How to Build Longevity and Security into Your Next Parking Structure -- and Keep it That Way!

June, 2003

While it's true that hindsight is 20/20, foresight during the design phase of any multi-level precast parking structure can also give the owner a very clear vision of future events. Foresight can result in significant cost savings when it comes to long-term resilience, maintenance and security.
With a precast/prestressed concrete parking structure, added durability can easily be built in from the start and help extend the life and structural integrity many more years beyond the normal lifespan. Some things to consider during the design stage include the following areas.
Ramp and slope
When designing typical grades in continuous ramp parking facilities, the slope should not exceed 6 percent on the parking floor areas; however, for non-repetitive short segments, parking floor grades up to 7 percent are acceptable.
Speed ramps (non-parking areas) should be limited to a 12 percent grade, unless pedestrians are specifically excluded (by use of signage) from entering those ramps. Designers should also keep in mind that, although allowable, ramp grades greater than 15 percent could be psychological barriers to some drivers, particularly on down-bound lanes.
When ramp grades change by more than 8 percent, a vertical curve transition should be used to avoid bottoming out of the vehicle's front and rear bumpers.
This is a very basic overview of ramp design and slope, which will vary according to the type of layout required. The first step the designer should take when designing a new precast/prestressed concrete structure is to determine the most economical, feasible structure to build, such as determining the allowable footprint, then the number of bays needed, the parking on each level, and parking circulation.
Maximum security
Concern about security in parking structures becomes greater each day, and the primary consideration for assuring pedestrian and employee safety is high visibility.
One solution lies in using design methods and building components that not only provide stability, but also serve to increase light and visibility. Using precast concrete single-story monolithic frames for the exterior, and wall columns for interior framing allows the designer to reduce or even eliminate the need for shear walls in the interior.
In addition, litewalls can serve as load-bearing shear walls for lateral stability, and glass-enclosed stair towers provide openness for natural light, and increase the safety and security for pedestrians.
When designing litewall openings, fall protection is required in the walls located adjacent to the ramp bays. This type of protection can be achieved by using cables, railings or fencing located within the openings.
Some precast manufacturers produce and ship these types of litewalls completely assembled as an economical alternative to field installation.
In addition to designing additional safety and security into the precast construction of a new project, Kim Eng, project manager with Gilbane Building Co., offers additional information about some new safety features for parking structures. Eng recently completed work on a precast parking structure for Bergen County in Hackensack, NJ.
According to Eng, "This [Bergen County] garage incorporates the latest in security technology. It has 28 closed-circuit television cameras to monitor the ramps, stairs, interior elevators and entrances with a digital recording computer, which can store the images for 30 days. The images can then be viewed at the Bergen County Police Headquarters during off-work hours.
"Emergency Call Stations are located on all levels at the three stairwells for safety and security. Entrance to the garage is gained by holding a magnetic-striped security card up to the card reader. A computer keeps track of the number of vehicles that enter and exit, and a 'Garage Full' sign at each entrance lights up when vehicle occupancy has been reached."
With the precast concrete options available today, designing parking structures that are bright, open, and equipped with the latest security equipment can help to remove many security concerns about parking structures.
Future maintenance
When construction of a new precast parking structure draws to a close, most precast concrete producers provide maintenance information to the owner to alert them about routine maintenance to their new structure.
While precast parking structures are quite durable and will offer decades of dependable service, periodic housekeeping, preventive maintenance and prompt repair of any damage can provide inexpensive ways for parking structures to maintain long-term durability.
Even simple procedures, such as using rubber-bladed snowplows and lifting them slightly off the deck surface when plowing, will go a long way to minimize or eliminate spalling the edges of precast members, as well as extending the longevity and performance of the joint sealant.
Mark T. Taylor, P.E., is the sales and marketing vice president of Nitterhouse Concrete Products, Inc. He can be reached at
mtaylor@nitterhouse.com.


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Housekeeping Recommendations
Housekeeping is generally performed by the parking structure operator and typically includes the following:
* Sweeping and Trash Collection.
* Window Cleaning.
* Elevator Maintenance.
* Parking Space Re-striping.
* Cleaning Light Fixtures and Replacing Lamps.
* Cleaning Lavatories, Offices and Waiting Areas.
* Removing Graffiti.
* Cleaning, Repairing or Replacing Signage.
* Maintaining Parking Equipment and Revenue Control Systems.
* Checking Security Systems.
Preventive maintenance
The small investment required to perform preventive maintenance on a regularly scheduled basis will go a long way in prolonging the life and value of a parking structure. It will also minimize the intrusion of water and de-icing sales into the concrete, and keep it looking good. The following are some of the items that are considered as preventive maintenance:
* Overall Wash Down.
* Sealing Cracks.
* Patching Potholes and Worn Spots.
* Reapplying Sealers.
* Repairing or Replacing Caulking.
* Maintaining and Patching Roofing Materials.
* Painting.
* Repointing and Recaulking Masonry.
* Tightening Guardrail Bolts and Strand.
* Inspecting and Cleaning Floor Drains and Downspouts.
* Inspecting Parapets, Bearing Pads and Exposed Metals.
* Maintaining HVAC, Electrical and Plumbing Systems.

Repairs
In certain environments where parking structures take a real beating, repairs may sometimes be necessary. Repairs can vary from minor surface repairs to structural reconstruction. Structural deterioration in parking structures is most often related to water leakage, corrosion, freeze/thaw or scaling deterioration and volume change movements. Surface deterioration is often related to weathering and ultraviolet deterioration of sealants and coatings. Repairs might include patching of potholes, removal and replacement of reinforcing steel, floor slab overlays, replacement of expansion joints or the replacement of bearing pads.
In a survey conducted by the PCI (Precast/prestressed Concrete Institute) based in Chicago, IL, 92 percent of parking structure owners said they would use precast concrete in another structure. The reason? Because the durability characteristics were excellent, the structures offered longer life, and both new and older structures exhibited fewer problems than other construction methods.
Design assistance
Industry organizations and associations such as the Precast/Prestressed Concrete Institute (www.pci.org), Mid-Atlantic Precast Association (www.mapaprecast.org), National Precast Concrete Association (www.precast.org), Architectural Precast Association (www.archprecast.org), etc., are constantly on top of the latest industry techniques and changing technology. PCI, MAPA or any PCI-certified precaster can provide you with the information you need to engineer and design the most appropriate garage to meet your client's needs.