×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Compression members governing equation

Compression members governing equation

Compression members governing equation

(OP)
HI all,

I'd like to know when we are determining that the H1-1 and H1-2 shall be used as governing equation in AISC-ASD Combined Stresses section, since there is no any provision for that in AISC-ASD. Most possibly we should calculate both of them and whichever is smaller that is the governing equation, right?

Additionally, related with compression members calculation, which is the most effective way of calculating the effective length factor (K) for steel or RC structures (preferably in equation/computerized manner)?
Googling reveals numerous way of determining it, e.g in British Standarts (5950:2000) gives 0.5 + 0.14*(k1+k2)+0.055*(k1 + k2) (non sway structures), there are also Duan–King–Chen Equations, Newmark  Donnell and French equations, but which one is most effective and gives accurate results? I really wonder how nowadays softwares calculates the effective length factor e.g. Sap2000, StaadPro, if someone can shed some light into that issue I'll appreciate it?

Regards,  

RE: Compression members governing equation

I don't understand a good bit of the question.

I believe the member has to satisfy both the H1-1 and the H1-2 equation, not the lesser of the two, per the provisions for that in AISC-ASD.

I assume you are referring to the K factor in two different planes for the same member?  But in that case, I can't think why you'd need to combine them.

RE: Compression members governing equation

(OP)
>I believe the member has to satisfy both the H1-1 and the H1-2 equation, not the lesser of the two, per the provisions for that in AISC-ASD.
I think so, I completely mis-treated it.

I'm not trying to combine them, I'll calculate the K factor for both principal axes of member. There are numerous ways to do it using alingment charts and formulation manner(which I prefer). AFAIU these ways give the different results(K factors) depending on the shape of structure. Regarding the steel structures which one is most effective way ?

One more thing comes in mind, how the K factor is calculated for a column in a frame if it has obliquely connected girders(connection problem is another issue), how much of their slendernes(girder members) will contribute to the distrubution ratio to Ga and Gb and how ? Can I simply assume the slenderness will be distributed with connection angle ?

Hope that it's clear enough,  

RE: Compression members governing equation

Just to clarify, I assume that we're talking about AISC - ASD 9th edition....not the AISC-13th edition ASD.   

The treatment of K factors will be significantly different between those two codes.  The newer code (13th edition) will normally allow a K value equal to 1.0 provided that your analysis meets certain restrictions.  The older code (9th edition) generally uses idealized assumptions or alignment charts.... see the commentary on Chapter C.   

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources