This document is available to the public through the national. This could possibly weaken the bridge foundation that increase the probability of bridge failures due to scour. If the scour analysis indicates a value that is greater than the thickness of the layer, remove that layer and recalculate the hydraulic variables. Contraction scour analysis at protruding bridge abutments. This chapter presents the data input required for computing contraction scour and local scour at piers and abutments. Evaluation of abutmentscour equations from nchrp projects 24.
Plan of action scour critical bridge report structure b16h. Consider a riprap or other scour countermeasure at every abutment. The data required are the main dimensions and the definition of the road. Hecras based scour design a quick guide by chris chatfield, p. Improvements made to this version of the software include bug fixes to the bridge scour calculators and the addition of a project mapping module. There is a new chapter on soils, rock and geotechnical considerations related to scour. The main objective of this study is to evaluate scour predictive formulae at a protruding abutment bridge in the compound channel, using multiple testing problem mtp in a geometrical model of an integral abutment bridge iab. Froelich based on empirical data derived from laboratory experience. Then continue the scour analysis with the next layer. If there are field conditions which render the scour countermeasure unnecessary, this condition should be supported in the scour report. Technical memorandumscour analysis for the hansen creek pedestrian bridge project the development of flood insurance rate maps firms. Dec 01, 20 bridge scour definition is that it is a process due to which the particles of the soil or rock around the periphery of the abutment or pier of the highway bridge spanning over a water body, gets eroded and removed over a certain depth called scour depth.
National academies of sciences, engineering, and medicine. Bridge abutment design michigan technological university. Click the ok button to accept the software disclaimer as shown in the following figure. Bridge scour calculations in hecras using methodology. Procedures for scour assessments at bridges in pennsylvania by peter j. Designers of treatments such as barbs, revetments, or weirs that are placed on or adjacent to streambeds.
In addition, the results of the scour analysis are to be used to determine the bridge inspection coding for item 1 scour. Us army corps of engineers scour and scour protection. For scour type selected this allows one to select the equation that you want to use. Scour design of bridge foundations shall be based on the estimated scour depth for the 1 percent chance 100year event. Bridge scour definition, causes, calculation of scour depth. The 2004 report limited the maximum moment of the pile to the limits provided by the aashto standard specifications for highway bridge design. The main objective of this study was to estimate the geometry of the equilibrium contraction scour at a protruding abutment bridge in the compound channel, using parametric analysis pa. Equation 15 is discussed on page 17 of ofr 2003295.
Froehlichs equation is based on 170 livebed scour measurements in lab flumes. The abutment on the right side is surrounded by an additional flat apron, which is implemented to control the local scour around the abutment. Procedures for scour assessments at bridges in pennsylvania. The abutment vulnerability assessment flow chart is intended to evaluate the relative vulnerability of a bridge to scour considering factors that affect abutment scour. Upon completion of a scour analysis for a new bridge the scour summary sheet for known foundations is to be completed and placed into inspecttech.
Scour critical bridge poa and recommendations for f17ae. Dependent on a length of protrusion into the channel that overexaggerates the depth of scour. The hire equation is based on field data at the end spurs in the mississippi river. Abutment and contraction scour processes and prediction examines bridgeabutment scour and the effectiveness of the leading methods used for estimating design scour depth. Oct 01, 2012 the usgs abutment scour field data primarily represents scour associated with clearwater scour conditions. Technical supplement 14b scour calculations purpose scour is one of the major causes of failure for stream and river projects. Scour by waves and currents no analytical methods available scour depth increases when even a small current is added to waves breaking waves increase scour over scour caused by currents alone inverted cone shape is similar for both cases rule of thumb estimate maximum scour depth using formula for currents alone prediction of scour. Usgs reports that document field investigations of abutment scour from south carolina, the national bridge scour database, maine, and alabama. Scour erosion at a specific location that is greater than erosion found at other. Overview of scour types and scour estimation difficulties faced at bridge abutments was investigated 4, and clearwater scour development at bridge abutments was presented 5. Therefore, findings in this investigation will be limited to this type of scour.
Countermeasures to protect bridge abutments from scour. Trends of abutment scour prediction equations applied to 144 field sites in south carolina by stephen t. Local scour occurred around the contraction leading edge of the model and the maximum local scour depth is located very close to the contraction edge. Monitoring scour critical bridges project 24072 countermeasures to protect bridge piers from scour project 24152 abutment scour in cohesive materials project 2420 prediction of scour at bridge abutments project 2426 effects of debris on bridge pier scour project 2429 scour at bridge foundations on rock. Trbs national cooperative highway research program nchrp webonly document 181. White openfile report 0064 prepared in cooperation with the pennsylvania department of transportation lemoyne, pennsylvania 2000. The scour depth contours are normalized by the model length l. Chapter 2 abutment forms and scour countermeasures to. This is a beginnerlevel webinar designed to familiarize hecras users with the scour analysis features of the program. C scour analysis spreadsheet hec18 evaluating scour at bridges, 4th edition fhwa nhi 01001 is the nysdot standard reference for analyzing contraction, pier, and abutment scour at bridges. The scour calculators follow the procedures presented in hydraulic engineering circular 18 hec 18, evaluating scour at bridges, fifth edition, 2012. Equation 15 maryland clearwater abutment scour depth equation. A tin file was created from the 2 foot interval mapping.
Hire derived from field data of scour at the end of spurs in the mississippi river. It is important to adequately assess and predict scour for any stream or river design. The flume test results below demonstrate that the flat collar surrounding the verticalwall abutment fails as a scour countermeasure. The resulting design should be checked using the estimated scour depth for the 0. Design abutment foundations in accordance with the provisions of chapter 11. The hydraulics unit has developed an excel spread sheet using the hec18 equations to input data, calculate scour parameters, and present the results in. The mapping module allows users to identify the locations of any analyses conducted within the hydraulic toolbox software on a user supplied image or an image taken from current aerial photography internet connection required. Abutment scour finally, enter data into the abutment tab. Abutments is a software that draws in cad the entire design of a bridge abutment plans, elevations, sections in 2d. An overview of scour types and scourestimation difficulties. Future editions of the guideline will include additional information covering the fbpier analysis software.
Trends of abutmentscour prediction equations applied to 144. Scour analysis for the hansen creek pedestrian bridge project. If these are used the spread footing foundations should be supported on drilled shafts. Abutment scour can be calculated using the hire equation or froehlichs equation. The entire guideline has been converted to the lpile analysis software. Geological survey, suite 200, 405 college avenue, clemson, sc 29631. Results for a wingwall abutment flume model with 45 deg wings without scaur and vorgaur products is shown in figure 3.