Formwork for Concrete Structures by R.L.Peurifoy and G.D- By EasyEngineering.net

86 Chapter Four
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Anchors may also be installed after the concrete is placed and
cured. A hole is drilled into the concrete to allow installation of a
threaded mechanical device, such as a helical coil or an expandable
nut-type device. After the threaded mechanical device is installed, a
bolt or all-threaded rod can be installed to fasten formwork, to secure
an existing concrete structure to a newly placed concrete member, or
to attach rigging for lifting the concrete member.
Self-threading anchors are available for light-duty applications.
The ultimate strength of these fasteners will vary, depending on the
diameter and depth of embedment of the anchor, and on the strength
of concrete in which it is installed. When properly installed in concrete,
the ultimate pullout load will range from 300 to 1,800 lb, and
the ultimate shear strength may vary from 800 to 1,600 lb.
There are a variety of types of anchors available from manufacturers.
The strength of an anchor is provided by each manufacturer. ACI
Committee 347 recommends a safety factor of 2.0 for concrete anchors
used in the application of formwork, supporting form weight and concrete
pressures, and for precast concrete panels when used as formwork.
A safety factor of 3.0 is recommended for formwork supporting
the weight of forms, concrete, construction live loads, and impact.
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References
1. “National Design Specification for Wood Construction,” ANSI/AF&PA NDS-
2005, American Forest & Paper Association, Washington, DC, 2005.
2 “Design Values for Wood Construction,” Supplement to the National Design
Specification, National Forest Products Association, Washington, DC, 2005.
3. “Plywood Design Specification,” APA—The Engineered Wood Association,
Tacoma, WA, 1997.
4. “Concrete Forming,” APA—The Engineered Wood Association, Tacoma, WA,
2004.
5. “Plywood Design Specification,” APA—The Engineered Wood Association, r
Tacoma, WA, 2004.
6. “Manufacturer’s Catalogue,” Dayton Superior Corporation, Parsons, KS.
7. “Manufacturer’s Brochure,” The Sonoco Products Company, Hartsville, SC.
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