ETL 1110-2-355
31 Dec 93
(4) Congestion and other construction problems
(2) Hooked #14 and #18 horizontal bars have
may become evident if reinforcement splices and
long extension lengths at their free ends (3 ft-5 in. for
development lengths are drawn to scale on the con-
#18 bars). If the free end protrudes a small distance
tract plans.
from the upper lift into a lower lift, it is permissible
to rotate the end from the vertical position until the
free end is out of the lower lift. This allows the
b. Splicing.
contractor to place the bar on top of the lower lift
after it has hardened. Alternatively, the free end can
(1) In general, the use of splices should be mini-
remain vertical and the lower lift can be blocked out
mized, and all contractor-added splices should be
to receive it (see Figure A-15). This minimizes the
carefully reviewed to ensure that they do not
number of reinforcing mats that the contractor has to
adversely affect structural performance. All splice
support during a concrete placement. The option of
locations and splice staggers should be in compliance
rotating the free end of the hook or blocking out can
with the latest ACI 318 recommendations and shown
be given to the contractor with reference to a note on
on the contract plans or indicated in the specifica-
the contract plans.
tions. In determining splice locations, the designer
can use the normal maximum fabricated length of
d. Reinforcement and waterstops. Waterstops
60 ft for horizontal bars. Forty feet is usually used in
detailing the maximum length for vertical reinforce-
will not be omitted or punctured so that the reinforce-
ment because of constructability limitations.
ment can run its normal path. Adding concrete cover
over the reinforcing bars or detailing reinforcement
(2) Numerous load cases cause inflection points
around the waterstop in the initial design can
and regions of high moments to vary. The designer
eliminate this problem (see Figure A-16).
should consider this phenomenon when locating
splices.
e. Geometric discontinuities. At blockouts (i.e.,
recess in a wall), flexural reinforcement must be
(3) U-frame locks require #14 and #18 bars to
terminated, usually in a standard hook, and structural
resist large bending moments. Large reinforcing bars
continuity reestablished by placing additional rein-
are difficult to fabricate, ship, handle, place, and
forcement under or to the sides of the blockout.
support. Large reinforcing bars also require mechani-
Added reinforcement should be developed past each
cal splices. Mechanical splices are difficult to
end of the blockout. Added reinforcement under the
inspect, the coupler adds to the congestion, and the
blockout probably requires widely spaced (larger than
possibility of installation error is greater than for a
6 in., ACI 318) noncontact lap splices. Additional
lap splice. Large reinforcement bars should be used
reinforcing, such as development length past the
only where required.
potential crack zone (ACI 318) or stirrups to control
cracking, may be required (see Figure A-17).
c.
Bending.
9-4. Fillets.
(1) Bends in reinforcement are usually made for
standard hooks, corner bars, and bar terminations.
a. Fillets are used in U-frame locks for many
Large bars have large bend radii that often interfere
reasons and in many locations. Fillets from the floor
with the placement of intersecting steel (see
to the wall in the culvert have many advantages and
Figure A-13). It is suggested that all bar bends be
disadvantages.
drawn to scale on the plan drawings to help identify
and correct reinforcing placement problems. Hori-
(1) Advantages. Fillets can reduce honeycomb-
zontal #14 and #18 bars with bends will cause prob-
ing in the main structural members, and permit the
lems since they will be tied to vertical bars set in
use of the lower design moments and shears which
hardened concrete that may have been placed without
occur at the toe of the fillet.
considering the large bend radii of the horizontal bar.
(2) Disadvantages. Disadvantages include:
As a result, concrete clearances will be sacrificed (see
planes of weakness in the construction joints of the
Figure A-14). A possible solution is to detail vertical
fillet, suspended forms for the fillet and culvert floor
bars along the bend of the large horizontal bars.
A-32
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