Award of Excellence: Parking Structures Category
University of Kentucky Parking Structure #2 Restoration and Expansion
Submitted by Carl Walker, Inc.
University of Kentucky Procurement & Construction
Carl Walker, Inc.
Messer Construction Co.
St. Paul, Minnesota
This $9,300,000 restoration project located on the main campus of the University of Kentucky (UK) involved in the restoration and expansion of a 5-level 800-space parking structure built in 1969. The structural system consists of cast-in-place post-tensioned concrete beams and one-way slabs. The primary slab reinforcement consists of unbonded button-headed post-tensioning tendons, with little or no supplemental mild reinforcing steel. A bonded button-headed post-tensioning system was used in the beams.
The existing parking structure was in poor condition, with up to 50% of the slab primary post-tensioning tendons broken or severely damaged due to chloride-induced corrosion. The other primary restoration challenge involved restraint issues. The original structure was tied to stiff stair tower elements in each of its four corners, which restrained the natural movement of the slab. This resulted in excessive tensile stresses in both the slabs and the stair tower elements that led to severe cracking on these areas.
A structural steel framing system was implemented to supplement the structural slabs to compensate for the deterioration of the primary slab tendons. This innovative repair approach resulted in lower costs, a more compressed construction schedule and far less disruption to existing operations. A total of 1365 steel beams were installed which included over 5000 epoxy anchorages for the connections. Some selective post-tensioning repairs were also completed.
The restraint problems were addressed by separating the stairs from the main structure by severing slab and beam elements. This involved complex detailing as the main structure slabs and beams were supported by the stair elements. This required redesign and re-anchoring of the post-tensioning tendons.