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.