Page 257 - Structural Steel Designers Handbook AISC, AASHTO, AISI, ASTM, and ASCE-07 Design Standards

Brockenbrough_Ch05.qxd 9/29/05 5:12 PM Page 5.37

CRITERIA FOR BUILDING DESIGN

CRITERIA FOR BUILDING DESIGN 5.37

3. The slab thickness above the steel deck must be at least 2 in (50 mm).
4. The deck must be anchored to all supporting members, with anchorage at a maximum spac-
ing of 18 in (460 mm). Stud connectors, a combination of stud connectors and arc spot (puddle)
welds, or other suitable approved devices may be used for anchorage.
5. For deck ribs oriented perpendicular to the steel beam, the concrete below the top of the steel
deck must be neglected in determining section properties and in calculating the concrete area A c .
6. For deck ribs oriented parallel to the steel beam, the concrete below the top of the steel deck
may be included in determining composite section properties and should be included in calculating
A c . Also, deck ribs over supporting beams may be split longitudinally and separated to form a con-
1
crete haunch. Further, when the nominal depth of the steel deck is 1 / 2 in (38 mm) or greater, the aver-
age width w r of the supported haunch or rib must be not less than 2 in (50 mm) for the first stud in
the transverse row plus four stud diameters for each additional stud.

5.8.6 Shear Connectors for Composite Beams

The horizontal shear at the interface between the steel beam and the concrete slab is assumed to be
transferred by shear connectors. For composite action in positive-moment regions (concrete in flex-
ural compression), the total horizontal shear force V′ between the point of maximum positive
moment and the point of zero moment is the least of the following three limit states:

Concrete crushing V′= 0.85f c ′A c (5.133)
Tensile yielding of steel section V′= A s F y (5.134)
Strength of shear connectors V′= ∑ Q n (5.135)

2
2
where A c = area of concrete slab within effective width, in (mm )
2
2
A s = area of steel cross section, in (mm )
ΣQ n = sum of nominal strengths of shear connectors between point of maximum positive
moment and point of zero moment, kips (N)
For composite action in negative moment regions of continuous composite beams where longi-
tudinal reinforcing steel is considered to act compositely with the steel beam, the total horizontal
shear force between the point of maximum negative moment and the point of zero moment is the
smaller of the following two limit states:
Tensile yielding of slab reinforcement V′= A r F yr (5.136)
V′ = ∑
Strength of shear connectors Q n (5.137)

where A r = area of adequately developed longitudinal reinforcing steel within effective width of
2
2
concrete slab, in (mm )
F yr = minimum specified yield stress of the reinforcing steel, ksi (MPa)
The number of shear connectors required between the section of maximum bending moment,
positive or negative, and the adjacent section of zero moment is equal to the horizontal shear force
V′ divided by the nominal strength of one shear connector.
The nominal strength, Q n , of one stud shear connector embedded in solid concrete or in a
composite slab is

Q = 05 A sc f E ′ ≤ R R A F u (5.138)
.
p sc
g
n
c c
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