1. Scope
This specification pertains to composite steel floor deck. Composite steel floor deck is cold formed steel deck which acts as a permanent form and as the positive bending reinforcement for the structural concrete. When suitably fastened, the steel deck also acts as a working platform for the various trades. After the concrete hardens, the steel deck and the concrete are interlocked by the shape of the deck, mechanical means, surface bond, or by a combination of these means.
2. Materials
2.1 Composite Steel Deck:
Composite steel floor deck shall be fabricated from steel conforming to Section A3 of the 1996 edition of the American Iron and Steel Institute, Specifications for the Design of Cold Formed Steel Structural Members, (AISI Specifications). The steel used shall have a minimum yield point of 33 ksi (230 MPa).
2.1a: Tolerances:
Panel Length: Plus or minus 1/2 inch (12 mm).
Thickness: Shall not be less than 95% of the design thickness.
Panel cover width: Minus 3/8 inch (10 mm), plus 3/4 inch (20 mm).
Panel camber and/or sweep: 1/4 inch in 10 foot length (6 mm in 3 meters).
Panel end out of square:
1/8 inch per foot of panel width (10 mm per m).
Commentary: Most composite steel floor deck is manufactured from steel conforming to ASTM Designation A611, Grades C and D or from A653-98a, Structural Steel.
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If the published product literature does not show the uncoated steel thickness in decimal inches (or millimeters), but lists gage or type numbers, then the thickness of steel before coating with paint or metal shall be in conformance with the following table:
| Type No. |
Design Thickness |
Minimum Thickness |
| In. |
mm |
In. |
mm |
| 22 |
.0295 |
0.75 |
.028 |
0.71 |
| 21 |
.0329 |
0.84 |
.031 |
0.79 |
| 20 |
.0358 |
0.91 |
.034 |
0.86 |
| 19 |
.0418 |
1.06 |
.040 |
1.01 |
| 18 |
.0474 |
1.20 |
.045 |
1.14 |
| 17 |
.0538 |
1.37 |
.045 |
1.30 |
| 16 |
.0598 |
1.52 |
.051 |
1.44 |
The tolerances reflect fabrication processes for steel deck products. Variation in cover width tolerances may be from trucking, storage or handling.
2.1b Finish: The finish on the steel composite deck shall be as specified by the designer and be suitable for the environment of the structure.
Commentary: Since the composite deck is the positive bending reinforcement for the slab, it must be designed to last the life of the structure; a minimum recommended finish is a galvanized coating as defined in ASTM A653-98a, G30 (Z090).
3. Design (Deck as Form)
3.1: The section properties for the steel floor deck (as a form in bending) shall be computed in accordance with the AISI Specifications.
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3.2a: Allowable Stress Design (ASD): The interaction of shear and bending shall be considered in the calculations. Bending stress in the deck shall not exceed 0.6 times the yield strength with a maximum of 36 ksi (250 MPa) under the combined loads of wet concrete, deck, and the following construction live loads: 20 pounds per square foot uniform load (1 kPa) or 150 pound concentrated load on a 1’-0” wide section of deck (2.2 kN per m). See Figure 1.
3.2b: Load and Resistance Factor Design (LRFD): The load factors for the construction shown in figure 1 and the resistance factors for bending, shear, and interior bearing shall be as required in the 1996 AISI Specification.
Commentary: The loading shown in figure 1 is representative of the sequential loading of wet concrete on the form. The 150 pound load (per foot of width) is the result of distributing a 300 pound man over a 2 foot width. Experience has shown this to be a conservative distribution and, if welded wire reinforcing is present the distribution is greater than 2 feet. The metric equivalent of the 150 pound load is 2.2 kN per meter of width. For single span deck conditions, the ability to control the concrete placement may be restricted and a factor of 1.5 is applied to the concrete load to address this condition; however, in order to keep this 50% load increase within a reasonable limit, the increase is not to exceed 30 psf (1.44 kPa)
3.3 Calculated theoretical deflection of the deck, as a form, shall be based on the load of the concrete (as determined by the design slab thickness) and the load from the steel deck, uniformily loaded on all spans, and shall be limited to L/180 or 3/4” (20 mm), whichever is smaller. Deflections shall be relative to supporting members.
See Figure 2.
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