Combined Welded and Bolted Steel Connection
Combined Welded and Bolted Steel Connection
(OP)
If I am making a wide flange beam to column connection and I provided a CJP weld at the flanges to develop moment, am I allowed to provided a bolted web plate connection as well to take the shear force?
I remember reading somewhere that you can't do that, because you may have to fail the welds in flanges to engage the bolts in shear at web.
I remember reading somewhere that you can't do that, because you may have to fail the welds in flanges to engage the bolts in shear at web.






RE: Combined Welded and Bolted Steel Connection
RE: Combined Welded and Bolted Steel Connection
I thought it was just a seismic thing as well. However, I want to make sure it does not apply to all types of loading.
RE: Combined Welded and Bolted Steel Connection
Perhaps in a static load application, you would fail the flange weld locally at the center of the flange, distribute the shear load to the bolted plate, and still have capacity left in the remaining flange weld? Obviously, under dynamic loading, this would be a prime location to initiate some kind of terrible unzipping failure mode.
Right or wrong, that's still a very common detail in many regions of North America. Could you start off with a bolted plate for erection and then have it welded up after the fact?
RE: Combined Welded and Bolted Steel Connection
RE: Combined Welded and Bolted Steel Connection
I'm not sure if you can do it for seismic connections. I know the FEMA documents show the web bolted, but the more current AISC prequalified connections don't appear to show the web bolted. Regardless, for non-seismic connections, bolt away.
RE: Combined Welded and Bolted Steel Connection
RE: Combined Welded and Bolted Steel Connection
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Combined Welded and Bolted Steel Connection
RE: Combined Welded and Bolted Steel Connection
Do the bolts have to be slip-critical, even for non-seismic loads? If so, where in the code does it say this?
RE: Combined Welded and Bolted Steel Connection
RE: Combined Welded and Bolted Steel Connection
RE: Combined Welded and Bolted Steel Connection
Paddingtongreen, the 2005 specification changed the long-standing rule that slip critical bolts in the same faying surface can share the load with weld. This has been acceptable to the code forever, but recent research has shown that it might yield unconservative results. The 2005 specification says that the bolts must be checked in bearing, with only half of their capacity used for resistance, when combined with welds. (Again, this does not apply to Abusementpark's connection.)
RE: Combined Welded and Bolted Steel Connection
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Combined Welded and Bolted Steel Connection
RE: Combined Welded and Bolted Steel Connection
RE: Combined Welded and Bolted Steel Connection
So at the point just before the welds are made, the bolts are in bearing contact with the shear plate / clip angles. Then the welds are made. From that point on, the welds will share the load with the bolts. We just assume that they do not, hoping that the shear connector is stiff enough to no deform under the shear load imposed after welding. If there is any deformation of the shear connector, then the welds will definitely start sharing a significant portion of the shear load.
RE: Combined Welded and Bolted Steel Connection
Well technically you are right and I agree with you 100%. However, when we detail the connection we design the shear plate/dbl angle for the shear loading (w. bolts), and the flange for the flange force due to moment, and that's that, no combined loading anywhere... I know that most of the stress due to shear and moment combination is closer at the flanges and the Full Pen welding and it bothers me to know that some engineers ask us to take the moment into the beam web when the flanges are failing at the full-pen weld location due to flange forces alone... I can't wait for more technical papers to come out with a design simple enough to make it practical... :)
RE: Combined Welded and Bolted Steel Connection
And what I mentioned above is the topic of the discussion I opened earlier in the topics. do you have any ideas?
RE: Combined Welded and Bolted Steel Connection
Generally speaking, I prefer to think of structural behavior in terms of "what is really happening" rather than "what we assume is happening". Some goes for pin vs fix connections, particularly column base connections. I would much rather create a 3D FEA model to see what is really happening, than just assume my column base is pinned (or fixed). Of course, time does not always allow me this luxury. But I see too many younger engineers just going on the assumption that their college professor (or text book) told them to use "all the time".
RE: Combined Welded and Bolted Steel Connection
RE: Combined Welded and Bolted Steel Connection
I do not believe the "pinned base" assumption has yet proved to be one of any serious consequence.
RE: Combined Welded and Bolted Steel Connection
My company has standard "pinned" column base plate details. They show the bolts clustered at the center of the column section to reduce the moment transfer.
In my opinion, this just exacerbates the prying / tension forces on the anchor bolts that don't know that they're not supposed to be restraining column rotations. Then they fail prematurely and indeed become pinned. Of course, baring the provision of other transfer mechanisms, you've also lost your ability to transfer shear through your pinned base. Ouch.
I get nervous about assuming a pinned condition unless the failure mode of the bolts is bolt yielding. And it's tough to make that happen with practical pedestal dimensions and the Appendix D stuff.
Some folks in my office will do a little of both. They design the frame assuming pinned column bases and then design the base plate to take 50% or so of the expected moment were the base fixed. The 50% is entirely arbitrary of course.