Lapping: In RCC structure, placing of a single bar may not meet the required length of the section. So it becomes necessary to join two bars, to meet the desire length. To join two bars, one bar should overlap another and it is called lapping of bar and the length overlap each other is caller lap length or overlap length.
Lap length is different for different concrete section.
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Calculation of Lapping Length:
Lapping is not permitted for reinforcement greater than No.11
lapping length for longitudinal reinforcements are as follows:
for Class A Splice: Lapping length will be the greater of 1.0Ld and 12 inch.
for Class B Splice: Lapping length will be the greater of 1.3 Ld and 12 inch.
Table: Splice Type
* Here Ld is the development length.
Lapping length for Tension Reinforcement (same as Longitudinal Reinforcement):
for Class A splice: Lapping length will be the greater value of
1.0 Ld and 12 inch.
for Class B splice: Lapping length will be the greater value of 1.3 Ld and 12 inch.
Here Ld is the development length.
Compression Lapping length of No.11 or smaller deformed bar
Shall be calculated as :
(a) for fy </= 60,000 psi lapping length is greater of 0.0005 fy*db and 12inch.
(b) for fy > 60,000 psi, lapping length is greater of (0.0009 fy-24)db and 12 inch.
Note: for fc'<3000 psi the length of lapping will be increased by one-third.
compression lapping should not permitted for bar greater than No.11 except permitted at code.
all informations are from ACI Code
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