Skewed Bridge Question – Bridge Geometry

[Yilu F.]

I’m working on a skewed bridge project and I have some questions on developing the bridge geometry.

The image is a sketch of my skewed bridge. EF is the pier. Θ is the skew angle.
(1) In the pier data editor, are ‘centerline station upstream’ = AB, ‘centerline station downstream’=DC?

(2) In the deck/roadway data editor, should I set ‘distance’ = BE or AH? Is ‘width’=EF or GH?
BE and EF are the distance along the flow path/stream centerline. AH and GH are perpendicular to the bridge.

(3) If I set up ‘Deck roadway and abutment skew angle’=Θ, I noticed that the pier looks narrower in the bridge culvert editor.

Dan C. posted in the following blog that ‘When skewing a bridge, the user reduces the bridge’s deck/roadway stationing by multiplying the values by cos Θ *b. The new bridge opening width becomes the equivalent length that is perpendicular to the flow lines passing through the bridge’.
(http://hecrasmodel.blogspot.com/2013/05/skew-angle-for-bridges.html)

Suppose my pier width=x ft, is the pier width I see in the bridge culvert editor the equivalent pier width, x*cos Θ?

If I set bridge ‘width’=EF, does HEC-RAS actually using EF*cos Θ as equivalent bridge width?

Thanks! Any help will be very appreciated.

[Chris G.]

(1) In the pier data editor, are ‘centerline station upstream’ = AB, ‘centerline station downstream’=DC? Yes.

(2) In the deck/roadway data editor, should I set ‘distance’ = BE or AH? Is ‘width’=EF or GH? I usually use EF, but it shouldn’t make much difference for a typical bridge.

(3) If I set up ‘Deck roadway and abutment skew angle’=Θ, I noticed that the pier looks narrower in the bridge culvert editor. Not sure why this is. Maybe the scale on the plot changed with the skewing of the deck and abutments?

Suppose my pier width=x ft, is the pier width I see in the bridge culvert editor the equivalent pier width, x*cos Θ? Yes, I believe so.

If I set bridge ‘width’=EF, does HEC-RAS actually using EF*cos Θ as equivalent bridge width? I do not think so.

[Yilu F.]

Return-path:
Envelope-to: [email protected]
Delivery-date: Wed, 22 Oct 2014 17:46:49 -0700
Received: from mail-vc0-f177.google.com ([209.85.220.177])
by joe.nabble.com with esmtp (Exim 4.72)
(envelope-from )
id 1Xh6Y8-0006UF-A7
for [email protected]; Wed, 22 Oct 2014 17:46:49 -0700
Received: by mail-vc0-f177.google.com with SMTP id hq11so5713vcb.8
for ; Wed, 22 Oct 2014 17:46:23 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
d=gmail.com; s=20120113;
h=mime-version:in-reply-to:references:date:message-id:subject:from:to
:content-type;
bh=i0BPz3PBg6wvorxgvZEUYsgNlUzNnoXvy8JuUvQUrA4=;
b=H/MPleIIPqg3QfZ3lbT2xlKvip7qqXcCAY2wmbLeRTuDmpcMhv67eWLnI1007cjc+n
oMyA52GCIB+3bbOPALbYXuStGME1raA4cHxPpzOGBX/tFIh/wtyIldIeMzfQGIWg1Mc6
z5+7D/kQvth4z2Lxt/B7euZse4Z3uinmlNyAwdOCvmvcNW8kjESKflwEZblYcUJTWsw8
vIQzjfe0sHhvrvERIauM209pZqfATtimxI+yfhceq7PRs+SYO9KcsjqzOiCZvdEhQ7iK
GcK/ZiPTuWjYLv7c4YUiWcSCnEhJ7QLqVn/bOaNGa72Um0bbIJQkS55uTWuinvJvAehz
C0Mw==
MIME-Version: 1.0
X-Received: by 10.53.1.131 with SMTP id bg3mr877217vdd.45.1414025183477; Wed,
22 Oct 2014 17:46:23 -0700 (PDT)
Received: by 10.31.56.143 with HTTP; Wed, 22 Oct 2014 17:46:23 -0700 (PDT)
In-Reply-To: <[email protected]>
References: <[email protected]>
<[email protected]>
Date: Wed, 22 Oct 2014 20:46:23 -0400
Message-ID:
Subject: Re: Skewed Bridge Question – Bridge Geometry
From: Yilu Feng
To: “Chris G. [via HEC-RAS Help]”
Content-Type: multipart/alternative; boundary=001a1134dfbcc3c31805060c6480
X-SA-Exim-Connect-IP: 209.85.220.177
X-SA-Exim-Mail-From: [email protected]
X-SA-Exim-Scanned: No (on joe.nabble.com); SAEximRunCond expanded to false

–001a1134dfbcc3c31805060c6480
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

Thanks, Chris!

Yilu=E2=80=8B

On Wed, Oct 22, 2014 at 1:30 PM, Chris G. [via HEC-RAS Help] < [email protected]> wrote:

> (1) In the pier data editor, are ‘centerline station upstream’ =3D AB,
> ‘centerline station downstream’=3DDC? Yes.
>
> (2) In the deck/roadway data editor, should I set ‘distance’ =3D BE or AH=
?
> Is ‘width’=3DEF or GH? I usually use EF, but it shouldn’t make much
> difference for a typical bridge.
>
> (3) If I set up ‘Deck roadway and abutment skew angle’=3D=CE=98, I notice=
d that
> the pier looks narrower in the bridge culvert editor. Not sure why this
> is. Maybe the scale on the plot changed with the skewing of the deck and
> abutments?
>
> Suppose my pier width=3Dx ft, is the pier width I see in the bridge culve=
rt
> editor the equivalent pier width, x*cos =CE=98? Yes, I believe so.
>
> If I set bridge ‘width’=3DEF, does HEC-RAS actually using EF*cos =CE=98 a=
s
> equivalent bridge width? I do not think so.
>
> Chris G.
> @RASModel
> http://www.therassolution.com
>
>
> ——————————
> If you reply to this email, your message will be added to the discussion
> below:
>
> http://hec-ras-help.1091112.n5.nabble.com/Skewed-Bridge-Question-Bridge-G=
eometry-tp1056p1058.html
> To unsubscribe from Skewed Bridge Question – Bridge Geometry, click here
> <http://hec-ras-help.1091112.n5.nabble.com/template/NamlServlet.jtp?macro=
=3Dunsubscribe_by_code&node=3D1056&code=3DbHVsdWZlbmcwOUBnbWFpbC5jb218MTA1N=
nwxNjMwNDEzOTQ0>
> .
> NAML
> <http://hec-ras-help.1091112.n5.nabble.com/template/NamlServlet.jtp?macro=
=3Dmacro_viewer&id=3Dinstant_html%21nabble%3Aemail.naml&base=3Dnabble.naml.=
namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.n=
aml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabb=
le.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-=
nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamesp=
ace-nabble.view.web.template.NodeNamespace&breadcrumbs=3Dnotify_subscribers=
%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_em=
ail%21nabble%3Aemail.naml>
>

–001a1134dfbcc3c31805060c6480
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

Tha=
nks, Chris!

Yilu=E2=80=8B=

On We=
d, Oct 22, 2014 at 1:30 PM, Chris G. [via HEC-RAS Help] &=
lt;[email protected]> wrote:

(1) In the pier data editor, are 'centerline station upstream' =3D=
AB, =C2=A0'centerline station downstream'=3DDC? Yes.

(2) In the deck/roadway data editor, should I set 'distance&#39=
; =3D BE or AH?=C2=A0 Is =C2=A0'width'=3DEF or GH? I usually use EF=
, but it shouldn't make much difference for a typical bridge.

(3) If I set up 'Deck roadway and abutment skew angle'=3D=
=CE=98, I noticed that the pier looks narrower in the bridge culvert editor=
.=C2=A0 Not sure why this is.=C2=A0 Maybe the scale on the plot changed wit=
h the skewing of the deck and abutments?

Suppose my pier width=3Dx ft, is the pier width I see in the bridge=
culvert editor the equivalent pier width, x*cos =CE=98? Yes, I believe so.

If I set bridge 'width'=3DEF, does HEC-RAS actually using E=
F*cos =CE=98 as equivalent bridge width? I do not think so.

=09
=09

Chris G.

@RASModel

http://www.therass=
olution.com

---

If you reply to this email, your message =
will be added to the discussion below:

http://hec-ras-help.=
1091112.n5.nabble.com/Skewed-Bridge-Question-Bridge-Geometry-tp1056p1058.ht=
ml

=09
To unsubscribe from Skewed Bridge Question – Bridge Geometry, click here.
NAML

–001a1134dfbcc3c31805060c6480–

[Andrew S]

Hi Chris,

How would you suggest modeling a bridge with multiple piers, some being skewed at different angles to the current? As an example, let’s say Pier 1 is skewed at 15 degrees and Pier 2 is skewed at 30 degrees. If I just use the centerline stations with no pier skew angle, will this accurately model the flow under the bridge? Or can I do a skew angle for each individual pier? Using HEC-RAS 4.1.0, and the bridge itself is also skewed if that helps.

Any feedback is much appreciated!

Sincerely,

Andrew

[cameron]

You could manually skew the data in excel including the piers and then enter in the skewed data into HEC-RAS. If the piers are circular, you would then need to include each pier in series. If the bridge never sees pressure flow, you could just model the piers and abutments as blocked obstructions.

[Author]

Posts