC frame buildings performed as expected given the intensity of the ground motion shaking during the Canterbury earthquake. Given the brittle nature of this type of structure, it was demonstrated that more significant structural damage and higher probability of collapse could occur when the buildings were subjected to alternative input signals with different frequency content and duration characteristics and still compatible to the seismicity hazard for Christchurch CBD.
At the time of review/writing of this paper, the 22nd February 2011 Mw 6.2 Christchurch earthquake occurred 10km from the Christchurch CBD. A very brief preliminary observation is included herein as it is very relevant to the discussion of this paper.
The Performance of Residential Houses in the Darfield Earthquake of 4 September 2010
G.J. Beattie, R.H. Shelton, S.J. Thurston & A.Z. Liu
ABSTRACT: The housing stock in the Christchurch area covers an age range from the late 19th century until the present day. A database of randomly sampled houses has been established and surveyed, in conjunction with the EQC inspection process. The paper describes the findings of the survey and comments on the effectiveness of the past and current design standards for such structures with regard to earthquake resistance. The need for modifications to the current standards are discussed.
The Performance of the Telecommunication Network in the Darfield Earthquake: A Success Story
Colin Foster, Robert Davey, Jamie Lester & Will Parker
ABSTRACT: Telecom New Zealand has an ongoing programme to improve the resilience of its telecommunications network to natural disaster. The investment made in this programme paid-off in the Mw 7.1 earthquake that struck 40 km west of Christchurch on 4 September 2010, where the network suffered no outages despite being exposed to severe ground shaking, loss of mains power supply and an abnormally high level of demand.
In this paper we discuss the main features of Telecom’s seismic protection programme, its post-earthquake emergency response system which was activated within hours of the event, the demand on the network immediately following the event and how this was managed, and the damage that was sustained by the network.
We draw some conclusions about the vulnerability of telecommunications networks to earthquake, and how to prepare for and manage the response to major disasters.