PROJECT SPOTLIGHT
O’Hare International Airport
Hangar’s Alley recently got a
new addition with American
Airlines Hangar 2. The hangar is eleven
stories high, with an interior clear height
of 85 feet. The hangar allows for entry on
both the north and south sides, with clear
spans of over 500 feet, and can support
two 777-300s and an A321 at one time.
With over 7,000 tons of structural
steel and large open spans, a large driven
pile foundation was selected to resist
the vertical and lateral loads. Thatcher
Foundations was the pile driving contractor
for this project. The pile foundation
consists of HP 14x73 piles to support the
interior columns with an ultimate compressive
capacity of 640 kips. The corners
of the structure were supported on HP
16x141 piles, installed both vertically and
at a 1H:3V batter angle, with an ultimate
compressive capacity of 1,720 kips and
an ultimate tension capacity of 860 kips.
This compressive load is the maximum
load on the pile section allowed by City
of Chicago Building Code, 42 percent
of the section yield strength, contingent
upon successful static load test results.
The specifications called for compression
and tension static load tests for on
the HP 16x141 piles and a compression
test on the HP 14x73. The static load test
piles were also dynamically tested, and
dynamic testing was specified on an additional
six percent of the production piles.
Dynamic testing was performed by GRL
Engineer’s Chicago office.
The subsurface conditions, shown
in Figure 1, can be described as mediumstiff
to hard, silty clay and medium-dense,
silty sand to a depth of 50 feet, followed
by hard clay and dense silt to a depth of a
little over 90 feet. The bedrock was hard
dolomite. For the most part, the bearing
layer was in the hard clay near the
By Travis Coleman, GRL Engineers, Inc.
Continued on page 91
PILEDRIVER | 89
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