Structural Concrete - Hassoun

278 Chapter 7 Development Length of Reinforcing Bars
Table 7.5
Lap-Splice Length in Compression, l sc
(in.), (f
c ′ ≥ 3ksi and
Minimum l sc
= 12 in.)
f y
(ksi)
Bar Number Bar Diameter (in.) 40 60 80
3 0.375 12 12 18
4 0.500 12 15 24
5 0.625 13 19 30
6 0.750 15 23 36
7 0.875 18 27 42
8 1.000 20 30 48
9 1.128 23 34 55
10 1.270 26 39 61
11 1.410 29 43 68
7.8.4 Lap Splice in Columns
The following special requirement are given in ACI Code, Section 10.7.5, for lap splice in columns:
a. If bar stress due to factored load is tensile and does not exceed 0.5f y in tension (≤ 0.5f y ), use
class B tension splice if more than one-half of total column bars spliced at same location, or
use class A splice if not more than one-half of total column bar spliced at same location and
alternate lap splices are staggered by l d .
b. If bar stress due to factored loads > 0.5f y in tension, use class B lap splice.
c. In spirally reinforced columns, lap-splice length within a spiral may be multiplied by 0.75
but may not be less than 12 in. In tied columns, with ties within the splice length having a
minimum effective area of 0.0015 hs, lap splice may be multiplied by 0.83 but may not be
less than 12 in., where h is overall thickness of column and s is spacing of ties (in.). Tie legs
parallel to dimension h shall be used in determining effective area.
h 2
h 1
(Parallel to h 1 dimension)
= 3 tie bar areas ≥ 0.0015h 1 s
(Parallel to h 2 dimension)
= 2 tie bar areas ≥ 0.0015h 1 s
Example 7.6
Calculate the lap-splice length for six no. 8 tension bottom bars (in two rows) with clear spacing = 2.5 in.
and clear cover = 1.5 in. for the following cases:
a. When three bars are spliced and (A s provided)/(A s required) > 2.
b. When four bars are spliced and (A s provided)/(A s required) < 2.
c. When all bars are spliced at the same location. Given: f c ′ = 5ksi and f y = 60 ksi.