Types of Mechanical Splices for Reinforcing Bars
|Publication Date:||1 March 2007|
In reinforced concrete design, the structural engineer is faced with the task of determining where and how reinforcing bars must be spliced in a structure. The structural engineer must do this because of his familiarity with the particular requirements of the structure. Drawings or specifications must clearly show or describe all splice locations and the performance required. The importance and necessity of clearly prescribing splice requirements is evident in two sections of ACI 318. Section 1.2.1 describes nine specific items to be included on the design drawings, details, and specifications. These items include Section 1.2.1.h, which requires that location and length of lap splices and reinforcement anchorage lengths be shown. Section 1.2.1.i requires showing the type and location of welded splices and mechanical connections of reinforcement. Section 12.14.1 of ACI 318 also addresses this subject, and states: "Splices of reinforcement shall be made only as required or permitted on design drawings, or in specifications, or as authorized by the engineer."
In the design of beams, columns, and slabs, lap splices are usually permitted. When lap splices of straight bar extensions cannot be used, or when their use causes congestion, field placing problems, or detailing or design problems, then mechanical connections, welded joints, or lap splice connections involving field bending and subsequent bar straightening may be used, as appropriate.
This report provides basic information about proprietary mechanical connections generally available in North America and known to the committee at the time the report was submitted for publication.* Design requirements and usage of mechanical connections, as well as capabilities and features of selected mechanical connection devices, are described.
Three basic types of mechanical connections are considered in this report. They are: (1) the "compressiononly" mechanical connection, which is also known as the "end-bearing mechanical connection," (2) the "tension-only" mechanical connection, and (3) the "tension-compression
In this report, pertinent terms are defined as follows:
Bar-end check-Check of the ends of reinforcing bars to determine whether they fit the devices intended for connecting the bars.
Coupler-Threaded device for joining reinforcing bars for the purpose of providing transfer of either axial compression or axial tension or both from one bar to the other.
Coupling sleeve-Nonthreadeddevice fitting over the ends of two reinforcing bars for the eventual purpose of providing transfer of either axial compression or axial tension or both from one bar to the other.
End-bearing sleeve-Devicefitting over the abutting ends of two reinforcing bars for the purpose of assuring transfer of only axial compression from one bar to the other.
Mechanical connection-Complete assembly of an end-bearing sleeve, a coupler, or a coupling sleeve, and possibly additional intervening material or other components to accomplish the connection of reinforcing bars.
It is beyond the scope of this report to cover welded splices or other currently available special proprietary splicing systems. Engineers are referred to the AWS code for welding reinforcing steel (ANSI/AWS D1.4) and the ASTM specifications for reinforcing bars, such as ASTM A 706 and ASTM A 615. Further discussion of the AWS code and welded splices is given in Reference 1.
*ANCON (MBT) mechanical connectors, which involve a clamping device generically different from devices described in the present report, are not included in this report because they were unknown to the committee at the time of final committee ballot on the report.