| The isolators were installed one at a time. First temporary hydraulic jacks were fitted to a column in such a way as to support the column so that it could not move, and then cutting a specific length out of the column at its base. An isolator was then placed into this gap along with an empty bladder device which, when injected with an epoxy resin would completely fill any remaining space. |
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| Before the first isolator was installed about a year's worth of preparation was necessary to strip the concrete cladding from each steel column, brace each column so that it would not be able to move during those critical hours when the column was cut and the isolator moved into place, and weld between 100 to 300 shear pins (Nelson studs) onto precise positions on each column. For this process each column had to be individually analyzed to determine where each of the 100 to 300 shear pins should be located in order to maximize it's load bearing capacity. |
Concrete cladding removed, shear pins and temporary
bracing installed, the basement is now ready for excavation.
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| After column bracing and shear pin installation were completed the basement was excavated in order to expose the column footings. In some areas excavation went as much as eight feet below the level of the original basement floor. |
At right: Columns braced, the entire basement was
excavated in order to enlarge the footings.
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| Over 20,000 cubic yards of earth was excavated from the basement. |
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| Once the footings were exposed each footing was drilled to accommodate steel rebar which in turn became the steel reinforcement for the enlarged footing. |
One of the larger footings is shown with initial rebar installed.
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| Various stages in the preparation of a footing for enlargement are shown above. |
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| Each footing was framed and then concrete poured. Once the enlarged footing was ready the isolator installation process could proceed. Hydraulic jacks and a steel beam were installed to keep the column from moving when it was cut through. |
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| Footings framed and ready for the pour |
Concrete pour |
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| Concrete has been poured |
Hydraulic jacks and temporary
support beams are in position |
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Hydraulic draw jacks are
installed |
Column is cut and old concrete
pier is removed |
Ready for isolator installation. |
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| Steel Riggers maneuver an isolator into place |
A row of isolators installed |
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| Completion of final welded connections |
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