Canterbury Structural Group Forum 2

6.00pm – 8.00pm, Wednesday 6 October 2010
Lecture Theatre E1, College of Engineering, University of Canterbury

This Canterbury Technical Clearinghouse meeting summary was prepared by Bruce Deam on behalf of the NZ Society for Earthquake Engineering (NZSEE). This final version (0.4 - 22 Oct 2010) contains corrections from most of the contributors. Click on contributor's names to send them an email message.

This Canterbury Technical Clearinghouse forum was chaired by the Canterbury Structural Group chair, John Snook (Linetech Consulting) who welcomed representatives from a wide range of groups and outlined the agenda for the evening’s meeting.

Bruce Deam (NZSEE and University of Canterbury) presented a brief summary of the Canterbury Structural Group Forum held a fortnight earlier.

Greg MacRae (University of Canterbury) noted that there were blog answers to a couple of the ten decision questions and presented a series of associated supplementary questions. He concluded with the hope that the other presenters would present answers to the questions during the meeting.

John Snook read a brief statement by Nick Harwood (Coffey Geotechnics and Canterbury branch coordinator of the NZ Geotechnical Society) outlining the proceedings of the NZGS Special Meeting held on 28 September. John displayed a copy of the NZGS Seismic Design Guidelines that may be of interest to stuctural engineers.

John Snook responded to a question posed as to whether there should be a common foundation design, noting that recommendations like this are likely, but not for a while.

George Hooper (as a former EQC Commissioner) outlined how he was assisting EQC with its external liaison in Canterbury. He indicated that EQC see the reconstruction as primarily an insurance problem rather than an engineering problem, because EQC is bound by the Earthquake Commission Act 1993 to:

Manage the claims process
Assist with effecting repairs to the damaged land and houses
Replace like for like, to as new
Pay out for any loss of land up to indemnity value.

He outlined the general principle that applies to any land remediation decision, namely that there should be no more risk than there was before this event. EQC makes an economic decision about whether the land should be restored and how best to do so.

He then indicated that:

The Tonkin and Taylor geotechnical reports are now with central government, who will assess whether remediation will be undertaken
EQC are planning to appoint (within a week) a head contractor to manage repairs costing between 10K & 100K
That land condition and performance requirements (as they were before the earthquake) need to be better understood
Homeowners always have the opportunity to pay for improvements on the pre-earthquake condition, should they wish to.

Dave Brunsdon (EQC and Kestrel Group) outlined how the newly formed engineering advisory group were beginning to address Greg MacRae’s questions 2 and 3 from an insurance driver perspective, noting that many cases will span both private and EQC arrangements. In particular, the advisory group are investigating the following aspects, with an intention to have an outline before the next CSG meeting:

The remediation options and expectations for owners
Practical and achievable options for house releveling
The need to consider the future performance objectives
Foundation and flooring recommendations for houses that are being rebuilt

In response to questions, George and Dave indicated that:

They expected that the head contractor would provide a clerk of works type function to provide the best interaction with TA's, but that the terms of work need to be defined over the next couple of weeks.
That central government have not yet decided how those homeowners who wish to manage their own repairs will work with the head contractor.
Everything is still in the planning phase and nothing has reached the execution stage yet. The focus is on informing the decisions over the coming weeks.
That some $100K EQC payouts have already been made.
Government policy (specifically the geotechnical unknowns) doesn’t appear to be hindering the claim settlement process.

Mike Stannard (Department of Building and Housing) gave a brief presentation about the Department of Building and Housing role in the response to and recovery from the Darfield earthquake and an overview of the new Canterbury Earthquake Response and Recovery Act. Significant damage has occurred and there are many challenges to be resolved needing good will from all parties. The response has already demonstrated this good will with many engineers and building inspectors volunteering their time to assist with the building safety evaluation process. There has been a very strong government response to support the people of Canterbury with many agencies providing resources and expertise.

The Department has been involved from the start, at the National Crisis Centre in Wellington and in the field assisting with building safety evaluation and assisting affected Councils with technical and regulatory advice. He indicated that the DBH are now focusing on providing advice to ensue a speedy recovery. Their ongoing involvement includes supporting the EQC process, supporting TAs to streamline the consenting process on a risk basis so that quality of construction is not reduced, providing guidance and information as necessary, increasing the number of Licensed Building Practitioners in the region and identifying and commissioning research gaps (e.g. pallet racking).

He stated that the Department was very keen to ensure that lessons from the earthquake were captured and improvements made, both technically to the Building Code as necessary, and to regulatory and other processes to improve resilience to future events.

He outlined how the Canterbury Earthquake Response and Recovery Act 2010 (or the digest version) allows Orders In Council to enable relaxation or suspension of provisions that may divert resources from efficiently responding to damage and minimising further damage. He noted that this established the Recovery Commission, which is to provide advice on priorities and become the central point of contact between local and central government. The first Order relating to building, the Canterbury Earthquake (Local Government Act 2002) Order 2010, was signed 12 days after event to provide initial Building Act changes. Points of note within the Act and subsequent Orders include:

Dangerous buildings now recognises the risk from aftershocks and from neighbouring properties
The building placards became s124 notices to avoid a transition phase (although the removal process for red and yellow tags is still being worked through)
enables the monitoring of earthquake-affected buildings
extends the exemption from the need to obtain building consents for some minor works and for the demolition of damaged houses or parts.

In response to questions, he indicated that:

There is a need to define a protocol for information sharing between the research and design communities.
The Building Act review by the DBH aims at achieving a more efficient and productive sector that stands behind its work. Consenting processes will allow streamlined processes for lower risk work and for work with good quality assurance processes. The earthquake is accelerating implementation of this in Canterbury to assist in the recovery. Being a Licensed Building Practitioner (LBP) will also provide certain exemptions and streamlining, hence the push to increase the number of LBP's in Canterbury.

Jasper van der Lingen (Chair, Canterbury branch of the NZ Institute of Architects) indicated that he appreciated the ability to talk together about the common issues. He then outlined the NZIA response to the earthquake, which was initially between local and national representatives to decide how to help. It was decided that the best approach was to appoint and promote an architectural ambassador to provide a focus and to act as a spokesperson for the NZIA. Ian Athfield (Ath), a past NZIA president, was the best candidate but unfortunately, the appointment and function became politicised, to the point that the public perception was that the ambassador was appointed by Mayor Bob Parker to redesign Christchurch. He concluded that Ath has handled the very complex issues very well, in spite of everyone flying blind.

Jasper then outlined the staged approach the NZIA are taking, with the first stage being an exhibition of things related to the earthquake. This will collate relevant information for what is a complex project so the problems can be understood in order to make meaningful decisions in the latter stages. They want to include all available community and public contributions, as graphics, talks and events so others can interpret what has happened.

The NZIA Exhibition scheduled for the end of November will provide big picture thinking on 5 platforms that will provide a good focus for the community, namely:

About where the city develops (or rezones)
Urban design for the ‘missing teeth’ buildings
How to restore and adaptively reuse heritage and character buildings
Residential patterns of use; asking whether suburbia or inner city housing are the right way to go.
Addressing how Christchurch transport and infrastructure can be improved rather than just rebuilt more sustainably.

John Buchan (Christchurch City Council) indicated that they are working on minor consents (e.g. EECA replacement of chimneys with other heating systems), some of their housing consents are being handled by other councils, commercial consents are by peer review to reduce their workload, and they are evaluating repair methods with the DBH. Theif Building Recovery Office is now operating. Building evaluation team working on placards. Exemptions are on web site. Encouraging preapplication meetings with BRO to work thfough how to proceed.

Bill Ellis (Waimakariri District Council) outlined how they were streamlining their operation using phone and email messages rather than relying on letters. They are opening an office in Kaiapoi and could re-engage some out-of-district contractors for the office. As an example of the streamlining, he and an engineer managed to add details satisfying durability, fire and weathertightness requirements to a structural design for a parapet using phone and email communications. This reduced the elapsed time negotiating the additional details to only 4 days, and the design has already been reused on two other buildings.

Ian McCahon (Geotech Consulting, on behalf of Selwyn District Council) indicated that they had surveryed 750 buildings and anticipate 300-500 consent applications so they need to be streamlined. One fastrack consent was issued on same day! The liquefaction in their district was different to that in Kaiapoi and Bexley. Existing consent holders were being sent letters suggesting that a precautionary approach is appropriate, with geotechnical checks before proceeding.

Shojiro Motoyui (Tokyo Institute of Technology) gave a presentation about ceiling damage during a recent japanese earthquake. He described the typical ceililing hanging system used in Japan and how there were unpublicised cases of ceiling damage during previous earthquakes, giving an example of a sloping gymnasium ceiling. They developed recommendations that the suspended ceiling should have 200 mm clearance from the surrounding structure and diagonal braces should be provided to reduce the swinging. Dramatic security camera footage and shaketable tests showed that the clipped-in connection between the hanger and the ceiling failed for a significant portion of the ceiling area. He concluded by showing that the recovery was improved by both reducing the damage and increasing the recovery rate.

Phil Johnston (Uretek, Christchurch) and Ian Barrett (Uretek, Auckland) outlined how Urerek can be injected through a 16 mm diameter hole through a foundation into the soil to improve the soil. They have a second rig arriving soon to supplement the trial work that has been carried out in the area. Engineering (2 pot) resin is injected into the ground but expansion of the resin provides the pressure to either compact the ground or to lift a footing. Their art is to provide confinement (e.g. one layer to confine and a second beneath). They lift by 1 mm to provide ‘support’ and progressively lift along the length of foundation to lift the whole foundation. They are still experimenting on the levelling tolerance that is required and techniques for high lifts. They are collaborating with other companies to develop methods for higher lifts.

Craig Lewis (Lewis Bradford) outlined the ethical issues, particularly working within the IPENZ Code of Ethics. He urged engineers to contact original designers wherever possible and to avoid countermanding a judgment provided by a colleague.

Craig then outlined some precautions and liability issues relating to engagement, the social responsibility to do domestic scale work, the need to delegate work appropriately, keeping good records, ensuring staff know their limitations (and check they ask for help) and that structural reports on public buildings should be sent to TA's. Craig's presentation

John Hare (Holmes Consulting Group) noted that a group were working on a definition of clause 121 (Meaning of dangerous buildings), but warned not to sign off on its current form. He also made the following additions to the observations he presented to the first forum; that engineers need to:

Note the 2.5 sec spectral response that implies that taller buildngs need additional attention.
Identify fractured mesh (i.e. as indicated by 5 mm or grater cracks)
Check secondary systems as they moved as far as the primary system.
Consider the whole building and how it responded, not just the presenting symptoms.
Identify vertically stepped shearwalls that are more obvious on a plan than when surveying the interior of the building.

Bruce Deam commented that:

The approximately 700 m deep alluvial soils would resonate at about 2.5 sec natural period
The 20-30 m layer of post-glacial soils would resonate at about 1.3 sec
Most buildings are likely to have experienced a form of resonant response during the 15 sec of strong shaking, as it only takes about 5-10 cycles to develop resonance
It is therefore unlikely that a longer duration earthquake would induce greater inertial forces within most structures

After some discussion, there was general agreement that the higher long period spectral accelerations that were presented to (but rejected by) the Loadings Standard committee during the 1990's should be reviewed for both Christchurch and other localities with deep alluvial soils.

The meeting concluded with general agreement that it was worthwhile holding and there would be another meeting at the same time on 20 October.

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