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Damage to Bridges Due to Medium Scale Flooding: A Case Study of the Iwane Ohashi Bridge

Author(s): Tomoya Matsuda; Yasuharu Watanabe

Linked Author(s): Yasuharu Watanabe

Keywords: Bed scouring; Bridge failure; Bridge pier; River disaster

Abstract: In July of 2018, a flood with return period of 1/15 years attacked the Yubetsu River basin in Hokkaido. The Iwane Ohashi Bridge located in the Engaru Town over the Yubetsu River suffered great damage. This flood resulted in a subsidence of abridge pier, causing a great deformation of the bridge girder, even though this bridge was designed based on the flood with return period of 1/100 years, which is quite larger than the flood scale targeted here. The detailed understanding of the reason of the damage will provide a useful insight into future management of the river and bridge. In this study, we investigate the main cause of this disaster in detail by using numerical model of flow and bed evolution, iRIC-Nays2DH. As the results of numerical calculation of two-dimensional bed variation, bars are not able to form during the high discharge condition. In the calculation which the bridge pier is modelled as an obstacle, the presence of the bridge pier greatly affects to the flow and bed evolution around the bridge pier, resulting in a deep scouring around the pier. This scouring might be the main factor causing the damage of the bridge.


Year: 2020

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