The Hastings Opera House Where to now? Ian Harrison – Chair EBSS ebss.org.nz 2 November 2015

Overview What is EBSS? EBSS website What do you need to understand to make a decision on the Opera House strengthening? Is the Opera House legally earthquake prone? Earthquake prone building test case What is the risk of the Opera House? How to make a strengthening decision – the cost benefit analysis Key decisions How EBSS can help How you can help EBSS.

What is EBSS? EBSS is a society established to: Improve the quality of the debate on seismic strengthening policies Lobby central and local governments to implement evidence based seismic strengthening policies Provide information to building owners who are adversely affected by the implementation of the current seismic strengthening policies Provide assistance to building owners who may have received poor advice from engineers on seismic strengthening matters.

EBSS website - ebss.org.nz Documents and other resources Submissions FAQs Campaign information and news Risk calculator – works out the life safety risk of different buildings in different cities (forthcoming).

What do you need to know 1.What is the legal position 2.What is the risk of the building 3.What are the costs and benefits of strengthening 4.When should you make a decision

The legal position It is said that the Opera House is an earthquake prone building because it is less than 34 %NBS There is no reference to a 34%NBS trigger point in the law The 34%NBS standard comes from an guidance document produced by the New Zealand Society of Engineering and promoted by MBIE We need to look at what the law actually says.

What is an Earthquake Prone Building? Building Act (2004) defines an earthquake prone building as follows:

What is an Earthquake Prone Building? A ‘moderate earthquake’ is defined in regulations as: an earthquake that would generate shaking at the site of the building that is of the same duration as, but that is one-third as strong as, the earthquake shaking (determined by normal measures of acceleration, velocity, and displacement) that would be used to design a new building at that site. It is a theoretical construct – it is unlikely to be observed in reality Strength of shaking is well understood – and is not very strong Opinions differ on what duration is and importantly how much difference it makes to the severity of the moderate earthquake

What does the law mean? Ultimate capacity means the point where a building is near to collapse So ‘will have its ultimate capacity exceeded in a moderate earthquake and would be likely to collapse’ means that there must be a reasonably high probability that an ‘earthquake prone building’ will collapse in a moderate earthquake This is logical. Earthquake strengthening is expensive, so strengthening should not be required if there is just a small probability of collapse.

NZSEE interpretation The New Zealand Society of Earthquake Engineering (NZSEE) has issued guidelines rely on an interpretation of the Act that of the Act that: Changes the words ‘ultimate capacity’ in 122(1)a to ‘ultimate limit state’ The ultimate limit state is a theoretical design point where there is a low probability of failure Ignores 122(1)b The consequence of this interpretation is that: “the 33% of the NBS that defines the Earthquake Prone trigger point is based based on a low probability of failure”.

NZSEE interpretation NZSEE legal definition shifts the goalposts – a long way The historical and theoretical evidence is that that the probability of collapse in a moderate earthquake in Hasting is very low – to put a figure on it 1:40,000 The Supreme Court has said that an EPB must be likely to collapse in a moderate earthquake - the test cannot be ignored The counterarguments It is ‘appropriate’ to substitute ultimate limit state for ultimate capacity Duration decreases the odds ‘Likely’ means ‘something that could well occur’

Earthquake Prone Building test case Owners of two Wellington building have sought a Determination from MBIE overturning the Wellington City Council’s Earthquake Prone Building designations on the grounds that the Council has not applied the legal test to identify an earthquake prone building. The determination was heard by the same individual who is a key player in the development of MBIE seismic policy advice MBIE developed the framework with the NZSEE and promoted it He found that the framework was just fine The case will be appealed to the District Court Another possibility is a judicial review of the Council’s (or other Council’s) policies If the Court finds the Wellington designations were unlawful this could have far reaching implications for other Councils’ designations

What is the risk? Individual life safety risk Life safety risk is the probability, or odds, that an individual will be killed in the Opera House in one year It depends on How much time the individual spends in the Opera House – more time increases the risk How frequently large earthquakes occur – the more frequent the higher the risk The chances of being killed if the Opera House collapses in a large earthquake. Life safety risk can be presented as the a number such as: 1:10,000,000. This means that individual who attends a given number of performances over a year will be killed on average once every 10 million years. The same approach can be taken to assess the risk of driving a car.

Life safety risk in the Opera House A simplified approach (using GNS Science data) 1.Identify the earthquake events and their frequency 2.Assess the probability of collapse or serious damage in each event 3.Assess the probability and individual dies when there is a collapse or serious damage 4.Calculate the life safety risk for each event 5.Add the three numbers. Average Frequency years Prob. of collapse/ serious damage % Prob. of death %

Life safety risk of a performance The calculations give us the life safety risk per year if a person is in the building every hour of the year We can calculate the risk per performance If you attend one performance each year it will take 110 million years before you can expect to die If you take one three hour car journey each year you can expect to die every 1.5 million years. The riskiest part of attended a performance is the car journey.

Benefits of strengthening Major benefit is the saving of lives A life is assumed to be worth $5m Make assumptions about occupancy (of audiences and full time workers) 52 performances with an annual occupancy of 500 Calculate the average number of lives lost per year without strengthening x value of a life: this the cost of earthquakes per year Work out the present value of the lives saved Do the same calculations with strengthening The difference is the benefit of strengthening.

Results OptionBenefits $’000Costs $’ % NBS % NBS33.510, An investment of $100 has a return of 30 cents Why the low benefits? Low occupancy Destructive earthquakes are rare

Key decisions 1. Should the Opera House be used now? The risk is very low No legal requirement to leave it empty. 2. Should the strengthening decision be made soon? Test case outcome could have an impact Practical outcomes of the new Act not locked in concrete Governments and Ministers come and go. 3. Should the building be strengthened to the NZSEE recommended level or above? Very limited reduction in risk from an already very low base No risk assessment in the the NZSEE recommendation Should the NZSEE be making across the board recommendations?

How EBSS can help building owners NZSEE description of buildings of buildings with NBS rating of less than 34% as ‘high risk’ gives the impression that they pose a substantial danger to occupants. There is no analysis underpinning this ‘high risk’ status This can be combatted by presenting the public with better information on building life safety risk EBSS can produce on request a notice that shows the life safety risk of different building classes in particular cities and towns.

How you can help EBSS EBSS needs: Donations Your time. If you have skills in the following areas and are prepared to help please contact us - Structural engineering - Computer based modelling - Public relations - Writing and editing - Administration. Contact:

‘Light’ reading Papers: All available in papers tab at ebss.org.nz This presentation Assessment of the Review of the Hastings Opera House project and subsequent assurance reviews Submissions to the Select Committee Error Prone Bureaucracy The Flaw in the Score The NZSEE’s %NBS risk measurement framework: Why it doesn’t work A Dummies Guide to Seismic Strengthening. Updates: Shorter pieces NBR: Over 20 recent articles on the topic. Many relate to EBSS.

EBSS building risk certificate