Award of Excellence: Longevity Category
Repairs to Paulina Street Parking Garage
Submitted by CTLGroup
University of Illinois at Chicago
R. Rudnick & Co.
The Paulina Street Parking Structure is an 1100-vehicle post-tensioned concrete garage built in 1976 and located at the University of Illinois at Chicago (UIC). The garage was constructed with 5000 psi (34.5 MPa) lightweight concrete and specified concrete cover over top conventional slab reinforcing was 3/4 in. (19 mm). By 1991, after 15 years of service, the garage had become a maintenance headache for the university due to ongoing corrosion and failing repairs.
An investigation was performed including a complete condition survey, investigation of tendon and anchorage conditions, laboratory testing, and structural design review. The solution recommended by the engineer and selected by the university was installation of a continuous bonded concrete overlay incorporating microsilica concrete and epoxy-coated reinforcing.
Repairs incorporated use of hydrodemolition to remove 1/2 to 3/4 in. (12.7 to 19 mm) concrete and maximize bond development between existing and repair concretes. A shoring and counterweighting system was developed to maintain structural integrity during repairs and to enhance service-load performance of the reinstated facility. The damaged slab post-tensioning system was rehabilitated. Detensioned and corroded tendons were replaced. Tendons significantly damaged by chipping hammers during a previous repair were also replaced. The repairs spanned two construction seasons and were completed in 1993.
The garage has required minimal maintenance since the 1993 repairs and is in better condition currently than it was prior to the 1993 repairs. In 2014, 21 years after repair completion, the garage exhibits only localized repair patches (significantly less than 5% of the garage surface area). Few, if any, tendon repairs have been performed since the completion of 1993 repairs and there is no evidence of ongoing tendon deterioration.