Kimley-Horn Team Transforms Durham Centre Parking Deck

Now imagine that this parking structure is deteriorating to a point of potential total re-construction.

Post-tensioned slabs were sagging to the point that portions of the garage had to be shut down for safety. Water leaked through from the plaza above to the point that gutters had been installed to catch the water and divert it to interior drains. The deck lighting was old and dark, creating an uninviting place to park.

Not a pretty picture if you are the owner or a tenant. This was the challenge faced by Kimley- Horns Durham Centre parking structure renovation team.

The Durham Centre parking deck renovation in downtown Durham, N.C., was different than most other renovation projects.

The facility serves as the structural base for an office tower, and as such, is the gateway for tenant staff and visitors.

In recent years, the parking deck and rooftop plaza had fallen into severe disrepair and the rooftop plaza needed a complete overhaul.

In addition, the original parking design resulted in significant exiting delays for patrons leaving the facility. The condition prior to renovations resulted in the public avoiding this facility at all costs, which reduced revenue potential.

The Kimley-Horn team was brought in to serve as the structural engineer of record, parking consultant, landscape architect and civil engineer.

Team Coordination Aids Project

Throughout the project, the team emphasized quality control and communication. A primary concern was how to proceed with the renovation work and still keep the office tower operable. As plaza demolition and construction progressed, pedestrian movement through the jobsite was adjusted.

The team coordinated with City inspectors to ensure public safety was maintained, including providing a four-level temporary stair to maintain proper egress.

Construction activity updates and a rendering of the finished project were posted at the main entrance tower, and daily emails were distributed to building tenants. These communication efforts kept the affected individuals and businesses informed and provided increased awareness and understanding of the project.

Quality Control Checks Ensure Progress

Quality control measures included weekly site visits from the design team, third-party consultant, and manufacturer representatives. The firms involved made it a policy to have two sets of eyes on everything to ensure the highest level of quality. A testing agency was also hired to inspect work as it was being completed to increase accuracy. Each level of quality control enabled the team to work in concert to produce a well-constructed project on schedule. Project specifications required additional quality checks to confirm warranty elements, including waterproofing, expansion joints, landscaping, hardscaping, parking equipment, security cameras, and lighting.

Structural Repair Creates Design Challenge

Repair of the structural posttensioned slabs within the garage was a primary design challenge. Due to the severity of degradation and the importance of the slabs structural integrity, several repair options including complete removal and reconstructionwere evaluated for effectiveness, compatibility, and overall life cycle costs.

During design, Kimley-Horn developed a cost-effective slab repair that minimized concrete demolition by creating a closure-pour at an existing construction joint, removing the corroded length of strands, and re-stressing (one in the opposite direction from original construction) to create a stable system.

Due to the intricate, complicated nature of repairing damaged posttensioning, special inspections were provided for the structural repairs, in addition to materials testing for all concrete placement. Timing this work during the winter months presented a significant challenge to the contractor, so blankets and heaters were used to prevent the cold temperatures from causing the concrete to cure too quickly, thus preserving its strength and durability.

New Exit Design Improves Traffic Flow

To address the original parking structures significant exiting delays, a new P2-level exit lane was added and existing parking control equipment was upgraded. These enhancements allow for accelerated movement out of the deck and into the downtown grid, while providing faster transaction times and a more reliable system.

The design team worked closely with the contractor to develop an effective, achievable phasing plan to accomplish all of the needed repairs, while maintaining access to the building above for patrons. The challenges included lack of any entry and exit access on each floor; one circulation ramp on the east half of the garage; one cashier booth on P1; police department vehicle storage; a minimum number of stalls; and safe, convenient pedestrian movements.

Rooftop Plaza Refurbished to Green Deck

The existing rooftop plaza consisted of a temporary wooden walkway and planter areas that created numerous tripping hazards. Several large tree planters were also present that resulted in water infiltration issues. As part of the deck renovation, these areas were completely refurbished.

New planters were designed with drought-tolerant and scale-sensitive landscaping. The existing planter areas were filled with lightweight structural insulation to create a flat surface for the pedestal paver system, reduce the total weight of the system and fill the voids created by larger planters built into the structure.

The updated design features:
* pedestal pavers to eliminate ponding water
* hot, rubberized asphalt waterproofing that protects the garage roof slab and lowers maintenance costs
* garden roof planter technology
* drought-tolerant plantings for year-round landscaping
* art pedestals for local artists;
* trellis structure to provide a shaded gathering space.

The result is a pedestrian-friendly plaza that serves as the office towers main entrance and a functional rooftop for the parking structure below.

Aesthetic Upgrades Include Signage, Lighting & Paint

While changes to the exterior facades were not necessary, the decks general aesthetics required significant upgrades. Interior rehabilitation efforts included LED lighting, signage, traffic coating, striping, and painting.

In addition to providing a completely new feel to the deck, these renovations also provide a higher level of service through improvements such as increased light output and uniformity, positive patron impression, easier navigation, a safer environment, and more durable structural slabs through minimized water intrusion.

The final result? The deteriorated facility was successfully renovated and rehabilitated, and was completed $300,000 under budget.