Uncapped Rectangular HSS Bearing on Masonry Wall 2

[waytsh]

Hi All,

I think this is a simple question but I am struggling with it nevertheless. Let's say you have an HSS beam with an open end (no end cap) and it is bearing on a masonry wall (or any other type of support). What equations are you using to determine the capacity of the HSS where it bears on the supporting element? I am using the 2010 AISC Specification.

Thanks!

 

[dik]

Just the area of the HSS... not really a good idea, maybe for light loads only. In a pinch you can increase the concrete bearing by considering the Area Loaded and the Area not loaded.

Dik

 

[KootK]

I like a bearing plate too but not all situations suit it. I guess you'd want to adapt the normal, wide flange checks to deal with:

1) Substrate bearing stresses.

2) Flexure in the bottom wall of the HSS.

3) Buckling in the side walls of the HSS.

 

[structSU10]

I would use the checks from design guide 24:

 

[waytsh]

I am not worried about the supporting surface at this time. That is a topic for another thread as I may have a situation where one end will be on a steel stiffened seat.

So basically take the Web Local Yielding and Web Local Buckling Checks in J10 and use 2t_w instead of t_w?

What flexure are you referring to in the bottom wall of the HSS? The uniform bearing pressure applied over the contact surface?

Thank you for the replies.

 

[JLNJ]

The shear is centered on the sidewalls, but the support reaction is on the flat of the bottom. I’m guessing that it’s this eccentricity which is giving you heartburn.

I would check flexure across the base with a moment arm of 2t. So 1/2 the reaction (two sides to a tube) times the radius length.

 

[waytsh]

StructSU10, good point. It does appear these equations allow for adaptation to my condition although I expect K1-2 and K1-3 will not be a factor in my scenario. Any idea what the difference is between a T-connection and a Cross-Connection for equations K1-5 and K1-6? Is K1-5 if the pate is only on one side and K1-6 if there is an opposing plate on the bottom?

 

[structSU10]

the T v cross is for branch loads for a truss situation. It is based on the force delivered to the chord by web members, so is likely not applicable.

The main thing I might do is make sure the effective length takes into account the end of the HSS - I believe it assumes you are towards the middle. Could be like the chapter J for steel beams where the capacity is cut in half or something.

 

[KootK]

So basically take the Web Local Yielding and Web Local Buckling Checks in J10 and use 2tw instead of tw?

Yup, that's what I had in mind.

What flexure are you referring to in the bottom wall of the HSS? The uniform bearing pressure applied over the contact surface?

Yup, see sketch below. I'd do this using elastic section properties in an attempt to make the thing stiff enough to assume uniform-ish bearing stresses.