Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations IDS on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Definition of bending & membrane stress..?

Status
Not open for further replies.

ansys1000

Nuclear
Oct 29, 2006
5
Hi!

I am working with ASME section III NF-3000, mainly with the plate and shell type supports.

When looking at the bending vs membrane stress do you look at the whole cross section? For example, consider a console (H-beam) with a moment load. The flanges will take most load but is this stress considered as bending or membrane? This stress is linearly varying over the whole cross-section but very uniform for the flanges. Should this stress be compared to Sm or 1.5*Sm?

Thanks!

Thomas

 
Replies continue below

Recommended for you

An I beam is not generally treated as plate and shell type, though you can do that.
The important point to account for is that, in the 1.5Sm limit for bending, the factor 1.5 is simply the ratio of the plastic modulus of a rectangular section to the elastic one. As it is a rectangular section, it applies only to unreinforced plates and shells.
To follow your example of an I beam, you can consider the flanges as plates, but then the stress is essentially membrane (=constant through thickness) so the limit is Sm. If you used a linear type approach instead of the plate and shell, then by using plastic collapse analysis, you would gain higher allowables, as the ratio plastic/elastic moduli is generally between 1.1 and 1.2 for I beams.

prex
: Online tools for structural design
: Magnetic brakes for fun rides
: Air bearing pads
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor