2107.2 TMS 402/ACI 530/ASCE 5, Section 220.127.116.11.1.1, Lap Splices
The minimum length of lap splices for reinforcing bars in tension or compression, ld, shall be but not less than 12 inches (305 mm). In no case shall the length of the lapped splice be less than 40 bar diameters.
db = Diameter of reinforcement, inches (mm).
fs = Computed stress in reinforcement due to design loads, psi (MPa).
In regions of moment where the design tensile stresses in the reinforcement are greater than 80 percent of the allowable steel tension stress, Fs, the lap length of splices shall be increased not less than 50 percent of the minimum required length. Other equivalent means of stress transfer to accomplish the same 50 percent increase shall be permitted. Where epoxy coated bars are used, lap length shall be increased by 50 percent.