Splices

Reinforced concrete structures are designed to behave monolithicly. Properly designed splices of individual reinforcing bars are a key element in transmitting forces through the structure and creating a load path. The architect/engineer provides location, lap length, and related information on structural drawings.

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SplicesSee how spliced rebar is installed.

There are three methods of splicing reinforcing bar: lap splices, mechanical splices, and welded splices. Lap splices are the most common. Lap splices are typically used for smaller-diameter method (#11 [#36] or smaller) reinforcing bars.

When there is not enough space for a lap splice, mechanical or welded splices are used. #14 [#43] and #18 [#57] sized reinforcing bars cannot be lap spliced.

Lap Splices

A lap is when two pieces of rebar are overlapped to create a continuous line of rebar. The length of the lap varies depend on concrete strength, the rebar grade, size, and spacing. CRSI's "Reinforcement Anchorage and Splices" includes tables of required lap splice lengths based on these variables.

Contact splices--in which the bars touch and are wired together--are preferred because they are more secure against displacement during construction. Non-contact lap-spliced bars should not be spaced too far apart.

Mechanical Splices

There are three basic types of mechanical splices:

"tension-compression," which can resist both tensile and compressive forces, "compression only," also known as the "end-bearing" mechanical splice, and "tension only."

The design of Mechanical splices are proprietary. The splices are supplied by a number of manufacturers across the U.S.

Welded Splices

In general, CRSI recommends against manual arc welding in the field. However, if necessary, field-welded splices are accomplished by electric arc welding the reinforcing bars together. Welding should conform to AWS D1.4/D1.4M, "Structural Welding Code - Reinforcing Steel" of the American Welding Society.

CRSI recommends against connecting crossbars by small arc welds, known as "tack welds." Tack welding is a factor associated with brittle failure of reinforcing bar assemblies.