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Proposed mechanism for mid-span failure of pile supported river bridges during seismic liquefaction
AbstractPile supported river bridge failures are still observed in liquefiable soils after most major earthquakes. One of the recurring observations is the mid span collapse of bridges (due to pier failure) with decks falling into the river while the piers close to the abutment and the abutment itself remain stable. This paper proposes a mechanism of the observed collapse. It has been shown previously through experiments and analytically that the natural period of bridge piers increases as soil liquefies. Due to the natural riverbed profile (i.e. increasingly higher water depth towards the centre of the river), the increase in natural period for the central piers is more as compared to the adjacent ones. Correspondingly, the displacement demand on the central pier also increases as soil progressively liquefies further promoting differential pier-cap displacements. If the pier-cap seating lengths for decks are inadequate, it may cause unseating of the decks leading to collapse. The collapse of Showa Bridge (1964 Niigata earthquake) is considered to demonstrate the mechanism. The study suggests that the bridge foundations need to be stiffened at the middle spans to reduce additional displacement demand.
HighlightsReview of collapse of pile supported river bridges.Mechanism to explain the midspan collapse.Study of collapse of Showa bridge.
Proposed mechanism for mid-span failure of pile supported river bridges during seismic liquefaction
AbstractPile supported river bridge failures are still observed in liquefiable soils after most major earthquakes. One of the recurring observations is the mid span collapse of bridges (due to pier failure) with decks falling into the river while the piers close to the abutment and the abutment itself remain stable. This paper proposes a mechanism of the observed collapse. It has been shown previously through experiments and analytically that the natural period of bridge piers increases as soil liquefies. Due to the natural riverbed profile (i.e. increasingly higher water depth towards the centre of the river), the increase in natural period for the central piers is more as compared to the adjacent ones. Correspondingly, the displacement demand on the central pier also increases as soil progressively liquefies further promoting differential pier-cap displacements. If the pier-cap seating lengths for decks are inadequate, it may cause unseating of the decks leading to collapse. The collapse of Showa Bridge (1964 Niigata earthquake) is considered to demonstrate the mechanism. The study suggests that the bridge foundations need to be stiffened at the middle spans to reduce additional displacement demand.
HighlightsReview of collapse of pile supported river bridges.Mechanism to explain the midspan collapse.Study of collapse of Showa bridge.
Proposed mechanism for mid-span failure of pile supported river bridges during seismic liquefaction
Mohanty, Piyush (author) / Dutta, S.C. (author) / Bhattacharya, S. (author)
Soil Dynamics and Earthquake Engineering ; 102 ; 41-45
2017-08-23
5 pages
Article (Journal)
Electronic Resource
English
Proposed mechanism for mid-span failure of pile supported river bridges during seismic liquefaction
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