Terminology
Terminology
(OP)
Being from the old school, I was curious as to why the engineering standard reference for "moment", which has been termed "foot-kips" for over 200 years, somehow morphed into the nonsensical term "kip-feet." Who started this and why?






RE: Terminology
RE: Terminology
Saves a letter (you know us engineers and efficiency)?
Rolls off the tongue better?
I don't know (although I suspect the latter has something to do with it).
RE: Terminology
M=wl^2/8
M=PL/4
M=Pab/L
I would be inclined to think it has more to do with that.
RE: Terminology
Never though about writing it the other way until reading your post.
RE: Terminology
RE: Terminology
When I considered the formulas that Jayrod mentioned, the force-distance nomenclature makes sense.
Hokie66's mention of an international standard (kNm) format is also reasonable.
However, my favorite answer is from Lomarandil --- it rolls off the tongue better (as long as you are speaking English, that is).
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RE: Terminology
RE: Terminology
kip-feet becomes nonsensical only to one who originally learned and has used foot-kips all of his life! Like I said, I'm "old school."
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RE: Terminology
length-force <--> energy
force-length <--> mechanical torque
"It is imperative Cunth doesn't get his hands on those codes."
RE: Terminology
AISC 9th Edition (1989) Kip Ft. (Page 2-149)
AISC 6th Edition (1963) Kip Ft. (Page 2-48)
AISC 5th Edition (1946) Kip Feet (Page 203) Notice it is spelled this time, not abbreviated.
Maybe "Kip Feet" has been hiding out longer than we realized.
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RE: Terminology
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RE: Terminology
Though pounds is a softer sound, so maybe that still fits in my theory about rolling off the tongue.
RE: Terminology
RE: Terminology
1934 Carnegie Pocket Companion
1917 Cambria Steel Handbook
1892 Pencoyd Wrought Iron & Steel In Construction
All three use either foot-pounds or inch-pounds. This is even when the magnitude of the numbers is large, say >> 100,000 inch-pounds.
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RE: Terminology
RE: Terminology
RE: Terminology
I dug up a Concrete Engineer's Handbook that my father had that was dated 1918, and it referred only to inch-lbs.
ACI's 1955 Reinforced Concrete Design Handbook uses ft-kips only.
My old Strength of Materials book dated 1951 uses ft-lbs only.
My textbook on Statically Indeterminate Structures dated 1951 refers to ft-kips throughout.
My textbook on Timber Engineering dated 1949 uses inch-lbs.
My PCI Design Handbook dated 1992 uses ft-kips throughout.
I have a Standard Handbook for Civil Engineers dated 1996 in which the chapter on concrete design refers to in-kips, the chapter on wood design shows in-lbs and the chapter on steel design uses kip-inches.
My 2001 design manual for Engineered Wood Construction uses in-lbs.
Hence, my conclusion from this interesting exercise and the input that all of you have made is that the term kip-ft seems to have appeared much earlier in steel handbooks and texts, and that how one refers to bending moment seems to be related to which discipline you are working in. Wood and concrete still seem to use the Distance-Load units while steel seems to have changed to a Load-Distance terminology.
Since I've mostly worked with concrete, I guess that's why I am hung up on the ft-kip reference. So, it looks like everyone is correct --- its just your own preference that counts.
Thanks to you all for your participation in this thread.
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RE: Terminology
RE: Terminology
I'm wondering if the lack of kips in the earliest documents you were looking at is more related to the fact that 'kilo' hadn't moved into common english usage yet. I'm going to see what the oldest engineering sources I have at home are, if I remember to, and see what they use. I'm pretty sure I have some stuff circa 1910.
I don't think metric started moving out of France and heavily French influenced regions prior to the mid-19th century, so it wouldn't surprise me that kilo wasn't common in the late 19th century in areas that weren't familiar with the system. I'm not really sure though.
RE: Terminology
RE: Terminology
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RE: Terminology
RE: Terminology
(Hope you have a sense of humor!)
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RE: Terminology
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RE: Terminology
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RE: Terminology
RE: Terminology
The problem with that system is that you never know which version you are going to be confronted with. Around 1960 this committee got got together and decided that the MKS (meter, kilogram, second) system wasn't good enough, so they expanded it to what is now called the SI (System International).
So now, you may have a bending moment that you had converted into kilogram-meters, and you are suddenly confronted with this thing called kiloNewton-meters. Now you'd think that they would have just made 1 kiloNewton = 100 kilograms, but no, you've got that little thing called gravity acceleration in there (to make a kilogram of mass equal to a kilogram of force), so it ends up being 101.97 kilograms. And don't even get me started on expressing psf in kiloPascals (kPa).
The bottom line is, both systems are purely arbitrary as to where you start, such as King Henry I stating that a one yard measurement would be the length of his arm. We in the US would have been much better off by adopting a decimal system throughout. Instead of making a foot = 12 inches, it should have been 10 units of something, similar to what is used in surveying where a 100 ft tape is broken down into tenths of a foot.
Basically, your favorite system will be the one that you were brought up with and are used to.
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RE: Terminology