Groningen Earthquake Structural Upgrading Risk Assessment of Falling Hazards in Earthquakes in the Groningen Region: Appendices 1-4
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Client: Nederlandse Aardolie Maatschappij Arup Project Title: Groningen Earthquake Structural Upgrading Risk Assessment of Falling Hazards in Earthquakes in the Groningen region: Appendices 1-4 229746_032.0_REP1009 Issue Rev.0.03 | 29 March 2016 This report was prepared by Arup in March 2016 This document is part of scientific work and is based on on the basis of a scope of services agreed with our client. information available at the time of writing. Work is still in It is not intended for and should not be relied upon by progress and the contents may be revised during this process, or to take account of further information or any third party and no responsibility or liability is changing needs. This report is in the public domain only for undertaken to any third party. the purpose of allowing thorough scientific discussion and further scientific review. The findings are only estimated Job number 229746 outcomes based upon the available information and certain External Ref assumptions. We cannot accept any responsibility for actual outcomes, as events and circumstances frequently do not occur as expected. Arup bv PO Box 57145 1040 BA Amsterdam The Netherlands 229746_032.0_REP1009 | Issue Rev.0.03 | 29 March 2016 Client: Nederlandse Aardolie Maatschappij Arup Project Title: Groningen Earthquake Structural Upgrading Risk Assessment of Falling Hazards in Earthquakes in the Groningen region: Appendices 1-4 Contents Appendix 1: The Falling Hazards Risk Model 1 1. Introduction 1 2. Background and Overview 2 3. The Risk Model, Step by Step 6 3.1 Definition of Earthquake Scenarios 6 3.2 Seismic Hazard – Earthquake Frequency 7 3.3 Debris Generation from Non-Structural Building Elements 10 3.4 Debris Travel and Hazard Range 26 3.5 Consequence of Debris Impact on People 28 3.6 Occupancy of At-Risk Areas 35 3.7 Calculation of Risk Parameters 42 4. Conclusions and Development Suggestions 46 4.1 Conclusions 46 4.2 Suggestions for Further Development 46 Appendix 2: Performance of Falling Hazard Objects in Earthquakes 1 1.Introduction 1 2 Rhine Valley Earthquakes 1 2.1 Liège 1983 2 2.2 Roermond 1992 3 3 Other European Earthquakes 5 3.1 Lorca 2011 5 3.2 Low Magnitude UK Earthquakes 8 4. North American Earthquakes 23 4.1 Seattle 1965 23 4.2 Nisqually 2001 26 4.3 Northridge 1994 26 5. Earthquakes in Australia and New Zealand 30 5.1 Newcastle 1989 31 5.2 Kalgoorlie 2010 36 5.3 Christchurch 2010-11 38 5.4 Gisborne 2007 49 5.5 Other New Zealand earthquakes 50 References – Appendix 2 51 Appendix 3: Fragility Assumptions for V1 Model 1 1. Introduction 1 2. Chimneys 1 2.1 Chimneys – Probability of Failure vs PGA 1 2.2 Chimneys – Damage State Distribution vs PGA 6 3. Parapets 9 3.1 Parapets – Probability of Failure vs PGA 9 3.2 Parapets – Distribution of Damage States vs PGA 14 4. Gables 15 Appendix 4: Occupancy Assumptions for OIR Calculation 1 229746_032.0_REP1009 | Issue Rev.0.03 | 29 March 2016 Client: Nederlandse Aardolie Maatschappij Arup Project Title: Groningen Earthquake Structural Upgrading Risk Assessment of Falling Hazards in Earthquakes in the Groningen region: Appendices 1-4 1. Introduction 1 2. Exposure Pathways and Who is at Risk 1 3. Proportion of Time at Risk 3 4. Differences between OIR and CR 4 229746_032.0_REP1009 | Issue Rev.0.03 | 29 March 2016 Client: Nederlandse Aardolie Maatschappij Arup Project Title: Groningen Earthquake Structural Upgrading Risk Assessment of Falling Hazards in Earthquakes in the Groningen region: Appendices 1-4 Appendix 1: The Falling Hazards Risk Model 1. Introduction This is the first appendix to the Falling Hazards Risk Assessment report prepared by Tony Taig and Florence Pickup of TTAC Ltd based on research and analysis carried out for NAM and Arup during 2014 and 2015. It provides an expanded description of the Falling Hazards Risk Model and the evidence on which it is based. At the heart of this risk model is the simple idea that the potential for harm outside buildings depends on the quantity of heavy material that falls through the air, and the area at risk into which it falls. Most seismic risk assessment involves definition of building damage states that relate either to the extent of structural damage or to loss of economic value. This study is different in that it uses volume of debris falling through the air outside buildings as the basis for definition of ‘damage states’ for non-structural building components. The model estimates the Community Risk (CR) to people in and around Groningen region buildings resulting from three particular exposure pathways: Passers-by exposed to debris falling outside buildings Building occupants running out into falling debris, and Debris falling through building roofs onto people inside. The model has been developed in parallel with an internet-based survey of buildings in the Groningen region, carried out by a team of 20 undergraduate students and recent graduates during the summer of 2015. Both the model itself, and the surveyed building features on which the risk assessment is based, provide rough approximations rather than definitive assessments for individual buildings. The purpose of the model is to help prioritise areas for more detailed, on the ground assessment, and to support the development of general rules that can be applied in such prioritisation. It is NOT intended, and is not suitable, for making definitive decisions about individual buildings and building elements. This Appendix provides Background on falling hazards and an overview of the risk model (Section 2) A step by step explanation of the model and how it works (Section 3), and Conclusions and suggestions for further development of the model (Section 4). Appendix 1: Falling Hazards Risk Model Description Page 1 Client: Nederlandse Aardolie Maatschappij Arup Project Title: Groningen Earthquake Structural Upgrading Risk Assessment of Falling Hazards in Earthquakes in the Groningen region: Appendices 1-4 2. Background and Overview In the absence of a risk model the importance of falling masonry outside buildings is difficult to assess. Widely used models such as HAZUS1 generally tend to model casualties outside buildings as a simple multiple of casualties inside, linked to damage states which broadly describe the extent of structural damage or loss to a building. A useful starting point in considering the seriousness of this issue is to review experience in previous earthquakes, particularly those in areas which, like the Groningen region, contain large populations of masonry buildings of a broadly North European style. Figure A1.1 shows the deaths from various causes that have occurred in all of the fatal earthquakes since 1980 in Northern Europe, North America, Australia and New Zealand (judged to be the most relevant in terms of the presence of large quantities of broadly North European style masonry). Figure A1.1 Deaths in Earthquakes Since 1980 Fatal Earthquakes involving N European Style Buildings (1980 to date) 200 180 Other/Indirect Causes 160 Collapse onto occupants - non-masonry 140 Outside (masonry falling outwards) 120 Collapse onto occupants (masonry) 100 80 60 40 20 0 Liège California Australia Roermond Northridge Christchurch 1983 1989 1989 1992 1994 2011 (night) (afternoon) (morning) (night) (night) (mid-day) M4.6, 4km M6.9, 19km M5.6, 12km M5.4, 15km M6.7, 18km M6.3, 5km The largest single contributor to fatalities, shown in yellow in the chart, has been the collapse of a small number of large buildings onto their occupants (in particular two concrete buildings in Christchurch Feb 2011, one in Newcastle NSW in 1989 and one timber framed building in Northridge in 1994). The next largest contributors taken together are the “Other/indirect causes” (which include road deaths, fires, heart attacks and personal injuries – frail elderly people falling and never recovering). The issue of falling masonry outside buildings was raised in the aftermath of all these earthquakes, but did not have lethal effects in any of them other than Newcastle and Christchurch, as the earthquakes occurred at night when the streets were quiet so few people were 1 Department of Homeland Security Emergency Preparedness and Response Directorate, FEMA, “Multi-hazard Loss Estimation Methodology Earthquake Model HAZUS®MH MR4 Technical Manual, US FEMA, 2003 Appendix 1: Falling Hazards Risk Model Description Page 2 Client: Nederlandse Aardolie Maatschappij Arup Project Title: Groningen Earthquake Structural Upgrading Risk Assessment of Falling Hazards in Earthquakes in the Groningen region: Appendices 1-4 exposed to risk. Reports on the Roermond, Liège and Northridge earthquakes all commented that, had the event occurred when the streets were busy, numerous deaths would have been expected outside buildings. Recognition of this hazard has led to the inclusion of special consideration for falling non- structural elements of buildings in the seismic building codes of earthquake-prone regions such as Japan, California and New Zealand2. The Christchurch earthquake of 22 February 2011 was the only earthquake in this set where large volumes of masonry debris were generated outside buildings at a time when the streets were busy. 41 people were killed by falling masonry, 36 of them outside and 5 inside the buildings from which the debris originated (three of whom were removing the organ from a church badly damaged in the previous earthquake). Elsewhere in Christchurch, in the residential Port Hills suburbs to the south of the city, a quite different hazard was experienced as large volumes of rock and boulders detached from hillsides and cliffs. Several houses at cliff tops fell with the cliff and over 100 boulders of diameter 1m or more rolled down slopes and penetrated houses. Five people were killed by rock falls, none of them in the houses penetrated by boulders, largely because those houses were empty at the time.