Bridge Pressure Flow Scour For Clear Water Conditions
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Bridge Pressure Flow Scour For Clear Water Conditions
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Author : U.s. Department of Transportation
language : en
Publisher: CreateSpace
Release Date : 2015-03-10
Bridge Pressure Flow Scour For Clear Water Conditions written by U.s. Department of Transportation and has been published by CreateSpace this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-03-10 with Technology & Engineering categories.
Bridges are a vital component of the transportation network. Evaluating their stability and structural response after a flood event is critical to highway safety. Bridge studies are usually designed with an assumption of an open channel flow condition, but the flow regime can switch to pressure flow when the downstream edge of a bridge deck is partially or totally submerged during a large flood. Figure 1 shows a bridge undergoing partially submerged flow in Salt Creek, NE, in June 2008. Figure 2 shows a totally submerged flow in Cedar River, IA, in June 2008, which interrupted traffic on I-80. Unlike open channel flows, these pressure flows create a severe scourability potential because scouring the channel bed is one of the only ways to dissipate the energy when passing a given discharge in pressurized flow. Although most bridge scour events are due to live bed scour, a maximum scour depth often results from clear water flows with a critical approach velocity for bedload motion. For bridge safety, this report emphasizes the equilibrium maximum scour of pressure flows in extreme clear water conditions. The objectives of the study were to collect a detailed high-quality dataset of pressure flow scour at a model bridge and to develop an analytical solution for pressure flow scour based on mass and energy conservation laws. To these ends, existing results in the literature were reviewed, and knowledge gaps were identified. Next, a series of flume experiments were conducted to examine the existing methods and test new hypotheses on bridge pressure flow scour. After, bridge flows were divided into three cases, and the mass and energy conservation laws were applied to each case, leading to hypotheses for pressure flow scour predictions. The hypotheses were tested with the flume data. In this report, an example procedure for calculating the maximum scour depth and scour profile is presented along with recommended research needs.
Bridge Pressure Flow Scour For Clear Water Conditions
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Author :
language : en
Publisher:
Release Date : 2009
Bridge Pressure Flow Scour For Clear Water Conditions written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with Bridges categories.
The equilibrium scour at a bridge caused by pressure flow with critical approach velocity in clear-water simulation conditions was studied both analytically and experimentally. The flume experiments revealed that (1) the measured equilibrium scour profiles under a bridge are more or less consistent across the channel width; (2) all the measured scour profiles can be described by two similarity equations where the horizontal distance is scaled by the deck width and the local scour is scaled by the maximum scour depth; (3) the maximum scour position is located under the bridge and at a location approximately 15.4 percent of the deck width from the downstream edge of the deck; (4) scour begins at approximately one deck width upstream of the bridge, and deposition begins at approximately 2.5 deck widths downstream of the bridge; and (5) the maximum scour depth decreases with increasing median sediment size but increases with higher levels of deck inundation. The analytical analysis shows that (1) bridge scour can be divided into three cases: downstream unsubmerged, partially submerged, and totally submerged; (2) for downstream unsubmerged flows, the maximum scour depth is an open channel problem where the conventional methods in terms of critical velocity or bed shear stress can be applied; and (3) for partially and totally submerged flows, the maximum scour depth can be described by scour and inundation similarity numbers, which has been confirmed by experiments with two sediment sizes (0.039 and 0.078 inches (1 and 2 mm)) and two types of decks with three and six girders, respectively. For application, a design and field evaluation procedure with examples is presented, including the maximum scour depth and scour profile.
Submerged Flow Bridge Scour Under Clear Water Conditions
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Author : U.s. Department of Transportation
language : en
Publisher: CreateSpace
Release Date : 2015-03-10
Submerged Flow Bridge Scour Under Clear Water Conditions written by U.s. Department of Transportation and has been published by CreateSpace this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-03-10 with Technology & Engineering categories.
Pressure flow (also known as vertical contraction) scour occurs when a bridge deck is insufficiently high such that the bridge superstructure becomes a barrier to the flow, causing the flow to vertically contract as it passes under the deck. A bridge deck is considered partially submerged when the lowest structural element of the bridge is in contact with the flowing water but the water is not sufficiently high to overtop the bridge deck. It is considered fully submerged when a portion of the flow overtops the bridge deck. Pressure flow generally only occurs in extreme flood events, but these types of events are relevant for estimation of scour. When flow is sufficiently high so that it begins to approach the elevation of the bridge deck, some of the flow may be diverted laterally to the bridge approaches. Since the bridge approaches are often lower than the bridge deck, this diversion may reduce the scour potential under the bridge. Designers must evaluate the effects of scour under the bridge as well as potential damage caused by flow diversion. An experimentally and numerically calibrated scour model was developed in this study to calculate the maximum clear water scour depth in non-cohesive bed materials under different deck inundation conditions. The theoretical formulation of the model is based on the conservation of mass of the water passing underneath the bridge deck. Particle image velocimetry (PIV) measurements and computational fluid dynamics (CFD) simulations were used to validate assumptions used in the derivation and verify calibration of parameters included in the scour model. As one of the important parameters in the pressure flow scour model, the separation zone thickness in the bridge opening was formulated analytically, calibrated experimentally, and verified by PIV and CFD analyses. The maximum scour depth was calculated by identifying the total bridge opening that resulted in the average velocity in the opening that is equal to the critical velocity of the bed material. This report summarizes a literature review on pressure scour and describes the physical and theoretical foundation for the model formulation. The newly collected flume data as well as PIV and CFD analyses are summarized. The model formulation is refined, tested, and compared to other approaches used to estimate pressure scour. Recommendations for model application are also provided.
Submerged Flow Bridge Scour Under Clear Water Conditions
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Author : Zhaoding Xie
language : en
Publisher:
Release Date : 2012
Submerged Flow Bridge Scour Under Clear Water Conditions written by Zhaoding Xie and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Bridges categories.
"Prediction of pressure flow (vertical contraction) scour underneath a partially or fully submerged bridge superstructure in an extreme flood event is crucial for bridge safety. An experimentally and numerically calibrated formulation is developed for the maximum clear water scour depth in non-cohesive bed materials under different approach flow and superstructure inundation conditions. The theoretical foundation of the scour model is the conservation of mass for water combined with the quantification of the flow separation zone under the bridge deck superstructure. In addition to physical experimental data, particle image velocimetry measurements and computational fluid dynamics simulations are used to validate assumptions used in the derivation of the scour model and to calibrate parameters describing the separation zone thickness. With the calibrated model for the separation zone thickness, the effective flow depth (contracted flow depth) in the bridge opening can be obtained. The maximum scour depth is calculated by identifying the total bridge opening that creates conditions such that the average velocity in the opening, including the scour depth, is equal to the critical velocity of the bed material. Data from previous studies by Arneson and Abt and Umbrell et al. are combined with new data collected as part of this study to develop and test the proposed formulation."--Technical report documentation p.
Submerged Flow Bridge Scour Under Clear Water Conditions
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Author :
language : en
Publisher:
Release Date : 2012
Submerged Flow Bridge Scour Under Clear Water Conditions written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Bridges categories.
"Prediction of pressure flow (vertical contraction) scour underneath a partially or fully submerged bridge superstructure in an extreme flood event is crucial for bridge safety. An experimentally and numerically calibrated formulation is developed for the maximum clear water scour depth in non-cohesive bed materials under different approach flow and superstructure inundation conditions. The theoretical foundation of the scour model is the conservation of mass for water combined with the quantification of the flow separation zone under the bridge deck superstructure. In addition to physical experimental data, particle image velocimetry measurements and computational fluid dynamics simulations are used to validate assumptions used in the derivation of the scour model and to calibrate parameters describing the separation zone thickness. With the calibrated model for the separation zone thickness, the effective flow depth (contracted flow depth) in the bridge opening can be obtained. The maximum scour depth is calculated by identifying the total bridge opening that creates conditions such that the average velocity in the opening, including the scour depth, is equal to the critical velocity of the bed material. Data from previous studies by Arneson and Abt and Umbrell et al. are combined with new data collected as part of this study to develop and test the proposed formulation."--Technical report documentation page
Stream Stability And Scour At Highway Bridges
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Author : Everett V. Richardson
language : en
Publisher: ASCE Publications
Release Date : 1999-01-01
Stream Stability And Scour At Highway Bridges written by Everett V. Richardson and has been published by ASCE Publications this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999-01-01 with Technology & Engineering categories.
Sponsored by the Water Resources Engineering (Hydraulics) Divsion of ASCE. This collection contains 75 papers and 321 abstracts presented at conferences sponsored by the Water Resources Engineering (Hydraulics) Division of ASCE from 1991 through 1998. The collection contains many new and expanded versions of the original papers and is designed to assist the practitioner with the concepts in evaluating stream instability and scour at bridges. Topics include: history of bridge scour research; bridge scour determination; stream stability and geomorphology; construction scour; instrumentation for measuring and monitoring; field measurement; computer and physical modeling of bridge scour; scour at culverts; and economic and risk analysis. One important paper contains 384 field measurements of local scour at piers made by the U.S. Geological Survey.
An Experimental Study Of Ice Effects On Scour At Bridge Piers
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Author : Decker Bradley Hains
language : en
Publisher:
Release Date : 2004
An Experimental Study Of Ice Effects On Scour At Bridge Piers written by Decker Bradley Hains and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with Bridges categories.
The results confirmed various field observations and demonstrated that the pressure flow condition and cover roughness influence the scour mechanisms, specifically, the type and depth of scour. The pressure flow condition shifts the location of the maximum velocity toward the smoother boundary and accelerates the rate of scour. At the same average velocity, the flow has a greater maximum velocity under a rough cover when compared to a smooth cover. Furthermore, these effects combine to influence the scour at bridge piers. For a rough cover and pressurized flow, typical of ice frozen to bridge piers, the maximum velocity in the flow shifts toward the bed, which is the smoother boundary. This results in live-bed scour with greater maximum depths of scour than under clear-water conditions at the same relative velocity.
Scour And Erosion
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Author : Liang Cheng
language : en
Publisher: CRC Press
Release Date : 2014-11-06
Scour And Erosion written by Liang Cheng and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-11-06 with Technology & Engineering categories.
The 7th International Conference on Scour and Erosion (ICSE 2014) was organised by the School of Civil, Environmental and Mining Engineering and the Centre for Offshore Foundation Systems at the University of Western Australia under the guidance of the Technical Committee 213 for Scour and Erosion of the International Society of Soil Mechanics and Geotechnical Engineering (ISSMGE). This biennial conference draws together leading academics, scientists and engineers engaged in scour and erosion research to present and exchange their latest scientific findings. These proceedings, together with the six previous proceedings dating from 2002, present a rare collection of technical and scientific developments in scour and erosion research which have been established over the last 12 years. This book includes state-of-the-art papers in scour and erosion from ICSE 2014, covering the 6 themes of: internal erosion, sediment transport, advanced numerical modelling of scour and erosion, terrestrial scour and erosion, river/bridge scour and erosion, and marine scour and erosion. The proceedings include 5 keynote lectures from world leading researches cutting across the themes of scour and erosion, together with 87 peer-reviewed papers from 19 countries. This book is ideal for researchers and industry working at the forefront of scour and erosion, both with application to rivers and marine operations.
Pier Scour In Clear Water Conditions With Non Uniform Bed Materials
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Author : Junke Guo
language : en
Publisher:
Release Date : 2012
Pier Scour In Clear Water Conditions With Non Uniform Bed Materials written by Junke Guo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Bridges categories.
"Pier scour design in the United States is currently accomplished through application of the Colorado State University (CSU) equation. Since the Federal Highway Administration recommended the CSU equation in 2001, substantial advances have been made in the understanding of pier scour processes. This report explains a new formulation for describing scour processes and proposes a new equation for pier scour design. A critical review of selected studies is summarized. A simplified scour mechanism is proposed in terms of a pressure gradient resulting from the flowstructure, flow-sediment, and sediment-structure interactions. An equilibrium scour depth equation is proposed based on this understanding of the scour mechanism and is validated and refined by a combination of laboratory and field data. The proposed equation is primarily applicable to clear-water scour conditions with non-uniform coarse bed materials."--Technical report documentation p.
Scour Manual
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Author : G.J.C.M. Hoffmans
language : en
Publisher: CRC Press
Release Date : 2021-03-08
Scour Manual written by G.J.C.M. Hoffmans and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-03-08 with Technology & Engineering categories.
Ever since the publication in 1997 the original Scour Manual has helped many practising hydraulic engineers to deal with scour processes near hydraulic structures. In recent years new insights, such as probabilistic calculations, offered new opportunities to design structures more economically. These new insights are included in this update of the original Scour Manual, which is focussing entirely on current-related scour. This manual provides the engineer with useful practical methods to calculate the dimensions of scour holes in the pre-feasibility and preliminary stages of a project, and gives an introduction to the most relevant literature. This updated Scour Manual contains guidelines that can be used to solve problems related to scour in engineering practice and also reflects the main results of all research projects in the Netherlands in recent decades. The so-called Breusers equilibrium method has a central role, which can basically be applied to all situations where local scour is expected. The method allows to predict the scour depth as a function of time, provided that the available knowledge about scour at the specific structure is sufficient. For structures with insufficient knowledge available, alternative scour prediction rules are presented. The treatment of local scour is classified according to the different types of structures. Each type of structure is necessarily schematised to a simple, basic layout. The main parameters of a structure and the main parts of the flow pattern near a structure are described briefly insofar they are relevant to the description of scour phenomena. New scour formulas for the equilibrium scour have been elucidated. Evaluating a balance of forces for a control volume, it is possible to develop scour equations for different types of flow fields and structures, i.e. jets, abutments and bridge piers. As many scour problems are still not fully understood, attention is paid to the validity ranges and limitations of the formulas, as well as to the accuracy of the scour predictions. This information can also be used to carry out a risk assessment using a safety philosophy based on a probabilistic analysis or an approach with a safety factor. Moreover, the information on the strength of soils is extended and aspects are addressed such as scour due to shear failures or flow slides, that can progressively damage the bed protection which might lead to the failure of hydraulic structures. This updated Scour Manual presents scour prediction methods and deals with practically related scour problems. Consultants and contractors were invited to provide case studies of realized projects, including the methods that were followed. These case studies will help with grasping the concept of scour by the flow of water. This manual provides the engineer with the latest knowledge and with case studies that show how to apply the formulas and their limitations.