283757893275

Structural Concrete Frames 405
The precast, hollow floor units bear on the rebate in beams. Slots cast in the floor units
accommodate steel tie bars, which are hooked over peripheral tie bars. The tie bars are
wired to loops, which are cast into beams. Structural concrete topping is spread, compacted
and levelled over the floor slabs and into the space between the ends of slabs and beams
to form an in situ reinforced concrete floor. Precast floor units bear either directly on
concrete beams or, more usually, on supporting nibs cast for the purpose. Ends of floor
units are tied to beams through protruding studs or in situ cast reinforcement so that the
floor units serve to transfer wind pressure back to an in situ cast service and access core.
The precast reinforced concrete wall frames, illustrated in Figure 6.50, that combine four
columns with a beam were used with drop-in beams as the structural wall frame system
Bronze strap
cast into unit
bolted to dowel
Stiffening
ribs
Horizontal support nibs
bear on beams
Web of
unit
Lightweight
concrete blocks
Four-column precast
concrete wall frame
Floor slab bears on
toe of beam secured
with dowels
Window unit
Drop-in
beam
Storey height units
Drop-in
beam
300 × 300 mm columns
at 1.8 m centres
Drop-in beam bolted
to nibs on frame
Sockets for dowels
Screed
Wall frames
in position
Expanded
polystyrene
Floor units with
concrete topping
Boot
section beam
Figure 6.50 Precast reinforced concrete wall frames.