The Hastings Opera HouseWhere to now?

Ian Harrison – Chair EBSS ebss.org.nz2 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 riskLife safety risk is the probability, or odds, that an individual will be killed in the Opera House in one yearIt 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 frequency2. Assess the probability of collapse or serious damage in each event3. Assess the probability and individual dies when there is a collapse or

serious damage4. Calculate the life safety risk for each event5. Add the three numbers.

AverageFrequencyyears

Prob. of collapse/ serious damage %

Prob. of death %

125 0.5 25

875 5.0 25

14286 24.9 25

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

Option Benefits $’000 Costs $’000

35-45% NBS 19.7 6200-6800

70-75% NBS 33.5 10,000-11000

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.

EBSS building risk certificate

EBSS Building Life Safety Risk Rating 7 Opera St. Hastings

Life safety risk information Building type Reinforced concrete low hight

Life safety risk 1: xxxxxx per year

Compared to driving a car xxxxx times safer

EBSS risk grade Very low risk

EBSS risk grades Odds of death over one year

Risk category

1 in more than 1,000,000 No effective risk

100,000 – 1,000,000 Very low risk

25,000 – 100,000 Low risk

5,000 – 25,000 Medium risk

Less than 5,000 High risk

1. Life safety risk based on 40 hours occupancy per week 2. The figures are averages for the building type. Particular buildings will have higher or

lower risks depending on their structural charactistics and other factors 3. The figures should be treated as broad orders of magnitude not as exact estimates 4. For more detail on the calculation methodlogy see ebss.org.nz 5.

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: ebss@ebss.org.nz

‘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.