Building Design and Construction Handbook - Merritt - Ventech!

CONCRETE CONSTRUCTION 9.69
length required for the smaller bar. It is permissible to lap-splice the large bar sizes,
Nos. 14 and 18, to No. 11 and smaller bars.
9.49.10 Mechanical and Welded Splices
As an alternative to lap splicing, mechanical splices or welded splices may be used.
When traditional lap splices satisfy all requirements, they are generally the most
economical. There are conditions, however, where they are not suitable: The ACI
318 Building Code does not permit lap splices of the large-size bars (Nos. 14 and
18) except in compression to No. 11 and smaller bars. Lap splices cause congestion
at the splice locations and their use then may be impracticable. Under certain conditions,
the required length of tension lap splices for No. 11 and similar-size bars
can be excessive and make the splices uneconomical. For these reasons, mechanical
splices or welded splices may be suitable alternatives.
Mechanical splices are made with proprietary devices. The ACI 318 Building
Code requires a full mechanical splice to have a capacity, in tension or compression,
equal to at least 125% of the specified ƒ y of the bar. End-bearing mechanical splices
may be used where the bar stress due to all conditions of factored loads is compressive.
For these types of compression-only splices, the ACI 318 Building Code
prescribes requirements for the squareness of the bars ends. Descriptions of the
commercially-available proprietary mechanical splice devices are given in ‘‘Mechanical
Connections of Reinforcing Bars,’’ ACI 439.3R, and ‘‘Reinforcement Anchorages,
and Splices,’’ Concrete Reinforcing Steel Institute.
For a full-welded splice, the ACI 318 Building Code requires the butt-welded
bars to have a tensile capacity of at least 125% of the specified ƒ y of the bar.
Welding should conform to ‘‘Structural Welding Code—Reinforcing Steel’’ (ANSI/
AWS D1.4), American Welding Society.
9.49.11 Anchorage of Web Reinforcement
Stirrups are reinforcement used to resist shear and torsion. They are generally bars,
wire or welded-wire fabric, either single leg or bent into L, U, or rectangular shapes.
Stirrups should be designed and detailed to be installed as close as possible to
the compression and tension surfaces of a flexural member as concrete cover requirements
and the proximity of other reinforcing steel will permit. They should
be installed perpendicular or inclined with respect to flexural reinforcement and
spaced closely enough to cross the line of every potential crack. Ends of singleleg,
simple U stirrups, or transverse multiple U stirrups should be anchored by one
of the following means:
1. A standard stirrup hook around a longitudinal bar for stirrups fabricated from
No. 5 bars or D31 wire or smaller sizes. Stirrups fabricated from bar sizes Nos. 6,
7, and 8 in Grade 40 can be anchored similarly.
2. For stirrups fabricated from bar sizes Nos. 6, 7, and 8 in Grade 60, a standard
stirrup hook around a longitudinal bar plus a minimum embedment of
0.014dbƒ/�ƒ� y cbetween
midheight of the member and the outside end of the hook.
Each leg of simple U stirrups made of plain welded-wire fabric should be anchored
by one of the following means: