Working Stress Design Web Bearing Capacity 1

[youngstructural]

Hello All;

I need to know a wee working stress design trick... I was once taught a quick little ditty of a working stress check to see if you need a stiffener to prevent web cripling. Has anyone else heard of this? Does anyone know the trick I'm talking about; Preferably with reference source?

Otherwise I would appreciate if anyone could tell me the current WSD check for knowing if your web needs stiffening for bearing/web crippling. I am not talking about support to the critical flange, or any design of the stiffeners proper, just the check to see if you need a stiffener.

Thanks in advance,
Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[BAretired]

Hello YS,

I have a snow covered driveway which you are welcome to shovel any time you feel so inclined. My roof is also covered with snow and all the downspouts are frozen solid, so in these suddenly warm temperatures, the gutters are dripping all over the driveway and will no doubt freeze tonight creating a skating rink for tomorrow.

Going back to the 1969 CSA S16 code, "Webs of rolled beams and welded plate girders shall be proportioned so that the compressive stress at the web toe of the flange to web fillets resulting from concentrated loads not supported by bearing stiffeners, shall not exceed 0.75Fy where Fy is the specified minimum yield point of the web; otherwise, bearing stiffeners shall be provided. The stress shall be calculated as follows:

(a) for interior loads,

R/(w*(N + 2k))

(b) for end reactions,

R/(w*(N + k))

where R = concentrated load or reaction (kips)
w = web thickness (inches)
N = length of bearing (inches)
k = distance from outer face of flange to web toe
flange-to-web fillet (inches)"

I'm not sure if this is what you remembered or not. All the best in N.Z.

Best regards,

BA

 

[youngstructural]

YES! Thank you BA... So much simpler in WSD terms than in Limit States; But the world must progress, and given computers the additional complexity of the Limit States Design is not really onerous. The WSD method is certainly quick, easily applied, and probably conservative given that LSD is always touted as being so much more efficient.

I intend to check this against the current Limit States provisions, however I'm confident it will be a conservative check... Perhaps I'll post the results of my analysis.

Thanks again,
Cheers,

YS

P.S. My office has to be 28 degrees if it's one... They've turned off the Air Con in preparation for winter (old offices, centrally controlled plant) and today just happens to be reasonably, and unseasonally, warm.... I think I'd take you up on the driveway if it meant I could get out of this heat! *smiles*

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...