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Scouring of pile group foundations is a common phenomenon for cross-river bridges and can produce significant damage in earthquake-prone regions. This study experimentally investigated the seismic failure mechanism and postearthquake vertical load-carrying capacity of scoured pile group foundations. Three identical 2 × 3 reinforced concrete (RC) pile group specimens were embedded in homogeneous medium density sand with an overall scour depth equal to five times the diameter of a single pile, and then were subjected to lateral cyclic loads applied to the pile cap in order to produce a predetermined damage state in the piles. Pushover in the vertical-downward direction (pushdown) was finally applied on these damaged specimens exhibiting a permanent lateral displacement to evaluate their residual load-carrying capacities. Experimental results show that the leading pile was more prone to seismic damage, as both the first aboveground and first belowground plastic hinges originally occurred on it. The embedded depth of potential plastic hinges in leading, middle, and trailing piles gradually increased. In addition, the extension of pile damage had a significant influence on the residual vertical load-carrying capacity and the corresponding vertical failure mode of the pile group. Reductions of 10.4%, 47.5%, and 73.8% in the vertical load-carrying capacity of these scoured pile group specimens were recorded when they previously suffered a displacement ductility of 1.75, 3.5, and 5.0, respectively. Based on the experimental results, a linear degradation formula on the normalized postearthquake vertical load-carrying capacity of pile groups with respect to the displacement ductility was developed. The experimental results presented in this paper could be used to validate the ductility capacity and residual vertical load-carrying capacity of pile groups numerically evaluated by using three-dimensional nonlinear finite-element models. This research represents also a first step

Previous research has shown that local scour at bridge piers is severely increased by the accumulation of woody debris around piers. However, due to the unavailability of accurate information regarding the characteristics of formed debris jams, the shape and dimensions of accumulations tested in previous laboratory experiments have had to be assumed. This article provides an assessment of debris-induced scour based on recently available knowledge about the relation between the potential dimensions of debris accumulations, the characteristics of flow, and debris elements. Clear-water scour experiments (with and without debris accumulation) were conducted using debris models with shape and size that correspond to the particular flow characteristics of each experiment. The results showed that scour depths obtained with flow-dependent debris accumulations were larger than without accumulations by a factor ranging from 1.18–2.19. The analysis of the scour depths affected by the accumulations suggested similar characteristics as well as dependence on the flow intensity, blockage area ratio, and depth ratio.

This report aims at presenting basic knowledge on bridge scour and the processes governing its evolution as well as summarizing the most common formulas used to calculate scour depth at bridges. Design procedures concerning bridge scour in several different countries are also discussed, including United States, Australia, and the United Kingdom. The situation in Sweden with regard to bridge scour is briefly reviewed and several case studies are presented where marked scour holes have been detected at bridges. Two cases of bridge failures in Sweden are included where local scour was the main reason for the collapse.Bridge scour is typically separated into pier, abutment, and contraction scour, where each mechanism is controlled by different physics and governing parameters. Each type of bridge scour is discussed separately in the report with sections on basic mechanisms, governing parameters, common predictive formulas, and concluding remarks.The report also includes a brief summary on the expected influence of climate change on bridge scour. Larger and more intense rainfalls in the future imply larger flows in the rivers with increased bridge scour as a result.The report deals only with scour induced by bridges; other types of scour, such as general scour due to longitudinal transport gradients in the river, scour related to secondary flows in river bends, or scour downstream hard bottom, are not discussed. Most of the formulas included to estimate bridge scour are valid for friction material and only a few examples are given that are applicable to cohesive sediment, mainly related to recommended design procedures from different countries. Also, the objective of bridge scour analysis is often to estimate the maximum scour depth, occurring at equilibrium conditions under a certain flow, implying that most of the formulas are valid for such conditions.

Junction flows originate from the interaction between a fluid moving over a wall with an obstacle mounted on the same surface. Understanding the physics of such flows is of great interest to engineers responsible for the design of systems consisting of wall-body junctions. From aerodynamics to turbomachinery and electronics to bridge hydraulics, a number of phenomena (drag, heat transfer, scouring) are driven by the behavior of the most prominent feature of junction flows: the horseshoe vortex system (HVS). Focusing on turbulent flows, the complex dynamics of the HVS is established through its unsteadiness and non-uniformity. The fundamentals of this dynamically-rich phenomenon have been described within the body of a rapidly-expanding literature. Nevertheless, important aspects remain inadequately understood and call for further scrutiny. This study emphasized three of them, by investigating the effects of: model scale, wall roughness, and bed geometry. High-resolution experiments were carried out using Particle Image Velocimetry (PIV). Statistical analyses, vortex identification schemes, and Proper Orthogonal decomposition were employed to extract additional information from the large PIV datasets. The time-averaged topology of junction flows developing over a smooth and impermeable wall was independent of the flow Reynolds number, Re (parameter that expresses the effects of scale). On the contrary, time-resolved analysis revealed a trend of increasing vorticity, momentum, and eruptions of near-wall fluid with Re. New insights on the modal dynamics of the HVS were also documented in a modified flow mechanism. Wall roughness (modeled with a permeable layer of crushed stones) diffused turbulence and vorticity throughout the domain. This effect manifested with high levels of intermittency and spatial irregularity for the HVS. Energetic flow structures were also identified away from the typical footprint of the HVS. Finally, a novel implementation of PIV allowed for u

Bridge scour dynamics are dominated by the complex interaction between the approach flow, the erodible bed and the foundation itself. Our basic premise is that fluctuating hydrodynamic forces due to the foundation-induced coherent vortices are responsible for the development of scour holes around bridge piers. This premise was tested here through a series of small scale more detailed laboratory experiments that were carried out at Virginia Tech (with rigid bottom and erodible boundary) and near prototype conditions performed at Waterways Experiment Station (with an erodible boundary). The pier based diameter Reynolds number, ReD, for all these experiments ranged from 26000 to nearly 106. A Digital Particle Image Velocimeter was employed to capture the unsteady dynamics of the flow and a new non-intrusive stereo-photogrammetric technique was developed to reconstruct the three-dimensional scour hole temporal evolution. Post-processing analysis of data reveals an intricate dynamic flow structure in the vicinity of the pier whose behavior is affected by ReD, scour hole stage and possibly bed porosity. Three separate phases of scour hole development were identified, with the initial one occurring more rapidly over a relatively short duration and accounting for nearly 75% of the total excavation., Primarily bibliographies of papers based on sponsored research.

An ice cover may be a major factor determining how alluvial channel morphology evolves in rivers, and a significant influence on bridge pier scour. This was confirmed with real-time monitoring of the bed elevation and extensive bathymetry measurements made in the Mississippi River, the Missouri River, and the White River in Vermont. In all cases, the sediment process was significantly different from what existing sediment equations would predict. This laboratory study examined the sensitivity of various parameters affecting sediment transport under ice. Twenty tests were conducted in CRREL's refrigerated flume using mean flow velocities in the clear-water scour range. Three surface conditions were modeled: open water, a floating cover, and a fixed cover, simulating ice frozen to the river banks and a bridge pier, with a superimposed hydrostatic head that could be created by an upstream ice jam. The ice cover was simulated using Styrofoam with both smooth and rough surfaces. Under clear-water scour, the equilibrium scour depths for the fixed and floating covers were similar, but up to 21% higher than those found for open water. The cover roughness altered the velocity distribution and caused live-bed scour even when the mean flow velocity was 0.86 times the critical velocity for bed movement. When the average velocity was 0.93 times critical velocity, the pressure flow caused live-bed scour. A combination of increased cover roughness and pressure flow resulted in the largest equilibrium scour depth.

INDOT is considering the deployment of fixed scour-monitoring instrumentation as part of a systematic response to the problem of scour around bridge piers. Fixed-in-place automated scour-monitoring devices measure the depth of scour at the point where they are installed. Unless they are installed at the location where maximum scour occurs, their readings may give a misleading estimate of scour potential. This raises a number of technical issues concerning their effective deployment and the interpretation of the collected data, which should be resolved in order to maximize the benefits to INDOT from using these monitoring devices. These include the location of maximum scour under different pier configurations and hydraulic conditions, as well as possible effects due to pier skewness and exposed footings. This report describes laboratory experiments that were performed to study these issues for various flow conditions and pier configurations. The experiments were conducted in a straight channel of rectangular cross-section located in the Hydromechanics Laboratory at Purdue University. The pier geometry was the same in all experiments, and was chosen to be similar to that of a prototype pier (in the US 52 bridge over the Wabash River), though exact scaling was not attempted. Both single and double (i.e., one upstream and one downstream) piers were studied. In general, for piers that were not skewed with respect to the flow, the location of maximum scour was as expected found in the immediate vicinity of the upstream nose of the up-stream pier. Nevertheless, even with relatively small skewness, for flow angle of attack less than or equal to 10°, the location of maximum scour may actually move downstream, either to the side of the pier or even away from the more upstream pier towards the downstream pier in the double-pier arrangement. Measurements at the nose of the upstream pier may therefore grossly underestimate scour in downstream regions if even slight skewness occu

The performance of an expert system (CAESAR for Catalog and Expert Evaluation of Scour Risk and River Stability) for an initial evaluation of scour and stream stability was assessed. Three alternative scour indices are used to compare with the evaluation results of CAESAR. These scour indices include the Observed Streambed Scour index, the INDOT Potential Streambed Scour Index, and the Simon Potential Streambed Scour Index. Ten bridges in Indiana are selected for evaluation in this study. The scour indices and the field inspection information required by CAESAR are retrieved from the USGS data base. In general, the results show that CAESAR is able to reflect current scour risks as well as the Observed Streambed Scour Index, and the results from CAESAR identifies more bridges as scour critical than the INDOT Potential Streambed Scour Index and the Simon Potential Streambed Scour Index. Because the INDOT Potential Streambed Scour Index and the Simon Potential Streambed Scour Index do not take into account the overall stream geometry, bank materials, channel and floodplain widths, and other considerations required by CAESAR, the results of these two indices are not as conservative as that given by CAESAR. It is concluded that the results from CAESAR may be used to estimate the scour risk of bridge piers.

INDOT is considering the deployment of fixed scour-monitoring instrumentation as part of a systematic response to the problem of scour around bridge piers. Fixed-in-place automated scour-monitoring devices measure the depth of scour at the point where they are installed. Unless they are installed at the location where maximum scour occurs, their readings may give a misleading estimate of scour potential. This raises a number of technical issues concerning their effective deployment and the interpretation of the collected data, which should be resolved in order to maximize the benefits to INDOT from using these monitoring devices. These include the location of maximum scour under different pier configurations and hydraulic conditions, as well as possible effects due to pier skewness and exposed footings. This report describes laboratory experiments that were performed to study these issues for various flow conditions and pier configurations. The experiments were conducted in a straight channel of rectangular cross-section located in the Hydromechanics Laboratory at Purdue University. The pier geometry was the same in all experiments, and was chosen to be similar to that of a prototype pier (in the US 52 bridge over the Wabash River), though exact scaling was not attempted. Both single and double (i.e., one upstream and one downstream) piers were studied. In general, for piers that were not skewed with respect to the flow, the location of maximum scour was as expected found in the immediate vicinity of the upstream nose of the up-stream pier. Nevertheless, even with relatively small skewness, for flow angle of attack less than or equal to 10°, the location of maximum scour may actually move downstream, either to the side of the pier or even away from the more upstream pier towards the downstream pier in the double-pier arrangement. Measurements at the nose of the upstream pier may therefore grossly underestimate scour in downstream regions if even slight skewness occu

Local scour is one of the most important causes on bridge failures during floods, and recent changes of river environments makes it difficult to predict the scour depth and design an appropriate protection works. In this study, firstly an analytical model to describe scouring process around a pier has been derived based on reasonable understanding of its essential mechanism . And then, manipulating this model, the similarity law to govern a distorted model test has been established, and furthermore, the subsidiary effects which cannot be reproduced even in a distorted model has been reasonably evaluated.

The Kansas Department of Transportation (KDOT) and most bridge consultants in Kansas have been using the DOS-WSPRO program and the KDOT scour spreadsheets to perform bridge hydraulics and scour analysis for the past several years. Unfortunately, DOS-WSPRO is a DOS program this is no l longer supported and it does not support the metric system. Consequently, the newer Windows-based hydraulics program HEC-RAS appears to be a logical choice to succeed DOS-WSPRO as the basic flow model in KDOT's bridge design and scour analysis program. HEC-RAS has gained considerable polarity in the engineering community and offers many options not previously available to hydraulic modelers. It also has a scour module and ahs an option, the WSPRO bridge analysis routine (henceforth called HR-WSPRO)., This study compared the HEC-RAS program with the DOS-WSPRO program and examined the HEC-RAS program with regard to scour analysis. The possibility of using the existing KDOT scour spreadsheets with output from the HR-WSPRO bridge routine was also considered. Finally, a literature review was performed to determine if any updates in the scour methods and new approaches to special conditions, such as the effect of debris or pressure flow affecting pier scour, were available.

CONTRACT # 510601, WORK ORDER # PIT 018, large percentage of bridges within the state of Pennsylvania are located over waterways. For such bridges, much of the supporting structure is positioned within the river or stream bed of the waterway. As a result, these bridges are susceptible to bridge scour, the washing away of fill around structures, which compromises the safety of the bridge. Bridge inspections have a limited frequency at which they can occur. In between these inspections, unmonitored and difficult to detect events may happen that create an immediate danger to the general public. The purpose of Work Order #18 (this research) was to create a prototype system for bridge scour monitoring that would provide continuous monitoring., The technique utilized for this particular bridge scour monitoring was detection using float out devices. The float out device concept is to bury transmitters at various locations around a bridge structure. These devices would then be released due to the scour’s removal of material around the device. A receiver on the bridge would receive the transmission and perform an action. A float out device system would provide an initial indication of scour severity for further investigation., To realize this technique, a prototype remote sensing system was designed to have three main components that work together to indicate bridge scour. The first component is a transmitter coupled with circuitry and encased such that it is watertight and can be buried under the materials surrounding the bridge structure. It is able to be armed such that it will remain dormant while buried and become active upon its release and rise to the surface of the water. Lastly, the communication link and time it takes the unit to rise are such that transmission of a message can consistently occur. This component in its entirety is referred to as the Sensor Unit within this document., The second component is a receiver coupled with circuitry that will be encased and installed on the bridge overpass. The receiver is able to store and interpret the RF messages sent by the Sensor Unit. Given this interpretation it is able to provide a visual indication of scour severity by interfacing with the third component described shortly. The receiver circuitry will have the capability to be powered continually. This component in its entirety is referred to as the Receiver Unit., The third component is a set of lights (LEDs) encased with its supporting circuitry. The purpose of these lights is to correspond to a particular Sensor Unit. This will allow for immediate comprehension by the inspector without having to be on the bridge. This component must be able to interface with the Receiver Unit as the light that will be lit is controlled by the Receiver Unit. This component in its entirety is referred to as the Light Indicator., This document contains documentation of the work done for Work Order #18. This document contains all analysis leading up to the system design as well as the rationale behind design decisions made. An initial assessment of what the Scour Monitoring System would be composed of and its functionality is found in the requirements section. A less technical overview of the system designed to meet those requirements can be found in the specifications section.

Problem, Estimation of potential long-term down-cutting of the stream bed is necessary for evaluation and design of bridges for scour and culverts for fish passage. Existing guidelines for assessing this potential long-term bed degradation (LTBD) in Maryland streams require expertise that may not be available and/or field studies that, depending on the project budgets, may be cost prohibitive, especially for replacement of county structures. The morphological techniques recommended by these guidelines also lack verification data and may lead to overly conservative estimates, unnecessarily large foundation depths, and consequently, significantly higher costs., Objective, The purpose of this study was to improve predictions of LTBD in non-urbanized Maryland streams through the measurement and analysis of stream bed and waterway structure survey data and plans. A primary objective was the development of equations for estimating potential LTBD in streams in Frederick, Carroll, and Montgomery counties.

SP109B4K, Estimation of potential long-term down-cutting of the stream bed is necessary for evaluation and design of bridges for scour and culverts for fish passage. The purpose of this study has been to improve predictions of this potential long-term bed degradation (LTBD) in Maryland streams through the measurement and analysis of stream bed and waterway structure survey data and bridge plans. Long-term bed degradation was defined as the vertical change in the channel profile other than that caused by local or contraction scour. A total of 30 sites—23 bridges, 2 culverts, 2 utility crossings, 2 embankment walls, and 1 concrete ford—in Frederick, Carroll, and Montgomery counties were selected for data collection. Drainage areas of these sites in the Blue Ridge and Piedmont physiographic provinces ranged from 1.7-25.9 mi2. At each sampling site, the vertical drop at the outlet of the structure was measured with a pocket rod and a hand level. These rapid measurements were conducted where a step, a series of steps, a steep section, or a riprap-protected streambed was at the outlet of a culvert or a bridge with a paved or riprap-protected invert or down-stream apron. Six factors that may influence a site’s risk of LTBD in the three western Maryland provinces were also investigated. These include (1) the valley slope, (2) the effective floodplain width, (3) discharge, (4) downstream channel entrenchment, (5) bed material size, and (6) downstream grade controls. The possibility of developing re-gional relations between watershed area and LTBD was evaluated for each physiographic province, but the data was inconclusive. Three relations between LTBD and five of the risk factors were examined: LTBD and valley slope; LTBD and an index combining Factors 1-4; and LTBD and an index combining Factors 1-5. A comparison of the resulting equations revealed that valley slope was as good a predictor of the susceptibility of a site to LTBD as the two indices that required additional data and co

C1978, Flooding and scour can be major threats to the integrity of bridges. During flood events, scour at bridge piers, and abutments can undermine the foundations of the bridge, causing significant damage or even total structure loss., Because scour occurs below the water level during a large flood event, it can be difficult to detect and may go, unnoticed unless a targeted inspection is performed., The Kansas Department of Transportation (KDOT) is required by federal mandate to establish and maintain a, bridge scour plan of action for all scour-critical bridges in the state. A plan of action can include the implementation of, scour countermeasures to protect and stabilize a bridge and/or scour monitoring. Bridge scour monitoring presents, multiple challenges for bridge owners, including state Departments of Transportation (DOTs)., This research project surveyed in situ and ex situ monitoring options with particular attention on warning, system options in the public domain. In situ monitoring can include portable and/or fixed devices for detecting bridge, scour. Ex situ monitoring implies a statewide system that issues scour alerts to trigger bridge closures and/or, inspections based on hydrologic conditions (rainfall and/or streamflow)., A systematic statewide system would be preferable for monitoring scour-capable events at bridges across the, state. KDOT could leverage existing United States Geological Survey (USGS) and National Weather Service (NWS), tools to monitor scour-critical bridges or pursue a vendor to offer a turn-key solution. For critical locations, additional, measures could be implemented at specific sites to offer more information or a higher level of monitoring.

SP409B4H, Estimation of potential long-term down-cutting of the stream bed is necessary for evaluation and design of bridges for scour and culverts for fish passage. The purpose of this study has been to improve predictions of this potential long-term bed degradation (LTBD) in Maryland streams through the measurement and analysis of stream bed and waterway structure survey data and bridge plans. Long-term bed degradation was defined as the vertical change in the channel profile other than that caused by local or contraction scour. A total of 41 sites in Frederick, Carroll, Montgomery, Baltimore, and Howard counties, Baltimore City, and Washington, DC, were selected for data collection. Drainage areas of these sites in the Piedmont Plateau physiographic provinces ranged from 0.2−62.1 mi2 . At each sampling site, the vertical drop at the outlet of the structure was measured with a pocket rod and a hand level. These rapid measurements were conducted where a step, a series of steps, a steep section, or a riprap-protected streambed was at the outlet of a culvert or a bridge with a paved or riprap-protected invert or downstream apron. Four of the six factors that may influence a site’s risk of LTBD were also investigated. These include (1) the valley slope, (2) the effective floodplain width, (3) discharge, and (4) downstream channel entrenchment. The possibility of developing regional relations between LTBD and either watershed area or percent impervious area was evaluated for the physiographic province, but the data were inconclusive. Two relations between LTBD and the risk factors were examined: LTBD and valley slope; and LTBD and an index combining Factors 1-4. A comparison of the resulting equations revealed that valley slope was as good a predictor of the susceptibility of a site to LTBD as the index that required additional data and considered more parameters. The relation between valley slope and LTBD was recommended to estimate LTBD for streams with slopes of less than 0.0

2007-0436, 2006-0413, The overall goal of this research was to improve MDOTs bridge scour prediction capability. In, an effort to achieve this goal, the research team evaluated scour prediction methods utilized by, state DOTs, conducted a field data collection project, and proposed an alternative approach for, pier scour prediction. Nine locations and twelve unique spans were selected for monitoring., During the investigation, seven episodic measurements resulted in detectable pier scour., Scour depths ranged from 0.7 to 1.5 feet with the maximum return period corresponding to a, seven-year flood event. No detectable scour events occurred at the continuous scour, monitoring locations. This investigation also included the use of a Jet Erosion Test (JET) to, experimentally determine if in-situ soil conditions could be correlated with measured bridge, scour. The JET was able to correlate erodibility with geotechnical properties such as dry unit, weight, soil type, and shear strength, but was not able to aid in the calibration and/or, modification of the scour predication equations. In conclusion, a modified HEC-18 pier scour, prediction equation was developed for application in Michigan using the National Bridge Scour, Database (NBSD). This revised scour prediction procedure could allow MDOT to more, accurately predict bridge scour and subsequently more efficiently design new bridge crossings, and/or modify existing bridges. Finally, experimental and analytical approaches developed, during this investigation provides a foundation for future research in the field of scour prediction.