Post-tensioned concrete provides a structurally efficient, reliable, and cost-efficient solution for the construction of concrete parking garages. By eliminating closely spaced joints found in other construction methods, properly designed post-tensioned parking structures are virtually crack-free, maintenance free and offer great aesthetic freedom and flexibility for today's architectural designs.
Millions of square feet of cast-in-place, post-tensioned parking garages are built in the United States each year. Post-tensioned parking garages continue to gain market share in terms of both the number of structures built and volume (number of spaces). When all of the factors are evaluated, it is easy to see why cast-in-place, post-tensioned concrete parking garages are the system of choice for the nation's hospitals, universities, developers, parking operators, commercial owners and public institutions.
Advantages of using post-tensioning for your next parking structure project:
- Initial and Life-Cycle Costs Savings: Post-tensioned structural systems often provide initial cost savings and better life-cycle costs when compared to other framing systems.
- Low Maintenance: Loss of parking spaces during maintenance work results in loss of revenue and inconvenience. Post-tensioned floors are relatively crack-free, resulting in minimal maintenance issues.
- Crack Control-Watertightness: Post-tensioned structural systems eliminate closely spaced joints and help ensure water-tightness by placing the floor in bi-axial compression, thereby controlling and counteracting shrinkage and flexural cracks.
- Smooth Riding Surfaces: The elimination of closely spaced joints results in a superior riding surface. Differential deflections across joints are not an issue in cast-in-place post-tensioned floors.
- Lighting and Security: The long spans, wide beam spacing, and flat surfaces provided by post-tensioned structures enhance lighting and improve patron security. The open structural systems also enhance lighting and create a more welcoming environment.
- Fire Resistance: The slab thickness and beam widths commonly used in post-tensioned structures provide fire ratings that meet code requirements.
- Functional Flexibility: Post-tensioned construction allows long column-free spans and is adaptable to other functional requirements of parking structures such as the need to accommodate slopes to drains, straight or curved ramps, warped surfaces that provide smooth transitions between ramps and level floors, and irregular plan layouts.
- Versatility: Cast-in-place, post-tensioned construction allows for versatility in structural layout. Structural floor configurations are virtually limitless. Cast-in-place forms can be used to create helical ramps, spiral ramps, compound slopes and more.
- Aesthetics: Curvilinear shapes and forms are easily achieved in a cost-effective manner with cast-in-place structures. Architectural treatments of exposed concrete are easily achieved.
- Reduced Structural Depth: Post-tensioning can reduce structural depths by one-third or more in comparison to other systems. In the case of underground parking garages, structural depth reduction is desirable to reduce excavation, soil retention system costs, and dewatering costs in sites with high water tables.
- Deflection and Vibration Control: The pre-compression, draped tendons and the monolithic nature of cast-in-place concrete garages significantly reduce deflection problems. The monolithic construction, continuity and rigid connections between beams and columns reduce vibrations.
- Lateral Loads: Monolithic connections between slabs, beams and columns provide rigid frame action to resist wind and moderate seismic loads.
- Seismic Loads: Post-tensioned parking structures performed well in the 1971 San Fernando, 1989 Loma Prieta, and the 1994 Northridge earthquakes. Research has shown that, under some conditions, unbonded post-tensioning improves the behavior of moment frames under seismic loads. Code provisions developed by the Building Seismic Safety Council allow the use of unbonded post-tensioning in ductile moment resisting frames.
- Structural Integrity: Research and experience have shown that post-tensioned structures inherently provide structural integrity under abnormal and catastrophic loading. Well detailed cast-in-place post-tensioned structures have significantly higher structural integrity, redundancy and resistance to catastrophic loading than precast systems.
- Construction Advantages: Both the time and cost of hauling prefabricated pieces from the plant to the job site and the need for heavy lifting are eliminated. Large panel flying forms, modular forming systems and ever improving concrete technology continue to enhance the construction speed and economy of cast-in-place post-tensioned parking structures.
- Economics: Over the life of the structure, the cost to maintain cast-in-place, post-tensioned parking garages is typically less than alternative systems.