Monthly Archives: February 2013

More Gumdrop bridges!

More Smithy wood bridge

David sent some more great information. Great stuff! Thanks David!

I didn’t know anything about the Wichert truss concept until I came across the Smithy Wood footbridge.

1) I discovered that there are many steel bridges of a certain age in the USA using the principle.
Its brilliant that Ron Bridle & his colleagues thought about it & then said to themselves “why can’t we do the same thing in concrete to cope with our potential foundation settlement problems?”

2) Wichert steel truss bridges in the USA
A couple more links about what may be one of, if not the first, Wichert truss steel bridge in the USA & a very long one also.

3) I attached a few photos I found as well. The Wichert plate girders (as opposed to the Wichert full truss) look to me just like a steel version of the Smithy Wood bridge.

4) Calculations
There are two books that I found that describe how to analyse the forces in a Wichert truss “by hand”, one dated 1932, the other 2010:

– “The Wichert Truss” by David B. Steinman (the famous one?)
D. Van Nostrand Company, Inc., New York, New York, 1932, PDF (6.8 MB)

– “Advanced methods of structural analysis” by Igor A. Karnovsky and Olga Lebed (based in Vancouver)
DOI10.1007/978-1-4419-1047-9 Springer New York Dordrecht Heidelberg London


Smithy Wood footbridge

David sent some great information so I stole it for a post! Thanks David!

The bridges on that stretch of the M1 subject to possible mining subsidence are all interesting but the Smithy Wood footbridge is really amazing. It has been in service since the 1960s, so now about 50 years old. Presumably it is inspected regularly as it spans across the M1, a strategically important & busy British motorway. From Google Maps Street View it seems to be OK at least superficially, even if it could do with a clean-up. The other 2 footbridges with a similar concept mentioned in the Motorway Archive link, Birdwell Quarry and Stainborough footbridges were replaced by steel truss through-bridges in 2006 & then demolished. It would be interesting to know why they needed replacement.

I found a (long at 169 pages but informative) transcript from the British Library of a recent interview with 83 years old engineer Ron Bridle, a bridge designer & one of the co-authors of the research paper by Sims & Bridle about concrete hinges. (See page 168, TBG. He’s a painter in retirement.):

Refer to pages 79 to 84 concerning the Wichert truss “rhomboid” details. According to Bridle, the Wichert truss is statically determinant & can tolerate some ground movements which is a reason why this detail was developed. At the same time the moment envelope is optimised. Reading this transcript & the other articles I gain the impression that the designers thought very carefully about what they were doing. They did tests in laboratory of the crucial details that they envisaged using before they were built. Why is it that current day comments on the Internet concerning such details including concrete hinges like the Freyssinet concrete hinge are mostly so critical?

For example the British government paper “Design of highway structures in areas of mining subsidence 1997 UK) linked here: states categorically in the section “Articulations, bearings & expansion joints…3.43” that “Concrete hinges shall not be used. They are difficult to inspect and remedial works are a problem when they fail….”. Caution is necessary but are blanket rules like that the best way? The devil is in the details. With the new materials & methods available today it may be possible to make even better concrete hinges? Nowadays standardised mechanical bearings & hinges bought off the shelf from specialist hardware companies predominate. The Freyssinet flat jack also seems to have disappeared from use.

Is this because the average engineers nowadays use suites of computer programs that “do everything” for them without the need to understand what is actually going on inside the concrete, or how to use Mohr’s circle (I’ve almost forgotten myself!) etc. Triaxial stresses probably mean little to them. However there are plenty of bridges built long ago & using concrete hinges that are still in pretty good health e.g.:

TBG is quite right to ask “how is it still standing up” though? Maybe sometimes our usual assumptions of forces being transmitted like “straight arrows” are over-simplified & not close enough to actual stress conditions inside the concrete. Bill Harvey asks a similar question in his paper entitled “The Coy Mistress” on the subject of masonry structures, “the question is not so much: ‘why did it not fall down?’ but “how did it stand up?”This requires a completely different approach to analysis, though simple calculations remain the best way forward.”
Worth a real site visit?

Every engineer should read the Happy Pontist today

Great post by the Happy Pontist today, link here.

In general, HP is discussing a specific case of a journalist berating engineers for criticizing a “proven” “serious” competition winning bridge. Like HP, I have to say the problem is one of engineers engaging in criticism too late. Yes, you can build anything if you have the money but should you.

Engineers should be in the conversation early, not to stop innovation but to vet it. To make sure projects are beautiful and constructable. If you have read this blog for a while you know I like the audacious projects, but I don’t like stupid engineering.

Finch asserts that criticism of the “handsome-looking” bridge has been “aggressive” and “moaning”, going on to request that “serious competitions with serious winners should not be the subject of professional sniping.”

Really? How absurd. Perhaps an appropriate title for this blog post might be “When journalists get the knife out they can be worse than engineers or architects”, and perhaps a humble blogger might suggest that “serious engineers should not be the subject of sniping from amateurs”.

Econtainer Bridge – yuck

Have you seen images for the prize winning econtainer bridge shown here on Archdaily?

The goal is to repurpose steel containers. I guess it is a noble idea but I doubt it will work. First, you probably have to clean and repaint containers so they can withstand the elements. I can’t imagine every container is rust free or structurally sound. Now you have a steel bridge that requires constant maintenance, not Eco friendly at all.

Next, since containers are not structural bridge elements, you will have to use extra supports to hold this whole caravan in place. You can’t weld containers together and hope it stays in place.

And finally, it looks awful. My opinion of course, but Imagine having to maintain this structure for 50 years, which is the bare minimum for a bridge lifespan.

I’m all for finding innovative ways to deal with preexisting materials but why does it always have to end with a structure that makes the blade runner future look like a paradise? Maybe the winning entry would be a new way to reuse the steel in the containers in a Eco friendly way? Then build a beautiful structure out of the recycled materials?

Part of sustainability, is respect for the community and I realize beauty takes many forms but really this is our future? This the best we can do? Geez, I hope not.

Bridges on the Aston-Sheffield-Leeds motorway

David sent me a great PDF (and pictures!) of concrete structures from 1969. Apparently, at least one bridge is still around according to the google earth pictures David found.

It is from Concrete Quarterly 80, Concrete and Cement Association, link here.

The bridge below is the Smithy Wood footbridge and seems quite ambitious for its day. The main span is 158 feet with 76 foot end spans. It has a feature called “tri-hinges” used for the first time on this bridge, developed by West Riding engineers. The hinges connect the rhomboid struts to the top of the piers, compression from three directions “assists the effective action of the concrete as a hinge.”





And this pier from another bridge is interesting….


Thanks David!

Structural Engineering Calculations – why keep them?

I’m curious what engineers do with their engineering calculations. Some owners, like department of transportations in various states, require you submit your structural calculations along with your finished bridge design.

But as far as I can tell, there is no national “requirement” that calculations have to be submitted or for that matter keep in any usable form. I was wondering what other countries ask of their structural engineers? Are the calculations the owners property?

If you don’t have to submit them, then do you keep them and for how long?

Finally, what is the point of keeping calculations? I understand the engineer can use them as a reference on future projects but I doubt anybody would look at past calculations unless, (cue scary music) dum dum dum, something goes horribly wrong and it is time to lawyer up.

Now, if you get to this point, is it prudent to have calculations especially ones that show you made a mistake? You already have a plan sheet that any engineer can go through and find mistakes, why would you need the original calculations? ( I’m not talking about ethics here)

So what is the point of having calculations laying around?


Update: no calculations here.

Vladimir Shukhov – Engineer

From the all knowing Wikipedia. Link.

It’s amazing how uninformed I am about past engineers. I have never heard about Mr. Shukhov but he did some great work in Russia.

Vladimir Shukhov is often referred as the Russian Edison for the sheer quantity and quality of his pioneering works. He was one of the first to develop practical calculations of stresses and deformations of beams, shells and membranes on elastic foundation. These theoretical results allowed him to design the first Russian oil tanker, new types of oil tanker barges, and a new type of oil reservoirs. The same principle of the shell on an elastic foundation allowed to theoretically calculate the optimal diameter, wall thickness and fluid speed for the fluid pipelines. Shukhov’s projects were instrumental in constructing:


San Francisco’s Bay Bridge redesign

I think Nader is an engineer…..

The most expensive public works project in California history, the new and vastly improved Bay Bridge is set to reopen on Labor Day weekend. In a conversation with the Daily News, architect Marwan Nader took time to reflect on the many challenges he faced along the way to make a structure that can endure the next major earthquake while living up to the Bay Area’s aesthetic standards.

Read more:

Update: I had to add this quote…..

“It is an engineering marvel that is amazing, but I just wish it was sexier, like a Santiago Calatrava bridge where aesthetics and structure are one and the same,” James Lord, one of the founders of the San Francisco firm Surface Design Inc. told the Daily News.

Wallace and Gromit from 123D Catch

I downloaded 123D Catch from Autodesk for my ipad and made a 3D image from my Wallace & Gromit clock. My wife gave me this clock about 10 years ago. Press the shoes and it says “time for walkers”.

Some screen captures from the 3d image, not bad for the first one..




Avery Bang ENR top news maker

    Hey I saw this coming ( link to ENR story)

… is an interview I did with Ms. Bang.

1) What got you interested in a career in engineering?
My father is a structural engineer, and as a child, visiting bridges and Frank Lloyd Wright houses on vacations was the norm. I guess I fit the stereotype, in that regard.

2) Could you give an overview of your role with “Bridges to Prosperity”.
My first project with Bridges to Prosperity was in 2006, as a student at The University of Iowa. We designed and built a 30-meter cable-suspended bridge near Santo-Tomas, Peru as our senior design capstone project.

My passion was ignited, and I joined B2P’s Board of Directors as the Director of the newly-formed (our project being the first) University Program. Following graduate school in Geotechnical Engineering at The University of Colorado at Boulder, where I worked with Engineers Without Borders Founder Bernard Amadei, I joined B2P as the first States-based full-time employee, as Director of Operations.

Nearly four years later, I am now the Executive Director, working with a small team of engineers and staff here in Colorado, supporting Program Staff in seven countries on four continents. It’s all quite exciting.

3) How can engineers help non-profit organizations?
Each non-profit is certainly unique, but speaking on behalf of B2P, we rely on the technical expertise and support of engineers. From design detailing, to drafting, field-based construction support to Corporate Social Responsibility financial support, engineers and their companies are at the core of our success.

We strive to minimize overhead expenses, by focusing staff efforts on defining global footbridge needs, and supporting volunteer engineers who do the actual design and training program development.

4) Any advice for new engineers?
I had a professor who claimed that we were to be the 1% of the population that makes life possible for the other 99%, which has always stuck with me. Careers that truly help people are not limited to medical or teaching fields as many incorrectly assume. So think big–find your passion within the field and think outside the box, both in terms of what the impact of your existing work is going to be on society, but also how you can select your career path to be both interesting and rewarding.

5) What do you do for fun?
Well, traveling is certainly a favorite of mine, but when I’m in the States, I enjoy rock climbing, reading, biking and jogging with my pup Levi. I’ve been known to love a bit of good live music as well.