Page 317 - Structural Steel Designers Handbook AISC, AASHTO, AISI, ASTM, and ASCE-07 Design Standards

Brockenbrough_Ch07.qxd 9/29/05 5:16 PM Page 7.1

Source: STRUCTURAL STEEL DESIGNER'S HANDBOOK

CHAPTER 7

FLOOR AND ROOF SYSTEMS

Daniel A. Cuoco, P.E.
President
Thornton-Tomasetti Group, Inc.
New York, New York

Structural steel framing provides designers with a wide selection of economical systems for floor and
roof construction. Steel framing can achieve longer spans more efficiently than other types of con-
struction. This minimizes the number of columns and footings thereby increasing speed of erection.
Longer spans also provide more flexibility for interior-space planning.
Another advantage of steel construction is its ability to readily accommodate future structural
modifications, such as openings for tenants’stairs and changes for heavier floor loadings. When rein-
forcement of existing steel structures is required, it can be accomplished by such measures as addi-
tion of framing members connected to existing members and field welding of additional steel plates
to strengthen existing members.

FLOOR DECKS

The most common types of floor-deck systems currently used with structural steel construction are
concrete fill on metal deck, precast-concrete planks, and cast-in-place concrete slabs.

7.1 CONCRETE FILL ON METAL DECK

The most prevalent type of floor deck used with steel frames is concrete fill on metal deck. The metal
deck consists of cold-formed profiles made from steel sheet, usually having a specified minimum
yield strength of at least 33 ksi, with 40 ksi becoming more common. Design requirements for metal
deck are contained in the American Iron and Steel Institute’s “North American Specification for the
Design of Cold-Formed Steel Structural Members.” (See Chap. 9.)
The concrete fill is usually specified to have a 28-day compressive strength of at least 3000 psi.
Requirements for concrete design are contained in the American Concrete Institute Standard ACI
318, “Building Code Requirements for Reinforced Concrete.”
Sheet thicknesses of metal deck usually range between 24 and 16 ga, although thicknesses out-
side this range are sometimes used. The design thicknesses corresponding to typical gage designa-
tions are shown in Table 7.1.
1
Metal deck is commonly available in depths of 1 / 2, 2, and 3 in. Generally, it is preferable to use a
deeper deck that can span longer distances between supports and thereby reduce the number of beams
7.1
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