September/October 2023 - 111

As indicated, by the comparison of
manual and automated data collection
for the First Load Series 0-180, there is
reasonable correlation between the two
methods of data acquisition. The data
indicate that approaching the typical
defined failure of 4 in (100 mm) of top
plate translation, the overturning
moment capacity of the foundation is on
the order of 2,900 kip ft (3,930 kN m). The
field testing provides that rotating the
direction of loading 45 degrees results in
a small capacity reduction of 50 kip ft
(68 kN m), indicating that the test
foundation has a relatively uniform
rigidity about the circumference. The
overturning moment capacity in the
45-degree direction was on the order of
2,850 kips ft (3,865 kN m). Additionally,
the field trial testing supported the
predicted foundation behavior calculated
using the team's preprocessor
and FE model.
FE Foundation Model
A STAAD-Pro analytic FE process
program supplemented by a tailored
preprocessor analytical tool provides a
predicted load capacity and foundation
reaction to aid in the design of the
foundation. The preprocessor developed
by the team generates the geometry,
structural properties and soil representation
for the FRP and steel foundations.
This facilitates satisfying project
specific criteria utilizing user-defined
parameters. The critical parameters
include subsurface soil design parameters,
the foundation number of box
stiffeners, wall thickness, overall depth,
size of foundation core and box
stiffeners, taper angle at bottom of box
stiffeners, and overall rotation of the
foundation. The top plate, connected to
the foundation core segments, can be
defined as a circle or as an equilateral
shape. The bolts connecting the foundation
to the structure can be configured
to closely match the location of the bolts
in the design documents. The user may
include the flange plate as part of the
model to account for the interaction with
the top plate.
Data reduction of full-scale lateral load test with comparison to STAAD Analysis - combined load series of
0-180 foundation axis and 45-225 foundation axis
The loading is defined as a combination
of three forces and three
moments in the global X, Y and Z
directions applied at the center of the
top plate. For eccentric loads, equivalent
decoupled centered loads are calculated.
The preprocessor displays a schematic
preview of the foundation configuration
to evaluate its constructability, e.g., the
proximity of the top plate bolts to the
foundation core or to the face of the
supported structure. The preprocessor
then creates a STAAD-Pro input file.
After the STAAD-Pro analysis is
conducted, the output file can be read
back into the Excel preprocessor to
provide a summary of the results
including deflections and lateral reactions.
STAAD-Pro post-processing
features may also be used to discern
compliance with design requirements.
Implementation in Two
Installed Projects
As discussed previously, initial analytical
and design work incorporating
conventional materials was a precursor
to the development of the FRP foundations.
Many of the lessons learned since
the mid-2010s development period
were applicable to the development of
the FRP design and installation guidelines.
One such project involved the
investigation of compression/bearing,
DEEP FOUNDATIONS * SEPT/OCT 2023 * 111

September/October 2023

Table of Contents for the Digital Edition of September/October 2023