Proper splicing of reinforcing bars is crucial to the integrity of reinforced concrete. The ACI Building Code states: "Splices of reinforcement shall be made only as required or permitted on the design drawings, in the specifications, or as authorized by the engineer." Great responsibility for design, specification and performance of splices rests with the engineer, and only the engineer who is familiar with the structural analysis and design stress, probable construction conditions, and final conditions of service can properly evaluate the variables to select the most efficient and economical splice method.
The traditional lap splice, when it will satisfy all requirements, is generally the most economical splice, and welded splices generally require the most expensive field labor. However, lap splices cause congestion at the splice locations, sometimes making their use impossible. The location of construction joints, provision for future construction, and the particular method of construction can also make lap splices impractical. In addition, the ACI Building Code does not permit lap splices in "tension tie members," or in #14 and #18 bars except for compression only, when spliced to smaller sized footing dowels.
In column design, consideration must also be given to the fact that lapped offset bars may have to come inside of the bars above and therefore reduce the moment arm in bending. When the amount of column vertical reinforcement is greater than 4 percent, and particularly in combination with large applied moments, the use of butt splices either mechanical connections or welded splices should be considered to reduce congestion, and to provide for greater design moment strength of the section at the splice location. The purpose of this article is simply to answer some of the questions concerning welded splices.