Another look at ATT I-40 bridge concepts

I missed the American Tobacco Trail Phase E project update meeting a couple of weeks back due to travel plans, but a reader was kind enough to send in the following photos of the scale models that have been put together giving a sense of the scale, massing and shape of two of the designs.

Though these two designs would be custom-design rather than off-the-shelf bridges, it's estimated that these would be no more expensive to build than a standard design, which is good news for the project budget -- a budget which ATT hero and trails advocate Bill Bussey points out erodes by almost $1,800 a day just due to inflation.

First up is my personal favorite, the cable-stayed "Triangle" bridge:

Here's a side view of the rendering from the survey circulated at the meeting:

Personally, as much as a Durham-firster as I probably am at times, I do appreciate the Triangle symbolism that works its way into the region's image, from the airport logo to the TTA buses to the great new headquarters of the Research Triangle Foundation. And it seems only fitting that a greenway that would connect the Triangle for pedestrians and bicycles -- eventually stretching through Durham, Chatham and Western Wake and connecting with other greenway facilities all the way into Cary and Raleigh -- would take on this shape.

Designer Steven Glover points out that the structure "can support itself as a cantilever as it is built," meaning that lanes on I-40 would need to be closed only for short periods of time to accommodate construction. (The rendering above also demonstrates the bridge's ability to take advantage of the berm-like rise on other side of the highway.) The support tower would be built first on one side of I-40, then the sections themselves built one piece at a time and supported by cabling.

The second option is an arch structure, seen here via the scale model and a conceptual rendering:

Like the "Triangle" bridge above, this structure would support itself by cantilevering on both ends; Glover's team points out that "the structure could appear as an open steel framework, an enclosed steel framework, or a combination of a tubular steel arch and a thin and slightly undulating concrete deck."

Option three would be the off-the-shelf bridge, shown in the rendering below. Although it arrives in preconstructed sections that can be connected on-site and lifted into place, there are certain "freeway closure constraints" that are required by NCDOT that apparently make this a more challenging installation:

All of these designs are merely concepts; feedback from the survey distributed at the recent meeting will be used to bring back a final, detailed design proposal this fall, with construction set to begin next summer.

Comments

[Freddie]

I personally like the first one as well as it is very unique and brings alot of character to the bridge...Seems simple but yet sleek...And like you said yourself, it symbolizes the Triangle...

[BluGopher]

For my tax dollars, the first design - the 'triangle' - gets my vote.
It would be interesting to set up a non-scientific poll for citizens to vote on the 3 design proposals.

[Will]

The triangle seems like the obvious choice of the three. IMNSHO...In My Not So Humble Opinion.

[John Schelp]

I really like the Triangle design. One hopes the Triangle will be on the northern side of I-40 -- pointing towards the middle of Durham, not pointing out towards the mall.

BTW, a survey was done to help choose a design. Emails were posted on several community listservs. Folks were asked to place a dot between the three choices, closest to their favorite design(s).

Here is the one-page survey you can print and fax (it doesn't indicate a deadline)...

http://media.newsobserver.com/content/news/durham/durham/story_graphics/20080430_bridge.pdf

Number 1, all the way.

[Seth Vidal]

Which one is fastest and cheapest to put in place? If they're all the same then one or two. If one of them will happen sooner then that one. If one of them will happen sooner and cheaper, then that one.

I don't really care what the bridge looks like from the interstate. I only really care that the bridge goes over I40 and that is is put in place quickly.

-sv

[Michael Bacon]

As much as I harrumph about the fictitious entity known as Raleigh-Durham and my general sentiment that the obsession with "region-wide" thinking has paralyzed us in a number of ways, the first design wins out as just being way cooler. The second design is very clean and unobtrusive, and has a certain elegance to it, and if this were for a road bridge, I'd probably be in favor of that one. But the first is a true landmark bridge, and calls attention very broadly to something which is a bike/ped facility. And that's just a very good thing in my book.

[Andrew Edmonds]

During the presentation, an audience member asked Grover if the prefab steel truss bridge might seem duplicative of the Raleigh pedestrian bridge, and didn't we want our own design?

Grover thought no, that this exact bridge is seen many times throughout the country. It's sort of a COTS bridge.

I agree with the questioner, though. I like the elegance of the arched bridge best. If the cable-stayed is built as shown, I would lobby for it to be known as the American Tobacco bridge -- since that support tower looks a heck of a lot like a capital "A". (Either that, or the "beam me up" bridge.)

[John]

According to the designers, the Triangle bridge, "has advantages... in ease of building and minimal disruption of I-40 traffic" (Durham News, 4/30/08).

[Tar Heelz]

All have something going for them. A big concern for me is how will the screening be designed along the bridgeway? Unfortunately, the modern age has made ugly screening commonplace (often nothing more than chainlink fencing).

Was this mentioned at the design meetings?

[Tanner Lovelace]

In response to John Schelp's post, if I remember correctly I think the support was going to be on the southern side, but there were indications that it could go on either.

Also, the deadline for the survey was May 7, so it's way past. Sorry.

I definitely like the cable-stayed bridge best too. Way to go for posting the pictures. Mine are still sitting on my computer waiting for me to upload them to flickr.

[Tanner Lovelace]

In response to Andrew Edmonds, I was the one that asked the question about the steel truss bridge being duplicative. I agree that the support tower resembles an A and was wondering how to add the extra "TT" onto it to symbolize ATT.

In response to Seth's question about costs, Steven Grover indicated that they were all pretty much in the same ballpark for both costs and construction times. They had already eliminated designs that were outside the parameters set for the construction of the bridge.

[Carey]

Does anyone know if and when they will rebuild/refurbish the bridge that is out along the trail south of I-40? I'm guessing it is about 2 miles south of Massey Chapel Road, possibly in Chatham County (but it may still be Durham). I can't remember if that is supposed to be included in upcoming improvements to the ATT. Thanks.

[JDC]

Add another vote for the first one with the cables.

But, like Seth, I'm mostly concerned with having a functional bridge over I-40, and fast.

[Mike]

I believe that they are supposed to pave the ATT from the Chatham County line north to the new bridge at interstate 40. I'm not sure if this includes the bridge you speak of Carey as I have not been past 40 on the ATT. Hopefully all the counties are stepping up and doing their part to complete the trail. I'd really like to ride down to Key West,FL one of these days and not have to compete with the cars/suvs. :)

[southdurhamite]

Yep, the first design. Can we stop the dawdling and just build it so that us po' folks out here in the sticks can bicycle in to a Durham Bulls game? And then light a fire under the Chatham commissioners to do whatever they are going to do to bridge Northeast Creek at the old railroad trestle.

I'm tired of my tax money going to consultants instead of actually getting the job done.

[Dan Clever]

There are actually two bridges south of I-40 that need to be refurbished and both of them are in Chatham County. Construction on both of these bridges as well as the trail in Chatham are supposed to begin this year, hopefully as soon as this summer. As for trail surface in Chatham County, the design calls for 12' wide granite screenings from Wake County to New Hope Church Road, and a dual surface trail between there and the Durham County line (10' wide paved-6'wide screening).

[Tom]

It appears that bids for construction of the Chatham County section of the ATT have been received (4.67miles plus bridges from Durham/Chatham to Chatham/Wake county lines. The low bidder will submit a construction contract to NCDOT for approval on Aug 7, 2008.
http://www.triangletrails.org/CHATBIDS.HTML

Construction is expected to begin in Sept, and be completed by June 09.

It would be great to get a status update from Mr. Brady in the Durham Public Works Dept on the I-40 ATT bridge and adjacent trails. There are many impatient bikers awaiting completion of this project, and we should do all we can to keep this project in the spotlight and on schedule.