described herein. Intermittently bonded precast units
or precast units with grouted shear keys will not be
(b)
Cast-in-place concrete slabs not
used as a diaphragm. In areas with SDS ≤ 0.25g
monolithic with supporting framing. When concrete
slabs used as diaphragms are not monolithic with the
(Figure 7-55), there is an exception permitting the use
supporting framing members (e.g., slabs on steel
of hollow-core planks with grouted shear keys and
beams), the slab will be anchored by mechanical
the use of connectors, in lieu of continuous bonding,
means at intervals not exceeding 4 feet (1.2m) on
for precast concrete members.
The exception is
center along the length of the supporting member.
permitted if the following considerations and
This anchorage is not a computed item, and should be
requirements are satisfied:
similar to that shown in Figure 7-52, Detail A. For
composite beams, anchorages provided in accordance
1. Procedure conforms with PCI-MNL-
with AISC provisions for composite construction will
120 seismic design requirements.
meet the requirements of this paragraph.
2. Shear forces for diaphragm action can
(c)
Cast-in-place concrete diaphragms
be effectively transmitted through connectors. The
vertically supported by precast concrete slab units. If
shear is uniformly distributed throughout the depth or
the slab is not supporting vertical loads but is
length of the diaphragm with reasonably spaced
supported by other vertical-load-carrying elements,
connectors, rather than with a few that will have
mechanical anchorages will be provided at intervals
localized concentration of shear stresses.
not exceeding 38t; thus, the provisions above will be
satisfied by defining LV as the distance between the
3. Connectors are designed for 0.6R times
mechanical anchorages between the diaphragm slab
the prescribed shear force.
and the vertical-load-carrying members.
This
mechanical anchorage can be provided by steel
4.
Detailed structural calculations are
inserts or reinforcement, by bonded cast-in-place
made including the localized effects in concrete slabs
concrete lugs, or by bonded roughened surface, as
attributed from these connectors.
shown in Figure 7-53. Positive anchorage between
cast-in-place concrete and the precast deck must be
5.
Sufficient details of connectors and
provided to transmit the lateral forces generated from
embedded anchorage are provided to preclude
the weights of the precast units to the cast-in-place
construction deficiency.
concrete diaphragm, and then to the main lateral-
force-resisting system.
(e) Metal-formed deck, Where metal deck is
used as a form, the slab shall be governed by the
(d) Precast concrete slab units. If precast
requirements of Paragraph (b) above.
Refer to
units are continuously bonded together as shown in
Paragraph 7-7e, where the deck is used structurally.
Figure 7-54, they may be considered concrete
diaphragms and designed accordingly, as previously
7 -124
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