A New Practical Method to Simulate Flood-Induced Bridge Pier Scour—A Case Study of Mingchu Bridge Piers on the Cho-Shui River

Jian-Hao Hong,Yee-Meng Chiew,Wen-Dar Guo,Cheng-Hsin Chen

doi:10.3390/w8060238

Jian-Hao Hong, Yee-Meng Chiew + Show 2 more

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https://doi.org/10.3390/w8060238

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Abstract

The evolution of bridge pier scour is very important for bridge safety warning and assessment. During typhoon seasons in Taiwan, the torrential river flow often causes scour monitoring instruments to fail in their attempt to measure the temporal variations of pier scour depths. To better understand the scouring phenomenon during a large flood event, this study proposes a fast and reliable method for bridge pier scour simulation. The proposed method consists of two main components: (1) a robust finite-volume hydraulic model that simulates the flow depth and velocities; and (2) two scour depth computation algorithms that predict the temporal development of the general and local scour depths. The greatest advantage of this method is that it is very straight-forward and reliable, giving bridge managers sufficient time to make an informed decision for bridge safety warning. Only a few hydraulic flow conditions near the bridge are necessary to simulate the scour depth evolution. Moreover, the method can be applied for both general and local scour simulations. To demonstrate the accuracy of the proposed method, field data collected using the “numbered-brick” method were performed at the Mingchu Bridge, which is located along an incised channel reach of the Cho-Shui River in Taiwan. The simulated water levels and total scour depths are in good agreements with the field data. Finally, to help bridge authorities responsible for making a decision towards bridge scour warning, a bridge safety curve (scoured bed level-discharge relationship) is proposed. Based on the results of two flood events, the study shows that the proposed method can quickly and accurately simulate the bridge pier scour.

Highlights

Bed scour at bridge foundations induced by floods is the leading cause of bridge failures
Because there is no tributary between the Chi-Chi Weir and Mingchu Bridge and that the channel slope in the river reach is relatively steep, is assumed flow discharge at the Because there is no tributary between the itChi-Chi
The results show that use of the proposed method for estimating the general and total scour depths is reliable when compared with the measured data

Summary

Introduction

Bed scour at bridge foundations induced by floods is the leading cause of bridge failures. The Kaoping Bridge failed at approximately 3 P.M. on 27 August 2000, several days after the flood induced by Typhoon Bilis had receded. 16 vehicles fell into the Kaoping River, causing injury to 30 people. In 2008, the failure of the Houfeng Bridge caused three vehicles to fall into the Da-Chia River, resulting in the death of six persons [2]. The bridge collapsed during the peak flow induced by Typhoon Sinlaku (i.e., at approximately 7 P.M. on 15 September 2008). Such disasters may be prevented if scour-critical bridges that have insufficient capacity to withstand the designed flood were identified and appropriate remedial work carried out. In the event that remedial works are delayed, a bridge safety warning

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Results

Conclusion