Temporary structures are usually constructed in a less precise manner than permanent structures. This is more so in a braced deep excavation where the walls are in constant motion as the excavation progresses downwards. During the assembly of walers and struts, there could be a small gap between the strut-waler connection due to fabrication imperfections. How does one decide whether the fillet weld connecting the strut to the waler need to be designed against compression due to possibility of such a small gap?
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How does one decide whether the fillet weld connecting the strut to the waler need to be designed against compression due to possibility of such a small gap?
In our office, we generally design welds to take compression load due to the exact reason you're specifying. Unless you can ascertain that you have full bearing between the two pieces (i.e., both pieces are milled to mate perfectly), I would say you should check compression on the weld.
For a code reference, the closest I can find is from the AISC 360-10 specification, section J1.1:
The required strength of the connection shall be determined by structural analysis for the specified design loads, consistent with the type of construction specified, or shall be a proportion of the required strength of the connected members when so specified herein.
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$\begingroup$ +1 I agree that you can only neglect compression in weld design if the parts are machined to fit, and that's never going to happen for temporary works such as excavation bracing. $\endgroup$– AndyTJul 31, 2015 at 16:57
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$\begingroup$ It would be good if you provide a code reference. Thanks. $\endgroup$ Aug 1, 2015 at 13:14
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$\begingroup$ @questionoverflow why do you need a code reference? This seems like a clear case of engineering judgment. $\endgroup$– hazzey ♦Aug 2, 2015 at 1:42
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$\begingroup$ @hazzey, engineering judgement comes with experience. It is easier to convince the management the necessity of using heavier welding if there are some supporting references. $\endgroup$ Aug 2, 2015 at 9:37
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1$\begingroup$ @questionoverflow, Please see my edit. I don't think you'll find a code reference that specifically says to design for your situation. It's implicit in structural design that you design for the expected loads based on rational structural analysis. If management doesn't like it, they are free to put their names on the design with their PE stamp. $\endgroup$– grfrazeeAug 2, 2015 at 15:40