I believe that you are right about the medieval trusses. Lehigh University has a "Digital Bridge Collection" where you can read many of the late 19th century books and papers on bridge design (mostly with trusses). Here is the link:
http://digital.lib.lehigh.edu/digitalbridges/browse.html

www.SlideRuleEra.net
www.VacuumTubeEra.net

Read a complete book on bridges and you will learn about Roman structures that included cross bracing trusses 2K years ago. They learned early about the benefit of the triangle. I have 'Bridges' by David J. Brown, Macmillan, '93. He illustrates early trusses in his chapter 'The Ancient World.'

"Likely built by proportions, not rational analysis "

No, not exactly.  None were built by rational (mathematical stress and strain) analysis, but all were built after rational analysis was applied.   

"Hmmmn.  Crown Prince Mayhem's truss bridge over in Leaking River broke when they built it with 10 x 10 pine beams 18 feet long - and they hung the builder the next day.  I'll use 12 x 12 oak beams only 16 feet long on my next bridge.......""  

Did Squire Whipple pioneer the complete structural analysis of the truss?  The previous trusses were done by trial and error.  

This was my understanding, at the time, back when I read Whipples book "An elementary and practical treatise on bridge building", which is available for download on Google books.

Used to read about structural engineering (mainly American engineers), Cross, Greene, Maney, James, Whipple, etc...  America was really at the peak during the 1800s and 1900s.  Things have certainly waned the last fifty years or so.  The airplane industry really pioneered most stuff during the middle 1900s--But then again Hardy Cross's contribution is a work in itself and stand alone during that time.

As far as I know Whipple developed the complete structural analysis of the truss, which brought the truss bridge to an entirely new level of forum and function--for the obvious reason that all the members could be sized appropriately.   

Would love to know if I am mistaken.  Maybe just an arrogant American?  We Americans are becoming fewer and further between, a few enclaves here and there, but the pragmatic, protestant, pioneers, are dwindling and few, America is a new place.  Let me know...
 

I looked through some of the old books I downloaded from Google. I have Whipple's Treatise from 1873 and one by E.W. Young also 1873. Both have a rational analysis but there are no references to any earlier work.

I also have one from 1837. It's a text book used at West Point. It has a rational analysis for arches and frames but nothing on trusses.

Hard to say if Whipple was the one who developed the rational approach.I recall reading about the collapse of a truss in England in the first half of the 19th C. It was designed by proportions, and as a result the whole approach to truss design changed.

I also read a book about the great cathedrals of Europe from the Middle Ages which said they were built by proportions. The builders would lay out the plan and then observe the shadows from the stakes; that would tell them how thick to make the walls. I dunno if I buy that.

Tumbleleaves - I don't think you're being arrogant. Americans are EXCEPTIONAL. Who bails out the world everytime there's trouble? The current thinking in this country that we have to lower our standards to the rest of the world rather than telling them to raise themselves to our standards. Reminds me of a story:

There was a poor farmer - a bitter man - who could barely raise enough food to support his family but what bothered him most was his neighbor, who was better off. It seams the neighbor had a horse to help with the plowing. One day, the first farmer is digging in the field and he comes across a lamp. He rubs it and a genie appears. The genie says, "I'll grant you one wish; anything you want."  As the farmer is thinking, he sees his neighbor plowing. He says to the genie, "kill the horse."
 

Quote:

Americans are EXCEPTIONAL. Who bails out the world everytime there's trouble?

The Canadians smile and nod, quietly.

Bill
--------------------
"Why not the best?"
Jimmy Carter

Squire Whipple is not very well known in Europe.

He appears to be a US contemporary of the great European engineers who designed, ANALYSED and built railway sheds and bridges all over Europe in the mid 1850s and onwards. Think of Eiffel and the English railway engineers.

The London Crystal Palace of 1851 was a huge truss supported structure. Although Paxton usually gets the credit, this structure was carefully analysed so that weight could be reduced. Fox, Henderson were the contractors.

Thanks to Hollywood, the image many Europeans have of 19th century US trusses is of large wooden railway trestles, which were presumably based on some kind of rational analysis or design code based on same. We don't hear enough of the likes of Whipple.  

Obviously a typo; should have been;
'Who else balls up the world everytime there's trouble?'
:)

DB Steinman tells of interviewing a bridge designer  about his analytical methods. Time frame, early 1900's. [DB was called in on a bridge truss failure problem on a small suspension bridge. A side span chord failed first on one side, then on the other side span.]

The designer pulled out a black book with a simple rule of thumb. DB saw that this was insufficient basis for the design, and he said so. DB was later black balled by the designer when DB applied for membership in an eng society. DB never again associated himself with that society. The bridge was rebuilt by DB according to better analytical practice.

Unfortunately, even in modern times engineers will perform insufficient analysis. You need the worry about all the details.