Concrete Column, Design by Capacity Reduction Factor, R?
Concrete Column, Design by Capacity Reduction Factor, R?
(OP)
I was perusing a concrete textbook and read up on designing concrete columns using a method described as the "R Method", which made use of a capacity reduction factor, R.
Is this method still allowed/in use? Does it go by a different name now? Why haven't I heard of it before? (Well, you know, besides the obvious...)
Is this method still allowed/in use? Does it go by a different name now? Why haven't I heard of it before? (Well, you know, besides the obvious...)






RE: Concrete Column, Design by Capacity Reduction Factor, R?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Concrete Column, Design by Capacity Reduction Factor, R?
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Concrete Column, Design by Capacity Reduction Factor, R?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Concrete Column, Design by Capacity Reduction Factor, R?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Concrete Column, Design by Capacity Reduction Factor, R?
RE: Concrete Column, Design by Capacity Reduction Factor, R?
KootK, the book was one I got from a recommendation by AELLC on this site. It's "Practical Design of Reinforced Concrete," by Russell S. Fling. Fling was chairman of ACI in the 1970's and the book is excellent. Here's what he wrote of the R Method (emboldened emphasis mine),
The R Method is approximate, empirical, relatively easy to use, and should be considered whenever applicable. It is limited to lu/r < 100 for braced columns and l'u < 40 for unbraced columns. It should not be used for columns hinged at both ends... The R Method may be overly conservative if the column is relative slender, has large eccentricities, has loads of long duration, has high concrete and steel strengths, has a low steel percentage, and is a component of an unbraced frame.
He also described the method as, "straightforward, unsophisticated, "quick and dirty"...(Fyi, he referred to the Moment Magnifier Method as "...enlightened, refined, longer..." and the Second Order Analysis Method as "...elegant, erudite but painfully slow...")
Moreover, he also wrote that, "In actual practice, many engineers will use the R Method more often than the Moment Magnifier Method because the first method requires fewer calculations with less chance for error, as well as saving the engineer's valuable time. Furthermore, the majority of columns require little if any increase in strength to allow for slenderness effects."
And here's the thing: the book was published in 1987...not that long ago in terms of concrete design "philosophy"...or so I thought. And yet I hadn't heard of it otherwise.
He also had some criticism of the method, but my point is that I was surprised that a man of his stature had so much positive to say so relatively recently about a method I hadn't heard of.