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Re: single angle compression members

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Ken:

Try the AISC specification "LRFD Specification for Single-Angle Members".
The 2000 Edition is bound in the 3rd LRFD Manual.  It is also available for
free download at AISC.ORG.

Keep in mind that the angles used in transmission towers are often gage
material, in the realm of AISI, not AISC.  Local buckling effects of
"slender compression elements" often dominate the design, making the
loading eccentricity less important.

Rick Drake, SE
Fluor, Aliso Viejo, CA

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                      "Ken Peoples"                                                                                                    
                      <kspeoples(--nospam--at)lvta.net      To: "Seaint" <seaint(--nospam--at)seaint.org>                                                        
                      >                                                                                                                
                      01/21/03 05:05 AM        cc:                                                                                     
                      Please respond to                                                                                                
                      seaint                   Subject:  single angle compression members                                              
                                                                                                                                       
                                                                                                                                 ..... 
                                                                                                                                       




Ever since I came across the section on single angle struts in AISC's ASD
9th Edition (page 3-55), I have been careful not to just do a calc. using
kl/rz and calculate Fa to determine the allowable axial compression load.
For example, the capacity of the L2x2 in Example 10 based solely on kl/r
would be 13.3 kips, but when the connection eccentricities are taken into
account, the allowable load is only 4.5 kips.  Obviously, this approach has
a significant impact on single angle compression member sizing.

Recently, two of my co-workers attended AISC's seminar on bracing and had a
chance to discuss the issue with Joseph Yura.  At that time, Joseph
indicated that there has been extensive testing of single angles by the
transmission tower industry (and others) and they have found the AISC
approach to be overly conservative.

I would like to find out where I can get accepted guidelines that
incorporate this test data.  Joseph also indicated that AISC is working on
this.  If this is the case, would it be possible to get an advance copy of
what they are proposing? (Charlie?)  We have a number of trusses for
conveyors that we are designing and I'm sure that this information would
result in considerable savings.

Thanks in advance,

Ken


Kenneth S. Peoples, P. E.
Lehigh Valley Technical Associates
1584 Weaversville Road
Northampton, PA 18067-9039
Phone: (610) 262-6345
Fax: (610) 262-8188
e-mail: kpeoples(--nospam--at)lvta.net






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