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APPENDIX 2F
MODEL SPECIFICATIONS
Chapter 2
Helical Foundation Systems
7.8.1.3 Helix Plate Material: The helix plates are factory welded to the lead or extension
shaft sections. Helix plates with outer diameters of 10, 12 or 14 inches are either
0.375 or 0.500-inch thick; 16-inch diameter helices are 0.500-inch thick. Helix
plates are manufactured with ASTM A572 Grade 50 steel with a minimum yield
strength of 50 ksi and a minimum tensile strength of 65 ksi. The helix plate finish
is either plain steel or hot-dip galvanized in accordance with ASTM A123.
7.8.1.4 Shaft Coupling Hardware: The lead and extension shaft sections are coupled
with four (4) bolts and nuts per coupled shaft section. The coupling hardware
consists of 2.000-inch heavy hex bolts conforming to ASTM A307 and heavy
hex nuts. The bolts and nuts are zinc coated in accordance with ASTM B633.
8
DESIGN AND PERFORMANCE REQUIREMENTS
8.1 Helical anchors shall be designed to support the specified tension load(s) as shown on the
project Plans. The overall length, helix configuration and minimum torsional resistance of a
helical anchor shall be such that the required geotechnical capacity is developed by the helix
plate(s) in an appropriate bearing stratum.
8.2 All structural steel anchor components shall be designed within the limits provided by the
American Institute of Steel Construction (AISC) Specification for Structural Steel Buildings
(AISC-360). Either Allowable Stress Design (ASD) or Load and Resistance Factor Design (LRFD)
are acceptable methods of analysis. Product testing in accordance with ICC-ES Acceptance
Criteria 358 may also be considered as an acceptable means of establishing system capacities.
8.3 Except where noted otherwise on the project Plans, all anchors shall be installed to provide an
ultimate torque-correlated capacity based on an ASD or LRFD analysis. For ASD, a minimum
factor of safety of 2 applied to the service or nominal loading shall be required. When an LRFD
analysis is required, the Owner shall provide applicable anchor design information including but
not limited to; factored loads, resistance factors and/or the required ultimate anchor capacity.
Factors of safety (ASD) or resistance factors (LRFD) may require modification to meet specific
deflection criteria stated on the Plans or drawings.
8.4 The required ultimate torque-correlated capacity shall be verified at each anchor location by
monitoring and recording the final installation torque and applying default torque correlations
per ICC-ES AC358. Site specific torque correlation factors may be determined by field tension
load testing as specified in Section 15.
8.5 Except where noted otherwise on the project Plans, each anchor shall be designed to meet a
corrosion service life of 50 years in accordance with ICC-ES AC358.
8.6 The anchor design shall take into account group efficiency from anchor spacing, soil stratification,
and strain compatibility issues.
