MaximusFebruary 10, 2012
Quake Final Expert Panel Report
This is a public service announcement from the Eye of the Fish: As the Expert Panel reported back yesterday with recommendations as to what NZ needs to do in regards to the earthquake strengthening of our buildings, and seeing as you all / we all in the urban design / architectural / engineering / construction field are going to be intimately affected by this over the coming months, years, and even decades, then I figure that the most useful thing the Fish can do right now is to relay to you the messages coming from the Expert Panel’s Final Report (download full and final report here) The following words are all theirs:
These recommendations have been assigned a priority of A (urgent), B (high) or C (moderate) according to the urgency of the need to take action on the recommendation. However, it is important that action is taken on all of the recommendations as soon as possible. The Panel recognises that the Department will need to schedule resources to implement these recommendations.
9.4 Summary of recommendations
The Panel makes the following recommendations to the Department of Building and Housing as a result of the technical inquiry into the structural performance of Christchurch CBD buildings in the 22 February 2011 aftershock:
Recommendation 1: Ground shaking/building response
Bring together a comprehensive study that examines the seismic response/performance of buildings in the Canterbury earthquakes, particularly the 4 September 2010 earthquake and the 22 February 2011 aftershock.
Such a study should relate building performance (for older and new buildings) and ground shaking measurements, and be aimed at improving the effectiveness and efficiency of earthquake-resistant design in New Zealand and elsewhere.
The study should address:
• the methods and assumptions used in building design, analysis, standards and practices
• the influence of vertical ground motions
• the effects of duration of earthquake shaking
• the basis for determining seismic hazard factors for building design, assessment and retrofit, particularly for large urban centres.
Recommendation 2: Geotechnical
Review geotechnical information standards required for urban areas in New Zealand and develop national guidelines for minimum standards of information.
Recommendation 3: Post-earthquake inspections
Review current methods for inspecting and reporting information on the structural condition of buildings following an earthquake.
Such a review should address:
• the need for legislation covering the structural assessment and rehabilitation of buildings affected by earthquakes
• the extent to which building owners are responsible for undertaking a more detailed evaluation of their buildings following earthquakes
• the need for public awareness and owner education programmes to improve the general understanding of the roles of post-earthquake inspections/evaluations and their limitations
• legislative requirements for the documentation of post-earthquake inspection information and public accessibility to such information.
Recommendation 4: General structural design issues
Reassess approaches to and general requirements for earthquake resistance in buildings.
See that necessary changes are made in the light of the Canterbury earthquakes.
Specifically, amendments should be aimed at:
• improving structural integrity and resilience
• limiting the irregularity of structures
• encouraging capacity design
• encouraging displacement-based approaches to design and assessment
• avoiding unintended interactions between structural and other parts of a building
• identifying and removing critical vulnerabilities
• introducing compulsory Design Features Reports for significant buildings – new or retrofit
• introducing tighter controls to trigger requirements for earthquake strengthening when buildings are altered or their use changed.
Recommendation 5: Specific structural design issues
Review detailed design requirements for structural design and amend them to resolve concerns identified in relation to:
• strength and ductility of walls and columns
• vulnerability of lightly reinforced concrete shear walls
• limits on axial load levels
• vulnerability of buildings with cantilevers and transfer beams
• strength and integrity of diaphragm connections.
Recommendation 6: Stairs
Issue a Practice Advisory to warn owners of buildings, especially those in flexible frame buildings, to check that the stairs are designed to accommodate appropriate levels of earthquake-induced displacements. (This is a recommendation from the Stage 1 Report and since that time the Department issued Practice Advisory 13: Egress Stairs: Earthquake checks needed for some, published September 2011, www.dbh.govt.nz/practice-advisory-13).
Develop revised criteria for stair support and protection of egress ways and incorporate them into the requirements for new designs and retrofits.
Recommendation 7: Construction quality and compliance
Review quality assurance processes in all phases of building design and construction, especially in light of the findings of these building investigations. Implement tighter controls and promote more designer involvement to ensure that design intentions are being achieved and that the work complies with the requirements of the approved design documents.
Recommendation 8: Concrete quality
Work with the concrete industry to review the in-situ strength of concrete achieved in a representative range of buildings around New Zealand and recommend any measures required to provide the necessary confidence that specified concrete strengths have been and will be achieved.
Measures considered should include further strength testing of in-situ concrete in existing buildings and revisions to standards and procedures covering the manufacture, delivery, placement and curing of concrete in new buildings.
Recommendation 9: Earthquake-prone buildings
Promote and implement measures, and associated enforcements and incentives that would result in:
• improved definitions of earthquake-prone buildings and more effective implementation of strengthening measures, particularly for buildings likely to fail in a brittle manner.
• a stronger appreciation of the (private and public) value of good seismic performance of buildings and the benefits of improvement action
• effective and economic retrofit strategies that improve the earthquake safety of buildings
• adoption by territorial authorities of strongly active policies to reduce the risk posed by buildings of low earthquake resistance
• improved public awareness that buildings not classified as earthquake-prone under the Building Act 2004 but which fall short of 100%NBS may nevertheless collapse in a major earthquake.