aect250 lecture 19

Lecture 19 - Page 1 of 8

Lecture 19 Steel Deck Steel deck, or sometimes called metal deck is used in steel framed construction as an intermediate structural system to distribute floor and roof loads to supporting beams. Decking is typically fastened to the steel supporting members by either puddle welds or powder-actuated fasteners. Although made of steel, it is NOT considered to be structural steel. Decking is corrugated having a typical cross-section resembling: The Steel Deck Institute, SDI, was established in 1939 in an effort to regulate the design, manufacture and installation of steel deck. Manufacturers complying with SDI specifications include Vulcraft, Canam Steel Corp. and United Steel Deck, Inc. Types of Steel Deck

There are 3 general types of steel deck roof deck, non-composite floor deck and composite deck. 1. Roof Deck

Roof deck is used primarily to carry lightweight roof construction. It is characterized by having relatively narrow bottom flutes so that there is a wider top flute to maximize the surface contact with rigid insulation. It comes in heights ranging from 1 up to 3 and in thicknesses ranging from 24 gage (thinnest) up to 16 gage (thickest). Depending on the section, roof decking can span as much as 15-0. Acoustical deck is available to control sound transmission through the decking. It is used for auditoriums, schools, etc., and is obtained by adding fiber sound-absorbing batts between the vertical webs of the decking. In addition, roof deck is available as cellular deck for use in placing electrical services or exposed underside. Data relating to roof deck may be found in the Vulcraft catalog p. 3 18.

Panel width = 24 36

Deck height Top flute

Bottom flute


Roof Deck Fastened to Steel Bar Joist

Roof Deck screwed or puddle-welded to top chord of steel joist

Built-up roof membrane

Rigid Insulation


2. Non-Composite Floor Deck

This type of deck essentially acts as a form to carry the concrete slab. It offers no additional strength to the structural steel beam as composite construction would. It ranges in height from 5/8 up to 3 and thicknesses of 26 gage up to 16 gage with spans up to 15-0. It is also available as acoustical deck or as cellular deck. Data relating to roof deck may be found in the Vulcraft catalog p. 19 - 40.

Welded wire mesh in concrete slab


3. Composite Floor Deck

Similar to non-composite deck, except composite deck is used for composite steel construction. Typically, the decking has built-in perforations that aids in the bonding to concrete.

Composite Floor Deck with headed shear studs welded to beams


Roof Deck Example GIVEN: A 1 Type F (intermediate rib) roof deck is to be used in a 3-span condition with a 7-0 span. The SERVIVE roof loads are as follows:

SERVIVE roof Dead Load = 15 PSF SERVICE roof Live Load = 20 PSF SERVICE roof Snow Load = 40 PSF SERVICE roof Wind Load = -8 PSF (uplift)

REQUIRED: Design the lightest-weight 1 Type F roof deck using the Vulcraft catalog.

Step 1 Determine maximum unif. load on deck:

Utilizing the 6 allowable stress design load combinations from the IBC Section 1605.3.1:

1) D 2) D + L 3) D + L + (Lr or S or R) 4) D + (W or 0.7E) + L + (Lr or S or R) 5) 0.6D + W 6) 0.6D + 0.7E

where: D = Dead Load = 15 PSF Lr = Roof Live Load = 20 PSF S = Snow Load = 40 PSF W = Wind Load = -8 PSF

7-0

3 spans (min.)

7-0 7-0

Steel roof deck

Steel support beams


Check all 6 load combinations and select worst case total load:

1) D = 15 PSF 2) D + L = 15 PSF 3) D + L + (Lr or S or R) = 15 + 20 = 35 PSF 4) D + (W or 0.7E) + L + (Lr or S or R) = 15 + 40 = 55 PSF 5) 0.6D + W = 0.6(15) + (-8) = 1 PSF 6) 0.6D + 0.7E = 0.6(15) = 9 PSF

Step 2 Refer to the Vulcraft Catalog page 4 for 1 Type F deck:

From Table above, use Vulcraft 1 Type F 19 Gage Roof Deck Allow. Load = 59 PSF > 55 PSF

3 span

Use

7-0 span


Non-Composite Floor Deck Example GIVEN: A floor framing plan for an office building is as shown below. The slab is 5 normal-weight concrete over 2.0 C Conform non-composite 2 deck as manufactured by Vulcraft. The superimposed SERVICE live load = 50 PSF and a total superimposed SERVICE dead load (excluding slab weight) = 38 PSF. REQUIRED: Design the lightest weight 2.0 C Conform non-composite deck assuming 3-span condition.

Step 1 Determine the uniform load on the decking:

Utilizing the 6 allowable stress design load combinations from the IBC Section 1605.3.1:

1) D 2) D + L 3) D + L + (Lr or S or R) 4) D + (W or 0.7E) + L + (Lr or S or R) 5) 0.6D + W 6) 0.6D + 0.7E

where: D = Dead Load = Slab wt. + Superimposed Dead Load = 51 PSF + 38 PSF = 89 PSF L= FloorLive Load = 50 PSF

Using Load Combination 2 from above:

Total Uniform Load = D + L = 89 PSF + 50 PSF = 139 PSF

4 @ 6-0 = 24-0

See Vulcraft catalog p. 28 for slab wt.


Step 2 Refer to Allowable Uniform Load table from Vulcraft p. 29:

No. of Spans = 3 Clear Span = 6-0 Total Uniform Load = 139 PSF

Step 3 Refer to Reinf. Conc. Slab Allow. Loads table Vulcraft p. 28:

Total Slab Depth = 5 Clear Span = 6-0 Superimposed Unif. Load = Total Load Slab Wt. = 139 PSF 51 PSF = 88 PSF

5

Use 2C20 Allowable unif. load = 173 PSF > 139 PSF

Use 6x6-W2.1xW2.1 W.W.F. Allow. load = 107 PSF > 88 PSF

Steel support beam

5 conc. slab over 2 - 20 Gage non-composite metal deck reinf. with 6x6-W2.1xW2.1 W.W.F.

aect250 lecture 19

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