Monthly Archives: June 2009

Top Ten (10) Bridge Engineers

TBG’s – Top 10 Bridge Engineers.

Obviously picking the greatest bridge engineers is open to all kinds of interpretations but hey, someone has to make a list. The engineers I have chosen have a number of things in common, they have moved the art of engineering forward while designing structures that are beautiful and stand the test of time.

Judging criteria:

  1. You have to be an engineer (naah to architects).
  2. You designed the bridge (actual structural calculations in addition to the concept).
  3. The design is a structurally reasonable bridge (meaning good engineering involved).
  4. Your bridge is attractive (eye of the beholder, in this case my eye).

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Vancover Land Bridge

I was just writing about adding greenery to a bridge a few posts back and voila, they already did one in Vancouver, Washington. Most pedestrian bridges look best when you are approaching them from the roadway. They are designed to be seen as a whole structure. This bridge takes a different approach and is geared towards the pedestrian crossing the bridge. In the Aspire magazine article you get some photos showing the meandering pathway across the bridge, lined with planters, and inlaid colored pavers.

My overall opinion is that it is a nice structure and the “strolling in the garden theme” is appealing but it’s not really a bridge. The bridge is secondary and just a means to an end. The landscaping is a little overdone compared to the landings on either side of the bridge. Maybe if it ended in a great sculpture garden and the bridge was the entrance to the park or to a museum?

Great overview picture here.

Oregon Bridges

When I first received my engineering degree I tried to get a job in Oregon. Eugene to be specific. My wife was offered a job at the University and I needed to find one. The best offer was to be the construction engineer on a new pedestrian bridge over the Willamette. The problem for me was, they had to be the winning bid on the project. And of course, they came second..

Hey is an old blog post by a local Oregonian Architect (and fellow Canadian!) about a highway bridge over the Willamette.   It gives some outside views of how a DOT chooses a bridge that I think is worthwhile reading. I like the fact that they care enough to speak out about the project. I was wondering when the last time a group of engineers wrote the paper complaining about a design?

Quote I don’t like but throw in engineers instead of architects:

It was important that architects weigh in on this topic. We rightly should be regarded by the public as leading voices on issues related to the built environment.

Here is the proposed bridge in question.

Spam and good comments

I have had a spam attack in my comments section, so if I deleted your comment, sorry about that.

I received a great comment from the Happy Pontist about my quick post on design choices.

I have included it down below because I think it is important for engineers to be aware of the decisions being made on a project. I have suffered through a number of projects where other “helpful” entities (think other offices or engineers) have “suggested” design directions for me. (I sure love air quotes, huh)

These suggestions are often required suggestions but the party giving the recommendations typically do not back up their advice with their signature. Being a professional engineer is a lot of responsibility and signing a plan should take a lot of thought.

Some great advice for engineers from H.P. (who always says it better..sigh)

This is maybe related … In the UK, we have a legal obligation when designing a bridge to consider how it will be safely built, used, maintained and eventually demolished. Often, designers only pay lip service this to requirement. Those of us who take it more seriously, however, are often frustrated when clients and others take decisions that in our view, reduce the safety of these activities e.g. a client who doesn’t want an access walkway or ladder because it spoils the appearance. When filling out the paperwork to record what I’ve done to meet my safety obligations, I make a point of recording the design decisions that I disagree with and which were made with others. The public will never know, but should the legal people every come after me, I’ve made sure the people responsible are recorded.

Something else I’ve done on one project is to produce a commentary on the design – why certain decisions were made, by whom, etc. Again, not for public consumption, but for the information of designers who may come later in the process. And again, it’s a good way of recording decisions made that you disagree with, although clearly it won’t be welcome on many projects!

Conde B. McCullough

Mr. McCullough became the State Bridge Engineer in Oregon in 1919, only six years after graduating from Iowa State University in 1910.  (A partial list of his bridges is here witha nice summary of his career. I would imagine he had help with the actual designs.)

As a bridge designer I admire his structures for their beauty and elegance but what I most admire is the fact that he did all these structures without a computer. I look at the bridges and think, “how the hell would I design that?”. No cadd for layouts, no calculators, no Internet! Yikes, what did they use an abacus?

Take a look at some of his bridges and tell me if you could design them using the tools of 1919. I wish I had the opportunity to build just one concrete arch like the one below. I would be a happy engineer.

http://www.1nova.com/photoblog/
http://www.1nova.com/photoblog/

Design Choices

Its been a busy week and its only Tuesday! Projects to finalize, emergency repairs and teaching have slowed my posting ability. One of the things that did bother me enough to get off my butt and write a post is the issue of design choices.

By that I mean how do the choices of others affect your design. (Really, I mean my design) For example, if you are working on a bridge repair the decisions of the traffic engineer will affect your plan. Staging, temporary barrier rails, lane closures may all come into play. If your designing a bridge, you face a large number of previously made choices that point your design down a path you may not have anticipated.

What I am really dancing around is the question of control. What happens when the designer has to sign for poor choices made, concerning a design, by “others”. (I’m really trying to stay out of trouble here…) I realize this happens to engineers all the time, but I am wondering how the public judges the final outcome?

I am really screwing this post up. Maybe I can sum up what I am trying to say by suggesting that all engineering plans should have a box on the front of the plan set saying “in spite of all the poor decisions, I did the best I could”. And yes, I am having a bad day….

Development Length of reinforcing steel

Its Friday and today I gave an overview of the development lengths required for reinforcing steel. If there ever was a duller class to teach at 7:30 in the morning, I have not come across it. (And the day after the midterm exam, yikes)

I’m a bridge designer who uses the AASHTO code but the course uses the American Concrete Institute (ACI) building code and commentary. I did find a handy guide by Dayton Superior, outlining bend diameters, hook lengths and other riveting facts about reinforcing steel. Download the pdf here. (Sorry, US units only)

whitecap.com

whitecap.com

Bridge Costs Post #1

Update: #2 – I put a link in my blogroll to a Bridge Costs Spreadsheet (excel). As I add costs to the sheet I will upload the latest version. (It does NOT contain anything else.) It is pretty plain but I will work on it.

Comparing the costs of bridges is a tricky thing, especially when you get into signature designs. But some measure of cost may help to evaluate the differences between designs. **Remember if you are buying a piece of Art, money is not the driving force behind the decision.

Starting point:

The most common cost for a bridge is the lump sum value but often engineers break that down into a square foot or square meter price. (I grew up with the metric system in Canada now I teach US units..) Additionally, the cost per square foot can be based on the roadway width, pedestrian width or the entire width of a bridge. To keep things easy I will use the entire width of a bridge for the cost area.

Bridge costs: (Using 1.6 US dollars to one British pound)
I started with my bridge and some others I found on the internet. (Everything is factual on the net, right?) The lengths and widths may be off but it gives a starting point for adding the cost dimension to the discussion. How much is too much, that all depends on who is paying.

I will start a database and post the costs as I find them. I know the Happy Pontist has provided costs for a number of pedestrian bridges on his/her blog. So that is a great resource for seeing what you get for your money. If you have some bridges to add to the list, please forward them.

Update:

The California DOT posts some useful bridge costs for typical bridges here.

London Millennium Bridge

Yes I have read about the wobble of the bridge when it first opened but i never saw this video. ( I realize it is old news but it is still interesting.)

Green Bridges

My last post showed a bridge concept over what I thought was a river but was instead a railroad system. (Seems fairly obvious in retrospect, thanks HP) But I still thought the trees lent a natural component to the bridge, which reduces all that harsh concrete. As an engineer I would hate vegetation on a bridge but as a pedestrian I think it would be very enjoyable.

Urban bridge gardens would be fun but I can see the problems. Leaves, brush, weight, water, missiles for kids, and a variety of other problems. I have seen some bridges with small planter systems but never any trees. Has anyone seen a bridge with trees on it? (Send the link!) I doubt any engineer has designed one but I would love to try!

Update: HP pointed out this bridge with trees.

www.foxysislandwalks.co.uk

www.foxysislandwalks.co.uk

What is the first thing that springs to mind?

I followed the link on the Happy Pontist to this bridge by cepzed designs in the Netherlands. The bridge will be built in Utrect, the fourth largest city in the Netherlands. (Hey I can google)The bridge has great access to the river(?) through openings in the bridge. (Although the image does not show the railing required to stop pedestrians from falling into the holes, yikes) It also looks like it could be built at a reasonable cost.

I think it is a very appealing design but the first thing that came to my mind was, how will you drain the water from the trees? Also how will a growing tree change liveloads as it grows? So, the first I think of, is the challenges of determining the loads, the span arrangements, and the construction sequence. I must be an engineer.

Take a look at the design and think about what comes to your mind. Me, I am going to go look for more bridges with plants on them.

cepezed designs rabo bridge

cepezed designs rabo bridge

Friday roundup

Friday roundup (or the lazy man’s blog post.)

The happy pontist has a number of good posts on tensegrity bridges. I never knew they existed but I am not a fan. I can’t stand pointy things and while it is interesting, the chaotic appearance hurts my head.(I’m not worthy)

Also from a HP is a great link to the deputy dog website and TRIDGES!  I want to design one! deputy dog also has some great pictures of a round bridge.

And my all time favorite. The bridge of death.