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Re: Bolt bearing on beam web

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At 03:42 AM 12/16/2004 -0800, you wrote:
List,

Consider a few W16X40 and W16X26 beams in a floor.
SC bolts have specified.
A fully bolted standard double clip angle connection
has been used for the beam to column connection.
The clips are bolted to the beam web and also to the
supporting column flange or web.
The reactions were not given in the plans but were
listed in general for various nominal beam depths.
A common value was given for all W16 beams.

I was checking the adequacy of the bolted connections.
The bolts (in double shear) were okay for both W16x40
and W16x26

While checking the bearing of the bolts on the beam
web, I found that the W16x40 (web thickness 0.305
inch) passed, while W16x26 (with web thickness of 0.25
inch) marginally failed.

I wish to ignore this.
My reasoning may please be examined and commented on.

1)The reaction given in general may merely be an upper
limit. In the case of the W16x26 beam it will most
likely be less than the reaction in beam W16x40. I
don't see any reason for extra end shear in the W16x26
beams. There is no post sitting on the  beam or a
secondary beam framing into it near the end.

2)This is an SC connection. So the bolts will be
tightened to such an extent that the clip angle  faces
will press firmly on either side of the beam web.
The beam web alone will not be subjected to bearing
against bolt surfaces. Two clip thicknesses pressed
firmly against the web on either side  will "assist"
the web. The combined thickness of two clips plus web
thickness is VERY Safe in bearing. We should not
single out the beam web thickness alone for this
bearing check due to the tremendous clamping force
introduced by the SC connection.


I agree with your analysis. Anyone can enter numbers in a formula and compare the answer to a standard value. I think this is a prime example of why engineers are engineers. It's the ability to look at the larger picture to determine the adequacy of a design. (I suspect if you were to calculate the friction force induced in the end clamp, plus your web bearing, with an appropriate factor of safety, you would likely find the necessary shear resistance you need.)



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