Resilient Buildings

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42 Build 141 April/May 201442 Build 141 April/May 2014

Build 141 April/May 2014 43

In this section

FEATURESECTION

44 What is resilience? 45 Built to last 48 Resilient building design 51 Your buildings

resilience 54 Resilience costs 56 Is it worth it? 59 Seismic technology showcase 64 Five drivers

66 Hazardous work

Violent weather and devastating earthquakes have turned attention to the challenge of

making our buildings more resilient. Is it too much to expect buildings to protect life and

be reusable shortly after a crisis?

Resilient buildings

44 Build 141 April/May 2014

What is resilience?

Resilient buildingsFEATURESECTION

RESILIENCE is a broad concept with many definitions but most include elements of the following, saying that resilience is the ability to:

absorb shock in a time of crisis recover the functionality of the building after a disaster or a sudden shock

operate appropriately even if parts of the building fail.

Another clear way of looking at resilience, as defined by the US National Infrastructure Advisory Council (NIAC), is the ability to reduce the magnitude and/or duration of disruptive events.

Four pillars of resilienceEight principal features are used to define building and infrastructure resilience some are complementary, others overlap. Thomas ORouke defined the four pillars

of how multi-hazards affect a building, structure or system is recommended.

Related featuresThe other four features of resilience that are commonly referred to capacity, flexibility, tolerance and cohesiveness overlap with the previous definitions.

Capacity is similar to robustness in that it is seen as the ability of a building or network to withstand disruption. However, capacity also incorporates redundancy to allow infrastruc-ture to absorb additional demand in a crisis.

Flexibility is the ability to be adaptable or change in response to external pressures, although this may be more applicable to networks than buildings.

Tolerance is related to how well a building behaves near its design boundary whether the system slowly fails as stress increases so there is time for life safety or collapses quickly when stress exceeds the buildings ability to cope. Tolerance is important in avoiding sudden collapse.

Cohesiveness refers to how well different parts of a building work together as a system. In order to incorporate cohesiveness into a resilience measure, building elements and their behaviour should be considered as part of a whole building system.

Resilience was the 2013 buzzword, and 2014 will see a continued focus on how to make individuals, communities, buildings and infrastructure

more resilient. But what does resilience mean?

BY PROFESSOR SUZANNE WILKINSON, DR SEOSAMH COSTELLO AND MAS0UD SAJOUDI, THE UNIVERSITY OF AUCKLAND

of resilience as robustness, redundancy, resourcefulness and rapidity.RobustnessRobustness is a key feature of resilience and refers to a buildings potential to cope with stress without failing or losing significant function. For infrastructure, this could be a networks ability to continue operating after being subjected to external pressures or disturbances.RedundancyRedundancy allows for alternative choices, decisions and substitutions in a building system so that there are different recovery options in the case of disaster or when under pressure.ResourcefulnessResourcefulness is the ability to manage the impacts of the crisis on the system or building, including mobilising effective people, processes and needed materials after a crisis, so rapid recovery can happen. Frederic Petit believes that, by incorporating resourcefulness into resilience, a system, building or structure can recovery quicker.RapidityRapidity looks at how quickly the function of a network, or the use of a building, can be restored after a shock. Rapidity is impor-tant for resilience of buildings so an analysis

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Resilient buildings FEATURESECTION

THE NUMBER AND INTENSITY of natural disasters in the last few years serve to remind us just how fragile our built environ-ment can be when faced with the forces of nature.

generated a 40 m tsunami that severely damaged or destroyed over 1 million homes and buildings.

In just the last few months, unprecedented storm activity in the UK has caused severe coastal erosion and flooding and displaced thousands of people. Here at home, the 2010 and 2011 Canterbury earthquakes highlighted our own vulnerability.

While these are all undoubtedly extraor-dinary events, much of New Zealands built environment is vulnerable to hazards such as earthquakes, tsunamis, volcanic activity, flooding, heavy snowfall, windstorms, droughts, landslides, fire and a range of manmade hazards. Lack of resilience can carry a high price tag.

Big losses highlight need to mitigateAccording to the Insurance Council of New Zealand, 2013 is likely to become the second most expensive year on record for weather-related damage, with over $174 million of insured costs arising from weather-related events. Nearly half this cost was created by damage to commercial and residential prop-erty during a single storm in September. And this is becoming a trend.

The Council believes that climate change is likely to cause stronger winds and

Built to lastThe global weather forecast is daunting, and earthquakes are a regular event. With insurance costs already climbing, we badly need buildings

that can stand up to the forces of nature.

BY NICK HELM, FREELANCE WRITER, TENPOINT COMMUNICATIONS, WELLINGTON

Heavy rain undermines a house in 2006.

In 2005, storm surge and flooding from Hurricane Katrina caused US$80 billion in damage in one of the most deadly events in US history. In 2011, the magnitude 9.0 Thoku earthquake off the coast of Japan



higher levels of rain in parts of the country already prone to flooding, underlining the need for New Zealand to focus on strategies to mitigate the effects of disaster in order to minimise economic losses and social disruption.

Designing in resilienceA way to successfully mitigate loss of life, property and amenity is to design buildings that are resilient to disaster, says Dr Suzanne Wilkinson, Professor of Construction Management at the University of Auckland.

Dr Wilkinson says a resilient building has the ability to absorb change and distur-bances in a time of crisis, quickly recover functionality after a disaster or sudden shock and continue to operate even when some components of the building fail. The degree of resilience, she adds, can be measured using eight key characteristics robustness, redundancy, resourcefulness, rapidity, capacity, flexibility, tolerance and cohesiveness.

The resilient design processFor both commercial and residential projects, a resilient design process begins with a careful investigation into how the building will be used. The designer should consider how the occupants will interact with the buildings systems each day and understand their expectations in terms of the level of service the building provides during and after disaster.

Hazard assessmentIts also important to accurately assess the hazards that the building will be exposed to now and in the future and the effects they will have on the buildings structure, occupants, functionality and surrounding infrastructure.

Much of New Zealand is prone to earth-quakes, so designers should consider the relative seismicity of the buildings loca-tion indeed, this is a requirement of the Building Code, which governs minimum

Take Christchurch Womens Hospital a 10-storey base-isolated building that remained fully operational immediately after both the September 2010 and February 2011 earthquakes.Standing up to galesIn order to create a building resilient to excessive wind loads generated by strong storms, hurricanes and tornadoes, designers should try to ensure the building envelope is robust and well sealed and strengthen the superstructure to withstand higher lateral loads and vertical lifting forces.

In parts of the US where extreme winds are common, for example, the National Institute of Building Sciences recommends additional bracing of roof trusses and gable ends, installing hurricane straps to strengthen the roof-to-wall and wall-to-foun-dation connections and placing coverings over doors, windows and other penetrations in the building envelope.Holding back the surgesOther effects of extreme weather, such as ground flooding or storm surge, are often best dealt with at an urban design level or by avoiding obvious high flood-risk areas such as river floodplains, estuaries and other low-lying coastal areas.

If this is not possible, the designer can boost the buildings resilience by creating adequate draining and waterflow systems for underground car parks, basements, ground floor levels, roofs and any other areas where water may collect. Critical systems, such as generators and heating systems can be placed as high above ground in the building as possible to avoid failure. Some aspects of tsunami hazards can be mitigated in the same way.

A broader pictureThese are just a few simple strategies to design a more resilient building. Of course, disaster resilience is not limited to buildings to be effective, it must also encourage a long-term commitment to resilience in our communities, infrastructure and people.

levels of mitigation for some hazards but there may be less obvious hazards to consider.

For example, a coastal location may be susceptible to tsunamis, sea-level rise and coastal erosion, while a high-altitude location may experience higher winds and excessive snow load and extended periods isolated from roads and the national elec-tricity grid.

As climate change advances and the severity and frequency of extreme weather events increases, all New Zealand locations are likely to be exposed to quite different conditions by the time the building reaches the end of its useful life in 50 or 100 years or more.

Sustainable doesnt mean resilientIt is also important not to confuse resilient design with sustainability, although the two are complementary in many ways. Even the most advanced green building that is designed, constructed and operated according to sustainable principles is not necessarily resilient to disaster.

A low carbon footprint, high-efficiency light bulbs and recycled rainwater dont count for much if the building collapses in an earthquake, power is cut or the ground floor floods in a bad storm.

Standing up to shakes, gales and surges Traditionally, structural components such as bracing, shear walls and moment-resisting frames have been used to resist earthquake shaking in a strength up to a limit approach. They are resilient to minor seismic events, but in a design level event, they are designed to fail slowly in the interests of preserving life.Strengthened against shakesMany modern earthquake resilience systems suffer no such limitations. Base isolation, post-tensioned frames and vibration damping systems have all been proven to greatly enhance a buildings capacity to withstand extreme seismic events.



TWO OF THE MOST vital components of a resilient community are functional buildings and a functional infrastructure. With the application of good seismic design practice, resilient buildings that continue to function as intended after an earthquake can be achieved.

While most buildings in Christchurch performed up to Building Code expectations especially for life safety the empty areas of the CBD and eastern suburbs are a stark reminder that resilience was not achieved to the extent that most of us expected.

Lessons from CanterburyThe New Zealand Building Code is a world leader and a very good tool to use as a starting point. However, its sheer scope and complexity means that it is very easy to get bogged down in the detail and lose sight of the bigger picture.

Following extensive experience gained after the Canterbury earthquakes and

preparation of national seminars on the findings and lessons learnt, we have distilled the lessons into six main themes.

Site location and conditions crucialAs building industry practitioners, we may not have much influence over building siting, but sometimes there is an oppor-tunity at the prepurchase stage. There are several things to look out for:

Low-lying coastal sites have potential for tsunami damage, particularly in vulner-able Pacific Ocean-facing areas and at the head of long tapering inlets. There are not many opportunities within the building sector for mitigation of this sort of hazard.

Low-lying riverside sites, particularly adjacent to estuaries, can be vulnerable to liquefaction. The key drivers are a high water table and loose fine-grained soils. Unfortunately, many New Zealand settle-ments sprung up in these areas because of the historical reliance on sea transport.

Hillside sites require extra care to achieve seismic resilience. Unless the land is poten-tially unstable, the engineering problems can usually be solved. However, usually the added complexity brings increased design fees and building costs.

The LIM for the property may alert you to location-related issues, but it is usually worthwhile checking the territorial author-itys hazard maps.

Reduce complexityComplexity may be caused by plan and vertical irregularity often unavoidable on hillside sites with split floor levels and differing structural systems. During the design process, some of these features arise as the designers try hard to accommodate the clients wishes.

What started out as a simple concept ends up as a complex structure, rapidly consuming design fees. While complex structures can be modelled relatively easily

Resilientbuilding design

The Canterbury earthquakes have firmly placed building resilience in the spotlight. As an industry, we did not perform as well as the public

expected how can we do better in the future?

BY ROGER SHELTON, BRANZ SENIOR STRUCTURAL ENGINEER



using todays computer analysis software, two detrimental effects come into play:

The structural designer loses the intuitive feel for the structure that will so often act as a warning that something is not right.

The dynamic behaviour of the structure under the earthquake ground motion is different to what was assumed in the loading standard.

The result is that the performance of the structure under earthquake action is more difficult to predict with certainty than a simpler structure.

It is worth adding that complex buildings are also more likely to have a higher risk of weathertightness problems.

Reduce weightThe desirability of reducing weight is pretty well accepted by most in the building industry. Besides seismic vulnerability, other downsides include bigger foundations and higher construction costs. Seismic weight can

be compensated for by more structure, but as we have seen, this usually adds building costs for equivalent building resilience.

Another angle is to plan the building with heavy items as low as possible. For example, it may be possible to locate plant rooms low in the building, where they will also be easier to service.

Structural stiffness is goodWhile there is a perception that the struc-ture needs to flex in an earthquake to survive, this is a concept focusing solely on the prevention of collapse. Today, and more than ever after the Christchurch experience, there is an expectation that minimisation of damage to buildings is essential for seismic resilience.

The primary way to achieve this is to provide a structure with sufficient lateral stiffness that its deflections under seismic action will be low enough to avoid damage to non-structural components and finishes.

The key measure here is the relative horizontal deflection between storeys engineers call this drift. If this is too great, brittle elements such as windows will shatter, service pipes will leak at joints, claddings may fall and, in the worst case, heavy elements such as stairs will slide off their supports with disastrous consequences.

There are clever ways to reduce structural flexibility, but usually the most effective way is more structure more bracing walls, bigger columns and beams.

The alternative is to provide separation between structural and non-structural components, but this comes with the price of more costly detailing and can create problems in achieving weathertightness.

Care with connectionsConnections between structural elements and between structure and non-structural components are vital in achieving

Hazard map for Porirua highlights the local issues.



building resilience. Connections are clearly the province of the structural engineer, but other members of the team also need to be aware of the importance of robust connections.

Examples of connection failures are ceiling collapses, cladding panels falling onto pedes-trian ways and, in the extreme situation, floor slabs parting from shear walls. The latter is also an example of faulty diaphragm design, which is an area receiving much attention from the structural engineering community at present.

Providing connections with sufficient structural ductility is essential. The whole load path from member to member must be considered. Frequently, the steel connection itself is quite robust, but the connection to the substrate can be friable or brittle. Examples are splitting of timber members

at fasteners such as bolts and pull-out or break-out of bolts and fixings cast into concrete members. Allowing for movement caused by the effects of temperature and shrinkage make connection detailing all the more important.

Connections are a classic case where it is very true to say that the devil is in the details.

Robust building servicesFailure of non-structural components including building services is typically the primary reason for non-occupation of a building. As we have seen recently in Christchurch and Wellington, this may lead to costly business interruption.

Failures can range from the movement of a domestic hot water cylinder up to leakage of a water pipe in a multi-storey commercial building. Most failures of non-structural

components in earthquakes are a result of excessive building deflection and the lack of structural stiffness, but toppling or falling due to lack of anchorage is also common.

One of the practical difficulties is the sheer number of items to be considered and the complexities of the arrangements often needed to fit systems into leftover spaces, for example, ceiling spaces.

A well developed plan for coordinating the activities of the various parties involved the architect, structural engineer, services engineer, HVAC contractor, ceiling contractor and sprinkler contractor at the very least is the only way to ensure that each partys requirements fit into the whole. An essential ingredient in this is ensuring that building models are shared at the design stage and that each team member is fully briefed before committing to pricing the job.

With planning, building services can survive earthquakes. Complex buildings present challenges.



Your buildings resilience

Organisations need to understand what resilience means for the buildings they inhabit or own. Here are some of the issues for an

organisation to consider as it works through the challenges ahead.

BY DR ERICA SEVILLE, RESILIENT ORGANISATIONS NEW ZEALAND, DAVID BRUNSDON, KESTREL GROUP, AND JOHN HARE, HOLMES CONSULTING GROUP

SINCE THE CHRISTCHURCH earthquakes, New Zealand organisations have been reviewing the resilience of the buildings they operate in. But resilience for buildings involves more than robust construction it includes links with the operational planning of the organisations that occupy them.

Steps to understandingStart by asking some questions to get a wider understanding of your buildings context:

Does your organisation own the building it occupies or is it a tenant?

Do you occupy one building or several, and are they in the same location or geographically spread?

Is the surrounding environment vulner-able to earthquakes and other hazards consider neighbouring buildings, key access routes and infrastructure services?

How important is your building to you?The concept of importance levels for different buildings is embedded in our design codes, with a high-occupancy

building such as a theatre designed to higher performance standards than one with low occupancy.

Similarly, buildings that support critical post-disaster functions, such as hospital operating theatres, are assigned an impor-tance level that requires they are both standing and usable afterwards.

These importance levels provide a broad hierarchy of societal performance objectives for buildings.

Organisations, particularly those with several buildings, should create performance objectives for their own premises. Look at how each building is used. How often are people inside and what equipment is there? How time-critical are the operations conducted in the building would being out of action for a few hours, a few weeks or a few months be a problem? How easy would it be to relocate if required?

Weighing up the risksWhen engineers assess buildings, they often focus on the %NBS the capacity and



performance of the building as a percentage of an equivalent new building built to todays Building Code.

However, this is a very broad metric, and organisations need to be savvier at understanding how their buildings are likely to perform in a major event. Talk of earthquake-proof buildings is a misnomer, as any building will fail if the forces are great enough.

There are several key questions to ask: What are the life-safety risks associated with how the building might fail will people be killed or injured?

Will the building remain functional after-wards it might not look pretty, but could people go back in and use the building?

How long would it take to repair the damage is it likely to be a quick fix or a demolish-and-replace job?

Depending on the design, some buildings may perform well on one or two of these criteria but poorly on the others. It is impor-tant to understand the level of the event at which functionality can become impaired and the safety of lives a concern.

Setting prioritiesDevelop a plan to progressively improve the resilience of your organisations building stock. Not every building needs to be serviceable after an event in many cases, simply getting people out unharmed is a sensible objective.

Think about your buildings resilience as an investment rather than a compliance deci-sion. What would it cost your organisation if a particular building became inaccessible for the foreseeable future?

Business continuity considerations are not just for hospitals and critical infrastructure organisations. Manufacturing organisations where equipment is hard to move and to replace at short notice and organisations that deliver time-critical services may see their business wiped out if they dont plan for such eventualities.

However, organisations spread across several locations may be able to temporarily

relocate capacity and may be less concerned with building resilience beyond Code expectations.

A few other things to considerAlso consider the non-structural elements of your building. Does it have heavy ceiling tiles or large items of furniture that create safety risks? Is equipment properly secured?

Are you likely to be left with a major repair bill and downtime due to damage to fixtures and fittings, such as wall linings or lighting or heating systems? Consider the resilience of the infrastructure services supplying your premises a multi-storey building isnt much use without power or water.

Think about the neighbourhood and what could prevent you and your staff accessing your building, even if it is undamaged. How well are the buildings contents protected? Is your basement storing valuable records or equipment that could be water damaged?

Also think about the different scenarios that could make your building unusable. Often, we focus on hazards that we have recently experienced. Think about where your building is located and other hazards it may be exposed to are these risks increasing because of climate change or how the neighbourhood is developing?

Review your tenancy agreementBuilding tenants that suffer damage can find themselves in a difficult position. Unlike owner-occupiers, tenants have little control over the time and way in which any damage is repaired.

After the Christchurch earthquakes, many tenants found themselves shut out and poorly informed about the future of their premises. Delays in the start of repairs rendered some business interruption policies ineffective, and organisations found themselves locked into tenancy agreements for premises that they no longer wished to occupy.

Any organisation that rents or leases a building should ensure that there are clauses in their agreement covering how the situation will be handled if the building

is damaged or becomes inaccessible or unus-able for any reason.

The time when a lease is signed is essen-tially the only opportunity to sort out these issues, so this is when it is important to get as much information as possible about the likely performance of the building.

Buildings %NBS just part of the issueNew Zealand has a legacy problem of older building stock that will take time to remedy. While it might be desirable for every building your organisation occupies to be optimally resilient, this isnt going to occur overnight.

Evacuating a building at 5 minutes notice when getting an engineers report that says it is less than


Knowing that, in the interim, the university would be occupying earthquake-prone build-ings, it decided to be open in talking about the risks. At the start of each semester, they talked to classes about earthquake preparedness, gave information about the risks of earthquake-prone buildings and answered questions.

Importantly, Berkeley demonstrated it was addressing the problem and has maintained staff and student engagement throughout.

If the University of Berkley can deal with this situation in one of the most litigious countries in the world, surely we can in New Zealand. The key is to demonstrably work on improving our resilience and not just leave it as tomorrows problem.

Dont simply rely on insuranceOne of the biggest lessons from the Canterbury earthquakes is that reliance on insurance is not necessarily the right answer. While it helps that a lot of insurance payouts are flowing into the local economy, over time, the premium payments will balance this, and the same cover, terms and conditions may not be available.

A combination of mitigation of lower-level risk and then using insurance as a top-up for disasters may be more cost-effective than simply insuring for every event.

Fully involve any consultants you useAny advisers engaged for engineering aspects or business continuity planning

should have a good appreciation and under-standing of the range of issues covered, and you should brief them on your specific context and needs.

For example, a structural engineer may address %NBS or the design of a new building as if the Building Code is the only require-ment to be met. But the Building Code is not focused on a businesss priorities it is there to protect life safety and to minimise risk of damage to adjacent properties. Buildings that are equally Code compliant may perform completely differently in terms of business continuity objectives.

The brief an organisation gives to consult-ants should reflect this. If a building must be operational after an earthquake, this should be stated. It may not require that the building be designed for the same impor-tance level as an emergency facility, but it might lead to building form or materials being used that are more damage resistant. At the least, the cost impact of this should be investigated.

Changes on several frontsConsidering these issues in an organisations planning is timely in the current environment where changes are occurring in both regula-tory and technical environments for buildings and earthquakes.

On the regulatory side, the Building Act (Earthquake-Prone Buildings) Amendment Bill has been introduced. While there is no

change to the threshold level defined for an earthquake-prone building, the intention to have all commercial and large residential buildings assessed within 5 years of the Bills passage is putting the spotlight on the performance of buildings in earthquakes.

At the end of 2013, WorkSafe New Zealand sought to clarify health and safety require-ments and earthquake-prone buildings by issuing a position statement for employers and owners on dealing with earthquake-related hazards.

This indicates that the Health and Safety in Employment Act does not seek to impose requirements for a buildings earthquake resilience at a higher standard than the Building Act.

At a technical level, the New Zealand Society for Earthquake Engineering in conjunction with the Structural Engineering Society and New Zealand Geotechnical Society will update their 2006 guidance document on assessing the seismic perfor-mance of existing buildings.

Destructive testing of 1- and 2-storey timber-framed buildings in 2013 by BRANZ for the Ministry of Education and Housing New Zealand Corporation has clearly shown these types of buildings have a much greater resilience than indicated by traditional engineering calculations. For more Visit www.resorgs.org.nz/Resources/

resources-for-business.html, where the booklet

Shut Happens is of particular interest.

Key actions for an organisation to assess their buildings resilience, and integrate this with business continuity management. Note that the engineering stages (shaded) are only part of the comprehensive consideration of resilience.


Establish your organisations time-

critical and access- dependent operations.

Consider how you would run a limited operation if denied

access for a day/week/ month.

Establish the level of performance

required from your buildings beyond life safety for example,

the time to restore different levels of

functionality.

Have an engineering and services review

of your building undertaken to see

how well it is likely to meet your performance

requirements.

Consider the surrounding

environment neighbouring

buildings, key access routes, reliability of

infrastructure services for different hazard

events.

Plan mitigation actions for the building appropriate to your

objectives and circumstances (e.g. owner or tenant) and your

investment priorities.

Develop a business continuity plan that reflects your current

situation and likely building and services performance. Continue to integrate

resilience planning into your business,

proactively evaluating and responding to

changes as they emerge.



Resilience costs

WE WANT BUILDINGS to be resilient, but what is resilience? On page 44, Suzanne Wilkinson summarises resilience as the ability to absorb shocks the ability for a building to recover its functionality quickly and continue operating even with partial failure.

Improving existing housingThe costs to make an existing house more resilient are typically those required to bring it up to current Building Code require-ments (see Table 1).

Wind resilienceRecent wind events have highlighted that, in some regions, existing fixings are inad-equate for the damaging storms that are expected quite frequently. In particular, lightweight roofs on houses built before 1999 in high and very high wind zones need additional fixings. Table 1 shows the costs for:

fixing the bottom two rows of purlins to the rafters or trusses

increasing the fixings from rafter or truss to the top plates.

Further details are available in BRANZ Study Report SR187 Retrofitting houses to resist extreme wind events.Seismic resilienceOld-style heavy masonry chimneys can cause extensive damage to roofs in an earthquake and should be demolished to increase resilience.

In many pre-1970 houses on timber or concrete piles, the lateral restraint and connection of the bearers to the piles is inadequate and can be improved.

As the focus turns to improving resilience, BRANZ has assessed the costs of some common measures to make houses more resilient.

BY IAN PAGE, BRANZ MANAGER ECONOMICS

HAZARD COMPONENT MITIGATION MEASURE COST ($)

Wind Truss roof Install fasteners - purlins and top plate 1,400

Rafters Install fasteners - purlins and top plate 2,200

Earthquake Chimney Demolish and replace with metal flue 8,000

Pile foundations Fixings to bearers, cross bracing 8,000

Flooding 0.5 m above floor level Raise house at same location 23,000

1.5 m above floor level Raise house at same location 30,000

Moisture Internal moisture Polythene ground sheet 1,500

Deterioration Roof and wall cladding Regular maintenance and painting every 10 years 7,000

COMMON MEASURES TO MAKE EXISTING HOUSES MORE RESILIENT

Table 1

Note: Based on the costs for a typical house, approximately 150 m2, weatherboard with sheet metal roof.


Flooding resilenceNew housing is very unlikely to be on flood plains, but many older houses are. The costs for raising houses start at about $23,000 and include pile bracing, access steps and service connections.Resilience to moistureA low-cost measure that improves the internal environment for all suspended floor houses is to reduce entry of ground moisture by spreading polythene sheeting over the ground and taping it around the piles.

At the same time, installers need to ensure water will not pond under the house.Positive net benefitValuing the benefits of these measures is quite difficult because it depends on the return period of the various hazards. Analysis in BRANZ Study Report SR285

House repair priorities indicates many of these measures are likely to have a positive net benefit under reasonable assumptions.

Measures for new housingBRANZ has done less work on costs and benefits of resilience measures for new housing, but these could include:

above-Code insulation to reduce depend-ence of external energy sources

using low-maintenance claddings installing lifetime design features that make the house easier to use and more flexible for all age groups

designing for external loadbearing walls only so the interior can be readily changed as occupant needs change.

As new buildings are covered by the Building Code and land zoning require-ments to protect against natural hazards

such as earthquakes, windstorms, floods and landslips, the life-safety risks from these hazards are covered.

Functionality concernsHowever, the building may not be usable for an extended period due to secondary damage, so resilience needs to consider functionality.

Angela Liu (see page 56) discusses this aspect for office buildings, where life safety is preserved but secondary damage to linings causes loss of access during repairs and has major cost effects on businesses.

BRANZ hopes to do more work in the future on quantifying the benefits of these measures.

For more BRANZ study reports can be

downloaded for free from the BRANZ Shop at

www.branz.co.nz.




BUILDINGS ARE CENTRAL to peoples lives, and their continuous function after a destructive event is a major challenge to the resil-ience of a city or even a country.

Buildings saved lives but at a costIt was not until the Canterbury earthquakes in 2010 and 2011 that people understood the importance of buildings continuing to function after a catastrophic seismic event.

One lesson from the earthquakes was that there is a significant gap between the performance criteria in the New Zealand Building Code and general societal expectations for building performance in earthquakes.

Most modern designed buildings in the Christchurch CBD achieved the Code-specified performance criteria at ultimate limit state the

Is it worth it?

buildings did not collapse, presenting a life safety issue. They were extensively damaged, however, and in many cases needed to be demolished and rebuilt, causing significant and lengthy disruption to business activities and normal daily living.

Damage was well beyond peoples expectations and resulted in a considerable cost to the country.

Looking for the financial thresholdThis research projects premise is that there will be a financial threshold at which the increase in the initial construction cost for a building will be balanced by the economic benefits over the entire building life cycle.

The current Building Code is performance-based with the aim of ensuring life safety. From an economic standpoint, information on the investment versus financial benefit relationship is urgently needed by all stakeholders to assist decision-making for targeted building performance. It will also be essential for consideration during future changes to the Building Act and Building Code.

Different building types and lateral seismic resistanceThis project considers the relationship between cost and benefit for typical building types.

Additionally, it will also look at the variations in the inherent resilience of different lateral seismic resisting systems. Potentially, different lateral seismic resisting systems could have very different earthquake resilience levels, and the determination of the seismic design level for a certain type of building is the result of a risk versus economic consideration.

Resilience of buildings to earthquake events is being studied separately for different lateral load resisting systems. A small sample

A current BRANZ research project is studying the economic benefit of designing buildings for increased resilience under seismic loading

throughout their entire life cycle.

BY ANGELA LIU, BRANZ SENIOR STRUCTURAL ENGINEER, GRAEME BEATTIE, BRANZ PRINCIPAL STRUCTURAL ENGINEER, AND IAN PAGE, BRANZ MANAGER ECONOMICS


of model buildings is being designed for each system and will be subjected to different earthquake intensities. A wide-ranging cost-benefit study will be carried out for the buildings entire life cycle to investigate whether higher performance is likely to be economically justified.

Indirect and direct costs studiedThe economic study includes both the direct and indirect costs from earthquake events, including aspects such as business interruption.

A comparison of the inherited resilience of different structural systems to earthquakes is being carried out in order to better inform stakeholders decision-making on the structural design.

First up reinforced concrete framesThe first stage of the project is well under way and has focused on reinforced concrete-frame structures. The subsequent stages of the research will focus on other structural types and a comparative study of the seismic performance of different structural types.

Two identical reinforced concrete-frame buildings were designed and analysed, with different lateral seismic load resisting systems. They were designed to the same current seismic design standards but using different ductility assumptions. As a consequence, the lateral load resisting systems of the two were different.

Findings raise issue with regulationsStructural analyses carried out so far have concluded that reinforced concrete-frame buildings designed to the same current seismic design standards would be expected to sustain different damage levels, and therefore different economic consequences, in the same design earthquake event if different ductility assumptions were made.

The study suggests that building structures of different structural systems would potentially be expected to achieve very different performance levels for the same design earthquake. This implies a very different economic scenario, especially over the life cycle of a building.

This is contrary to the principles used in developing the current building regulations. In these, buildings designed according to the current design standards are meant to achieve the same minimum building performance levels, regardless of the structural types and design assumptions.

Study outcome to better inform allThis project runs until late 2015 and expects to better inform owners, engineering practitioners, banks and insurance companies and the building regulation policy-makers about the balance that needs to be struck between acceptable levels of risk and the costs of mitiga-tion and resilience.



T H E C A N T E R B U R Y E A R T H Q U A K E S revealed a widespread desire that buildings should not only survive a big shake, they should also remain free of major damage and be functional immediately after.

Until recently, the accepted seismic design of buildings focused on preserving life. However, Christchurch has discovered

Seismic technology showcase

New seismic-resistant building design developed in New Zealand and worldwide over the last decade is at the forefront of the Christchurch

rebuild, as these case studies illustrate.

BY PHIL STEWART, FREELANCE WRITER, TECHNICAL AND ENGINEERING WRITING, AUCKLAND

country in the last 3 years and is now having a major impact on Christchurch construction.

Kilmore Street Medical Centre three world firstsConstruction of the $40 million Kilmore Street Medical Centre includes three world firsts in seismic-resistant design.

It features the first ever application of steel PRESSS technology in a building. This struc-tural system dissipates earthquake forces without residual building deformation.

The PRESSS (PREcast Seismic Structural System) element consists of steel-braced frames that are free to rock laterally during an earthquake before tensioning in the bracing pulls the frames back into place when the shaking stops.

The system was developed initially for use in reinforced concrete frames, but research shows it is viable for steel too.

Kilmore Street Medical Centre three world firsts in seismic design.

the painful social and economic effects of having almost an entire CBD of buildings still standing but unusable or unable to be repaired.

Seismic-resistant design places a primary focus on keeping buildings damage-free and usable, not just staying upright. It has been applied to a handful of buildings across the



The building also features the worlds only use of two energy dissipation units in a single building. These units act like expendable fuses they absorb the massive energy that is directed into them. They may be damaged or destroyed, but there is no impact on the building.

One of the fuse types is steel fuse rods located in between the PRESSS steel-braced frames, coupling them together. These rods consist of a mild steel round bar that is designed to yield in axial tension and compression to dissipate energy.

The other represents another world first a lead extrusion device developed at the University of Canterbury that has never been used before. This takes the form of a steel

shaft with a bulge in it that is surrounded by lead. As the building moves in an earth-quake, the shaft is pushed up and down, causing the lead to flow around the bulge. This dissipates huge amounts of energy.

These technologies make Kilmore Street an ambitious build, requiring special detailing at joints and engineering input for temporary works during construction. Its a lot to pack into a 3-storey building.

However, the clients aim was clear. They wanted a building that would remain fully operational in the immediate aftermath of any earthquakes as big as those in 2011 and 2012. The result is a building 80% more seismically resistant than Building Code requirements.

St Elmo Courts expanding the use of base isolationThis 6-storey building will be the first office building in Christchurch to employ base isolators in the foundations to dissipate earthquake energy. It is also designed to behave elastically meaning no residual damage in a 100% Bui lding Code earthquake.

Base isolation reduces the forces put on a building by partially isolating it from the shaking ground. The buildings foundations are placed on multiple energy-absorbing bearings that shake and absorb much of the grounds movement, meaning the structure above receives lower forces. The technology has been in worldwide use for over three

Steel fuse rods installed in between steel-braced frames with lead extrusion dampers at base Kilmore Street Medical Centre.


decades and was pioneered in New Zealand through the use of lead-rubber bearings.

Interestingly, building owners the Owens Family say that, at $150,000, the 16 base isolators are less expensive than the build-ings sprinkler system.

The building also features a mix of concrete and timber for its structural frame. The columns are made from precast concrete, and the beams are hollow laminated veneer lumber (LVL) timber members, a combina-tion that is new to the industry.

The timber beams are post-tensioned with horizontal steel cables that provide strength to pull the beams back into line after a major shake. The cable ends are attached to shock-absorbing steel components that can double as energy-dissipating fuses in major earthquakes. These seismic-resisting timber solutions were developed at the University of Canterbury by the Structural Innovation Timber Company (STIC) a BRANZ, New Zealand and Australian universities research and development group. St Elmo Courts will be the countrys tallest building containing STIC-developed technology.

5153 Victoria Street base-isolated lightweight steel frameA new 3-storey building at 5153 Victoria Street will receive advanced base isolation and a relatively lightweight steel structural frame.

Instead of conventional lead-rubber base isolators, designers have chosen double concave slider bearings, where a puck sits between concave top and bottom stainless steel-lined plates. Under shaking, the plates and puck slide sideways across each other a distance of up to 40 cm, with the massive friction between them acting as an energy release for the buildings frame.

Further adding to seismic resistance, the buildings steel framework will be inherently lighter than an equivalent concrete structure. The lighter building weight generally means reduced forces are generated during an earthquake, making the job of force resist-ance easier for the buildings frame.

Leighs Construction headquarters novel foundation solutionThe new Leighs Construction headquarters in central Christchurch will be built to

Base-isolated lightweight steel frame building 53 Victoria Street, Christchurch.

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Urban village new technology for foundations and slabs.

188% Building Code strength, meeting the standard normally applied to essential structures such as hospitals.

At its Manchester Street location, earth-quake damage to the soils created a big difference in soil strength at each end of the site. This meant that foundation depth and strength requirements were vastly different from one side of the building to the other.

Extensive ground testing to 24 m deep was followed by an open-minded search for the ideal piling type. To best suit the soil conditions, high-pressure grout piles were selected, and 160 of these were installed.

This piling technique involves auguring into the ground combined with injection of high-pressure binders that spread into the soil. The binders mix with soil particles to create a stronger and more solid soil mass. This pile type is normally used for highway stabilising, and its application represents a first for Christchurch buildings.

Breathe New Urban Village new slab and foundation technologyA 72-dwelling development opposite Latimer Square that won the Breathe New Urban Village design compe-tition will feature two new s e i s m i c - re s i s t a n t technologies t h a t

focus on managing damage to foundations and floor slabs.

The 8,100 m2 complex of terrace houses and low-rise apartments will be built by an alliance that includes local Holloway Builders and Italian engineering firm Cresco. Cresco are bringing technologies known as Seismat and Armadillo to the project and to New Zealand for the first time.

Seismat is a passive load transfer device that provides an alternative to base isolators for dissipating energy. A section of Seismat is placed between two concrete slabs or column sections and its near-frictionless properties mean that the two members can move laterally and dissipate large amounts of energy harmlessly. A piece of Seismat contains four layers two panels of Teflon and air sandwiched between two thin HDPE mesh external sheets.

Armadillo is a concrete floor slab form-work that uses recycled high-strength cardboard units to create a voided biaxial

slab that provides high rigidity and strength even in expansive soils. It represents a big step forward from the conventional use of polystyrene blocks to form slabs, providing a slab that is lighter and stronger and has under-slab ventilation voids built-in.

Importantly, Armadillo formwork addresses the problem of concrete slabs settling and tilting during and after earthquakes. The system allows fast relevel of the foundation because, with greater slab strength, only the perimeter of the slab needs to be jacked up after settlement there is sufficient inherent strength for the centre of the slab to rise without internal jacking.

Pres-Lam construction technology, devel-oped at the University of Canterbury, is also being considered in the project to increase seismic resistance. Pres-Lam takes PRESSS thinking and applies it to timber buildings structures are designed to flex and rock at their joints to dissipate energy and then be pulled back into place by steel tendons.



Five driversBuildings with insufficient seismic strength are key contributors to deaths and building losses. Better information is needed for owners and potential

buyers on a propertys seismic risk, a research programme finds.

BY TEMITOPE EGBELAKIN AND PROFESSOR SUZANNE WILKINSON, UNIVERSITY OF AUCKLAND

Currently, these appraisals are not in property valuation reports unless requested. Property professionals generally include a disclaimer on any related seismic risks in their valuation report, reducing the scope and rights that may be exercised should litigation ensue.

As one research respondent said, Most times when making real estate investment decisions, we assume risk from rare disaster events such as earthquake is negligible compared to other market risks.

If valuation and property standards mandate the inclusion of seismic risks in a valuation report, the relative importance can be attached to seismic risks in investment decisions.

2. Sharing informationA seismic risk information system could encourage improved seismic retrofitting. The importance of this information has been confirmed in previous studies, and evidence from Christchurch shows the effect on earth-quake vulnerability when it is lacking.

The Canterbury Earthquakes Royal Commission recommended that the Christchurch City Council consider compiling and making available a public database of all PH

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The severely damaged CTV building.

THE CANTERBURY EARTHQUAKES Royal Commission reported that the magnitude of building collapses from the earthquakes is evidence that owners of earthquake-prone buildings are not adopting appropriate risk-mitigation measures in their buildings.

Cost, risk perception and the effectiveness of mitigation measures have been identified as factors influencing property owners seismic retrofit decisions.

Retrofitting could be encouragedResearch at the University of Auckland and Massey University identified five ways to encourage retrofitting:

Seismic risk appraisal in property valua-tion assessment.

Provision of a unified seismic risk informa-tion system.

Mandatory disclosure of seismic risk infor-mation in property market transactions.

Accuracy in earthquake risk assessments with low-cost engineered solutions.

A risk-based insurance premium system.

1. Seismic risk appraisalSeismic risk appraisal in property valua-tions is an important enabler for increasing seismic retrofits.


bore logs previously recorded in the CBD, in addition to those made for future buildings.

A unified system would help property market stakeholders access a buildings seismic risk data. This information could influence the price-setting and valuation process of individual property transactions, enabling informed investment decisions to be made.

3. Mandatory disclosureMandatory disclosure of risks would increase the extent to which people are aware of seismic risks in the market, allowing them to make appropriate property investment decisions.

One comment was, It is difficult for all market stakeholders to know the issues around seismic risks unless the law mandates that it must be disclosed. Most owners and real estate agents will prefer to be silent on such issues because it will affect their business transactions.

Findings after the Canterbury earthquakes showed that the owner of the CTV building was unaware of the buildings seismic risks at the time of purchase. If the owner had been aware of the buildings vulnerability, the cost of retrofitting could have possibly been factored into the investment decision and retrofitting work undertaken.

insurers are helped in setting accurate premiums

information irregularities between insurers, reinsurers and financial institu-tions are reduced.

Once accurate risk assessment has been made, reliable low-cost engineered solu-tions could be further developed and implemented.

5. Risk-based insurance premiumsWhile risk zones play an important part in insurance premium estimations, there appears to be a lack of importance placed on these by insurers and reinsurers.

Generally, insurance premiums are not calculated in terms of risk-based analysis, leading to high premiums, even for buildings that have been retrofitted to high seismic performance standards.

Insurance premiums should reflect risk and take into account mitigation actions undertaken on the building.

Where buildings are retrofitted well beyond minimum requirements, the owners should be rewarded with premium discounts. Research suggests that combining earth-quake insurance with compliance to seismic retrofitting of earthquake-prone buildings will encourage owners to adopt mitigation measures.

If owners and property retailers are obliged to disclose a buildings seismic risk to prospective buyers or tenants at the point of sale or lease, building occupants would demand buildings that ensure their safety. Accurate risk information to buyers, insurers and lenders would result in an informed property market and possibly force down the property value of non-retrofitted earthquake-prone buildings.

Building owners are likely to increase investments in seismic retrofitting if they perceive a potential loss of revenue or tenants.

4. Accurate earthquake risk assessmentsand low-cost engineered solutionsThe Canterbury earthquakes showed the importance of accurate earthquake risk assessment in earthquake risk mitigation. Often they are based on rough estimates and probability of earthquake occurrence and can be inaccurate.

The challenge is for earthquake hazard mitigation professionals to develop reliable methods of estimating seismic risks, as most seismic mitigation decisions are based on the outcome of the assessed risks.

The benefits of improved risk assessment are: enhanced risk estimation and the adop-tion of adequate mitigation measures in retrofitted earthquake-prone buildings


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THE RECENT FLOODS and storms in the UK have been a stark reminder of the devas-tating effects that natural hazards can have on our homes, towns and communities.

New Zealands vulnerabilityAs an island nation on the boundary of the Pacific and Indo-Australian tectonic plates and lying in the roaring forties wind system,

significant economic losses, unsurprising given that the Canterbury earthquakes were among the most significant natural disaster events in the world.

However, considering the annual occur-rences of different types of natural hazard events worldwide, floods and storms outweigh other events. This is important when focusing on the wider community impacts rather than just the economic losses.

Figure 1 provides a breakdown of natural hazard losses with the recent Canterbury earthquakes removed, providing a repre-sentative history of losses.

Australian Building Resilience Rating ToolSimilar assessments of insurance losses in Australia shows that cyclones, storm and flood damage have had a devastating effect on the country (see Figure 2).

Because of the increased frequency and destructive effects of hazard events, the Insurance Council of Australia identified the

Hazardous work

BRANZ is working with an Australian organisation on a building resilience project. Its outcome will be a rating tool that ranks building

materials resilience on a scale of 15.

BY MARK JONES, BRANZ BUILDING PERFORMANCE MANAGER

Flooding surrounding houses in Lower Hutt, near Wellington.

New Zealand is particularly susceptible to a range of natural hazards and extreme events.

In recent years, the country has expe-rienced a number of these, resulting in increasing costs to the building industry, homeowners, councils, government and the insurance industry.

Although earthquakes are relatively low- frequency events, they account for the most



need to improve the resilience of Australian residential properties against natural weather hazards.

As part of this, the Council and Edge Environment formed the Australian Resilience Taskforce to develop the Building Resilience Rating Tool for residential properties. The aim is to generate a resilience score for individual houses, taking into account the hazard profile, location of the house, section details, house type and the individual building materials used in construction (Figure 3).

Building Resilience Knowledge DatabaseBRANZ has recently been working with the Australian Resilience Taskforce in devel-oping a Building Resilience Knowledge Database a resilience evaluation database and framework for building materials and products that is based on product testing and evaluation as well as existing data sources assessing the resilience of products and systems.

The Building Resilience Knowledge Database, which will provide a repository of information to support the Building Resilience Rating Tool, complements BRANZs previous research on durability assessment, verification and service life assessments.

As many of the hazards are similar in both countries, the materials resilience information

Storm/high wind35%

Flood37%

Inundation and storms58%

Earthquake20%

Bushfire11%

Cyclone13%

Hail18%

Cyclone4%

Tornado2%

Uncategorised2%

Figure 3: Building Resilience Rating Tool hazard profile.

Figure 2: Insurance losses from natural disasters in Australia 19672013.Figure 1: Insurance losses from natural hazards in New Zealand 19682012. (Excludes the Canterbury earthquakes.)

will also form a key part in the development of a similar rating tool within New Zealand.

BRANZs resilience testingThe resilience testing regime involves testing products under standardised conditions to different hazard exposures, underpinning a 15 qualitative rating scale.

Work to date at BRANZs resilience test facility has focused on the durability and resilience of materials subjected to inunda-tion and storm conditions. This includes examining the retention of key properties for a variety of generic timber, fibre-cement and reconstituted wood-based flooring materials.

Property recovery as a function of drying time has been monitored, with work continuing on the immersion resistance of structural wall and wall lining components. Further testing methodologies assessing other hazards will be adopted in the future.

Test results typically relate to the extent of failure severity and, where available, will be translated into 15 ratings and incorporated into the database, under generic materials. The higher the rating, the higher the resil-ience of that material or component to a specific hazard.

Greater understanding provides benefitsSuccessful implementation of the rating tools will enable a greater understanding

of the impact of incorporating resilient materials and design in New Zealands dwellings as well as a better understanding of the effects of extreme weather events on materials and buildings.

This will also provide further information on the cost-benefit of different amenity and materials choices, options for mitigation strategies on existing houses and the benefits of house maintenance. For more Further information on the rating tool

and knowledge database can be found at www.

buildingresilience.org.au.

Resilient Buildings

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