If its pinned, a spot weld at the corners and at maybe at 12" intervals.
If fixed, a filet weld all around should do it.

Thanks for the reply.
I was tginking the same but are you sure as I still have my doubts.

Fixed means no rotation at the support. Just because you weld it to something doesn’t mean that something can’t rotate. Assuming a fixed condition is not conservative.

For hinged, don't weld it at all. Under load, the corners will lift.
For fixed to supports, i.e rigidly connected, fillet weld all around plate. If supports rotate, plate is not fixed.

BA

My earlier reply seems to have gone...

Checkered plate is often used for moveable covers and would be considered pinned all around. Sometimes they are loose plates with a 'handle or ring' for lifting, sometimes they are hinged on one side, again with a 'handle or ring' for lifting. It's not often that the edges are fixed. Permanent covers can be welded in place and the fixity caused by the distance from the edge of the opening to the location of the weld. This may be an inch or two and for a 1/4 checkered plate, this would create a relatively fixed edge condition. Also if the checkered plate is part of a floor and has a series of channels or angles in a grid pattern as support... the interior portions would be almost a fixed end condition.

Since checkered plate covers are nearly always not fixed at the perimeter, nearly always they fall into the pinned condition. The corner lever moments are nearly always small and negligible.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

As others have said in most case it really would seem fairly unconservative to approach your typical checker plate installation with fixed edges. I think I've seen the spreadsheet online, I've never really seen much good guidance for online engineers unfamiliar with design approaches to checker plate flooring. If anybody has a good guidance source that they use I'd be enthusiastic to see it. My checker plate designs originally came from rules of thumb and have evolved to almost 'what works'. Checker plate design is mostly about deflection control in what I do.

Regarding edge fixities, only a tiny amount of edge movement required to effectively make checker plate a pinned connection and the joists are often of lower torsional rigidity too. So a fixed edge assumption can end up quite unconservative.

Thanks for replies.