@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-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-7971, title = {The Selection and Scaling of Ground Motion Accelerograms for Use in Stable Continental Regions}, journal = {Journal of Earthquake Engineering}, year = {2021}, month = {04/2021}, abstract = {

This paper presents an application of the Conditional Mean Spectrum (CMS) methodology for sourcing accelerogram records for use in dynamic analyses of structures in intraplate regions of lower seismicity. The main challenges with deriving CMS for selecting and scaling accelerograms in regions of lower seismicity stem from the paucity of representative strong motion data and event recurrence data. A step-by-step illustration of the methodology is presented using the south-eastern Australia (SEA) region as an example. The study involves making use of a diversity of Ground Motion Prediction Expressions (GMPEs) including a recently developed regionally adjustable Component Attenuation Model (CAM). Three different schemes using a weighted averaging of candidate GMPEs were adopted and a comparison of predictions demonstrated only minor differences confirming the robustness of the modelling. The CMS constructed in this study have been used to develop a proposed suite of scaled accelerograms for SEA.

}, keywords = {Component attenuation model, Conditional mean spectra, earthquake, engineering, ground motion selection, stable continental region}, doi = {https://doi.org/10.1080/13632469.2021.1913456}, url = {https://www.tandfonline.com/doi/abs/10.1080/13632469.2021.1913456?journalCode=ueqe20}, author = {Yiwei Hu and Nelson Lam and Scott Menegon and John Wilson} } @article {bnh-7017, title = {Axial Load Variation of Columns in Symmetrical RC Buildings Subject to Bidirectional Lateral Actions in Regions of Low to Moderate Seismicity}, journal = {Journal of Earthquake Engineering}, year = {2020}, month = {06/2020}, pages = {1-29}, abstract = {

Columns in building frame systems are subjected to the combined action of bidirectional horizontal loading and axial load variation during an earthquake. Whilst the behaviour of RC columns under unidirectional and bidirectional lateral loading with constant axial load is understood well, the behaviour under bidirectional lateral loading with axial load variation is rarely studied, especially for limited ductile RC columns prevalent in regions of low to moderate seismicity. This paper begins with a numerical study that aims to obtain the generalised patterns and range of axial load variation in RC building columns. To this end, a case study building is subjected to a suite of 15 ground motions, representative of low to moderate seismic regions, in OpenSees. This is followed by an experimental study in which limited ductile high-strength RC columns are tested under bidirectional lateral loading and two different axial load variation protocols, namely synchronous and nonsynchronous variable axial loading protocols. The results of the numerical study demonstrated that axial load variation of the columns in an RC building is primarily dependent on the response spectral acceleration corresponding to the fundamental period of the structure in the two orthogonal horizontal directions and/or the vertical direction. The results of the experimental testing showed that nonsynchronous axial loading (compared to constant and synchronous axial loading) results in the lowest collapse drift capacity and energy dissipation of the RC columns.

}, keywords = {Axial load variation, bidirectional loading, drift capacity, earthquake, RC columns}, doi = {https://doi.org/10.1080/13632469.2020.1772151}, url = {https://www.tandfonline.com/doi/abs/10.1080/13632469.2020.1772151?journalCode=ueqe20}, author = {Saim Raza and Scott Menegon and Hing-Ho Tsang and John Wilson} } @mastersthesis {bnh-8097, title = {Collapse behaviour of limited ductile high-strength RC columns under multidirectional earthquake actions}, volume = {Doctor of Philosophy}, year = {2020}, school = {Swinburne University of Technology}, address = {Melbourne}, abstract = {

Raza (2020) employed experimental, numerical and empirical methods to develop a fundamental understanding of the collapse behaviour of limited ductile high-strength reinforced concrete columns, designed as per Australian concrete standard, under multidirectional earthquake loading. The adequacy of the requirements of the concrete design standard in Australia was assessed and adequate design recommendations were proposed to ensure collapse prevention of such columns in a major earthquake event. The research outcomes are expected to have important implications for the earthquake safety of building stocks in Australia and globally.

}, keywords = {actions, Behaviour, Collapse, ductile, earthquake, high-strength RC columns, limited, multidirectional}, doi = {http://hdl.handle.net/1959.3/456529}, url = {https://researchbank.swinburne.edu.au/items/10dd9ce0-2aa2-4a20-b78b-dd5695225dbe/1/}, author = {Saim Raza} } @article {bnh-7378, title = {Cost-effective mitigation strategy development for building related earthquake risk: annual report 2019-2020}, number = {614}, year = {2020}, month = {09/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {MELBOURNE}, abstract = {

This annual report contains a summary of research undertaken by 4 partner institutions towards the development of cost-effective seismic retrofit methods for vulnerable Australian buildings in the 12-month period from July 2019 through June 2020.

Progress has been made in 4 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
  3. advance an end-user focused research utilization project in the area of community risk reduction. This is done through an Earthquake Mitigation Case Study of the historic town of York in Western Australia
  4. commencement of an End-User Utilisation Project with York Shire Council and the WA Department of Fire and Emergency Services through a Natural Disaster Resilience Program funded grant.

The first of the above components is being researched in the Universities of Adelaide, Melbourne, and Swinburne. This work includes investigation of existing building seismic capacities and development of retrofit techniques. The second area is being studied by Geoscience and the work includes estimating direct and indirect losses associated with building damage and benefits from seismic retrofit. The third component is being 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. The last component only started at the end of 2019 but is extremely exciting. To date, the project team has identified several URM buildings in the York Shire to act as {\textquoteleft}exemplars{\textquoteright} for seismic retrofit. The first of these, the York Residency Museum building, has been seismically assessed, retrofit solutions recommended, local consultants (engineering and building contractors) have submitted a report and estimated costings for the rehabilitation work and Council is now in discussions with the contractor.

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.

}, keywords = {building, earthquake, mitigation, risk, strategy}, issn = {614}, author = {Michael Griffith} } @article {bnh-7186, title = {Earthquake mitigation of WA regional towns: York case study - final report}, number = {596}, year = {2020}, month = {08/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {MELBOURNE}, abstract = {

Earthquake hazard was only fully recognised for Australian building design in the early 1990{\textquoteright}s following the Newcastle Earthquake of 1989. This has resulted in a significant legacy of Australian buildings that are inherently more vulnerable to low to moderate earthquake generated ground motion. Having accessible knowledge of the most effective measures to retrofit older masonry buildings will enable and encourage the strengthening of buildings resulting in more resilient communities.

Western Australia has a region of elevated seismicity inland from Perth where there are located several older regional towns having a predominance of older unreinforced masonry (URM) buildings. In 1968 the town of Meckering was devastated by an earthquake (Gordon et al, 1980), which destroyed the town{\textquoteright}s URM building stock and damaged URM buildings in other neighbouring towns. The town of York, situated approximately 37km from the epicentre was also significantly damaged (Everingham et al, 1982). The combination of high hazard and vulnerability in this region points to a need for informed mitigation measures.

This project entailed undertaking a mitigation implementation study of York, Western Australia{\textquoteright}s oldest inland town, which has many valuable historical buildings that are vulnerable to damage by a large earthquake. This utilisation project sits beneath and draws upon the vulnerability and economic modelling research outcomes of the BNHCRC project {\textquotedblleft}Cost-effective Mitigation Strategy Development for Building related Earthquake Risk{\textquotedblright}. Utilising the outcomes of the project a range of mitigation strategies have been virtually applied to the town{\textquoteright}s URM buildings. This has enabled an assessment of the effectiveness of these interventions on community risk and emergency management (EM) logistics in the context of rare, but credible, earthquakes.

In this report the research and its outcomes are presented and discussed. Further, recommendations are made for future retrofit strategy implementation in York and more broadly in Western Australia. In particular, a new NDRP project is described that will build upon this BNHCRC project in testing the application of the measures in actual retrofit work undertaken in York. This BNHCRC project has been led by the University of Adelaide (UoA) with project partner Geoscience Australia (GA). The end users are the Shire of York and the WA Department of Fire and Emergency Services (DFES) with valuable contributions made by the WA Department of Planning, Lands and Heritage. Through the workshop activity reported there have also been valuable guidance from Engineering Heritage, WA, and the Insurance Australia Group (IAG).

}, keywords = {earthquake, mitigation, regional towns, york}, issn = {596}, author = {Martin Wehner and Hyeuk Ryu and Michael Griffith and Mark Edwards and Neil Corby and Itismita Mohanty and Jaroslav Vaculik and Trevor Allen} } @article {bnh-7481, title = {In-plane response of perforated unreinforced masonry walls under cyclic loading}, journal = {Journal of Structural Engineering}, volume = {146}, year = {2020}, month = {06/2020}, abstract = {

This paper presents the results of an experimental study into the behavior of perforated (containing openings) unreinforced masonry (URM) walls subjected to cyclic in-plane lateral loading. Damage to perforated URM walls during previous earthquakes has revealed that the in-plane response is mainly influenced by the pier and spandrel geometry, as well as the level of axial compressive stress on the walls due to gravity loading. The study focused on masonry typologies representative of historical URM buildings in the Australian context. To investigate this behavior, eight full-scale URM walls with semicircular arched openings, double wythe thickness, and materials representing masonry construction from the mid-19th to mid-20th century were constructed for pseudostatic cyclic in-plane testing. The experimental program considered varying spandrel depths and pier widths and the imposed vertical loading on the piers was also varied to observe the lateral load capacity and the variation of pier-spandrel failure modes. The test results showed that the in-plane capacity and the failure modes were significantly affected by changes of wall geometry and the imposed vertical precompression loading. Predictions of wall strengths, in-plane stiffnesses, and failure modes according to ASCE guidelines show that the guidelines agree well with the test observations.

}, keywords = {earthquake, lateral loading, unreinforced masonry}, doi = {https://doi.org/10.1061/(ASCE)ST.1943-541X.0002657}, url = {https://ascelibrary.org/doi/full/10.1061/\%28ASCE\%29ST.1943-541X.0002657}, author = {Milon Howlader and Mark Masia and Michael Griffith} } @article {bnh-7476, title = {Wellington{\textquoteright}s Earthquake Resilience: Lessons from the 2016 Kaikoura Earthquake}, journal = {Earthquake Spectra}, volume = {36}, year = {2020}, month = {08/2020}, pages = {1448-1484}, abstract = {

Wellington city, the capital of New Zealand, experienced substantial damage and impacts from the 2016 Kaikoura earthquake, despite its relatively large distance of 60 km from the source of the earthquake. This article draws on impact observations from this event to discuss critical issues for Wellington{\textquoteright}s earthquake resilience. Ground motion characteristics exhibiting substantial amplifications in native and reclaimed sites, including basin effects, liquefaction of reclaimed land at the port of Wellington, characteristic structural and non-structural damage to mid- and high-rise buildings, and socio-economic impacts on community are explored in detail. The main thrust of the article is to discuss implications of these observations, identify needs, and stimulate actions across a wide range of earthquake science, earthquake engineering, and socio-economic disciplines to achieve adequate resilience levels for Wellington, and other cities facing similar seismic risks.

}, keywords = {basin effects, building damage, earthquake, earthquake resilience, ground motion, lifelines, liquefaction, reclaimed land, socio-economic impacts, Wellington}, doi = {https://doi.org/10.1177/8755293020919426}, url = {https://journals.sagepub.com/doi/abs/10.1177/8755293020919426}, author = {Misko Cubrinovski and Brendon Bradley and Kenneth Elwood and David Johnston and Caroline Orchiston and Timothy Sullivan and Liam Wotherspoon} } @article {bnh-5433, title = {Cost-Effective Mitigation Strategy Development for Building Related Earthquake Risk Annual Report 2017-2018}, number = {464}, year = {2019}, month = {03/2019}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {
This project arose out of the on-going research efforts by the group involving\ structural engineering academics at the Universities of Adelaide, Melbourne and\ Swinburne with Geoscience Australia experts all working towards seismic risk\ reduction in Australia. Most of the research team are actively involved in the\ revision to the Australian Earthquake Loads standard (AS1170.4) as well as being\ members of the Australian Earthquake Engineering Society which is a Technical\ Society of Engineers Australia. The devastating impact of the 2010{\textendash}11\ earthquakes in the Christchurch region on the New Zealand economy and\ society has further motivated this group to contribute to this CRC{\textquoteright}s aims of risk\ reduction for all natural hazards in Australia.\ This project addresses the need for an evidence base to inform decision making\ on the mitigation of the risk posed by the most vulnerable Australian buildings\ subject to earthquakes. 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.
}, keywords = {cost-mitigation, earthquake}, author = {Michael Griffith and Hossein Derakhshan and Elisa Lumantarna and Hing-Ho Tsang and John Wilson and Nelson Lam and Mark Edwards and Martin Wehner} } @article {bnh-5742, title = {Cost-effective mitigation strategy for building related earthquake risk - annual report 2018-2019}, number = {498}, year = {2019}, month = {07/2019}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

This annual report contains a summary of 12-month research undertaken by 4 partner institutions towards the development of cost-effective seismic retrofit methods for vulnerable Australian buildings. Progress has been made in 3 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; and
3) Advance an end user focused research utilization 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 is being researched in the Universities of Adelaide, Melbourne, and Swinburne. This work includes investigation of existing building seismic capacities and development of retrofit techniques. The second area is being studied by Geoscience and the work includes estimating direct and indirect losses associated with building damage and benefits from seismic retrofit. The last component is being 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.

}, keywords = {building risk, cost-effective, cost-mitigation, earthquake, risk}, issn = {498}, author = {Michael Griffith} } @conference {bnh-6389, title = {Development of Cost-effective Mitigation Strategy for Limited Ductile Reinforced Concrete Buildings}, booktitle = {Australian Earthquake Engineering Society 2019 Conference}, year = {2019}, month = {12/2019}, address = {Newcastle}, abstract = {

With the new awareness that most Australian reinforced concrete (RC) buildings have not been designed to withstand seismic actions, and are considered to have limited ductility, it is essential to consider retrofitting options. This study aims to evaluate the seismic performance of an archetypal Australian RC building, and then implement various retrofit techniques to find the most suitable retrofit. The structural performance of the buildings before and after various retrofitting were compared to study the effectiveness of the proposed methods as well as the effect on the seismic hazard design factor. SeismoStruct software was used to perform the nonlinear analysis of the structures. This paper contributes to a research with the overall aim of assessing the seismic performance of existing buildings and their expected failure modes, impact of retrofitting measures, and the associated costs.

}, keywords = {earthquake, existing structures, limited ductility buildings, performance validation, seismic evaluation and retrofitting}, url = {https://aees.org.au/wp-content/uploads/2019/12/55-Raneem-Alazem.pdf}, author = {Raneem Alazem and Elisa Lumantarna and Nelson Lam and Scott Menegon} } @conference {bnh-6385, title = {Earthquake Management Logistics for York, WA, Pre and Post Mitigation}, booktitle = {Australian Earthquake Engineering Society 2019 Conference}, year = {2019}, month = {12/2019}, address = {Newcastle}, abstract = {

Rare Australian earthquake events can cause extensive damage and present significant logistical challenges for emergency management agencies and local governments. Evidence of this can be seen from recent earthquake events that include the 2010 Kalgoorlie earthquake and the 1989 Newcastle earthquake of 30 years ago. Emergency managers do not experience damaging earthquakes on the same regular basis as storms, floods, and bushfires and therefore don{\textquoteright}t always fully understand the consequences they may face. Scenario modelling can provide insights to inform response and recovery by emergency management and recovery agencies as well as demonstrate how these impacts can be moderated by the retrofit of the most vulnerable building types.

The Shire of York is partnering with the WA Department of Fire and Emergency Services (DFES), the University of Adelaide and Geoscience Australia in a collaborative project that explores the current earthquake risk in the heritage town of York, Western Australia, and how the risk could be moderated through targeted retrofit. The project forms part of the Bushfire and Natural Hazards Cooperative Research Centre project {\textquotedblleft}Cost-effective Mitigation Strategy Development for Building Related Earthquake Risk{\textquotedblright}. This paper describes the approach taken and the predicted consequences modelled for a range of credible earthquake scenarios. Significantly, based on the recommendations from a stakeholder workshop in York on the 9thAugust 2018, it is also assessing how these consequences would be moderated in future decades through two rates of retrofit uptake in the town. This work is informing emergency management planning by DFES and the Shire of York. It is also illustrating the benefits of targeted community level retrofit to address the risk posed by the community building types most vulnerable to earthquakes.

}, keywords = {earthquake, Emergency management, modelling, retrofit, senario}, url = {https://aees.org.au/wp-content/uploads/2019/12/70-Hyeuk-Ryu.pdf}, author = {Hyeuk Ryu and Mark Edwards and Martin Wehner and Stephen Gray and Michael Griffith and Jaroslav Vaculik and Neil Corby and Trevor Allen} } @article {bnh-5929, title = {Economics of natural hazards annual report 2018-2019}, number = {512}, year = {2019}, month = {09/2019}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

Our project aims to provide information on the economic, social and environmental impacts of natural hazards (tangible and intangible), in order to help hazard managers in their decision making. We investigate the impacts of hazard mitigation on intangible (non-market) values, to shed light on the real (total) costs and benefits of natural hazards.

Our main focus is on developing tools and materials that will provide natural hazards managers with information on the value of mitigation and how intangible (non-market) values affect the costs and benefits of mitigation activities.
Our project will have 4 key outcomes:

  1. Provide an online platform for the intangible values database (called the Value Tool for Natural Hazards). The tool will be updated and maintained beyond the project so that managers can easily integrate intangible values in their analyses.
  2. Fill major knowledge gaps identified in the literature on intangible values that are affected by the management of natural hazards and improve the value tool with this new knowledge.
  3. Develop a Quick Economic Analysis Tool for the evaluation of the (tangible and intangible) costs and benefits of mitigation options that enables managers to conduct economic analyses in weeks rather than months.
  4. Create a Free Online Course on the application of economics to the assessment of natural hazard management options.

This year, we have progressed in the 4 outcomes outlined above:

  1. A website has been created for the Value Tool. Both the database and the guidelines can now be downloaded from http://valuetoolnaturalhazards.com. As per the agreement between UWA and BNHCRC, the tool will be freely accessible to end-users and external users. The website also includes the relevant disclaimer information and instructions that users of the tool must agree to comply with.
  2. A survey instrument has been designed and road-tested in a focus group for the original non-market valuation study. The next step in this process will be to test the survey in the Shire of York (WA), where we will estimate non-market values associated with cultural heritage and mental health.
  3. The draft (Beta) version of the Quick Economic Analysis Tool (QEAT) has been completed. QEAT is currently being improved to include an easy-to-use sensitivity analysis, to be able to perform the analysis of several management options concurrently and to include a summary dashboard where all results are summarised in an easy-to-read manner. These additions are key aspects that our end-users have mentioned in the past as important to include in a tool such as this one. The Tool now needs to be validated with case studies.
  4. Equipment for creating the online videos is being purchased (e.g. green screen for background, microphone and tripod for computer). Filming of the videos will commence in July 2019.

The utilisation outputs from our project this year involved the development and distribution of tools that help natural hazard managers integration intangible (non-market) values in their decision making. The Value Tool for Natural Hazards and the accompanying guidelines are now available online and can be easily downloaded by end-users of the BNHCRC or other organisations. The Beta version of the Quick Economic Analysis Tool (QEAT) is in the process of being improved to include key aspects that were highlighted by end-users as important to include in a tool as this one.

This year there were 4 publications from the project: 3 peer-reviewed and one non-peer reviewed (see Project Publications 2018-2019 section below).

}, keywords = {Bushfire, cost-effective, cyclone, earthquake, economics, Emergency management, Flood, Natural hazards, risk management}, issn = {512}, author = {Veronique Florec and Abbie Rogers and Atakelty Hailu and David J Pannell} } @article {bnh-5487, title = {Final report on vulnerability of as-built and retrofitted URM buildings}, number = {474}, year = {2019}, month = {03/2019}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

As reported in the previous project reports {\textquotedblleft}Fragility Curves for URM Buildings{\textquotedblright} (Derakhshan and Griffith, 2018) and {\textquotedblleft}Fragility Curves for Retrofitted URM Buildings{\textquotedblright} (Vaculik and Griffith, 2018), fragility curves are an important tool for estimating the economic loss due to earthquakes. In this report, Fragility is used as a proxy for Vulnerability.\  As a follow-up to the work presented in the previous two reports, this report presents fragility curves for {\textquoteleft}as-is{\textquoteright} and {\textquoteleft}retrofitted{\textquoteright} URM buildings in terms of {\textquoteleft}probability of exceedance{\textquoteright} versus {\textquoteleft}peak ground acceleration{\textquoteright} (PGA) for four damage ratios, D1 {\textendash} D4. With this additional information, it will be possible to estimate the reduced damage due to seismic retrofit for cost-benefit analyses for a range of earthquake scenarios in order to ensure cost-effective seismic strengthening policy.

With this in mind, the remainder of this report should be treated as an addendum to the previous two project reports (Derakhshan and Griffith, and Vaculik and Griffith, 2018), hereafter referred to as the August and October 2018 reports.

In the October 2018 report, we described the methodology used to produce empirically-based fragility curves for seismically strengthened URM buildings on the basis of performance reported for 78 heritage-listed buildings in Christchurch during the 2010 and 2011 earthquake sequence.\ 

Empirical fragility curves for the global damage of strengthened buildings have been derived using the simplifying assumption that the PGA to cause a particular probability of a given damage state in a strengthened building can be obtained as a scalar multiple of the probability to cause the same damage state in the unstrengthened building. On the basis of this assumption, PGA scaling multipliers are calibrated which can be used to apply a rightward shift to the unstrengthened building curves (from the August 2018 report) to produce the corresponding curves for strengthened buildings. These multipliers were calibrated using the Christchurch earthquake damage data for two levels of retrofit. It was found that a multiplier of 1.4 produces good agreement for buildings with a full building strengthening level of retrofit, and a multiplier of 1.1 for buildings with partial or incomplete strengthening.\  These relatively low values are a result of the fact that the unreinforced masonry buildings in Christchurch were retrofitted as many as 50 years ago when seismic strengthening technologies for URM buildings were in their infancy.\  With advances in our understanding and improved retrofit technologies of today, where the seismic strengthening techniques have been experimentally validated, slightly higher scaling multipliers of 1.25 and 1.6 are justified and were used to generate the fragility curves for partial and full seismic retrofit, respectively.

}, keywords = {Built Environment, earthquake, URM}, author = {Jaroslav Vaculik and Michael Griffith} } @conference {bnh-6388, title = {How Safe is Safe Enough? Melbourne Case Study}, booktitle = {Australian Earthquake Engineering Society 2019 Conference}, year = {2019}, month = {12/2019}, address = {Newcastle}, abstract = {

Residual risk exists in our buildings even if they were designed in conformance with modern codes of practice. The risk of being killed by earthquakes in Melbourne was discussed in the AEES 2018 Conference (Tsang et al. 2018a). This follow-up paper attempts to address a fundamental question in seismic design: {\textquotedblleft}How Safe is Safe Enough?{\textquotedblright} Various approaches have been implemented or proposed in the last decade for setting risk-targeted performance requirements for seismic design. A target collapse risk limit for a single building may be considered very low by some; however, the aggregated risk for society could become significant, especially for a metropolitan city like Melbourne. This paper introduces an approach proposed by the authors (refer Tsang et al. 2019for full details and discussion)for evaluating the adequacy of existing code level for collapse prevention and life safety by comparing societal risk functions based on regional earthquake loss modelling with a proposed regulatory requirement that aims to limit the earthquake mortality rate to {\textquotedblleft}as low as reasonably practicable (ALARP){\textquotedblright}. The proposed approach is then applied to Melbourne in a case study. The results show that the earthquake fatality risk for society appears to be unacceptable.

}, keywords = {building, Collapse, earthquake, Earthquake fatality, F-N function, Societal risk}, url = {https://aees.org.au/wp-content/uploads/2019/12/66-Hing-Ho-Tsang.pdf}, author = {Hing-Ho Tsang and James Daniell and Friedemann Wenzel and John Wilson} } @conference {bnh-6027, title = {Mitigating earthquake risk in Australia}, booktitle = {2019 Pacific Conference on Earthquake Engineering and Annual NZSEE Conference}, year = {2019}, month = {09/2019}, abstract = {

Earthquake risk is not limited to tectonic plate boundary countries. While less frequent, significant earthquakes can occur in intraplate countries like Australia which can have severe consequences. For Australia this is particularly the case as earthquake hazard has not been recognised in the design of buildings and community infrastructure for most of the country{\textquoteright}s settled history. Significant risks exist where community assets are by their nature inherently vulnerable to strong ground shaking. This paper describes three initiatives that are assisting Australian emergency management, infrastructure managers and local government to prepare for and mitigate these risks.

The first of these highlights how the characteristics of geological hazards differ from severe meteorological hazards. The very non-linear nature of impact severity with longer average recurrence interval earthquakes is demonstrated and how this information is supporting emergency management planning including capacity sharing between Association of Southeast Asian Nations (ASEAN) countries in the region is described. Secondly, the paper describes how this research is developing knowledge of the factors behind the vulnerability of critical infrastructure facilities and the options to mitigate these. The software tool System for Infrastructure Facility Resilience Analysis (SIFRA) is described which enables infrastructure facility components to be examined in the context of physical vulnerability, system criticality, repair cost and restoration time. Finally, a utilisation project of the Bushfire and Natural Hazards CRC working with the local government of York Shire in Western Australia (WA) is described. The project is providing information on the effectiveness of targeted retrofit of the heritage town of York to rare earthquakes and how this action by property owners can be incentivised.

}, keywords = {earthquake, mitigation, Vulnerability}, url = {http://db.nzsee.org.nz/2019/Oral/8C.05\%20Edwards.pdf}, author = {Mark Edwards and Muhamman Rahman and Hyeuk Ryu and Martin Wehner and Neil Corby and Michael Griffith and Jaroslav Vaculik} } @conference {bnh-6384, title = {Modelling the vulnerability of old URM buildings and the benefit of retrofit}, booktitle = {Australian Earthquake Engineering Society 2019 Conference}, year = {2019}, month = {12/2019}, abstract = {

The Shire of York is partnering with the WA Department of Fire and Emergency Services (DFES), the University of Adelaide and Geoscience Australia in a collaborative project that will examine the opportunities for reducing the vulnerability of the township of York to a major earthquake. The project forms part of the Bushfire and Natural Hazards Collaborative Research Centre (BNHCRC) project {\textquotedblleft}Cost-effective Mitigation Strategy Development for Building Related Earthquake Risk{\textquotedblright}. The township of York has a number of valuable historical buildings that contribute greatly to the town{\textquoteright}s economic prosperity and, at the same time, are vulnerable to earthquakes.

One of the benefits of retrofitting an old building is the reduction in physical building repair required following a damaging earthquake. To evaluate this benefit it is necessary to know the vulnerability of the unmitigated building and how this changes following retrofit.

This paper describes the approach taken to quantitatively estimate the vulnerability of unmitigated and retrofitted pre-WW1 unreinforced masonry (URM)buildings typical of the buildings found in York. Challenges in estimating vulnerability are discussed. Vulnerability curves are presented for one of six generic building types subjected to a range of retrofit scenarios and the economic benefit of each retrofit scenario is presented and discussed.

}, keywords = {earthquake, retrofit, URM, Vulnerability}, url = {https://aees.org.au/wp-content/uploads/2019/12/02-Mark-Edwards.pdf}, author = {Mark Edwards and Martin Wehner and Hyeuk Ryu and Michael Griffith and Jaroslav Vaculik} } @article {bnh-6336, title = {Seismic fragility assessment of nonstructural components in unreinforced clay brick masonry buildings}, journal = {Earthquake Engineering and Structural Dynamics}, year = {2019}, month = {12/2019}, abstract = {

The results of an investigation of the probability of earthquake damage to nonstructural unreinforced masonry (URM) components are presented. The components include parapets, chimneys, and out-of-plane loaded facades typical of low-rise pre-1940 construction in Australia and New Zealand. The study is based on a street survey of component geometry, in situ data on material strength, and simplified mechanical models. Uncertainties in capacity and demand were quantified based on, respectively, stochastic and deterministic approaches. The damage probabilities were compared with relevant guidelines and empirical damage data from three earthquakes. The study established a link between the qualitative damage states reported in existing guidelines and the quantitative URM component damage states. While some median damage state thresholds correlated well with the data from the guidelines, a larger dispersion value was found in the current study due to the large variations in component properties. Comparisons with empirical data suggest that the developed fragility data provide a realistic estimate of nonstructural component damage that occurred in similar buildings, with a reasonable level of conservatism. The outcome is useful in rapid assessment of the seismic risks due to nonstructural component collapse in URM precincts.

}, keywords = {Damage, earthquake, seismic risk, unreinforced masonry}, doi = { https://doi.org/10.1002/eqe.3238}, url = {https://onlinelibrary.wiley.com/doi/pdf/10.1002/eqe.3238}, author = {Hossein Derakhshan and Kevin Walsh and Jason Ingham and Michael Griffith and David Thambiratnam} } @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} } @mastersthesis {bnh-4679, title = {Seismic assessment of reinforced concrete walls in Australia}, year = {2017}, month = {09/2017}, school = {University of Melbourne}, address = {Melbourne}, abstract = {

Some non-ductile reinforced concrete walls in buildings were observed to perform poorly in the 2011 Christchurch earthquake, with most of the lives lost from the event caused by the collapse of buildings that relied on these structural elements for lateral support. Reinforced concrete (RC) walls are widely used throughout the Australian building stock as the primary lateral support elements. It is possible that some of these structural elements would perform poorly in a very rare earthquake due to the low standard of detailing that is currently required in Australia, as well as the low earthquake return period that the Building Code of Australia stipulates for their design. The aim of this research has been to assess the seismic performance of reinforced concrete structural walls, both rectangular and C-shaped, in Australia, a region of low-to-moderate seismicity. The current Australian Standard for Earthquake Actions, AS 1170.4:2007, stipulates earthquake hazard values that are based on a seismic hazard map that is over two decades old. A probabilistic seismic hazard analysis was conducted for most of the capital cities in Australia using the AUS5 model to provide a more accurate prediction of seismic hazard in Australia. The results indicate that for some cities, such as Melbourne, the response spectrum is expected to be higher for large return periods in comparison to the design spectra derived using AS 1170.4:2007. Furthermore, a site response study was conducted using equivalent linear analyses to investigate the amplification of the soil response as classified in AS 1170.4:2007 using a range of ground motions that would be expected in Australia. The primary conclusions from the study showed that there can be a large dependency of the soil amplification on the intensity of the earthquake ground motions for the softer soil classes. Moreover, the low intensity ground motions resulted in a higher spectral shape factor for soil class Be and Ce in comparison to factors derived from the current AS 1170.4:2007. An investigation was undertaken to find the displacement capacity of rectangular lightly reinforced and unconfined walls using a finite element modelling (FEM) program, with emphasis on finding the equivalent plastic hinge length. A Secondary Cracking Model (SCM) was formulated, which is a simple, mathematical model that has the potential to predict if a RC wall has a sufficient longitudinal reinforcement ratio to enable {\textquotedblleft}secondary cracking{\textquotedblright} to occur. The SCM has been validated by comparison with results from the FEM analyses. Equivalent plastic hinge length equations were derived for the rectangular walls that were observed to form secondary cracking and a single, primary crack, and this can be used to predict the displacement capacity of these walls. This estimate of the displacement capacity assumes that the inelastic rotation that occurs over the inelastic region at the base of the wall can be modelled using an equivalent plastic hinge length over which the curvature is assumed to be a constant value. These estimates of the equivalent plastic hinge length are more appropriate for RC structural walls commonly found in Australia due to the parameters used in deriving them (e.g. mechanical properties of steel, longitudinal reinforcement ratio). Moreover, some expressions for the equivalent plastic hinge length that have derived by previous researchers were found to be inappropriate for the walls analysed in this research; these were particularly inaccurate for walls that do not have sufficient longitudinal reinforcement to force secondary cracks to form. The new expressions provide better estimates of the displacement capacity of lightly reinforced and unconfined walls when compared with recent experimental observations. One of the most widely used and popular cross-sections used in structural design of RC walls is the C-shaped section. There is a paucity of information available on the inelastic behaviour of such elements, and virtually no experimental data exists on non-rectangular concrete walls with inferior details commonly found in regions of low-to-moderate seismicity. An extensive number of nonlinear pushover analyses have been conducted based on FEM to investigate the seismic behaviour of C-shaped walls with detailing commonly found in Australia. Based on the FEM results, the SCM, that has been developed for rectangular walls, was found to be able to predict the potential of a single-crack forming in the walls. The direction of loading and mode of bending was found to be particularly important for the seismic performance of these walls. A non-ductile failure was observed for the majority of the walls investigated due to crushing of the unconfined concrete at the ends of the flanges in the governing direction of loading. Further analyses were conducted in the FEM program but with confined boundary ends to emphasise the importance of such structural detailing in allowing some plastic behaviour to be achieved for the governing direction of loading. The equivalent plastic hinge lengths derived from the extensive number of FEM analyses correlated poorly in comparison to the estimates from a number of expressions that exist in the literature, including a recently developed equation specifically for C-shaped walls. Therefore, equivalent plastic hinge lengths were derived from these results and for each direction of loading. A program has been written in MATLAB to derive vulnerability functions for low-rise, mid-rise and high-rise buildings in Australia that use structural walls as their lateral force-resisting system. The city of Melbourne was used as a template for conducting the analyses, and a dataset of thousands of buildings obtained from the National Exposure Information System (NEXIS) and Census of Land Use and Employment (CLUE) databases was included in the assessment. The displacement capacity of each of the buildings was estimated using a moment-curvature analysis followed by a plastic hinge analysis. A range of artificial earthquakes from GENQKE and real earthquakes from the PEER ground motion database on {\textquotedblleft}weathered bedrock{\textquotedblright} conditions were obtained. These ground motions were subsequently used in equivalent linear analyses using the program SHAKE2000 to find the site response at the surface of different soil columns from shear wave velocity profiles taken predominantly from sites around Melbourne. The National Regolith Site Classification Map was used to estimate the soil conditions underlying each of the building sites. The acceleration and displacement response spectra resulting from these ground motions were used to represent the seismic demand for different site conditions in the capacity spectrum method and to ultimately estimate the vulnerability of the buildings. Thus, vulnerability functions were derived from the results.

}, keywords = {AS3600; buildings, earthquake, emergency management., Intraplate, low-to-moderate}, url = {http://hdl.handle.net/11343/192443 }, author = {Ryan D. Hoult} } @conference {bnh-6028, title = {Analytical development of seismic retrofit technique for RC beam-column joint using single diagonal haunch}, booktitle = {24th Australian Conference on the Mechanics of Structures and Materials}, year = {2016}, month = {12/2016}, publisher = {Swinburne University of Technology}, organization = {Swinburne University of Technology}, address = {Perth, Australia}, abstract = {

Exterior beam-column joint is typically the weakest link in a limited-ductile RC frame structure. The use of diagonal haunch element has been considered as a desirable seismic retrofit option for preventing brittle failure of the joint. Previous research has been focused on implementing double haunches, whilst the performance of using single haunch element as a less-invasive and more architecturally favourable retrofit option has not been investigated. Hence, the feasibility of using single haunch system for retrofitting RC beam-column joint is explored in this study. This paper presents the analytical development of the technique and illustrates its effectiveness by showing the changes in the shear demand at the joint.

}, keywords = {building, construction, earthquake, engineering, retrofitting, risk management}, author = {Zabihi, Alireza and Hing-Ho Tsang and Emad F Gad and John Wilson} } @conference {bnh-1890, title = {Seismic Performance of Typical C-Shaped Reinforced Concrete Shear Cores in Australia}, booktitle = {Australian Earthquake Engineering Society Conference 2014}, year = {2014}, abstract = {

Limited-ductile reinforced concrete structures have been known to perform poorly when subjected to large seismic ground motions. Many buildings in Australia rely on reinforced concrete shear-cores as their primary lateral load resiting system, but these are only required to have a low standard of detailing as per the current concrete material standards AS 3600. While there is some literature available on the numerical and analytical modelling of rectangular shaped shear walls, non-rectangular shear walls have not been extensively analysed. {\textquotedblleft}C-shaped{\textquotedblright} shear walls are commonly found enclosing a service core, lifts, stairs and toilets. This paper presents a study which looks at the seismic performance of C-shaped shear walls with different steel reinforcement ratios for low, mid and high-rise buildings. The current earthquake actions code AS 1170.4 has been used for a preliminary design of the walls using a force-based design approach within which the intention is to satisfy the performance objective of life safety in a 500 year return period earthquake design level event in Melbourne. The displacement capacity of these different core walls has been calculated using a Displacement-Based Assessment procedure and complemented with finite element modelling program SeismoStruct. The results of a probabilistic seismic hazard analysis (PSHA) using the AUS5 recurrence model that has been conducted for the city of Melbourne has been used to calculate more accurate predictions of the displacement response spectra for 500 and 2500-year return periods. The C-shaped core walls have then been assessed by comparing the displacement capacity at different structural performance limit states to the displacement spectra derived from the current earthquake loading code AS 1170.4 and the spectra results from the PSHA for both the 500 and 2500-year return periods and for soil classes Be and De.

}, keywords = {AUS5, Australia, capacity, concrete, Core, displacement-based, earthquake, limited-ductile, low-to-moderate, PSHA, seismicity, spectra, unconfined, Walls}, author = {Ryan D. Hoult and Helen M. Goldsworthy and Elisa Lumantarna} }