Shame on me if I am not fully grasping the heart of this conversation, but it strikes me that the arithmetic of converting from English to Metric units and vice-versa is easy. It's the growing up thinking in one versus the other and the size standards of the products that are manufactured and used in the built environment that are the challenge. You grow up developing a "feel" for inches, feet, yards, miles, pounds, horsepower, (pecks and bushels if you work on a farm) etc., and being called upon later in life to "translate" that "feel" into different units can be a challenge, although the math of doing so, and the myriad of tools available today that will quickly do it for you is easy. But if you couple that "feel" with the fact that builders in the U.S. think (and purchase products) in terms of 2 in X 4 in (which aren't) 4 ft X 8 ft sheets, 3/4 inch thick, 3/8 and 1/2 inch diameter, etc. and consider an entire society built upon structures constructed from pieces made to those units, then the notion of conversion becomes very daunting indeed. Anyone can quickly tell you that a 4 X 8 feet sheet of plywood or drywall is 1219.2 mm X 2438.4 mm, but what you'll see in metric countries is that off the shelf sizes are 1.25 m x 2.5 m, 2.8 m, 3.0 m & 3.2 m with some even saying that a 1200 mm X 2500 mm is a 4 ft X 8 ft equivalent, but does that readily and conveniently fill a 4 ft X 8 ft hole? Some industries in the U.S., autos and electronics for example, can fairly easily convert to metric (although don't get started on things like whether a 9 mm wrench works on a 3/8 in nut). But the built environment – the infrastructure and the living spaces – is a long way away from thinking and being in metric.

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David Vanaman P.E., M.ASCE

Assistant General Counsel

WSP USA Inc

Herndon VA

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Original Message:

Sent: 04-19-2018 13:08

From: Chad Morrison

Subject: UNIT OF CALCULATION

Computers can handle units like champs. The problem occurs when manuals written for use with hand calculations tend to omit units in formulas and constants. The computer will immediately flag a conflict. It is not that I entered the formula wrong... it was that the formula as it appears in the manual does not display the units! This occurs in ASCE 7 and the Aluminum Design Manual among others.

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Chad Morrison P.E., M.ASCE

Professional Engineer

Greenville RI

Original Message:

Sent: 04-19-2018 09:39

From: John Turner

Subject: UNIT OF CALCULATION

I think tools like MathCAD may both hinder and help "unit awareness". Many people do a poor job of fashioning equations, usually opting to simply list and compute digits without considering the units. Unit-aware software helps maintain units and identify missing or misused factors.

Half of my (literal) Engineering 101 class was on using dimensions in forming/deriving/filling equations. When this is done, it really does not matter what units, or mixture of units, is used. You can compute apples plus oranges, as long as you know the proportion of apple that is equivalent to an orange.

Ironically, the people saying that we should force everyone to a single set of units are probably the ones who shortcut the most. People who understand units and math don't really have a problem switching between them. We also understand that numbers without units are meaningless.

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John Turner CSP, P.E., M.ASCE

Dallas, TX

Original Message:

Sent: 04-17-2018 11:36

From: Alvaro Villamizar-C

Subject: UNIT OF CALCULATION

I can´t understand why in these times of computers and calculation tools, civil engineers that have been taught to do all kind of calculations, have problems with measurements units.

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Alvaro Villamizar-C P.E., M.ASCE

Port Coquitlam BC

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