Riprap Failure at Circular Bridge Piers |
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Authors: | Jens Unger Willi H. Hager |
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Affiliation: | 1Ph.D. Student, Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie, ETH Zurich, CH-8092 Zurich, Switzerland. 2Professor, Versuchsanstalt für Wasserbau, Hydrologie und Glaziologi, ETH Zurich, CH-8092 Zurich, Switzerland.
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Abstract: | Riprap of bridge piers is placed to prevent scour and to secure the pier from failure. Riprap is therefore an addition to a pier to increase its performance against scour. The present research intends to present three basic scour mechanisms associated with circular-shaped bridge piers in rivers first, to introduce then a number of selected experiments for a range of hydraulic, geometric, and sedimentologic conditions, and finally to describe a novel procedure for assessing the safety of these river elements against failure. This procedure is based on the Shields diagram relating to sediment entrainment in a uniform and flat sediment bed subjected by a water flow. The Shields approach is extended for the presence of a circular-shaped pier that is protected by a circular-arranged riprap layer of equal size elements. The design procedure presented in the following thus reduces to the entrainment condition of a pier for equal riprap and the sediment sizes and to the Shields entrainment condition when the pier diameter degenerates to 0. |
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Keywords: | Bridge failure Bridges, piers Riprap Scour Water flow |
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