Structural Design Standards – have your say  

Hi Jason,

I completely agree with the need for a retaining wall standard. Currently there is a lack of guidance for design of retaining walls. I am already currently using AS4678 and its partial factors to check design of ‘continuous walls’ for long-term capacity utilising the drained soil properties supplied by geotechnical engineers (passive resistance using c’ and φ’). We found this usually governs timber walls for when k1=0.6 for long-term loading. We came across this problem some time ago and are in the process of writing a SESOC article.

If you would like to discuss more regarding AS4678, feel free to contact me.

Regarding your questions,

• What thoughts do SESOC members have about joint AS/NZS standards compared to exclusive NZ standards? Do members find it useful to have harmonised trans-Tasman standards? Do not mind as long as is referenced in building code or able to achieve compliance. Not too informed on the implications of NZ vs AS/NZS standards apart from timeframe to release them.
• What role do you think SESOC should have in the development of New Zealand’s structural design standards? Currently there is very little collaboration between Standards New Zealand and SESOC on this topic, and SESOC is simply sent a request to have a representative on the committee. Gather feedback from relevant  practicing structural engineers in the field to be passed on to NZS. SESOC represents the engineers who use these standards on a day to day basis and I think it is important the standards are written with this in mind. 
• What thoughts do have on the recent practice of multiple amendments to standards instead of the issuing of entirely new standards, such as Amendment 3 to NZS 3101 for example? Amendment preferred as changes can be tracked a lot easier
• Would members find it useful to have forward knowledge of when Standards committees were being formed and when new standards were scheduled to be released? Very.  Perhaps a small section in the sesoc journals with things in progress.
• Internationally it is usual for a standard to be revised every 4-6 years. How often do you think our New Zealand structural design standards should be revised? Revised as necessary but should be checked regularly and thoroughly to ensure it is still relevant.
• Currently there is no formal continuity between one standards committee and the next, and therefore no succession planning. Would you prefer to see standing committees for Standards, or at least some formal succession planning? I think this will be very difficult to do. I believe the standards and their commentaries should be detailed enough that the next committee can pick it up so this is not required.
• Currently there is no direct link between knowledge gaps identified by standards committees, and research being undertaken. Do you think that more formally targeted research planning to directly support standards development would be helpful? 
• People who participate on standards currently receive no remuneration, and in many cases have to pay their own travel and accommodation costs. Do you think that this arrangement is appropriate? Do you think that SESOC should contribute members’ funds to aid in standards development? Absolutely think some sort of arrangement is required, I think this would detract field experts who are already busy with jobs from contributing. 

Jamie

Is there not a guideline just published by MBIE (Module 6) on the design of retaining wall (with good examples)? https://www.building.govt.nz/assets/Uploads/building-code-compliance/b-stability/b1-structure/geotechnical-guidelines/module6.pdf  

I’d say in general harmonising AS/NZ standards is good if it sufficiently addresses our unique regional concerns and supply chain differences. Then obviously you have to weigh up the pros and cons about update cycles, citing cycles, number of member representation on the committee.

Yes, there is an example for timber pole retaining wall but it is using a working stress design method and uses a factor of safety. AS4678 utilises a LFRD method which I think is a statistical life-safety approach and suits AS/NZS1170 closer. (AS4678 is already referenced in AS/NZS1170 commentary for earth retaining structures)

Jamie

I agree with Jamie that AS4678 utilises a LRFD method which I think is a statistical life-safety approach and suits AS/NZS1170 closer. I think, the correct term is LRFD method and not LDRF method.

Belated thoughts:

• What thoughts do SESOC members have about joint AS/NZS standards compared to exclusive NZ standards? Do members find it useful to have harmonised trans-Tasman standards?
  I think the core Standards that relate to seismic design of major buildings are best kept New Zealand specifc.
  For other Standards it seems wise to spread the development burden beyond our rather small pool. Whether this means joint AS/NZS, or adoption of ISO/ASCE/ACI/Eurocode should be considered on a case by case basis by appropriately qualified engineers.
• What role do you think SESOC should have in the development of New Zealand’s structural design standards? Currently there is very little collaboration between Standards New Zealand and SESOC on this topic, and SESOC is simply sent a request to have a representative on the committee.
  For core structural Standards SESOC should have much more of a partner role – helping establish priorities and needs for review.
• What thoughts do have on the recent practice of multiple amendments to standards instead of the issuing of entirely new standards, such as Amendment 3 to NZS 3101 for example?
  I am strongly of the view that new issues should be published with a new date – e.g. NZS 3101:2017 rather than Amendment 3. This would be consistent with typical international practice, easier for referencing/version control, and need have no downside – e.g. changes could still be identified in the current manner by amendment bars.
  This preference is emphasised by the length of time that amendments currently take to develop (seemingly ≈5 years for major Standards), but would remain even if development was quicker.
• Would members find it useful to have forward knowledge of when Standards committees were being formed and when new standards were scheduled to be released?
  Yes
• Internationally it is usual for a standard to be revised every 4-6 years. How often do you think our New Zealand structural design standards should be revised?
  We should be consistent with international practice – noting that ‘revision’ is not a synonym for ‘rewrite’. ACI 318 for example is revised every three years – but large parts typically remain untouched from one release to the next.
• Currently there is no formal continuity between one standards committee and the next, and therefore no succession planning. Would you prefer to see standing committees for Standards, or at least some formal succession planning?
  Standing committees (or at least standarding ‘core groups’ of 4-5) would be useful for the major Standards.
  Succession planning is a good idea – but not a panacea. The loss of institutional knowledge when long term contributors become unavailable cannot really be replaced by a handover.
• Currently there is no direct link between knowledge gaps identified by standards committees, and research being undertaken. Do you think that more formally targeted research planning to directly support standards development would be helpful?
  I would presume this was intended to be covered by having University representatives on committees – or by SESOC etc reps communicating needs. If there is a problem in this area, I think it would largely be addressed by the standing groups suggested above.
• People who participate on standards currently receive no remuneration, and in many cases have to pay their own travel and accommodation costs. Do you think that this arrangement is appropriate?
  No it is not appropriate. Development of core Standards is a key part of ensuring the performance of New Zealand buildings meets the Building Code, and as such in my view should be substantially funded from the Building Levy.
  Do you think that SESOC should contribute members’ funds to aid in standards development?
  No more than is currently the case. It is not for us to subsidise this development.