38 V1.0 • Composite and Non-Composite Design Guide
1.12 Composite Deck-Slab Tables
The composite deck-slab load tables are intended to provide
a designer with easy to use design aids for common compos-
ite deck-slab conditions. The tables provide uniform load in
both allowable and factored superimposed loads. Factored
diaphragm shears are provided for composite deck-slab sys-
tems for lateral design. Diaphragms may be attached with
a variety of attachments to supports including traditional arc
spot welds, power actuated fasteners (PAF), and self-drilling
screws. Factored shear tables for diaphragms with steel
reinforcing and headed shear stud anchors are provided for
high shear diaphragms. All of these tables are supported with
complete composite deck-slab properties including bending
moment, vertical shear, and section properties to aid in the
design of conditions exceeding the scope of the tables.
Superimposed Uniform Load Tables
Uniform superimposed load is the load which the composite
deck-slab can carry in addition to its self-weight. Both allow-
able and factored superimposed loads are provided. The
superimposed load tables assume that the minimum tempera-
ture and shrinkage reinforcement is not adequate to develop
negative bending resistance at supports, therefore all spans
are treated as simple spans.
Most floor systems are designed using allowable stress design
(ASD). The allowable superimposed load tables present the
maximum uniform load based on the allowable bending
strength, allowable vertical shear, and a deflection limit of
L/360. ASD assumes that the superimposed load is primarily
live load and is conservative for dead loads.
Load and Resistance Factor Design (LRFD) is recommended
for conditions in which the majority of the superimposed load
is dead load, and the maximum superimposed load is the
limiting design criteria. The factored superimposed loads in
the tables do not include a deflection check. The designer will
have to check the service load deflection to ensure that the
deflection meets the projects deflection serviceability require-
ments when using an LRFD approach.
Composite Deck-Slab Properties
For conditions exceeding the scope of the uniform load tables,
composite deck-slab properties are provided in the tables.
The properties can be utilized as part of the solution for con-
centrated loads, deflection limits, or spans not included in the
superimposed load tables. The properties include both allow-
able and factored moments, and vertical shear for determining
the capacity of the composite deck-slab system. Cracked,
uncracked, and the average of cracked and uncracked
moment of inertia are provided to assist in determining the
deflection of the deck-slab system.
Factored Diaphragm Shear
The IAPMO ER-329 report presents composite steel deck-
slab diaphragm shears using a load and resistance factor
basis. The diaphragm shears presented are factored shears.
Composite steel deck-slab systems have traditionally been
designed using allowable stress design (ASD), in part because
manufactures have presented allowable shears. These shears
were based on research and engineering studies dating back
to before LRFD was commonly used for steel design. The
factored shears presented in the IAPMO ER-329 report work
seamlessly with the design of the lateral force resting system
for steel and concrete buildings designed using the LRFD
approach. The designer does not have to convert the lateral
forces to ASD when selecting a factored diaphragm from the
Factored shears are provided for a variety of fastener types
to supports. This range of fasteners reflects a full range of
building types that composite deck-slab systems are used in.
Wide Flange Multi-Story Steel Construction: Arc spot
welds are the traditional method for attaching composite
deck to structural steel support members. This method
provides good shear performance and is applicable to
a wide variety of support steel, from heavy wide flange
beams to light weight open web steel joists. Welded steel
headed stud anchors are commonly used for composite
beam design. They are also a good choice to transfer large
diaphragm forces into the composite deck-slab system.
This system is ideal for high shear diaphragms on wide
flange beams and requires the use of welded wire fabric or
reinforcing bars in the slab.
Open Web Steel Joist Mezzanine and Floor Systems:
Composite steel deck-slab systems can be attached with
arc spot welds, however, power actuated fasteners (PAF)
are an ideal cost effective method of attachment to light
structural angles used for open web steel joist framing.
PAF selection is dependent on the support steel thickness.
(See figure 1.13.12)
Cold-Formed Steel Mezzanine and Floor Systems:
Self-drilling screws are the best choice for attaching com-
posite steel deck to cold-formed steel framing. Common
examples of this application include: cold-formed steel
framed multi-story mini-storage buildings, mezzanines,
and conventional cold-formed steel stud, and joist framed
Composite Deck-Slab with Cellular Deck
Cellular composite deck panels can be conservatively
designed using the non-cellular deck-slab tables. The super-
imposed loads, vertical shear, and moment of inertia can be
conservatively used for the design, based on the gage of the
beam section of the cellular profile. This ignores the contribu-
tion of the steel used for the bottom pan of the cellular deck.
Maximum unshored spans for cellular deck-slab system are
listed with the cellular deck section properties.
Allowable Stress Design
Historically, most composite steel deck-slab systems dia-
phragm shear tables have been presented using an allowable
stress design basis. To compare composite steel deck-slabs
designed using ASD basis, it is recommended that the ASD
shear demand be converted back to an LRFD basis. This can
be accomplished by dividing the required allowable shear by
0.7 ASD seismic factor, for seismic controlled designs, or 0.6
ASD wind factor for wind controlled designs.