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Reduce Negative Coefficient 10%

Reduce Negative Coefficient 10%

Reduce Negative Coefficient 10%

(OP)
If a negative coefficient is reduced 10%, does the number become larger or smaller. For example, if -1.0 is reduced 10%, does it become -1.1 or -0.9? In other words, is the magnitude reduced or numeric value reduced?

The context is a footnote in ASCE 7-10 Minimum Design Loads for Buildings and Other Structures figure 30.4-1 (or ASCE 7-05 figure 6-11A) that states: "Values of GCp for walls shall be reduced by 10% when θ ≤ 10°"
Figure 30.4-1 is used to calculate wind loads and the coefficient can be positive or negative.

RE: Reduce Negative Coefficient 10%

-1.0*0.9=-0.9 as far as I know.

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RE: Reduce Negative Coefficient 10%

Your post contains both the question: “is the magnitude reduced or numeric value reduced?”
And the answer: “"Values of GCp for walls shall be reduced by 10%”

RE: Reduce Negative Coefficient 10%

reduced means the number gets lower. After all zero is arbitrary.

f-d

¡papá gordo ain’t no madre flaca!

RE: Reduce Negative Coefficient 10%

Reduced (probably) means subtract.

How much to subtract? 10%

10% --> 0.1

-1.0*0.1=-0.1

-1.0 reduced by -0.1

-1.0 - (-0.1) = -0.9

Having gone through that exercise, codes need to be clear, precise and unambiguous. This language is not.

RE: Reduce Negative Coefficient 10%

Quote:


reduced means the number gets lower. After all zero is arbitrary.

f-d

Technically, 'reduced' means 'made smaller', not lower.

A large negative number is still large.
A small number is closer to 0, either positive or negative.

That said, in the original, the coefficient itself is not negative, and the language refers to making the coefficient smaller.

RE: Reduce Negative Coefficient 10%

(OP)
Thank you for the responses. The wording could be more precise (less ambiguous). I like Fattdad and Mint Juleps reasoning; but which one is right? I checked at work today, and the same language is in the 1998 and 2002 editions of the code. I plan to contact the ASCE 7 wind committee and propose changes to this language.

RE: Reduce Negative Coefficient 10%

i guess the word "reduce" is open to interpretation ...
1) does it refer to the magnitude ? (ie get closer to zero)
2) does it refer the numerical value (so a -ve number would get more negative)
if you're dealing with a code, then i'd ask around for the generally accepted interpretation.

Quando Omni Flunkus Moritati

RE: Reduce Negative Coefficient 10%

I've always taken "reduced" to mean "closer to zero", but now I'm wondering if that is correct.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

RE: Reduce Negative Coefficient 10%

There is a big difference between "If a negative coefficient is reduced 10%" and "If a negative coefficient is reduced by 10%".
If a negative coefficient is reduced 10% ==> NC - 10%
If a negative coefficient is reduced by 10% ==> NC * 0.9

Good Luck
--------------
As a circle of light increases so does the circumference of darkness around it. - Albert Einstein

RE: Reduce Negative Coefficient 10%

Quote (CajunCentruion)

There is a big difference between "If a negative coefficient is reduced 10%" and "If a negative coefficient is reduced by 10%".
If a negative coefficient is reduced 10% ==> NC - 10%
If a negative coefficient is reduced by 10% ==> NC * 0.9

No there isn't.

If a negative coefficient is reduced 10% ==> NC - 10% Expressed properly is NC - (NC * 0.1) --> NC * (1-0.1) --> NC * 0.9

RE: Reduce Negative Coefficient 10%

If negative coefficient is "increased" by 10%, it will be (NC + 10%), in other words NC x 1.1.

So if negative coefficient is "reduced" by 10%, it should be NC x 0.9.

RE: Reduce Negative Coefficient 10%

If you turn the air conditioner "up" are you making the temperature in the room colder or warmer?

f-d

¡papá gordo ain’t no madre flaca!

RE: Reduce Negative Coefficient 10%

Not too many answers from civils or structurals here. Maybe you've got the wrong forum. I'd ask those who use the code in question. I'd also ask which answer yields the most conservative and/or sensible result. And to fattdad, my answer is warmer. My wife of course disagrees.

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