Seismic Retrofitting of Bridges

Donald Kirkcaldie

Seismic Retrofitting of Bridges

Donald Kirkcaldie

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Examples of VulnerabilitiesExamples of Vulnerabilities

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Examples of VulnerabilitiesExamples of Vulnerabilities

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Examples of VulnerabilitiesExamples of Vulnerabilities

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Examples of VulnerabilitiesExamples of Vulnerabilities

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Common Vulnerabilities & ShortcomingsCommon Vulnerabilities & Shortcomings

Span Collapses arising from:• No linkage between spans and support

• Inadequate overlap of spans with supports

Inadequate structural detailing:• No diaphragms between girders at supports

• Inadequate confinement and shear reinforcement of columns, pier walls and piles, especially at plastic hinge locations

• Main flexural reinforcement lapped in plastic hinges

• Insufficient shear capacity in pile caps

• Lack of joint shear reinforcement

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Common Vulnerabilities & ShortcomingsCommon Vulnerabilities & Shortcomings

Ground instability issues:

• Instability of approach embankments at bridge abutments

• Liquefaction of the site subsoils• Loss of soil strength in granular soils due to build up of pore

water pressure• Inward flow of soils towards the river channel or low ground• Approach embankments raft on top of the inward flowing

liquefied soils resulting in large forces on structural elements

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SH7 Kowai River BridgeSH7 Kowai River Bridge

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SH7 Shale Peak BridgeSH7 Shale Peak Bridge

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SH1 Otaki River BridgeSH1 Otaki River Bridge

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Wellington Urban Motorway Shell Gully BridgesWellington Urban Motorway Shell Gully Bridges

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SH1 Waikanae River BridgeSH1 Waikanae River Bridge

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SH2 Pakuratahi River BridgeSH2 Pakuratahi River Bridge

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Wellington Urban Motorway Thorndon OverbridgeWellington Urban Motorway Thorndon Overbridge

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Some Papers on Seismic RetrofitsSome Papers on Seismic Retrofits

Stuart CR, “Seismic Retrofitting of Highway Bridges in NZ”, Applied Technology Council Report ATC-12-1, 1985

Chapman H, Lauder M, & Oakden G, “Seismic Screening of Bridges in New Zealand”, 12th World Conference on earthquake Engineering, 2000

Chapman HE, Kirkcaldie DK, Lauder M & Oakden G, “Seismic Security of State Highway Bridges: Screening and Retrofit – Progress Summary”, 2002 NZSEE Conference

Kirkcaldie DK, Hobman H,& Saul GJ, “Seismic Assessment and Retrofit of the Shell Gully Bridges”, 2005 NZSEE Conference

Wood JH, Chapman HE, Gregg GC & Kirkcaldie DK, “Seismic Assessment and Retrofit of Waikanae and Pakuratahi River Bridges”, 2007 NZSEE Conference

Kirkcaldie DK, Brabhaharan P, Murashev M, & Kotze R, “Seismic Improvement of the SH3 Cobham Bridge and SH1s Clarence River Bridge”, 2009 Austroads Bridge Conference

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ConclusionConclusion

For areas of low seismicity the most important initial retrofit to consider is to prevent span collapses:

• Link spans to supports

• Provide adequate span – support overlap