Cantilevers from hell

Scott5114 · December 21, 2009, 10:30:38 AM

Quote from: architect77 on December 21, 2009, 07:40:50 AM

I wish someone would create a "Cantilevers from Hell" thread for those extremely far-reaching overheads that appear to be pushing the limit.

Make it so.

myosh_tino · December 21, 2009, 01:57:15 PM

Not quite sure what Architech77 means by "extremely far-reaching overheads that appear to be pushing the limit" but sign bridges of that style are very common in California...

wytout · December 21, 2009, 02:02:26 PM

well here's one where the arm's obscenity is a relative thing I guess. I mean it's long, but maybe not the longest. TOO long for the puny little sign attached to the CENTER of it though. That's for sure....

Brandon · December 21, 2009, 03:17:39 PM

A goody from IDOT, complete with over-extended arm, on I-355 south just before Army Trail Road:

http://maps.google.com/maps?hl=en&ie=UTF8&ll=41.943977,-88.037953&spn=0,359.995505&t=h&z=19&layer=c&cbll=41.944095,-88.037705&panoid=exbyGQR0CNZ-169c3UY5Dw&cbp=12,189.09,,0,-3.32

The far left of the sign used to hold a "FREEWAY ENDS" sign until December 1989.

And yes, IIRC, it is button copy.

un1 · December 21, 2009, 03:35:49 PM

The MTO never puts them far out, only close in. Unless they are on a grade, I think the Gardiner has some that are far out.

Ian · December 21, 2009, 03:36:28 PM

yanksfan6129 · December 21, 2009, 06:39:55 PM

Quote from: PennDOTFan on December 21, 2009, 03:36:28 PM
I think he is trying to say cantilevers that are way to far out onto the highway and may be one to many signs on one cantilever. I may have some examples of what this thread is about:

http://picasaweb.google.com/Iansignal/NewHampshireTrafficSignalsAndRoadSigns#5353723149624562194

The shield for US 4 is also 3di width on that sign, yet the I-393 shield looks squished. Odd.

Ian · December 21, 2009, 07:24:56 PM

Quote from: yanksfan6129 on December 21, 2009, 06:39:55 PM
Quote from: PennDOTFan on December 21, 2009, 03:36:28 PM
I think he is trying to say cantilevers that are way to far out onto the highway and may be one to many signs on one cantilever. I may have some examples of what this thread is about:

http://picasaweb.google.com/Iansignal/NewHampshireTrafficSignalsAndRoadSigns#5353723149624562194

The shield for US 4 is also 3di width on that sign, yet the I-393 shield looks squished. Odd.

Yeah, I noticed the same thing.

architect77 · December 21, 2009, 10:35:09 PM

These cantilevered assemblies must resist the force being applied from the sign's weight. This force essentially doubles with every foot of distance between the sign and support post. A 200 lb. overhead jutting out 20' is the same as supporting a 4,000 lb. sign 1' from the post. So whether it's the distance, use of skinny trusses, or huge signs being supported which you know weigh a sh*tload, anyone know of any "cantilevers from hell"?
NCDOT might be getting a tad over-confident....

Overhead on Raleigh's Beltline. I grew up in Louisburg.

Ian · December 22, 2009, 08:16:02 PM

Not a cantilever, but a very wiiiide sign gantry that could be shown here (there are many like these accross New Hampshire):

helping Ian solve a problem with directly linking to Picasa images ... is it working yet?

Yup, I think I may have got it!

mightyace · December 22, 2009, 09:03:04 PM

One of Tennessee's many Cantilevers from hell:

This one on I-65 NB near Exit 74

2009-12-22 I-65 Exit 74 TN 254 by mightyace, on Flickr

Sorry about the low image quality, I just had my Droid phone with me today. Now while it's 5mp, I'm still learning and I don't know why it's just 640x480.

hbelkins · December 22, 2009, 09:16:07 PM

Tennessee actually had a sign assembly like this fall on I-65 last year, correct?

mightyace · December 22, 2009, 09:17:53 PM

Quote from: hbelkins on December 22, 2009, 09:16:07 PM
Tennessee actually had a sign assembly like this fall on I-65 last year, correct?

Yes, they did on SB I-65 near Exit 68. This is a section of highway I travel on almost daily. I commented on this in another thread.

https://www.aaroads.com/forum/index.php?topic=1324.msg30976#msg30976

EDIT: Added link.

mightyace · February 02, 2010, 07:31:06 PM

During my "website weekend," I got a few more examples uploaded to Flickr:

I-65 NB @ TN 96

I-65 NB @ TN SSR 255 - Harding Place

Secondary signage for TN 840 exits off of I-65 NB

US 31 SB @ Saturn Parkway

Of the ones I've gotten so far, I think this one takes the cake:

TN SSR 255 WB @ I-65

joseph1723 · February 02, 2010, 08:05:56 PM

Here's the widest one I've seen in Ontario so far:
ON 427 NB at ON 27 collector transfer

This one just has a wide BGS on it:
ON QEW Hamilton Bound at Cawthra

I think MTO only started using a lot of cantilevers structures in the past five or so years. I recall almost all of the signs before then were one sign bridges. Both of the cantilevers pictured replaced a older sign bridge though. I've seen more and more supports for cantilevers getting installed now.

aswnl · February 05, 2010, 08:17:48 AM

Some examples from Europe:

shoptb1 · February 05, 2010, 08:45:39 AM

Quote from: aswnl on February 05, 2010, 08:17:48 AM
Some examples from Europe:

This example, in particular, looks as though it would be less-than-optimal for supporting the sign-load, unless this sign is made from lighter materials than its North American counterparts. I remember seeing a study a few years back regarding the various cantilever designs used in the United States (comparing single-support (monotube), and various double-support truss designs) and one of the largest factors was related to additional snow/ice load in the winters. Single-support cantilevers were shown to be the worst for colder climates. This sign looks to be near Giessen (north of Frankfurt a.M.), so I'm guessing that they would also deal with winter precipitation. Anyone else have any thoughts here?

aswnl · February 05, 2010, 04:09:31 PM

The largest factor on overhead signs isn't (added ice) weight, but windforce.

Chris · February 05, 2010, 04:19:57 PM

Italy sometimes installs these monsters:

(don't get me started on the horrible Italian signage)

shoptb1 · February 05, 2010, 05:20:34 PM

Quote from: aswnl on February 05, 2010, 04:09:31 PM
The largest factor on overhead signs isn't (added ice) weight, but windforce.

Yeah, for some reason, I think this study was specifically related to winter-related conditions, but they also factored wind-force into all of the calculations. At any rate, that single-beam design would still have a lot of stress on a single point.

shoptb1 · February 05, 2010, 05:23:39 PM

Quote from: Chris on February 05, 2010, 04:19:57 PM
Italy sometimes installs these monsters

What the hell is that truss? I'll give it to the Italians on one mark...they love their artistic design.

architect77 · February 06, 2010, 12:43:26 AM

Quote from: Chris on February 05, 2010, 04:19:57 PM
Italy sometimes installs these monsters:

Now I've seen everything: cable-stayed overhead signage. That's hilarious.

Michael · February 09, 2010, 09:00:03 AM

^^ I think it's pretty cool. It reminds me of those high-rise construction cranes.

shoptb1 · February 09, 2010, 09:01:50 AM

Quote from: Michael on February 09, 2010, 09:00:03 AM
^^ I think it's pretty cool. It reminds me of those high-rise construction cranes.

I think it looks awesome. It's gotta be the textbook definition of 'overkill' though

architect77 · February 10, 2010, 12:37:23 PM

I don't like it, because this structural technology and visual expression doesn't match the task being performed. Cable-stayed bridges are gorgeous solutions for spanning great distances. These gantries are the equivalent of little Golden Gate Bridges holding up overhead signs.

The Bay Bridge's SAS span is going to be something... For me, the most amazing aspect of this project is that some sections will rest on bedrock, while the others are anchored in mud and silt, but they're connected as one structure able to withstand an 8.0 magnitude quake. They even buried an array of pipes in the mud to hopefully channel away the water that causes liquefaction and its associated instability.

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Cantilevers from hell