MadSci Network: Engineering

Re: Why is a bridge piling called a 'bent'

Date: Wed May 1 22:16:48 2002
Posted By: Chas. Hague, Staff, Bridge Design Department, Alfred Benesch & Co, Consulting Engineers
Area of science: Engineering
ID: 1018929274.Eg


 I congratulate you on finding out for yourself what a bent is, and for 
asking a Really Good question!  So far, I've asked the 4 or 5 oldest 
engineers I know;  the vice-chairman of the American Railway Engineering 
and Maintenance Association timber bridge committee;  about half of the 
Union Pacific Railroad's engineering department;  the chief bridge 
engineers of the Illinois Central and Rock Island railroads;  many members 
of the Structural Engineer's association;  a writer of historical 
mysteries who is an excellent researcher; plus consulted the Oxford 
English Dictionary, the American Heritage Dictionary, and Webster's 
Unabridged;  Plus a half-dozen etymology dictionaries.

None of them had an answer.  The first published use that the OED had was
1815, and it says that the word is "U.S. in origin".  but not where it 
comes from. Its use as a frame in a building goes back to 1600.

Most jobs have special names for things they use.  In structural
engineering, for example, we have "bent", but also "Stringer", "trestle" (a
bridge made up of stringers and bents), "Web",  "flange", "stiffeners" and
Girders (a bridge part made up of flanges held apart by a web, braced with
stiffeners).  "Screed" is the theoretical line that a road surface 
follows, and also the machine that strikes off concrete to that line.

Special language like that has a purpose.  Not, mind you, just to
confuse outsiders and elevate  the status of the people in the know.  It
specifies and clarifies what is being discussed, so that everyone involved
knows exactly what is going on.  For example, if a foreman says "We need to
replace a pile in that third bent" his workers know exactly what he means.
Likewise, if the captain of a sailboat says "Trim the mainsheet!"  the crew
knows exactly what rope to pull and which way.  Saying "pull the rope on 
the big white thing that direction" takes longer and has a larger chance 
for error.  I know of a case where a train was wrecked because one man 
misunderstood a single word.   

As for "bent" -- Here are a few guesses, based on what I learned 
researching your question:

(1)  the word "bent" also means inclined.  The outer piles of a bent lean 
inwards, (we call this "battered"), in order to resist sideways forces.

(2)  One of the definitions of  "bend" means to bind things together in 
parallel.  So a group of pilings could be described as being "bent 
together".  Also things placed parallel were said to be a "bend".

(3) Early frames were assembled on the ground and hoisted up into position.
Raising something like that might be said to be "bending" it upwards.

(4)  The support for the cover of a wagon, or some tents, is a hoop shape 
bent from a thin wood sapling.  A building bent is a similar shape and 
fills the same role.

Are any of these right?  I don't know, though I'm kind of fond of #1.  
I'll have to ask some engineer who was around back in 1815.  I'm going to 
keep my ears open, just in case someone does know.

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