Shear Flow Diagram in J section of thread 507-405875

[chicopee]

What does the shear flow diagram look like for the top flange of the J section. A sketch would be appreciated.

 

[mike20793]

It's a function of the shear in the section, so it starts at it's maximum near supports and goes to zero at the point of zero shear (simply supported spans only). AISC allows us to use a uniform distribution of studs for composite beams and this seems to be the general consensus with welds in built up shapes, though I'm not sure where it is codified (maybe the plate girder provisions in AASHTO). I'm sure someone else will know exactly where.

 

[chicopee]

The problem with the J section of the thread in question is the discontinuity in the "q" value at point of support of the top flange. With "q" being average throughout the cross section, the max value for the left side of the top flange would be q*1 where as the right side would be q*2. Would that be correct?

 

[BAretired]

Yes, that is correct. If a vertical load is placed at the shear center, the bending stress is identical across the 3" width of top flange. The flange force due to bending is twice as much in the 2" leg as the 1" leg and the only way for these forces to get into the flange is by shear across the thickness of the flange. Thus the shear flow is as you have stated.

BA

 

[BAretired]

Upon re-reading your last post, I may have misinterpreted your intent.

With "q" being average throughout the cross section, the max value for the left side of the top flange would be q*1 where as the right side would be q*2. Would that be correct?

If q is the shear flow at the top of the web, then shear flow in the 1" portion is q/3 and shear flow in the 2" portion is 2q/3 where they meet the web. They both taper down to 0 at the flange tip.

The average shear flow in the 1" portion of flange is q/6 and for the 2" portion it is q/3.

BA

 

[chicopee]

Thanks, BAretired , I see it now with this asymmetrical section.