Challenges of designing a garage in shoppers’ paradise

By Kermit D. Bright, P.E., and Krishna G. Saha, P.E.

Kansas City’s Country Club Plaza is a historic 14-block district featuring more than 120 stores and 30 restaurants and cafes, as well as a residential community. The ornamental architectural detail of the complex is a Spanish motif, with stucco buildings and red tile roofs.

The new parking structure incorporated this look, actually appearing more like another building with an ornate Spanish-style faade, rather than a garage.

In addition to designing load transfers, connecting to four existing buildings and designing pedestrian entrances to each, the Kansas City Saks Parking Structure – owned by Highwoods Properties, Kansas City, Mo.- needed not only to fit within the historical context of the surrounding Country Club Plaza, but also to integrate a waterproofing system because the parking is designed above retail space.

Time constraints added pressure for the general contractor – Kansas City, Mo.- based JE Dunn Construction Co.- and the entire architectural and engineering design team. Because the parking structure is located in a dense urban area that supports retail operations vital to the local economy, construction could not begin until the holid ay shopping season was over. Yet, it was imperative that it be completed by the next holiday shopping season.With less than nine and a half months from the start of demolition of the old structure until shoppers could park and enjoy proximate retail, the parking structure was not without challenges to the project team. Here are the key challenges, and how the planning, engineering, and construction team met them.

Building challenges

The defining challenge of this project was the unique adaptation to existing conditions.

Engineers with Structural Engineering Associates of Kansas City, Mo., together with the architect, Gastinger Walker Harden Architects, Kansas City, were ca lled upon to provide a series of engineering and architectural designs singular to the project. The design included several phases that included temporary components necessary to keep the center operative and open for business throughout the entire process.

Massive corrosion within the structure from years of ice and salt was not cost effective to repair. Therefore, the designers determined that the existing parking garage needed to be demolished. Once the old structure was removed, the team was able to accurately locate the connection points to the surrounding buildings. The team learned that the garage floor level couldn’t line up with all of the varying levels of the existing building floors. Armed with that information early on, the project leaders and engineers were able to design elevated walkways to connect the new garage to the existing buildings at the required elevations and levels.

Since buildings existed on either side, links were needed to connect to the garage, in addit ion to providing exits to the garage.The exit levels varied with each building – some were on the second floor, others on the third floor.

The buildings were designed to move indep endently and freely of each other. To continue to permit this, engineers designed a slide connection on the garage that allowed the other buildings to move and shift independently. The sliding connection for hori zontal movement has the capacity to compensate for the attached building’s movement.

To meet the current code requirements, a fire exit staircase was added to the existing building on the east side of the garage structure. Engineers were challenged to provide a structural system that would allow the new stair to overhang from the new garage structure because the existing building was not capable of supporting the stair. They devised a plan that used a diagonal brace with a tieback to the new garage for support.

The location of retail stores immediately below a multi-level parking garage was another test of skill for the design team.

Waterproofing the garage to protect the stores below required extra planning and design. Engineers used a unique concrete sandwich by placing a waterp roofing membrane on top of a precast structural deck, adding high-density insulation and a non-structural, cast-in-place concrete topping slab above it. The concrete topping slab creates the driving surface of the garage.

Laye ring the various materials precluded leaks to the sensitive retail space below, and also served as a sound barrier.

Time-saving efforts With only a nine-month window from the time of demolition to the required completion of the new garage structure, engineers conside red options of cast-in-place versus precast concrete. The final design choice of precast double tees with a cast-in-place topping slab offered economy as well as time efficiencies.

Selecting a precast manufacturer – Rinker Materials Inc., located in Marshall, Mo.- to fabricate precast elements offsite permitted construction at the same time the existing garage was being demolished and the new foundation was being poured.When the foundation was ready, precast erection began immediately with columns, beams, and long-span double tees. Structural Engineering Associates’ project leaders estimated that by using precast and continuing the design process simultaneously, six months could be shaved off the project schedule.

Of course the inevitable result of this design-build project was that some of the embedded connections in the precast walls did not line up with the embeds in the double tee. Since they were both precast pieces, engineers were ch a llenged to provide simple, adaptable, alternate connection for the contractors in the field. The connection incorporated another steel plate with anchors drilled into the concrete. Instead of the plate being embedded in the concrete and discrete, the corrected connection is clearly visible.

Conclusion Proficient engineering, hand-in-hand with the total precast concrete structural system, a ll owed this project to be completed in record time – 9 months – with little disruption to the shopping center.

Architectural concrete panels cast with form liners, as well as reveals and an integrally colored mix, complements tile mosaics and large metal panels inset into punched windows. Ornamental iron infill was used over openings to ensure ventilation and to add a decorative touch.

Fitting in beautifully with the Spanish architecture of the upscale shopping district, engineers had created an unobtrusive, and, yes, stylish parking garage. But most of all, they delivered a safe, secure, convenient, and leak-free structure for retail owners and shoppers alike.

Kermit Bright, P.E., is president of Structural Engineering Associates, Inc., and Krishna G. Saha, P.E., is vice president. They may be reached at 816- 421-1042.