An old parking garage had experienced settlement in the past and was previously repaired with auger cast piles that were doweled into the existing strip footing of the garage. The steel connections from the footing to the auger cast piles from this previous repair were shearing on the exterior edge of the footing, likely due to corrosion. This had caused the perimeter wall of the garage to lean outward. The floors of each level were supported on this wall and began to lose contact with the below supporting elements. Structural integrity and safety of the occupants became a concern. Further, the owner wanted to remodel the garage and adjacent building.
Further repairs would be very difficult as the adjacent seven story building was only 20 feet from the structure and its footing was approximately 12 feet higher than the footing of the parking deck which needed to be addressed. There were also only 3 foot sections of workable footing face between the previously installed auger cast piles.
To prevent further movement of the wall during construction, post tension cables were run across two levels of the parking deck in order to hold the walls together. Then, a row of 29 auger cast soldier piles were installed to allow for 20-foot-deep excavation without risking settlement of the adjacent seven story building.
Alpha Foundations installed 27 Foundation Supportworks 350 series push piers to depths ranging from 35 to 50 feet along the exterior face of the footing. These piers were attached to the footing with a retrofit bracket assembly with an approximate allowable capacity of 45 kips per location. After the piers were installed, they were hydraulically loaded and the footing was lifted approximately 0.5 inches and stabilized. Alpha Foundations also repaired two staircases in the parking deck with seven Foundation Supportworks 287 series helical retrofit piers. One hundred forty-four linear feet of CarbonArmor carbon fiber was stitched over existing cracks in the garage staircases in order to stabilize cracks that had occurred. The interior operations were completed after hours to allow for continued use of the parking deck. The total retrofit installation was completed in just 14 days.