tallbridgeguy

The Charles bridge in Prague is considered one of the most famous structures in the Czech Republic and it is currently being renovated. This article describes some of the problems you face when you try to restore a historic bridge.

A local preservation association, called ASORKD, has charged that the renovation has been poorly handled and the historic nature of the bridge is being lost.

Everything you look at has been poorly handled, including the balustrade, because it was not overseen. That is why we need the project to be stopped. If it isn’t, we’ll all be very unpleasantly surprised in a year’s time.

The engineer in charge from Mott MacDonald, Jiří Petrák, counters with,

I appreciate to be able to help Charles Bridge and for me to participate is the highest reward in my bridge engineering career. I feel we have been criticised for some steps along the way that are still on-going. The bridge is not finished. When we hand it over to the client and to the public, I think these kinds of comments will disappear.

Historic bridge renovations are difficult and like most old structures it is often easier to remove material until you hit a solid foundation. But if you do that, you can also alter the nature of the bridge and lose what made it special.

Which leads to another question, how much of an old bridge can you replace before it is considered a new structure?

Since no one reads this blog on Sunday (or most days) I thought I would repost one of my original ideas for the Calgary bridge competition and remark how similar it is to the Buckland and Taylor entry…(B and T should have curved their walkways the right way and added a great big meeting area!)

I did too think of this before the competition, I just thought it was toooo simple….doah! (But their graphics are cool…)

I was reading an article on the Happy Pontist written by an architectural critic who feels an old, maybe historic bridge, should be saved at all costs. Which got me thinking about when it is appropriate to replace a bridge.

Lets deal with the simple stuff first, if the bridge is rundown, old and non-historic, it is usually easy to get agreement on replacing the bridge with something new. The trouble starts when a local community falls in love with a structure. (It also helps when the structure has historic significance.)

Take the bridge I helped replace as an example. It was a 640′ long, four span Warren truss placed on the historic register in 1998. The bridge was in bad shape when we looked at it in 2005. The choice was to rehabilitate the truss or build a new bridge.

To keep the truss would have required repainting and strengthening for modern loads. To paint the structure, since it was covered with red lead paint, would have required putting a shroud around the bridge as it was sand blasted and repainted. (Can’t have lead falling into the river.) This was estimated to cost about a $1 million dollars.

The piers were limestone blocks, held together with mortar, built in 1899 for the first bridge at the site. (The piers were reused for this second bridge.) It was very difficult to estimate how strong the limestone piers were and how long they would last. Strengthening the piers may have affected the look of the piers and destroyed their historic value.

Finally the truss had a narrow roadway width of 24′ feet and a limited vertical clearance of 14′. (Modern bridges typically have a 40′ roadway for two lanes of traffic and a minimum of 16′ or more of vertical clearance. (The bridge was often hit by large trucks turning onto the structure.)

The cantilevered sidewalks were in poor shape with large holes in the walkways. A quick estimate was $2-3 million to rehabilitate the truss. A new bridge, with a 32′ roadway, a 10′ foot sidewalk and a 5′ foot sidewalk would cost around $5-6 million.

If I fixed up the old bridge I could not guarantee how long the bridge would last (who knows what kind of steel is in the deck, or how rusty some hidden elements are..) but if I built a new bridge I could reasonably expect a 100 year lifespan.

So the question remains, when is it responsible for an engineer to replace a historic structure?

It is Thanksgiving day in America. Thanks to everyone who visits my cheesy blog!
After all that turkey (unless your a vegetarian..) you need something to sit and watch.

One of the things I want to do is incorporate moving sculpture on a bridge. Here are a couple of cool videos covering moving Art.

I think we need to look at other structures to get some ideas for our bridge designs. MVRDV is a Dutch architectural firm who designed the new Market Hall under construction in Rotterdam. It is a mixed-use structure with shopping, housing and businesses. Imagine a huge airplane hanger with people instead of planes…..

Still the design will become a meeting place for the city and I like the idea of trying something new.

Here is another post on dezeen.com about a new pedestrian bridge by Olafur Eliasson, who brought you the New York city bridge waterfall.

Living in a non-earthquake state (except for a little sliver) I rarely have to worry about designing for earthquake forces. I used to live in California and as you can imagine, earthquakes are an extreme event you better think about….(Mark Yashinsky from BPOD knows way more than I do about this topic.)

It looks like a 9.0 earthquake event would do a lot of damage to Oregon’s bridges (and to everything else!).  The article in OregonLive suggests that another earthquake like the one in 1700 would cost over one billion dollars in damages and sever the highway 101 link along the cost. (Hey my brother lives in Oregon, yikes!)

An earthquake such as the big one that hit the Pacific Northwest in 1700 would wipe out many of Oregon’s bridges, cause billions of dollars of damage, make much of U.S. 101 and Interstate 5 impassable and sever all road connections between the coast and the Willamette Valley.

It’s a dire scenario that the most sober of scientists see as inevitable.

Although this scenario may be true I doubt Oregon’s biggest problem would be the loss of bridges, more likely is the loss of costal populations.

But the point (finally) is my question about design forces on a bridge. Would it be worthwhile to design new bridges for an extreme event that happened 300 years ago?

I was looking around for other blogs about bridge engineering. Not an image blog (no offense image blogs!) but an engineer or engineers discussing current projects like the Happy Pontist.

I see a lot of architecture blogs where architects discuss their work and I was wondering if there were more bridge engineers out there discussing their work?

If you find some please point them out to me. Thanks!

The Wisconsin DOT is looking at replacing three bridges that carry up to 350,000 vehicles a day, in three weekends. Quite a feat!

Hello from San Antonio! I gave a presentation today on my Keosauqua bridge design and I “think” it went over well….its hard to tell with engineers. My jokes may have fallen a little flat, plus my talk was right before lunch. (see its not me!)

Thanks to all the sponsors of this event for letting me come and present!

I will post some images from the talk, a little later.

On another note The Happy Pontist does a great job recapping the goings-on in the Calgary pedestrian bridge world. I still maintain the final competeing bridges are all fine but I didn’t think that was the point of the competition.

Its odd to enter a competition with a Calatrava bridge as a goalpost and then find the finalists went cheaper rather than more expensive. Except for the cable stay, I can’t imagine the other bridges look like they cost $25 million dollars. PLUS I still dislike the foundations the arch designs are using on the island. I predict the cable stay will win. (Although I have been way off in my predictions so far.)

Imagine that, a cable stay bridge downstream from the King of cable stay designers! That just seems odd…

WOW, what happened to the innovative ideas in the St Patrick Bridge competition?

The three finalists are fine but not the most daring of the competitors…so what happened and are the finalists the best of the lot?

I think the Calatrava bridge going over budget (see post below) scared the innovation right out of them…..I have nothing nice to say about the competition right now so I better wait and see how others view this development.

The Calgary Sun had this tidbit,

“The advisory committee agreed that the bridge should be simple and elegant, and that the scale of the structure, in relation to the site and its surroundings, be complimentary and not be overwhelming. Public commentary also supported this direction and we believe that we have three strong, feasible concepts to move forward with.”