Reproducing Field Measurements Using Scaled-Down Hydraulic Model Studies in a Laboratory

Seung Oh Lee,Seung Ho Hong

doi:10.1155/2018/9091506

Seung Oh Lee, Seung Ho Hong

Open Access

https://doi.org/10.1155/2018/9091506

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Abstract

Little efforts have been made to the value of laboratory model study in closing the gap between results from idealized laboratory experiments and those from field data. Thus, at first, three bridge sites were selected and equipped with fathometers to find the bed elevation change in the vicinity of bridge pier over time. After and during the flooding, the stream flow variables and their bathymetry were measured using current viable technologies at the field. Then, to develop and suggest a laboratory modeling techniques, full three-dimensional physical models including measured river bathymetry and bridge geometry were designed and fabricated in a laboratory based on the scale ratio except for the sediment size, and the laboratory results were compared with the field measurements. Size of uniform sediment was carefully selected and used in the laboratory to explore the scale effect caused by sediment size scaling. The comparisons between laboratory results and field measurements show that the physical models successfully reproduced the flow characteristics and the scour depth around bridge foundations. With respect to the location of the maximum scour depth, they are not consistent with the results as in the previous research. Instead of occurring at the nose of each pier, the maximum scour depths are located further downstream of each pier column in several experimental runs because of the combination of complex pier bent geometry and river bathymetry, and the resulting unique flow motions around the pier bent.

Highlights

General purposes of physical hydraulic modeling are reproduction and/or duplication of actual flow phenomena in a laboratory. us, with the help of successful physical hydraulic modeling, the effects of selected flow parameters around various hydraulic structures, such as different shape of orifices [1], T-shaped spur dike [2], bridge pier, and so on, can be examined using well-controlled laboratory experiment. is study is an experimental investigation of local pier scour throughout the reach of a bridge section under clear-water scour conditions using scale-down full bridge geometry and river bathymetry
Numerous studies for the prediction of bridge scour depths have been conducted using physical modeling in laboratory and using numerical simulation [4, 5], the topic is still challengeable when the resultant scour depths are applied to large-scale prototype because most of the current scour prediction formula are based on laboratory experiments which have been implemented with simple channel and bridge geometry even though most of bridge foundations in the field have complex geometry and the channel shape is site specific
Comparisons of velocity distributions for all river models showed good agreement with the eld measurements. e shapes of the cross section and bed elevations along the bridge deck were well reproduced in laboratory experiments including the maximum pier scour depths in front of the pier. e close agreement between eld and laboratory measurements appears to validate the modeling strategy presented in this study in

Summary

Introduction

General purposes of physical hydraulic modeling are reproduction and/or duplication of actual flow phenomena in a laboratory. us, with the help of successful physical hydraulic modeling, the effects of selected flow parameters around various hydraulic structures, such as different shape of orifices [1], T-shaped spur dike [2], bridge pier, and so on, can be examined using well-controlled laboratory experiment. is study is an experimental investigation of local pier scour throughout the reach of a bridge section under clear-water scour conditions using scale-down full bridge geometry and river bathymetry. Numerous studies for the prediction of bridge scour depths have been conducted using physical modeling in laboratory and using numerical simulation [4, 5], the topic is still challengeable when the resultant scour depths are applied to large-scale prototype because most of the current scour prediction formula are based on laboratory experiments which have been implemented with simple channel and bridge geometry even though most of bridge foundations in the field have complex geometry and the channel shape is site specific. The measurements of scour depth at complex bridge piers in the field for the validation of lab results are tricky because of the safety and economical reason Under these circumstances, scale-down physical modeling is suggested that can reproduce the prototype flow characteristics and scour patterns including location of the maximum scour depths, which may not be at the nose of the pier as in idealized laboratory studies.

Hydraulic Modeling Procedure

A Profile

Results and Discussion

Summary and Conclusions