According to the ENR Mountain States 2017 Regional Forecast, it has been a busy few years for the Colorado construction industry. By the end of November 2016, $16.6 billion new construction starts had been recorded. The boom doesn’t seem to be ending anytime soon with future predictions being on track to meet or beat those numbers. While companies enjoy the boom, labor, material and cost efficiency demands keep the pressure on. Can your high rise design address these construction difficulties by incorporating post tensioned concrete in the design?
It can, and more.
ECONOMY OF POST TENSIONED CONCRETE
In the 50’s and 60’s, U.S. builders began to adopt post tension concrete technology for its economical benefits. Published in Concrete Construction Magazine in 1965, was a comparison between conventional rebar and post tensioning in the same west coast apartment complex project. The builder concluded that, from design estimates to the finished project, the post tensioned buildings absolutely saved money. Since then, post tension construction blossomed to become a common factor in concrete construction elements across the country.
CAN POST TENSIONED CONCRETE REDUCE MY COLORADO CONSTRUCTION COSTS?
Colorado, with its many areas of expansive soils, stands to reap well the cost benefits of post tensioned concrete. You can:
- Reduce slab thickness by up to 30 percent while increasing resistance to soil deflection.
- Replace five to six pounds of rebar with about 1 pound of post tensioning steel.
- Excavate to a shallower depth.
- Use lighter forms and less re-shoring.
- Save hoisting costs.
- Place longer runs between joints and supports.
- Save on labor costs by having less material to prepare and place and less ground preparation.
HOW DOES POST TENSIONED CONCRETE PERFORM?
Because pre-stressed concrete reduces tensile stress, including from the dead load, it’s performance in almost every building type exceeds that of ordinary reinforced concrete. The compressive force of the post tensioned tendons can eliminate most cracking. If any cracks form, they remain tight. The Post-Tensioning Institute cites the performance value of post tensioned concrete in expansive soils. The institute also hails pre-stressed concrete for its overall greater reliability and its ability to control deflections whether on the ground or above.
WILL POST TENSIONING ALLOW MORE DESIGN FREEDOM?
Without a doubt, stronger, thinner slabs allow for much more liberality in design. Architects can shape interior spaces around 20-foot spans and devise either taller ceilings or more floors. Possessed of greater tensile strength, post tensioned concrete works well for longer cantilevered elements. Regardless of the purpose of the high rise, these design advantages may be enough to win the bid.
CASE STUDY: TRUMP INTERNATIONAL TOWER, HONOLULU
Building in Hawaii has its challenges, and building a luxury hotel/condominium tower at water’s edge in Honolulu with serious land and envelope restrictions is daunting. However, contracting for the planned Trump International Tower at Waikiki, the professionals at Benjamin Woo Architects LLC, Guerin Glass Architects and Baldridge & Associates Structural Engineering put their heads together to design a 19-floor unique structure incorporating post-tensioned concrete. Their creative engineering enabled more livable space and superior resistance to seismic activity and wind, above what conventionally-reinforced concrete could have provided.
While not particularly burdened with cost restrictions, never the less, the team knew better than to waste resources. By utilizing pre-stressed concrete in the design and build, they created a commercially desirable building with less concrete and steel than other similar Honolulu structures. This efficiency reduced the building weight by 30 percent and unintentionally earned it LEED points for innovation.
BARTON SUPPLY: YOUR COLORADO FRONT RANGE POST TENSIONING RESOURCE
While post tension technology continues to spread throughout the construction industry, it can still be tough to find post-tensioning experts to assist in the engineering and technical placement of your concrete. Post tensioning follows different code requirements, and errors between the architect’s and shop drawings can cause dramatic failures. Therefore, we recommend you contact us at Barton Supply as you develop your high rise plans. Our professional team offers expertise in all types of reinforced concrete, including post tensioned, and will be happy to consult on your project.