Construction of Southwestern Bell Telephone Company's 1150-car, 11-floor parking garage at their Texas headquarters complex presented an exciting challenge for the design development team and for the contractor. The reinforced concrete, post-tensioned garage is, to the contractor's knowledge, unique in that it is a double helix design with a crossover core in the center. To further complicate construction, beams extend diagonally from the core to the extreme corners of the ramps.
"We determined early on that we had to get the core out in front of the ramp forming, but that presented a problem of how to handle the continuous post-tensioning tendons and rebar at the core-ramp interface, where five beams intersect at approximately the same elevation." Contractor, architect, owner and structural designer worked together to solve the problem.
Part of the solution came in the form of column forms that split in the middle rather than the corner, allowing steel and tendons to extend through the forms while pouring the core structure. Also, special sleeves for future tendon installation and racks for supporting the rolls of tendons while awaiting ramp forming were used.