HEC-RAS tutorial on single bridge
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Transcript of HEC-RAS tutorial on single bridge
Prepared By
Group 10
Salma Nasrin Siddique 0916008
Nazia Hassan Choudhury 0916010
Nureen Faiza Anisha 0916011Course no. WRE 404Course name: Computer Application in Water Resources Engineering Level/Term: 4/1Dept. of Water Resources Engineering, BUET.
Introduction
Overview
Methodology
Notes and recommendations
HEC-RAS can be used to analyze a river reach that contains a single bridge crossing.
This presentation demonstrates the procedure of analyzing a river reach that contains a single bridge of simple geometry and that stands perpendicularly to the flow.
Input : Geometric Data + Flow Data
Plan 01
High Flow Method as press/weir
Plan 02
Energy Method for High FlowAnalysis
Review of Results
Adjustment of Contraction and Expansion Reach Lengths
New Plan
Energy Method for High Flow Analysis
New Plan
High Flow Method as press/weir
Comparison of Results
Open HEC-RAS Software
File
Open Project
Destination Folder
Desired Project(.prj format)
1. River System Schematic
2. Cross Section Geometric Data
3. Bridge Geometry Data
4. Ineffective Flow Areas
5. Bridge Modeling Approach
6. Steady Flow Data
Options
Add bridge/Culvert
Define station number
Deck/Roadway Editor
Input Data
Pier
Input Data
Geometric Data Editor
Cross-section
Options
Ineffective Flow Area
Geometric Data Editor
Bridge/Culvert Icon
Bridge Modeling Approach
Select Methods and enter Coefficient of Discharge
Main Program window
Edit
Steady Flow Data
Steady Flow Data Editor
Input boundary conditions and discharge
Steady Run icon (main program window)
Steady Flow Analysis
Option
Critical depth output
Plan
Define New plan and Short ID
Compute
Note:We run p/w as plan 01We run energy method as plan 02
View profile icon(main program window)
Options
Plans
Select desired plans
Contraction Length
Fc2 : Main channel Froud number at section 2
Fc1 : Main channel Froud number at section 1
Qob : The overbank flow at section 4
Q : The total flow at section 4
nob : The manning’s coefficient for overbank at section 4
nc : The manning’s coefficient for main channel at section 4
Lobs : The average length of bridge obstructions
Expansion Length
One dimensional model can predict only one resulting water surface, therefore, the fluctuations along the cross section will NOT occur in the HEC-RAS model as they do during the actual event. Hence, there will be some errors.
If the observed data are already in collection, the water surface profiles calculated by the model can be calibrated with help of it if necessary.
The locations of the cross sections and the values selected for the expansion and contraction coefficients in the vicinity of the bridge are crucial for the accurate prediction of the energy losses through the bridge structure. Hence adjustments yield better results.