Stair Tower at Quantico Marine Base
Restored With Atlas Piers
Overall view of the job site. The settled stair Tower is visible to the
left of the original structure.
PROJECT SUMMARY |
|
| Engineer: |
U. S. Department of the
Navy |
|
|
| Owner: |
U. S. Marine Corps |
Repaired By: |
Structural Solutions |
| Piers Required: |
Eight (8) |
Average Depth: |
Eight Feet (8') |
| Part Number: |
AP3(PA)-3500.160 |
Amount of Lift: |
0" to 3/16" |
| Driving Force: |
68,250 lb.
(Avg.) |
Factor of Safety: |
2.1:1 (Working
Load) |
| Lifting Force: |
32,702 lb.
(Avg.) |
|
2.4:1 (Ultimate
Load) |
|
THE PROBLEM:
Several years ago Stair Towers were added to the older structures at the
Quantico Marine Base for emergency exits. In the case of Building 2007, the Stair
Tower’s foundation was not situated on suitable soil to support the load. As a
result, the foundation settled and the Stair Tower began to rotate away from the original
structure. These photographs show the failing Stair Tower. Note the separation between the
Stair Tower and the original structure at the fascia. Safety was also a concern as
separations also occurred at the connections between the stair landings and Marshall Hall,
the original structure.
|
|
These photographs show the
failing Stair Tower. Note the separation between the Stair Tower and the original
structure at the fascia. Safety was also a concern as separations also occurred at the
connections between the stair landings and Marshall Hall, the original structure.
THE SOLUTION:
The Corps of Engineers specified Atlas
Piers as the solution to the settlement. A Pier was specified at each corner
nearest to Marshall Hall. These would serve as pivot points when the outer portion of the
foundation was raised to the specified elevation. Six additional Atlas Piers were specified across the back of the Stair
Tower and around the outer corners. The Piers were driven to firm bearing. Each pier was
then tested and verified by a Department of the Navy inspector to at capacity of at least
65,000 pounds.
Above, a technician is
preparing the foundation to accept the Atlas Piers.
Note that the footing is notched to allow the piers to be mounted directly under the stem
wall. The face and the bottom of the footing are carefully prepared prior to installation. |
|
 |
After each pier was
driven to a firm bearing stratum, the piers were load tested and verified by the U.S.
Navy. The photograph above right shows a 50-ton ram applying a test load while the
technician monitors the pressure gauge. The Structure was lifted evenly and gently using
a hand pump, manifold and a series of 25-ton hydraulic rams. One ram was mounted on each
pier. The lifting force was monitored on a pressure gauge. |
| SUCCESS! The Stair Tower was successfully lifted and rotated back to nearly the original
position. Six of the Atlas Piers now carry a
total working load of nearly 200,000 pounds.
|
THE
SOLUTION!
Atlas Piers
•
High Strength
• Economical
• Rapid Installation |
|
|
Atlas
Piers |
INSTALLATION
SUMMARY |
Pier
Installation Log
| Location |
Lifting
Force,
pounds |
Driving
Force,
pounds |
Ultimate
Cap.,
pounds |
Working
F.S. |
Ultimate
F.S. |
| Pier #1 |
32,702 |
65,000 |
80,000 |
2.0 : 1 |
2.4 : 1 |
| Pier #2 |
32,702 |
66,000 |
80,000 |
2.0 : 1 |
2.4 : 1 |
| Pier
#3 |
32,702 |
70,000 |
80,000 |
2.1 : 1 |
2.4 : 1 |
| Pier #4 |
32,702 |
70,000 |
80,000 |
2.1
: 1 |
2.4 : 1 |
| Pier #5 |
32,702 |
65,000 |
80,000 |
2.1 : 1 |
2.4
: 1 |
| Pier
#6 |
32,702 |
78,000 |
80,000 |
2.4
: 1 |
2.4
: 1 |
|
|
|
|
|
|
| Pier #7* |
N/A |
66,000 |
80,000 |
N/A |
N/A |
| Pier
#8* |
N/A |
66,000 |
80,000 |
N/A |
N/A |
|
Results
Approx.
Lift
inches |
Depth to
Bearing
feet |
| 3/16" |
8'-4" |
| 3/16" |
8'-0" |
| 3/16" |
8'-8" |
| 3/16" |
7'-8" |
| 2-1/4" |
6'-10" |
| 3/16" |
8'-5" |
|
|
| 0 |
5'
- 6" |
| 0 |
9'
- 0" |
|
|
|
|
