Modeling Inline Structures

using HEC-RAS

Version 3.1

In Line Structures Can be used to model in-line gated

spillways, overflow weirs, drop structures, and dams.

Modeling method is very similar to bridges and culverts.

Weir shapes are either ogee or broad crested.

Gates are either radial (tainter) or vertical lift (sluice).

Up to 10 groups of gates with up to 25 identical gates per group are allowed for each in line weir.

Identical gates must have same type, size, elevation, and coefficient.

Uncontrolled overflow area is also an option.

In Line Structures

Cross-Section Locations

Suggested cross-section locations are the same as for bridges and culverts.

In Line Structure

Typical Cross-Section 2 with ineffective flow areas defined.

In Line Structure

Typical Cross-Section 3 with ineffective flow areas defined.

Uncontrolled Spillway

In Line Structure

Begin by selecting InLine Structure button from Cross-Section Editor.

Select Lateral Structure button from Cross-Section Editor for lateral weirs.

In Line Structure

Brings up window similar to culvert and bridge windows.

In Line Structure

Must add structure as first step.

In Line Structure

Brings up window to input cross-section location of the structure (weir)

In Line structure

Adds a plot of the upstream cross-section to the window.

Note you can edit the upstream cross-section from this button.

In Line StructureClick on the Weir/Embankment button...

Which brings up the Weir Editor Window

In Line Structure

After filling in the data...

In Line Structure

… the plot is updated to show the embankment.

In Line StructureClick on the Gate button...

Which brings up the Gate Editor Window

In Line StructureAfter filling in the data ...

Default values shown

Free Flow Condition

TEBEHE

C

Under free flow conditions the orifice cofficient is not used. Orifice flow occurs with the submerged condition.

C

In Line Structure

… the plot is updated showing the gates.

Chapter 8 of the Hydraulic Reference Manual describes the hydraulic

computations through gated spillways.

Chapter 6 of the User’s Manual provides explanation for the various

fields of the Inline Gate Editor.

Gate openings are input through the Steady Flow Data editor

2 gate groups

All gates opened same height

Each profile modeled separately

The End