Source of Load Criteria to design Compression flange bracing?
Source of Load Criteria to design Compression flange bracing?
(OP)
For as long as I can remember, the load used to design compression flange bracing of I-beams and/or trusses was 2% of the compression flange load.
I am now being challenged to show where this value comes from. Is it written in code, or is it simply an industry accepted standard.
Also, what premise is this 2% criteria based upon. Does it change if the loading condition is due to loads generated while the structure is being crane lifted?
Thank you in advance for your response.
I am now being challenged to show where this value comes from. Is it written in code, or is it simply an industry accepted standard.
Also, what premise is this 2% criteria based upon. Does it change if the loading condition is due to loads generated while the structure is being crane lifted?
Thank you in advance for your response.






RE: Source of Load Criteria to design Compression flange bracing?
"On the basis of a study of a number of hypothetical initial-curvature and load mis-alignment conditions, Zuk (Reference 1) confirms the customary practice of designing each lateral support for 2% of the total compressive force that exists concurrently in the compression flanges of the laterally braced beam or girder. ...... Recent studies by Lay (Reference 2) have demonstrated the correctness of this rule as extended to plastic design."
Reference 1: Zuk, W. "Lateral Bracing Forces on Beams and Columns," ASCE Journal, Engineering Mechanics Division, Vol 82, No EM3 (July 1956)
Reference 2: Lay, M.G., and Galambos, T.V., "Bracing Requirements for Inelastic Steel Beams," ASCE Journal, Structural Division, Vol 92, No ST2 (April 1966) p. 207
Jim Emanuel, S.E.
RE: Source of Load Criteria to design Compression flange bracing?
RE: Source of Load Criteria to design Compression flange bracing?
RE: Source of Load Criteria to design Compression flange bracing?
RE: Source of Load Criteria to design Compression flange bracing?
For seismic application, 2002 AISC Seismic Provisions talk about 2% in various sections and 6% at links of eccentrically braced frames. The new AISC Seismic Design Manual may have updated information but I do not have a copy yet.
RE: Source of Load Criteria to design Compression flange bracing?
RE: Source of Load Criteria to design Compression flange bracing?
Um, did I say (or imply) that it didn't? Or is there something in my post that is incorrect?