Key Message and Lessons on Buildings

Transcription

1 Sharing Lessons from Great East Japan Earthquake with the World Technical Workshop in Hyogo, Kobe Key Message and Lessons on Buildings October 12, 2012 At JICA Kansai Office in Kobe, Hyogo, Japan Dr. Tatsuo Narafu Senior Coordinator for International Cooperation

2 Damages to Buildings by the Great East Japan Earthquake Damages - Residential: Total collapse 107,779 units Half collapse 117,019 units Burnet 263 units Partially damaged 434,327 units - Non-residential: damaged 32,445 build. Most of total collapse buildings are by the tsunami, not shaking motion

3 Before Damage by the tsunami to wooden houses Natori, Sendai City, Miyagi After

4 Damage by the tsunami to wooden houses Most of houses in heavily inundated areas were washed away Source: Yamada-machi

5 Damage to steel structures Steel structures also got heavy damage even though structural members withstood Source: BRI and NILIM 5

6 Not a few RC building got damages by scouring, buoyancy, liquefaction Source: BRI and NILIM 6

7 Most of RC building structures showed good performance Many submerged RC buildings got no damage in structural members but. Source: BRI and NILIM 7

8 The best way against tsunamis is escape to safe places 8

9 Tsunami shelters as a second best solution In case no safe places nearby For people who could not escape quickly such as elderly, disabled 9

10 Japanese Government elaborated a guideline on tsunami escape buildings Technical requirements - Lateral loads by tsunami currents - Enough height above tsunami current and other risks Publicity activities and escape drills Management of buildings especially on easy access at emergency

11 History of the Guideline on Tsunami Escape Buildings The first technical guideline published by Building Center Japan (BCJ) in October 2004 Cabinet Office of the Japanese Government (CO) elaborated it to a comprehensive one based of survey results of the Indian Ocean Earthquake and Tsunami Dec Revision by Ministry of Land, Infrastructure, Transport and Tourism (MLIT) Nov. 2011

12 Application of the guideline to areas exposed to tsunami risks An escape building in Aceh, Indonesia by JICA Source: JICA

13 Very Strong Shaking Motion in Wide Area by the Great East Japan Earth quake Very strong shaking motion was observed in wide area The largest peak acceleration (Tsukidate): 2,933gal (max. horizontal element: 2,700gal 18 observatory station in 6 prefectures recorded acceleration more than 1,000gal Source: NIED

14 Damages to Buildings by Shaking motion of the Great East Japan Earth quake Damages to buildings on current building code are within expected range Old buildings based on former codes suffered seriously Retrofitting of sub-standard buildings is a keen issue to mitigate disasters The situation is similar to that of the Great Hanshin-Awaji Earthquake Remarkable facts regarding to buildings - liquefaction in wide area - effects by long period shaking motion to skyscrapers - damages to non-structural members/materials - performance of buildings of seismic isolation and response control

15 Lessons the Great Hanshin-Awaji Earthquake in 1995 Many buildings and houses collapsed

16 New houses constructed based on the latest design codes suffered little The most significant lesson is to promote retrofitting old houses and buildings of sub-standard for disaster mitigation 16

17 A new law was enacted to promote retrofitting in 1995 Various encouragements are prepared 17

18 Vulnerability of buildings in developing countries ( Bantul, DIY, Indonesia: most seriously damaged area) Buildings collapsed, furniture withstood

19 Earthquake intensity scale MMI Scale (Modified Mercalli Intensity) - MMI VII or larger: furniture fall - MMI X or larger: some of buildings collapse (such as stone masonry) JMA Scale - JMA 5- or stronger: furniture fall - JMA 6+ : some of buildings collapse Collapse occurs by far stronger shaking than falling of furniture in developed countries Descriptive table of Modified Mercalli Intensity (USGS)

20 Devastating earthquake damages in developing countries especially on non-engineered houses Kashmir Earthquake 2005, Pakistan

21 Typical vulnerability: Breaks at connection of structural members

22 Typical vulnerability: failure at connection of structural members No break of rebar was found in field surveys in affected areas Rebar seemed to come off Affected buildings by 2006 EQ in Bantul, DIY, Indonesia

23 Social background of the vulnerability: Little attention of engineers to nonengineered houses stated by UNISDR It remains something of a paradox that the failure of non-engineered buildings that kill most people in earthquakes attracts the least attention from the engineering profession. UNISDR (United Nations International Strategy for Disaster Reduction) Living with Risk 2004 version

24 Challenge to mitigate damages in developing countries Comprehensive approach is necessary - Technical solution: appropriate technology, feasible to local workers, affordable to low/middle income people - Dissemination of technical solution - Awareness raising of people and communities

25 Summary The best way against tsunamis is to escape to safe places In case there is no such places or others, tsunami escape buildings could be a solution Enhancement of seismic resilience of buildings/houses is a key issue to mitigate earthquake damages Buildings in developing countries are very vulnerable Comprehensive approach consisting of appropriate technology, dissemination and awareness raising is recommendable

26 Thank you for your attention