@article {bnh-7952, title = {Cost-effective mitigation strategy development for building related earthquake risk - final project report}, number = {657}, year = {2021}, month = {04/2021}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

This final report contains a summary of the research undertaken by the research team from four partner institutions towards the development of an evidence base to inform decision making on the mitigation of the seismic risk posed by the most vulnerable Australian buildings subject to earthquakes.\  Without this evidence base, it is impossible to make cost-effective and economically justifiable decisions by building owners and government officials on all matters concerning seismic strengthening of existing and design of new buildings.\  While the focus of this project is on buildings, many of the project outputs will also be relevant for other Australian infrastructure such as bridges, roads and ports, while at the same time complementing other {\textquoteleft}Natural Hazards{\textquoteright} CRC project proposals for severe wind and flood.\ 

In order to achieve the overall project aim, work was undertaken on three complementary fronts to:

  1. Understand the seismic vulnerabilities of existing unreinforced masonry (URM) and limited ductile reinforced concrete (LDRC) buildings and methods to address them through seismic retrofit;
  2. Risk assessment of the building stock through development of an economic loss model with trial evaluations for a regional town (York, WA) and a metropolitan area (Melbourne); and
  3. Advance an end-user focused research utilisation project in the area of community risk reduction. This is done through an Earthquake Mitigation Case Study for the historic town of York in Western Australia.

The first of the above components was researched in the Universities of Adelaide, Melbourne, and Swinburne. This work included investigations of existing building seismic capacities and development of building specific retrofit techniques. The second area was studied by Geoscience Australia and the work includes estimating direct and indirect losses associated with building damage and benefits from seismic retrofit.\  The delivery date for the Melbourne CBD trial evaluation was delayed due to Covid-19 impacts but the revised delivery date of March 2021 has been agreed by the CRC. The last component was conducted utilizing the research findings in the two other areas in collaboration with the Western Australia Department of Fire and Emergency Services, York Shire Council and its residents.

Finally, using the new damage loss models and costings for seismically retrofitting buildings, recommendations are made for the development of seismic retrofit guidelines and policy based on the strong evidence base being developed by this CRC project team.

As a consequence, the project has been extremely successful with several end-users implementing the research outputs.\  York Shire Council has embarked on seismic retrofit of up to three buildings in the Shire as demonstrations to other building owners of the cost-effectiveness as well as helping to develop the local expertise amongst the building profession to implement these simple seismic strengthening techniques.\  The project has also resulted in a follow-on project in Western Australia to expand the building typologies from York to include three additional typologies that are common in the rest of WA.\  The retrofit strategies for all nine typologies will be made publically available through web sites.

}, keywords = {buildings, cost-effective, earthquake, mitigation, risk, strategy}, issn = {657}, author = {Michael Griffith} } @article {bnh-8215, title = {Cost-effective mitigation strategy development for building related earthquake risk {\textendash} Melbourne case study}, number = {707}, year = {2021}, month = {09/2021}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

Earthquake hazard was not fully recognised in Australian building design until the mid-1990{\textquoteright}s. This oversight has resulted in a legacy of vulnerable buildings that can be readily damaged in moderate to severe Australian earthquakes. In particular, older unreinforced masonry (URM) buildings built with the architectural styles, materials and construction details used in the United Kingdom are particularly vulnerable. Australian earthquakes have highlighted the vulnerability of this building type. These events include the Adelaide Earthquake of 1954, the Meckering Earthquake of 1968, the Newcastle Earthquake of 1989 and the Kalgoorlie Earthquake of 2010, all of which damaged pre WWII masonry buildings in particular.\  Buildings of this style are present in the older centres of our major cities, and Melbourne has a very significant number of these. As shown in this research, in number nearly half of the buildings in the Melbourne central business district are of this type of construction. The damage to these buildings can greatly add to human casualties as a result of falling masonry elements. Further, the severity of damage and losses can impede the recovery of cities like Melbourne physically, economically and socially. Finally, many of these buildings have heritage value to communities that residents may want preserved.

This document reports on the final deliverable for Project A9 Cost-effective mitigation strategy development for building related earthquake risk of the Bushfire and Natural Hazards Collaborative Research Centre (CRC). It builds on the masonry component research of the University of Adelaide in this project and is a milestone for Geoscience Australia. The work follows the utilisation project entitled {\textquotedblleft}Earthquake Mitigation of WA Regional Towns: York Case Study{\textquotedblright}, that was jointly delivered by GA and the University of Adelaide. The utilisation project developed original condition and mitigated vulnerability models for six URM building types. In this project, these outcomes have been applied to the much larger Melbourne CBD exposure.

The project had the following key components:

The work required the development of the three fundamental risk elements of earthquake hazard, community exposure and building vulnerability. It also entailed the assessment of the economic loss measures associated with human injury, contents losses, rental income, commercial property leasing, and business activity. Additionally, it included the application of the semi-intangible value placed on human life to society. Each of these are described below.

Earthquake hazard

This study has drawn upon the latest understanding of the Melbourne region earthquake hazard by utilising the recently released National Seismic Hazard Assessment (NSHA 2018) (Allen et al, 2018a). The bedrock hazard from this assessment shows Melbourne to have a {\textquotedblleft}low{\textquotedblright} earthquake hazard by global standards but significant by Australian standards. The hazard is further amplified by the presence of the sediments deposited by the Yarra River.\  These soil effects increase the hazard, particularly those in the study region south of the Yarra River. The effects of soil amplification can double the severity of shaking in some areas.

Community exposure

The definition of the building assets in the study region utilised several sources. The available state government building data integrated into the National Exposure Information System (NEXIS) was accessed and supplemented by an engineering survey database developed and maintained by GA for the Australian Reinsurance Pool Corporation. This was further refined by a desktop review of all masonry buildings utilising available street level imagery. In total there were 1,543 buildings in the study region, and 687 of these were identified as URM.

The assessment of human activity was achieved by utilising research undertaken outside of this project. This research utilised a population model developed by downscaling a destination zone based telecommunication model with pedestrian counts, the Melbourne traffic control systems movement counts, and building floor area information. Using this work it was possible to define the local human exposure at the time of the scenario event, particularly those in damaged buildings and those potentially exposed to falling masonry during a rapid onset earthquake event.

Building vulnerability

The building vulnerability assessment work for the URM building stock was a direct utilisation of the six vulnerability types identified in the earlier York WA mitigation study. This included the vulnerability in present condition, and that with mitigation measures applied to the vulnerable elements. To complete the context, the vulnerability of other building types was attributed using a suite of models developed through an adaptation of US HAZUS models, reference to \ heuristically developed models from a GA facilitated UN workshop (Maqsood et al, 2014), and through heuristic adjustments by the project team. This vulnerability of non-URM buildings remained a constant in the study as mitigation of these buildings was not considered.

Economics of cost assessment

The economic assessment considered a broad range of measures. These ranged from the direct costs to property owner, building occupiers, and businesses through to health care costs and the partially intangible value placed on the loss of a human life. The aim was to provide scalable information on benefits versus cost to a range of decision makers and investors. Importantly, the measures where not comprehensive and so represent a lower bound to the actual avoided impacts mitigation achieves. For example, the cost of emergency response, clean-up and community recovery support were not considered. Neither was a macro-economic perspective developed to capture non-impacted businesses that would benefit from a stimulus in business activity such as in the construction industry, the supply of home appliances, soft furnishings and drapery. Significantly, the value of avoided heritage building loss was considered through the utilisation of metrics developed by a UWA led CRC project.

Scenario impacts and risks

The study considered a single rare earthquake scenario having an annual likelihood of 1/5,000 of causing the targeted bedrock shaking severity beneath the Melbourne CBD, or greater. This likelihoods corresponds with a 1\%, chance of this shaking severity being exceeded in the next 50 years. For the event the injuries and other losses within the scope of this study were assessed using the human exposure corresponding with 11:00am of Monday through to Thursday. The losses ranged from $737m for building damage only, through to $1.66b for the other monetary costs considered.\  The value of human life lost increased this to $3.97b. Where 25\% of the masonry building stock was retrofitted, over 30 years, these losses reduced by approximately 16\%.

The reduction in injuries if this event occurred in 30 years time was also evaluated. Serious injuries reduced by 16 and deaths by 98 persons. Urban Search and Rescue logistics would also reduce correspondingly.

In a similar manner, the long term financial risk of the Melbourne CBD study region was evaluated for building damage. It was presented as the average annualised loss for the URM building stock and for the entire study region buildings. It was also forecast 30 years into the future and the financial risk reduced by 38\% for the URM building stock and by 10\% across the entire study region buildings.

Discussion and outcomes

Earthquakes occur frequently in Australia with over 100 events greater than magnitude 3.0 (ML) recorded within the Australian continent every year by Geoscience Australia. The smaller and more frequent events are typically non-damaging, whereas the less frequent larger events can be very damaging when they occur close to a community. This plays out in the economics of strengthening older structures where the benefits of avoided building damage and contents losses through retrofit for earthquake are not a full offset for the significant costs.\  Other avoided costs associated with business losses, lost wages, health care costs, and the value placed on human life, do increase the sum significantly but are not realised by the property owner. While not all avoided costs were considered, this project indicates that the justification for retrofit based solely on a financial investment may be difficult to demonstrate for URM buildings in Melbourne.

As was also illustrated by the earlier York study, there are other considerations for the retrofit of URM buildings in the Melbourne CBD and in other older business districts in the city. If a rare earthquake occurred locally during a period of high public exposure there would be considerable loss of life. This research has shown that if a 5,000 year Return Period (RP) event (5.5 Mw) occurring on a business day approximately 100 people would die with close parallels to the 2011 Christchurch Earthquake outcome for masonry structures (42 fatalities). This may point to cheaper levels of retrofit with the objective of tying back elements that could cause casualties, rather than having the aim of avoiding economic loss.

Further, following a rare, but credible, earthquake high value heritage buildings would be lost. The research has shown that the willingness to pay by just the residents of the City of Melbourne LGA adds a notional 10\% of the total benefits of the mitigation program.

SUMMARY

The project has applied a range of retrofit measures for a suite of six URM building types developed as part of Project A9 to a very large population of URM building found in the Melbourne CBD. These measures have been demonstrated to reduce the physical vulnerability of each building. The project has also translated this vulnerability change into broader metrics that form an evidence base to inform decisions to retrofit.

The project has also demonstrated the benefit of retrofit through a virtual retrofit of a major city CBD. These benefits include reduced post event logistics for emergency management and the local government, reducing financial losses to building owners, businesses, and reducing injuries and fatalities. It has also demonstrated that retrofit reduces the long term financial cost of earthquake hazard, thereby making risk transfer through insurance uptake more affordable. Finally, it has demonstrated how valuable heritage structures can be progressively preserved for the future by protecting them from future credible earthquakes.

}, keywords = {buildings, earthquake, Melbourne, mitigation, risk, strategy}, issn = {707}, author = {Hyeuk Ryu and Martin Wehner and Jaroslav Vaculik and Valdis Juskevics and Mark Edwards and Michael Griffith and Itismita Mohanty and Stuart Butt and Neil Corby and Trevor Allen and Robert Hewison} } @article {bnh-8130, title = {Cost-effective mitigation strategy development for flood prone buildings {\textendash} final project report}, number = {691}, year = {2021}, month = {07/2021}, institution = {Bushfire and Natural Hazards CRC}, address = {MELBOURNE}, abstract = {

The motivation for this project arises from the experience and observations made during the 2011 and 2013 floods in Australia, which caused widespread devastation in Queensland. Considerable costs were sustained by all levels of government and property owners to effect damage repair and enable community recovery.

A fundamental reason for this damage was inappropriate development in floodplains and a legacy of high risk building stock in flood prone areas. While the vulnerability and associated flood risk for newer construction is being addressed (moderated) by new standards (ABCB, 2012), building controls and land use planning, the vulnerability associated with existing building stock remains. This vulnerability contributes disproportionally to overall flood risk in many Australian catchments.

The Bushfire and Natural Hazards Collaborative Research Centre (CRC) project entitled Cost-effective mitigation strategy development for flood prone buildings addresses this issue and is targeted at assessing mitigation strategies to reduce the vulnerability of existing residential building stock in Australian floodplains. The project addresses the need for an evidence base to inform decision making on the mitigation of the flood risk posed by the most vulnerable Australian houses and complements parallel CRC projects for earthquake and severe wind.

The project has developed a building classification schema to categorise Australian residential buildings into a range of typical storey types. Mitigation strategies developed nationally and internationally have been reviewed. A floodproofing matrix has been developed to assess appropriate strategies for the selected storey types. All appropriate strategies have been costed for the selected storey types through the engagement of quantity surveying specialists. Vulnerability curves have been developed featuring reduced losses achieved through appropriate mitigation strategies for the five selected storey types.

Furthermore, selected building materials/systems have been tested to ascertain their resilience to floodwater exposure. These tests were aimed at addressing knowledge gaps in the areas of strength and durability of building materials during immersion.

A research utilisation project with NFRAG, AIDR and FMA as key stakeholders commenced in 2018. The project has developed generalised vulnerability functions for use by floodplain managers who may not have detailed exposure information.

In concluding the project, cost benefit analyses of mitigation options were conducted at three levels of resolution. These have added to cost versus benefit work already completed by the project team for Launceston as a utilisation project. The results are an evidence base to inform decision making by government and property owners on the mitigation of flood risk by providing information on the cost effectiveness of different mitigation strategies.

This report describes the research methods, project activities, outcomes and their potential for utilisation.

}, keywords = {buildings, Flood, mitigation, strategy}, issn = {691}, author = {Dale, K and Maqsood, T and Martin Wehner} } @article {bnh-7196, title = {Benefit versus cost analysis and optimal cost effective mitigation strategies}, number = {598}, year = {2020}, month = {08/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {MELBOURNE}, abstract = {

This report forms part of the output to a research project entitled {\textquoteleft}Cost effective mitigation strategy development for flood prone buildings{\textquoteright} within the Bushfire and Natural Hazards Cooperative Research Centre. The motivation for this project arises from the experience and observations during the recent flooding in Australia in 2011, 2013 and 2015, which caused widespread devastation in Queensland. A fundamental reason for this damage was inappropriate development in floodplains and a legacy of high risk building stock in flood prone areas. The BNHCRC project aims to address this issue and is targeted at assessing mitigation strategies to reduce the vulnerability of existing residential building stock in Australian floodplains.

Previous project steps towards achieving this goal have included the development of a building schema to categorise the Australian residential building stock and a literature review of mitigation strategies developed nationally and internationally. The review categorised strategies into elevation, relocation, dry floodproofing, wet floodproofing and the use of flood barriers. Five typical storey types which represent the most common residential buildings in Australia have been selected to evaluate the above mentioned mitigation strategies.

\ Each mitigation strategy has been costed through engagement of a professional quantity surveyor and the application of the mitigation strategies and resultant reduction in susceptibility of damage has been quantified in the form of vulnerability models for mitigated storey types.

This report presents an assessment of the cost-effectiveness of flood mitigation strategies to residential buildings in Launceston Tasmania through a benefit versus cost analysis. The benefit versus cost analysis requires assessing loss both pre-and post-mitigation for a range of flood likelihoods with the difference being the benefit. The costs of the applied mitigation are then compared to the benefits with a benefit versus cost ratio of greater than 1.0 indicating an economically viable decision.

In the research presented here the mitigation options were typically assessed as cost-effective when considering damage to the rersidential buildings with the probable maximum flood extent.\  An important modelling assumption was to assume that the existing levee system that does provide a level of flood protection to Launceston was not in place (i.e. the City was unprotected). The results here are also only for one catchment and its behavior and also for the building stock in Launceston. The use of temporary flood barriers around the area with the highest flood hazard was the most cost-effective measure.

Work will continue with cost versus benefit analyses planned for other locations with different building stock configuarations and different catchment type behaviours. The result will be an evidence base to inform decision making by government and property owners on the mitigation of flood risk. The evidence base will feature information on the cost effectiveness of different mitigation strategies and optimal solutions for different cases of building and catchment types.

}, keywords = {benefit, buildings, cost analysis, Flood, mitigation, strategies}, issn = {598}, author = {Maqsood, T and Dale, K and Martin Wehner} } @article {bnh-6901, title = {Cost-effective mitigation strategy development for building related earthquake risk}, number = {565}, year = {2020}, month = {05/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

The CRC project Cost-effective mitigation strategy development for building related earthquake risk\ is seeking to address the need for an evidence base to inform decision making on the mitigation of the earthquake risk posed by vulnerable Australian buildings. It aims to develop information related to more vulnerable Australian building types in the following areas:-

This report describes progress made against the last component which undertook some trial runs to estimate business income loss and rental income loss and provided a complete work plan for estimating direct health care cost.

The economic loss modelling approach aims to encompass the information needs of a range of decision makers. These view benefits through different {\textquotedblleft}lenses{\textquotedblright} and at differing scales. For this research they include:-

This report presents the methodological progress in estimating the proprietary and wage/salary income loss due to business interruption, direct health care costs and the casualty costs to society due to injury and loss of life in the context of the forthcoming Melbourne city case study. The report corresponds with the 30 June 2019 project milestone deliverable {\textquotedblleft}Reporting on Economic Evaluation of Mitigation Strategies and Building Level{\textquotedblright}.

}, keywords = {buildings, cost-effective, earthquake risk, mitigation strategy}, issn = {565}, author = {Itismita Mohanty and Mark Edwards and Hyeuk Ryu and Martin Wehner} } @article {bnh-6781, title = {Final report on vulnerability of as-built and retrofitted LDRC buildings}, number = {551}, year = {2020}, month = {03/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

Previous Bushfire and Natural Hazard CRC (BNH CRC) reports have presented the fragility curves for reinforced concrete buildings that are supported by reinforced concrete walls and moment resisting frames, and the fragility curves for this type of buildings with four retrofitting options. This study presents the vulnerability curves for these buildings presented in terms of damage factor, which is the ratio of the repair cost to the replacement cost for the buildings. This report contributes to the project {\textquotedblleft}Cost-effective mitigation strategy development for building related earthquake risk{\textquotedblright} which is aimed to develop knowledge to facilitate evidence-based informed decision making in relation to the need for seismic retrofitting, revision of codified design requirement, and insurance policy.

}, keywords = {as-built, buildings, retrofit, Vulnerability}, issn = {551}, author = {Elisa Lumantarna and Nelson Lam and Hing-Ho Tsang and Emad F Gad and John Wilson} } @article {bnh-6782, title = {Progress report on case study CBD precinct}, number = {552}, year = {2020}, month = {03/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

The CRC Project A9 entitled {\textquotedblleft}Cost-Effective Mitigation Strategy Development for Building Related Earthquake Risk{\textquotedblright} is seeking to address the need for an evidence base to inform decision making on the mitigation of the earthquake risk posed by vulnerable Australian buildings. It aims to develop information related to more vulnerable Australian building types in the following areas:

This project also includes a case study to demonstrate the utility of the research with central Melbourne identified as the locality. Central Melbourne has a concentration of older unreinforced masonry buildings so the case study will examine the current risk posed by these and how they can be mitigated through application of the measures developed in this CRC project. Significantly this project will link to the concluding utilisation project on York and will integrate research outcomes on heritage value to be developed by the CRC project {\textquotedblleft}Economics of Natural Hazards{\textquotedblright} led by the University of Western Australia. This progress report describes the scope, the research elements and status of these, and the process by which they are being integrated into the final research outcomes. It also provides background to a requested variation to delay the final deliverable and associated CRC payment to enable other research outputs to be integrated.

This report corresponds with the 30 September 2019 project milestone deliverable {\textquotedblleft}Progress Report on Case Study CBSD Precinct{\textquotedblright}, BNHCRC reference 3.1.2.

}, keywords = {buildings, cbd, Decision making, earthquake risk, mitigation}, issn = {552}, author = {Hyeuk Ryu and Martin Wehner and Mark Edwards and Itismita Mohanty} } @mastersthesis {bnh-6863, title = {Seismic Retrofitting of Reinforced Concrete Beam-Column Joints Using Diagonal Haunch}, year = {2020}, month = {04/2020}, school = {Swinburne }, address = {Melbourne}, abstract = {

The thesis investigates the feasibility of using single diagonal haunch with post-installed anchors for improving the seismic performance of limited-ductile beam-column joints in reinforced concrete structures. This straightforward, less-invasive and architecturally-favourable solution can result in reducing the effect of seismic actions on buildings and consequently diminishing casualties.

}, keywords = {beam-column joints, buildings, earthquakes, reinforced concrete structures, seismic performance}, url = {https://researchbank.swinburne.edu.au/items/4730e574-60a5-421c-a619-f2def494e1a2/1/}, author = {Zabihi, Alireza} } @article {bnh-6129, title = {Progress report on costing of limited ductile reinforced concrete buildings}, number = {520}, year = {2019}, month = {10/2019}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

{\textquotedblleft}Cost-effective mitigation strategy development for building related earthquake risk{\textquotedblright} under the Bushfire and Natural Hazards Cooperative Research Centre (BNHCRC) aims to develop knowledge to facilitate evidence-based informed decision making in relation to the need for seismic retrofitting, revision of codified design requirement, and insurance policy. Previous report has presented vulnerability assessment of two types of reinforced concrete (RC) buildings, RC buildings that are mainly supported laterally by limited ductile RC walls and buildings that are supported jointly by limited ductile RC walls and RC frames. The analyses demonstrate buildings that are jointly supported by RC walls and frames to be more vulnerable. This report presents summary findings of the vulnerability analyses along with descriptions for the types of damage observed for each performance levels with the aim of estimating cost of repair for this type of buildings.\ 

}, keywords = {buildings, concrete, emergency recovery, engineering, risk and safety}, issn = {520}, author = {Elisa Lumantarna and Nelson Lam and Hing-Ho Tsang and Emad F Gad and John Wilson} } @article {bnh-5625, title = {Vulnerability Functions for RC Shear Wall Buildings in Australia}, journal = {Earthquake Spectra}, volume = {35}, year = {2019}, month = {02/2019}, pages = {27}, chapter = {333-360}, abstract = {

This research investigates the development of analytical fragility functions for reinforced concrete shear wall buildings in Australia. A building stock for the city of Melbourne is used in conducting an assessment of these types of structures. The assessment uses the best information available for selecting the building parameters applicable to the low-to-moderate seismic region, site soil class, expected earthquake ground motions, and site response. The capacity spectrum method is used to derive vulnerability functions for low-, mid-, and high-rise reinforced concrete shear wall buildings. Although there is a paucity of earthquake damage data available in Australia, some comparisons are made using the results from the fragility functions derived here to the damage data from the Newcastle earthquake in 1989.

}, keywords = {buildings, earthquake, Emergency management, engineering}, doi = {10.1193/120717EQS251M}, url = {https://www.earthquakespectra.org/doi/abs/10.1193/120717EQS251M}, author = {Ryan D. Hoult and Helen M. Goldsworthy and Elisa Lumantarna} }