Tapered Beams

[MikeC7920]

Hello,

im a relatively new engineer and i was asked by a co-worked if i knew how to design tapered beams (beams with varing inertias)

i have never done any deisgn of tapered beams and have no idea how to go about it

my main questions are what values do i use for calculations, average I or local I (would it be necessary to integrate :S) and for the calculation of compression resistance do i use local values or can average values suffice - this also makes me wonder does the neutral axis move downward with the beams taper along its length under a uniformed distributed load (if so is this just the slef weight that causes this)

Does anyone have solid(error free) examples of this that i can reference?

this would be much appreciated
thank you in advance,
Mike

 

[DST148]

Try recent thread507-316278.
You may also search other threads on this topic.

 

[spats]

Web-tapered members were previously covered in Appendix F of the 1989 AISC Specification. I can't find it in the 2005 Specification.

 

[ajh1]

AISC Design Guide 25 covers web-tapered sections. That document has effectively superceded the old Appendix F.

 

[JoshPlumSE]

They got removed from the specification with the 3rd edition of LRFD.

However, AISC and MBMA have released a new design guide for the design of tapered wide flanges. I would say this is the new standard for the design of these members. The design process is a bit more involved / complex than it used to be.... Though it is probably also a lot more rational. I don't think it imposes as severe restrictions on these members as the old ASD and LRFD specifications did.

 

[JoshPlumSE]

I meant to put this link in my previous post.

http://www.aisc.org/store/p-2116-design-guide-25-frame-design-using-webtapered-members.aspx

Josh