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Re: Reinforcing existing steel members

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I haven't reinforced too many compression members, but I know the article. I would treat the column in the way described however. With regard to beams, I've done a lot more of this type of reinforcing. There has been research for some time which shows that the ultimate strength of composite beams, whether shored or unshored, is the same. This can apply to composite wide flange steel-concrete slab or to a wide flange under load with a WT welded to the bottom. I generally use LRFD for renovations, so I don't deal with superposition of stresses, etc. The ultimate strength of the section can be based on the overall section, but the deflections should be viewed incrementally. You really use this assumption every time you design a composite floor system, where the bare beam (unreinforced section under load) carries the dead load and the composite beam (reinforced section) resists the total load.

Eric Ober
Cagley and Associates

Hyndman, Keith wrote:

Reference: AISC Journal 4th qtr 1990 "Reinforcing Steel members and the Effects of Welding"
by R.H.R Tide

This article and several written prior to it, states that the "strength of
columns reinforced under load and under no load are identical."  This
brought me to question some of the practices on my own office where we have
sized reinforcement of steel members by subtracting out the existing
(actual) stresses, resulting in an overly conservative design.
So I thought I'd write to the audience to see if this philosophy is widely
held.

Also is this approach true for tension and bending members?

Ultimately I'd like to convince my "crusty cohort" to change his ways, to a
more efficient approach.

Thanks,

Keith Hyndman, P.E.
khyndman(--nospam--at)engineeringsi.com
Engineering Solutions Inc.
436 Creamery Way, Suite 100
Exton, PA 19341
Phone: 610-423-6237
Fax: 610-524-1317

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