![]() ![]() Opening height is obtained by subtracting the upstream internal bridge section Minimum Channel Elevation of 220.49įrom the upstream Maximum Low Chord Elevation of 236.37, and is equal to 15.88. The upstream left abutment station of the bridge is computed by CHECK-RAS as 4969.30. The required data to compare the ineffective flow stations can be obtained from the Summary Table of StructureĬheck and the detailed information of each structure in the CHECK-RAS report file for the Structure Check. The computed left ineffective flow station at Section 3 (LIfStaCU) is equal to the upstream leftmost abutment station ofĮach group of structure (LAbutStaU) minus the maximum height of the bridge or culvert or gate opening of that group. The left ineffective flow station should be adjusted. The selected left ineffective flow station of 4959.3 The computed left ineffective flow station of 4953.42 is less than The velocity head at Section 3 is more than 0.5 In order to explain how CHECK-RAS computes the ineffective flow stations, the ST IF 06 message at RS 3.3 is copied from theĬHECK-RAS report file and displayed below. Review the resulting report and you will see the message ST IF 06 at RS 3.3 and RS 3.2 under Ineffective Flow Check. When prompted with the message: "You need to specify allowable surcharge." Click the "Yes" button. Select the profiles for the floodway and select the Structure check button on the program menu bar. Open the saved project (STFW03.prj) in the CHECK-RAS program and extract the data. Generate a report file from the File menu.Īfter generating the report file for use with the CHECK-RAS program, please save the project. Open windows except the main HEC-RAS window. We will use CHECK-RAS to evaluate the location of the ineffective flow stations. However, we do not know whether they are placed at the recommended locations according to HEC-RAS. You will notice that the ineffective flow stations are outside the bridge opening area. On the downstream side of the bridge (Section 2), a Ineffective flow areas should be placed 10 feet away from each side of theīridge opening (abutments). In other words, if Section 3 is 10 feet from the upstream bridge face, the On the upstream side of the bridge (Section 3) the flow is contracting rapidly.Ī practical method for placing the stations of the ineffective flow areas is toĪssume a 1:1 contraction rate in the immediate vicinity of the bridge. Should be placed outside the edges (abutments) of the bridge opening to allow for theĬontraction and expansion of flow that occurs in the immediate vicinity of the bridge. Upstream toe of the embankment or the wing walls and Section 2 is located at theĭownstream toe of the embankment or the wing walls.) In general, these stations The ineffective flow areas should be set at stations that will adequately describe theĪctive flow area at Sections 3 and 2 of the structure. The following paragraph isĮxcerpted from the HEC-RAS Hydraulic Reference Manual. Placement of ineffective flow stations at a bridge on pages 5-6. The HEC-RAS Hydraulic Reference Manual, Version 2.2, September 1998, provides guidance on the Use the "Zoom In" option under Options menu to enlarge the view of the bridge opening area. After closing the "Steady Flow Analysis" window click the "View Cross Sections" button from the main HEC-RAS window. Open the project file (STFW03.prj) with the HEC-RAS program and select plan 01 from the "Steady Flow Analysis" window. WinZip archive referenced here, and unzip the files to one directory on your local computer. If you do not have those files please download the files that are available in the The same project file, plan files, geometric files, and the flow file from the previous monthĮxercise will be used. To this mailing list if you have questions or feedback concerning other situations Should perform to resolve the statements in the messages.Īn example of an ST IF 06 message is provided in this bulletin. It will also explain what other related computation steps the user Some messages are related to one another, such as Message ST IF 06 and Message This exercise will make the user aware of the fact that This messageĭeals with the placement of ineffective flow stations at Section 3 and SectionĢ of the structure. This month's exercise will explain the CHECK-RAS message ST IF 06. Please download cr_nov01.zip (in WinZip format) Structure Section, and Section 3 are within the abutment stations, indicating that theĮncroachment stations are blocking the opening area of the structure. The previous month's exercise discussed the CHECK-RAS message ST FW 03.ĬHECK-RAS will print this message if the encroachment stations at Section 2, Relationships among the Abutment Stations, Ineffective Flow Stations, andĮncroachment Stations at a Bridge (Continued from previous month's exercise). ![]()
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