Repair of large opening in composite decking

[Vertical-Eng]

I have a building with 4.5" concrete over 2" metal decking with a 5'x4' hole cut in it in order to bring up elevator machines. They want this filled in a repaired once the elevator mod is completed. I'm looking for examples or ideas on patching a hole this size.

I figured I could use a slightly oversized metal deck and shore it up and either weld (fillet or spot) around the perimeter. Or I could use concrete screw anchors to attach it. Then epoxy rebar that matches existing with proper development length, then pour concrete.

Please advise on where this might have problems or if you have any recommendations.

Thanks.

 

[RattlinBog]

Do you have nearby girders and enough room to frame the opening with new beams from below? Then attach new decking, place reinforcement, and pour concrete. This would just end up being a non-composite, simple span of slab, if you can live with that for your load demands or other requirements.

 

[Enable]

The method proposed by RattlinBog is the most common that I've seen. If you can just treat it as an infill piece then adding some secondary framing members off the existing is an easy go (shown below with new members in red). Alternatively, overlap new decking and dowel as required for your topping (perhaps roughen edges and add a bonding agent to existing concrete). Shore the decking during the pour and remove shores after the required strength gain is achieved.