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APPENDIX 2H
DOCUMENTATION
Chapter 2
Helical Foundation Systems
ESR-3074
|
Most Widely Accepted and Trusted
Page 4 of 9
Q
ult
= K
t
T
(Eq. 2)
Q
all
= 0.5 Q
ult
(Eq. 3)
Where:
Q
ult
= Ultimate axial tensile or compressive capacity
(lbf or N) of the helical piles. For axial tension,
pile ultimate axial load capacity must be limited to
55.1 kips (245.0 kN).
Q
all
= Allowable axial tensile or compressive capacity
(P4) (lbf or N) of the helical piles. For axial tension,
pile allowable axial load capacity must be limited
to 27.6 kips (122.5 kN).
K
t
= Torque correlation factor. (See Table 5.)
T = Final installation torque, which is the final torque
recorded at the termination (final) depth of the
installed pile during the field installations (lbf-ft
or N-m).
4.1.6 Foundation System:
The ASD allowable capacity
of the FSI helical foundation system in tension and
compression depends upon the analysis of interaction of
brackets, shafts, helical plates and soils; must be the
lowest value of P1, P2, P3 and P4; and must be no larger
than 60 kips (266.9 kN).
4.1.6.1 Foundation System (2012 and 2009 IBC):
Under the 2012 and 2009 IBC, the additional
requirements described in this section (Section 4.1.6.1)
must be satisfied. For all design methods permitted under
Section 4.1.1 of this report, the allowable axial
compressive and tensile load of the helical pile system
must be based on the least of the following conditions in
accordance with 2012 and 2009 IBC Section
1810.3.3.1.9:
Allowable load predicted by the individual helix bearing
method (or Method 1) described in Section 4.1.5 of this
report.
Allowable load predicted by the torque correlation
method described in Section 4.1.5 of this report.
Allowable load predicted by dividing the ultimate
capacity determined from load tests (Method 2
described in Section 4.1.5) by a safety factor of at least
2.0. This allowable load will be determined by a
registered design professional for each site-specific
condition.
Allowable capacities of the shaft and shaft couplings.
See Section 4.1.3 of this report.
Sum of the allowable axial capacity of helical bearing
plates affixed to the pile shaft. See Section 4.1.4 of this
report.
Allowable axial load capacity of the bracket. See
Section 4.1.2 of this report.
4.2 Installation:
4.2.1 General:
The FSI helical foundation systems must
be installed by FSI trained and certified installers. The
FSI helical foundation systems must be installed in
accordance with Section 4.2, 2012 and 2009 IBC Section
1810.4.11, site-specific approved construction documents
(engineering drawings and specifications), and the
manufacturer’s written installation instructions. In case of
conflict, the most stringent requirement governs.
4.2.2 Helical Pile Installation:
The helical piles are
typically installed using hydraulic rotary motors having
forward and reverse capabilities. The foundation piles
must be aligned both vertically and horizontally as
specified in the approved plans. The helical piles must be
installed in a continuous manner with the pile advancing
at a rate equal to at least 85 percent of the helix pitch
per revolution at the time of final torque measurement.
Installation speeds must be limited to less than
25 revolutions per minute (rpm). The lead and extension
sections must be attached to the drive head with a
product adaptor supplied by FSI. Torque readings must
be taken at minimum intervals corresponding to each lead
or extension section length and at final termination depth.
The lead and extension sections are connected with the
coupling bolts and nuts described in Section 3.2.1, and
tightened to a snug-tight condition as defined in Section
J3 of AISC 360. The final installation torque must equal or
exceed that as specified by the torque correlation method,
to support the allowable design loads of the structure
using a torque correlation factor (K
t
) of 9 ft
-1
(29.5 m
-1
).
The installation torque must not exceed 7,898 ft-lbs
(10 708 N-m). See Section 5.0 for further installation
conditions of use.
4.2.3 Retrofit Bracket Installation:
1. An area must be excavated to expose the footing with
an excavation approximately 3 feet (914 mm) square
and with a depth of about 13 inches (330 mm) below
the bottom of the footing. The soil is removed below
the bottom of the footing to about 9 inches (229 mm)
from the footing face in the area where the bracket
bearing plate will be placed. The vertical and bottom
faces of the footing must, to the extent possible, be
smooth and at right angles to each other for the
mounting of the support bracket.
2. Notching of footings may be needed to place the
retrofit bracket directly under the wall/column.
Notching must be performed, however, only with the
acceptance of the registered design professional and
the approval of the code official.
3. The bearing surfaces of the concrete (bottom and side
of footing) must be prepared so that they are smooth
and free of all soil, debris and loose concrete so as to
provide a full and firm contact of the retrofit bracket
plates.
4. The edge of the lead section shaft must be located
about 1
1
/
2
inches (38 mm) from the bottom edge of the
footing with a required angle of inclination of 3.0 ± 1.0
degrees from the vertical. Installation must be as
described in Section 4.2.2.
5. When the final bearing depth is reached, the pile
shafts are cut to approximately 13 inches (330 mm)
above the bottom of footing.
6. The external sleeve must be placed through the
bracket body and over the shaft. Once under the
footing, the bracket must be rotated 180 degrees
toward the footing. The bracket must be raised up to
the footing and held in place while the thread rods and
cap plate are attached.
7. The cap plate and all thread rods and tightening nuts
must be installed to snug the bracket to the bottom of
the footing.
8. Soil must be placed and compacted adequately up to
the bottom of the bracket prior to structural lift or load
transfer.
9. A lift cylinder can be used to lift the structure to
desired elevation and to transfer the designated
portion of the foundation load to the helical pile
system.