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It depends on steel bars either in tension or compression.
To avoid this complication in various codes, normal pratice is take 50 times diameter of steel bars eighter in tension or compression. Overlap for 32mm rebar will be =32*50=1600mm or 1.6m
Overlap for 20mm rebar will be =20*50=1000mm or 1.0m. Better to reduce spacing of rings(strips), if ovelap is near the support in case of column or beam.Please refer to details mentioned below by Amercan Concrete Institute(ACI) and British Code (BS)
ACI 318:08 provisions for lap length
Lap length in tension
Section 12.15.1 of the ACI 318:08 specifies the tension
lap lengths for class A and class B splice as 1.0ld and
1.3ld respectively but not less than 300 mm. Section
12.15.2 of CAI318:08 specifies tension lap splice
condition. Since in practice class B splice condition is
more common it was considered in this research.
Lap length in compression
Section 12.16.1 of the ACI 318:08 specifies the compression
lap length as 0.071fydb for fy ≤ 420MPa and 0.13fy – 24
for fy > 420MPa but not less than 300 mm in both cases.
These values are applicable for 21 < fc’≤ 70 MPa (normal
strength concrete). For fc’≤ 21 MPa, lap length shall be
increased by one-third. 48 times diameter of steel bar.
BS 8110:97 provisions of lap lengths
Lap length in tension
As per section 3.12.8.13 of BS 8110:97; in general, the lap
length in tension = 1.0 times tension anchorage length.
Lap length in compression
Section 3.12.8.15 of BS 8110:97 specifies the lap length
in compression = 1.25 times compression anchorage
length.
