All parking structures require a diligent maintenance program to ensure long-term durable performance. Broad categories for maintenance of parking structures are generally accepted as: Housekeeping, Preventive Maintenance, and Structural Repairs. Within these categories are specific items that require periodic attention. Precast, prestressed concrete parking facilities, by their unique design, require maintenance tasks that may be slightly different than those of other construction types. We will define the types of maintenance tasks specifically required for precast, prestressed concrete parking structures.
Housekeeping
Housekeeping maintenance involves those items that enhance the aesthetic appeal and functional performance of the parking facility. The users of the parking structure tend to consider their parking experience as satisfactory if the facility is clean and safe. The owner or the operator of the structure generally performs these tasks on a scheduled basis. Housekeeping maintenance involves the following tasks:
- General Cleaning: Trash removal, drain cleaning, sweeping, window cleaning
- Floor Wash: Annual high pressure wash down, oil stain removal
- Expansion Joints and Control Joints: Cleaning of debris
- Painting: Periodic touch-up of painted surfaces
- Landscaping: General upkeep of planting materials
- Doors and Hardware: Check for proper operation
- Striping and Graphics: Re-paint parking stripes and graphics
- Lighting Fixtures: Clean lens and replace burned out lamps
- Elevator: Cleaning and maintenance
- Signs: Cleaning and repair
- Graffiti: Removal
- Security System: Check for proper operation
- Parking Equipment, Revenue Control System Maintenance: Check for proper operation
- Janitorial Services: Lavatory, office, waiting areas
These duties typically fall to the parking structure operators, because they generally have a primary interest in maximizing operating revenues and keeping operating expenses within budget while providing safe and convenient parking to attract the user. The housekeeping items listed above should be performed by the operator.
Prevention Maintenance
Preventative maintenance involves a periodic checkup, cleaning, and restoration of all components including structural, architectural, and mechanical elements as well as equipment maintenance and safety systems. This type of maintenance prevents premature deterioration of the structure and unexpected failure of mechanical components. Minor problems discovered and corrected with preventative maintenance will prevent expensive future repairs.
The owner has basic control over the durability of a parking structure. If the owner chooses to invest in durability-enhancing features in the original construction, preventive maintenance and future repair costs will be smaller. Therefore, it is recommended that the owner, not the operator, be responsible for preventive maintenance.
Preventative maintenance should include a yearly checkup of structural, architectural, and mechanical components to verify proper performance. For the structural system, the checkup should include a visual inspection of all structural components, preferably by a structural engineer experienced in the design and construction of precast parking structures. Of particular importance in structural system maintenance is the drainage and sealants. Over time, poor performance of these elements can lead to serious structural problems. Equipment maintenance may be performed by the owner or operator in accordance with the manufacturer’s recommendations. Revenue control equipment, life safety systems, elevators, and security systems are vital ingredients for maintaining the parking structure in proper working condition. Specifically, the annual structural checkup involves the following tasks:
Structural Systems Maintenance
- Double Tee Floor Members: Visually inspect for delamination, spalling, cracking, and scaling. Check flange connections for weld failures or corrosion damage.
- Floor and Roof Deck Members: Visually inspect for spalling, cracking, and scaling. For field-applied cast-in-place toppings, also visually inspect for delamination. Check pretopped double tee flange connections for weld distress or corrosion damage.
- Beams, Columns, and Spandrels: Visually inspect for spalls, cracks, and/or delaminations.
- Stair and Elevator Towers: Check handrails, stair treads and landings, metal or precast stair members, walls, and roof for deterioration. Check concrete adjacent to handrails for signs of distress.
- Exposed Steel: Check for corrosion of bearing plates and welded connections. Check grouted connections for rust stains.
- Bearing Pads: Visually inspect all bearing pads for signs of distress.
- Sealers and Deck Coatings: Check for tears, abrasions, delaminations, and/or other deterioration.
- Joint Sealants: Check all joint sealants for signs of deterioration and leaks.
- Expansion Joints: Check for signs of deterioration.
- Drainage: Check for leaking, areas of inadequate drainage, and clogged drains. Check roof of stairs for leaks.
- Cable Barriers: Visually inspect for damage to anchorage points. Check tightness of cables.
- Tripping Hazards: Check curbs, stair thresholds, and floor surfaces for potential tripping hazards.
Structural Repairs
Even the best maintained parking structures may require some structural repairs during their service life. Parking structures are subject to harsh environmental exposure, dynamic loading conditions, extreme temperature variations, and destructive chemical attacks from de-icing materials. If required, structural repairs must be designed and specified by a structural engineer experienced in parking structure repair techniques. Repairs that may be required for older precast structures include the following:
Concrete Deterioration
More common in cast-in-place portions of the structure such as field placed toppings and pour strips than in precast concrete components. Deterioration mechanisms include:
Scaling: The shallow disintegration of cement paste at the concrete surface. Usually associated with freeze thaw cycles, scaling produces an unsightly rough surface that poses a tripping hazard and recesses for water ponding. Repairing with a surface overlay or topping is common.
Spalling: Fracturing of the outer surface of concrete from rebar corrosion or isolated impact loads. Spalls tend to have a surface area of several inches and depths of 1 in.or more. Repairing of spalled areas should include a structural assessment to determine the cause of the spall along with a specification of proper repair materials that are compatible with the base concrete properties.
Cracking: Well distributed fine cracks are typical and normal for non-prestressed concrete elements. A typical cracking can occur from mishandling precast units, improper placement, finishing or curing of cast-in-place toppings, thermal movements, corrosion of embedded metal, structural overload, or from foundation settlement. Minor non-moving cracks in deck surfaces are non-structural and need only a surface seal to prevent water intrusion.
Structural cracking requires an engineering appraisal to determine the origin of structural degragation and proper repair specifications.
Delaminations: Fractures which occur below and parallel to a concrete surface. In precast parking structures, these typically occur in field placed toppings due to corrosion of reinforcing steel or due to improper placement (surface preparation) of the cast-in-place topping. Extensive delamination requires engineering evaluation and significant remedial repair to stop the deterioration process.
Expansion Joints
Expansion joints are typically installed on structures with lengths greater than 300 ft, structures with irregular shapes, or to isolate stair and elevator towers. Their purpose is to limit the build-up of stresses in structural members or connections due to volume change movements created by seasonal temperature variations and customary drying-shrinkage of concrete. Expansion joints work by providing a flexible link between two separate portions of the structure. Typical movements will range from 1 to 3 in. which can be accommodated by a variety of joint styles and brands.
When expansion joints deteriorate or malfunction, water leakage through the joints may lead to deterioration of the concrete structure. Frequent monitoring, cleaning and repair of local damage will extend service life, but frequent problems require a specialist to evaluate and resolve.
Connection Distress
Thermal movements or structural overload can occasionally create cracking or distress in connections between precast members.Connections, which can consist of welded plates, bolted plates,bolts through members or bearing pads between members serve a variety of functions during and after construction of the structure.For this reason, it is recommended that an experienced engineer familiar with precast concrete construction investigate any sign of connection distress.
To download your free complete copy of the “PCI Maintenance Manual for Parking Structures” follow this link:
http://www.pci.org/pdf/publications/parking/MNL_136_04.pdf.
If we have already completed a parking structure project with you, a hard copy of this manual was provided at project close-out with all of our warranty documentation.
As a loyal teammate of your parking garage design and construction team Coreslab Structures (TAMPA) Inc. wants to thank you for allowing us to be a part of your team and encourage you to use our expertise throughout the service life of your parking structure.
Sincerely,
The Management Team
Coreslab Structures (TAMPA) Inc.