"We knew QA/QC was going to be critical," says Lorentz, characterizing the complex reinforcing system as "quite the jigsaw to put together." After AEC and Choate 3D-modeled everything, onsite inspection and metrology became key. For instance, the anchor sleeve system, which was prefabricated, was laser scanned a total of four times prior to concrete placement: at fabrication; delivery; installation; and for as-builts.
"There were hundreds of individual components that went into building each foundation, all of which had to relate back to each other to within 1/16 of an inch in every dimension, X, Y and Z," Palmer says, adding that failing to meet tolerances would result in the drivetrains not aligning.
Construction of the 15-MW test rig's load application unit (LAU) structure—the vertical structure that houses the gearbox and drivetrains—was another feat, says Tuten. For instance, after the initial positioning of the galvanized-steel load disc, but before concrete placement, the massive prefabricated ring "looked a little below datum" to him. But that was by design.
"We had to anticipate what the theoretical deflections are during construction [versus] during service," explains Lorentz. "What are the deflections going to be from a dead load? And how do we get it back to a relief position and a zero position at end of construction?"
Installing the 15-MW gearbox posed the final hurdle. Once it arrived at the Port of Charleston, it took roughly one month to get the item in place. Tuten explains it this way: "A 341-ton gearbox does not go anywhere very fast, and if it does you're in real trouble."
To accommodate its installation, the contractors left a roughly 20-ft-by-20-ft portion of the structure unbuilt. That meant that installation of such items as flooring and utilities that support that eastern-most portion of the building couldn't begin until the gearbox was in place.
The storm of construction now over, Clemson is preparing to start commissioning the test rigs, a process that should finish later this year.
