Signature bridges 1

Excellent article on signature bridges and some of the challenges they present.
I like it specially because it articulates some of my own thoughts on the subject.

I would like to know what other bridge engineers think

http://enr.construction.com/opinions/viewPoint/archives/071012.asp

and for the article itself:

http://enr.construction.com/opinions/viewPoint/2007/docs/071012-Building-Better-Bridges.pdf

 

[HgTX]

From the article:

Signature Bridge Economics 101:
It is difficult to compare unit costs of one bridge to another as each bridge has a unique foundation and superstructure design, and potentially wide variations in labor, equipment, and material costs. However; in current dollars, a basic short or medium span steel girder or prestressed girder bridge can be built for $100 to $200 per square foot of deck area. By comparison, a sampling of cable stayed bridges built over the past twenty years shows the range to be more like $400 to $800 per square foot of deck area. In some cases this increase in cost is warranted due to site conditions and span lengths.

Real Bridge Economics 101: You can't compare "basic short or medium span" birdges to cable-stayed bridges, which are typically long spans, or at least medium.

And are there really *that* many signature bridges going up to warrant a 20-page rant on the subject?

That said, most well-designed bridges look pretty good if you just leave them alone and keep the architects' hands off them.

Hg

Eng-Tips policies: faq731-376

 

[kelowna]

I agree with you HgTX, you can not compare the construction costs of medium span bridge projects and large span bridge projects. However, the point can be made that some bridge projects have huge differences in cost, more that it would appear to be reasonable, and I think that that is the point of the article.

Comparations are never fair, but the Cooper River Bridge in SC was built for about 630M USD (including foundations and approaches). On the other hand, the new East Bay Bridge project will cost about 6,300M USD, with 1,400 M USD for the superstructure alone (no foundations) of the main span (no approaches), with a span size relatively similar and both bridges on seismic areas.
As I said, comparations are never fair, but it seems to me that the cost for a 'signature bridge' can be quite significant. Does it warrant an article? I think it does, this is a growing trend, 23 M USD for a footbridge (Sundial Bridge) is quite a bit of money.

I am not opposed to signature bridges, I just think that people has to understand what the issues are.

And yes, keep architects away

Cooper River Bridge

http://www.donaldmacdonaldarchitects.com/news/n_images/cooper_post_cour/july2_spec.pdf

New East Bay Bridge

http://en.wikipedia.org/wiki/Eastern_span_replacement_of_the_San_Francisco-Oakland_Bay_Bridge

Sundial Bridge

http://en.wikipedia.org/wiki/Sundial_Bridge_at_Turtle_Bay

 

[graybeach]

Signature bridges are more than just structures - If a community thinks it is worthwhile to make it special, why not?

Architects are annoying, but I do not agree that we should keep the the away completely. After a basic configuration that makes sense structurally is established, let them pretty things up. They can also help with laying out piers and other elements in a way that is harmonious with the environment but not bad structurally. I have had some good experiences with architects working this way.

I have had bad experiences too with architects that try to dictate structural shapes that create huge moments, have fatigue issues, or are be difficult to inspect and maintain.

 

[bacon4life]

My state has a requirement to spend 1% of any project on art. Seems like we should have then engineers do the design, and then use 1% to make it more pleasing.

 

[cwrugrad]

kelowna, I couldn't make myself read all 21 pages of that article, sorry.

I think I get the gist, though, and my perspective is that the public should get a nice-looking bridge if it's in a prominent, visible location where what it looks like really matters.

I do notice, though, that when the public is asked for opinions on different bridge-configuration options (or, for that matter, when the public volunteers opinions), the all-important price-tag information is too often either missing completely or not shared in a way that really brings it home.

The public ought to be asked, would you be willing to pay $x more in taxes for "y" years to get THIS pretty type of bridge instead of THAT ordinary-looking type of bridge?

And bridge details or types that are not as safe as alternatives should just be nixed, in my opinion, no matter how pretty they might be.

 

[BRGENG]

As a designer of both Buildings and Bridges I most say we need to keep Architect’s away from bridges. Just look at how Architect’s shop around for lower fee’s from Structural and MEP, this way they can have higher profits. Do you want them to get a hold of your bridge fees? Do you want an Architect to try and take over your project?

The earliest Architect’s were really Engineer’s, the structure’s they designed were works of art. Think of the great monuments of the World, do you ever hear of anyone talking about the floor plan, the colors, or the fixtures? No, you see the structure, the arches, beams, walls, etc. That’s why a bridge Engineer is basically an original Architect. So in a way you can say that Architect’s already design bridges, they just have PE stamps and not AIA stamps.

 

[Dinosaur]

Cwrugrad,

You hit the nail on the head. The public is not aware of the costs and the government is not pushing to give it to them.

In the US, most money is allocated to a region by formula. If you have so many miles of road, so much population, ..., you get "X" dollars of funding from the higher government levels. If you spend it all on one bridge, you don't get anything else for the rest of the cycle. But the public doesn't know how all this works. They just think they can get it all on this project and it comes out of the "big pot". But it really comes out of their small pot. And then they complain about the roads with potholes in their area.