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RE: Steel Connections

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Title: RE: Steel Connections

<<  aL=3 in. (distance from weld line to bolt line)  >>

>Why are these tables formulated with such an excessive aL distance?  In
>practice this distance is more on the order of 1 3/4" using minimum edge
>distances and minimum weld clearances.

The Astaneh procedure for the design of shear tabs (single-plate connections) is a prescriptive one that injects a little bit of the seismic design philosophy for lateral framing into the shear tab. What I mean is, there are many dimensional requirements like the 3 in. distance from weld line to bolt line, that are intended to ensure that the shear tab will have ductile failure modes controlling over brittle ones. that way, the shear tab will take a lot of punishment before it can no longer carry gravity loads.

More specifically.... the recommended plate dimensions, edge distances, spacings and distance between the weld line and bolt line are all intended to ensure that the plate can deform as the bolts bear against the holes. The welds are sized to develop the strength of the plate so weld rupture will not control. The plate thickness is limited as a function of bolt diameter so that bolt bearing deformations will occur before bolt shear.

If you choose to use an alternative approach or violate one or more of these recommendations, you probably still have a connection that can carry the design load. But you will likely be changing the modes that control the failure of the connection, and possibly shifting a rupture limit state to the front of the list.

Charlie