ISpot welding thin trapezoidal sheets(floor deck) acceptable? 2

[IJR]

We usually specify 0.1cm thick 5cm rib height for trapezoidal sheet to form a floor deck with a total 10cm concrete(5cm in ribs + 5cm additional).

We do not usually use studs(technique not well established here) and instead we use self-tapping screws to attach the sheets to beam flanges, with ribs perpendicular to beam.

Some erectors have told me that they dont usually use screws and instead they simply weld the sheet to the beam flange.

Is this an acceptable procedure. Isnt the 0.1 cm thick sheet too thin for this weld.?

Any comment will be highly appreciated.

IJR

 

[Taro]

Yes, this is a very common practice in the U.S.. Most deck manufacturers have recommendations for puddle welding their product. Also, AWS D1.3 Structural Welding Code - Sheet Steel is a good reference.

 

[JAE]

In the U.S.A. roof decks are attached to supporting steel framing with welds, screws, or power driven fasteners.

In the case of welds, the Steel Deck Institute recommends not using welded connections for 22 gage (0.749 mm) or thinner deck material.

Normally, the welder applied a spot weld of either 5/8" (16mm) or 3/4" (19mm) to the deck, burning through the deck and developing a circular "puddle" weld. Basically, the weld contact between deck and support is a circular ring with the center area of deck burned away.

We normally prefer the screws or fasteners as the welders come in a variety of skill levels. I've seen projects where I've walked into the building during the day, looked up and saw stars.....essentially places where the welder missed the beam or joist and burned through the deck. Difficult to visually verify every deck weld, although SDI provides a higher level of shear capacity for welds as opposed to screws.

Here's a paragraph from a U.S. deck manufacturer:

"Welds should be made by qualified operators following AWS D1.3 specifications. Approximate checks on weld quality can be made by placing one end of a long panel over a support and attaching it only to that support with two welds six inches (150mm) apart. The far end of the panel can be moved in the diaphragm plane by a workman until shear distress is noted in the weld. The welds should be sufficient to cause local distortions in the panel around both the welds and should show good perimeter contact between welds and the panel. For 22, 20 and 18 gage (0.75mm, 0.91mm, 1.2mm) panels, the weld should not shear aacross its contact plane on structural supports else the welding temperature may have been too low for adequate penetration."

Hope this helps, IJR!

 

[Taro]

Good info, JAE. We require the welder to be light gage certified, so quality control is better. Also note that thin material can be welded if you provide weld washers.

 

[IJR]

Taro and JAE

Do you want to tell me about weld washers?

Thanks for the great inputs

IJR

 

[Taro]

Weld washers are pieces of steel (usually 14 gage) with holes in the middle that are placed on top of the deck. They provide extra material so that plug welds can be made where otherwise the puddle weld would burn through the thin decking.