Page 333 - Structural Steel Designers Handbook AISC, AASHTO, AISI, ASTM, and ASCE-07 Design Standards
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FLOOR AND ROOF SYSTEMS
FLOOR AND ROOF SYSTEMS 7.17
FIGURE 7.18 Typical short-span floor framing for a FIGURE 7.19 For economical framing, joists are sup-
high-rise residential building. ported on wind girders.
regardless of their orientation (Fig. 7.19). This arrangement takes advantage of the substantial members
required for lateral-force resistance without appreciably increasing their sizes to carry the joists.
The service core of a high-rise residential building, containing stairs, elevators, and shafts for
ducts and pipes, usually is framed with lightweight, shallow beams. These are placed around open-
ings to provide substantial support for point loading.
Because of lighter dead and live loads, columns in residential buildings are much smaller than
columns in office buildings and usually are less visible. Orientation of columns usually is determined
by wind criteria and often is oriented as indicated in Fig. 7.20. However, seismic loads (if applicable)
and/or P–∆ effects may control in the longitudinal direction, and in that case, additional lateral-load
resisting elements such as frame bracing or shear walls can be added.
7.11 TRUSSES
When relatively long spans are involved, trusses are frequently selected for the floor-framing
system. As for open-web joists, mechanical ductwork can be easily routed through the web openings.
Shear connectors can be added for composite action with the floor deck. Increased future loadings
can be accommodated at a minimal cost premium by oversizing the web members and their con-
nections and providing additional shear connectors in the original design.
FIGURE 7.20 Typical framing plan for narrow, high-rise building orients
columns for strong-axis resistance to lateral forces in the narrow direction.
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