The primary components of a reinforced masonry system are the masonry units, grout, mortar, and reinforcement. The masonry units, grout, and mortar resist compressive stresses. Generally, the reinforcement (horizontal and vertical) protects against only tension stresses. However, confinement can be added to make the reinforcement also resist compressive stresses.
Reinforcement is installed as the masonry is constructed. Splices are required to provide continuity in the reinforcement.
Traditionally, reinforcement uses lap splices. However, the code-required lengths have steadily increased because of research studying the performance of lap splices. Increased lap lengths affect constructability as well as cost, particularly for low-lift construction which relies heavily on splices. Additionally, the International Building Code (IBC) does not allow lap splices for bars larger than No. 9. Therefore, masonry contractors need to be aware of other splicing options available.
This article discusses lap slices and mechanical splices and offers a method for cost comparison that contractors may refer to when developing data for specific applications. Welded splices are another option, but are not included because of their specialty nature.
Lap splices
Lap splices are constructed by overlapping the reinforcement and encasing them in grout. The bond between the grout and reinforcement within the overlap zone transfers the stresses from one bar to the next, thus creating a continuous load path.
Historically, lap length is based on the grade and size of reinforcement and a minimum strength grout. The lengths are usually specified as a function of the diameter of the reinforcement; the larger the reinforcement, the longer the minimum required lap splice.
A lap splice is usually constructed with the reinforcement overlapping in the cavity between two wythes, or in the same core of hollow units of clay brick or concrete masonry, while maintaining the required minimum clearances between the reinforcement and the inside faces of the units. This approach can create congestion in some types of reinforced sections, particularly those with two bars in one core and assemblies with larger sized reinforcement. These congested conditions can also hinder the proper placement of grout.
Lap lengths in the 2002 Building Code Requirements for Masonry Structures reported by the Masonry Standards Joint Committee (MSJC), and the 2000 and 2003 editions of the International Building Code (IBC), have increased over previous editions. Required lap length varies based upon bar size, masonry strength, and cover over the reinforcement. The 2005 MSJC further refines the formulas for the lap lengths, which are reduced in comparison to the 2002 provisions, but still increased compared to the 1999 edition.
The formulas for the different code editions are:
In current and previous codes, lap splice lengths must be 50% longer for epoxy-coated reinforcement. Tables 1A and 1B show the lap lengths for various MSJC standards for uncoated and epoxy-coated reinforcement.
