June 2006
cases, square bays in the range of 28 to 36 feet have been used with steel framing. Steel fram-
ing is typically used because of flexibility for future changes (which might require floor penetra-
tions) and speed of construction.
311 Basic Design: The use of steel framing has resulted in a predominant use of braced
frame lateral systems. Moment frame systems have been used in lower seismic zones. A hybrid
system, Special Truss Moment Frames (STMF), has been developed and incorporated into the
building codes since the publication of the Red Book. This system may have applications within
the VAHBS, such that the trusses could be located within the interstitial space, leaving the func-
tional space free of braces. However, truss design would require close coordination with other
systems to avoid conflicts with distribution channels in the service zone.
311.1.1 Typical Structural: Bays Most of the structural steel hospital designs for both VAHBS
and elsewhere employ square structural grids with columns spaced between 28 to 36 feet.
While the dropped girder system described in the Red Book has been implemented successfully
at the Houston VAMC, it is not a common application. To provide access through the S2 zone,
regularly spaced openings in the floor beams and girders can be provided. Castellated beams
could be considered for this purpose.
311.2 Lateral Force Resisting Elements: The VAHBS calls for concrete shear wall cores to
be placed around the service bays and at the end of the service module. However, concrete
walls create challenges to both medical planning and future flexibility. Steel braced frames can
be used to replace these elements. Moment frames and STMF are other options for steel
framed structures. These systems are more appropriate for low and moderate seismic regions
due to their structural flexibility and the challenges associated with meeting building drift limits
stipulated by building codes and VA.
Vertical loads on interstitial platform (floor) systems are typically transferred to the beams above
through rods, which do not have any lateral force resisting capability. Lateral loads generated
by the weight of the interstitial platform system and any other dead loads on the interstitial plat-
form are transferred through the metal deck to the interstitial framing to the columns. Though
these loads are likely to be small, all elements along the load path should be evaluated. For
analysis simplification, the mass of the intersti-
tial platform may be lumped at the functional
floor.
311.3 Relationship Between Main Structural
Members: This approach is applicable for the
cast-in-place concrete system envisioned by
VAHBS. If structural steel is used, many of the
recommendations would result in increased
cost.
312 Generic Design Options: This section
identifies four basic structural options (cast-in-
place concrete with prestressed beams, steel,
VA Medical Center
precast concrete, and reinforced concrete).
San Antonio, TX, 1973
General cost indications are presented that may (not VAHBS, but used interstitial space)
not be correct for present conditions.
SUPPLEMENT TO RESEARCH STUDY REPORT
VA HOSPITAL BUILDING SYSTEM
SECTION 4-6
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