Aci 315-99 supersedes aci 315-92 and became effective August 31, 1999

3.7.8 Column spirals
3.7.8.1 General—Spirals shall be provided with 1-1/2
extra turns at both top and bottom. The height (or length) of
a spiral is defined as the distance out-to-out of coils, includ-
ing the finishing turns top and bottom, with a tolerance of
plus or minus 1-1/2 in. (40 mm). Where a spiral cannot be
furnished in one piece, it may be furnished in two or more
sections to be field welded, or with additional length at each of
the ends of each section to be lapped in the field, 48 diameters
minimum, but not less than 12 in. (300 mm). The sections must be
identified properly by mark numbers to ensure proper assembly.
When radial prefabrication is required
Bars are to be prefabricated when either radius or bar length is less 
than tabulated value
Bar size, No.
Radius, ft (mm)
Bar length, ft (mm)
3 (10)
5 (1500)
10 (3000)
4 (13)
10 (3000)
10 (3000)
5 (16)
15 (4500)
10 (3000)
6 (19)
40 (12,000)
10 (3000)
7 (22)
40 (12,000)
10 (3000)
8 (25)
60 (18,000)
30 (9000)
9 (29)
90 (27,000)
30 (9000)
10 (32)
110 (33,000)
30 (9000)
11 (36)
110 (33,000)
60 (18,000)
14 (43)
180 (54,000)
60 (18,000)
18 (57)
300 (90,000)
60 (18,000)

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 315-15
DETAILS AND DETAILING OF CONCRETE REINFORCEMENT
Spacers are sometimes used for maintaining the proper
pitch and alignment of the spiral and, when used, must con-
form to the minimum requirements of a table in the support-
ing reference data section. Maximum length of spacers is
that of the spiral plus one pitch. One alternative method to
using spacers is to ship the spiral as a compressed coil and tie
it in place in the field. The project specifications or subcon-
tract agreements should be written clearly to cover the sup-
ply of spacers or field tying of the spiral reinforcement.
The height of one-piece assembled spirals for fabrication
and shipping is limited to 25 ft (7500 mm) unless special
handling arrangements are made. For greater heights, spirals
must be field spliced by lapping or welding. Spacers can be
provided. Spirals are also used in piles, but these do not fall
within ACI 318 (318M) definition of a spiral and are usually
made of light wire and relatively large pitch.