Web Buckling

[KHCEng]

I have a machined rib and want to check the web buckling. What dimension should I use for the web width? Usually I would use the dimension from the mid-line of the surrounding stiffeners but a less conservative view may be to use the dimension from the inside surface of the stiffeners. What is the general view?
Also rather than assuming SS edge conditions is there a way to calculate a rotational stiffness value so that the edge condition is somewhere between SS and fixed.

 

[rb1957]

i think stiffner CL are commonly used to define the panel size, and this'd allow you to claim the rotational stiffness of the stiffener. the more you move away for here (stiffener inner face or the tangent of the fillet rad), the less stiffness you can get (reasonably). more difficult is when you have a thickness pad-up near the stiffener.

if the stiffener is thicker than the panel then you have more rotational support along the edge of the panel. fully fixed is clearly the less conservative thing to assume. one thing to consider is waht are the consequences of buckling ... if a panel on the rib buckles (elastically) would the rib collapse ?

Quando Omni Flunkus Moritati

 

[crackman]

The following paper presented at the 6th FAA/DOD?NASA conference on Aging Aircraft in 2002 has a good comparison with testing between a riveted stiffened web, an integral web, and an integral web with cutouts. It depicts the points of max bending stress near the stiffener, at the start of the radius, in the post buckled condition. It was a good reference for me years ago when doing a fatigue analysis of a rear spar which buckled well below limit load. Good luck.

"Investigations of Post Buckling Behaviors of Monolithic Bulkhead by Test and Analysis for Large Transport Aircraft" by C.Hsu, Tzon, and Chan, The Boeing Company, Phantom Works."

 

[KHCEng]

crackman, thanks for the reference, "Investigations of Post Buckling Behaviors of Monolithic Bulkhead by Test and Analysis for Large Transport Aircraft" by C.Hsu, Tzon, and Chan, The Boeing Company, Phantom Works."
A quick search on google did not find anything. Can you suggest how I get a copy.