HOK, Inc., Washington D.C.
How to construct buildings taller, decrease construction costs, create better usage of space, improve sustainability, while maintaining serviceability is always a goal for developer/architect/engineer and contractor. Already a common construction method for high-rise buildings the use of Post-Tension (PT) slabs has numerous positive impacts on the design and economics of a building.
Post-Tension slabs can be thinner than conventionally reinforced slabs while having the same strength capacity. PT slabs have greater spans and therefore allow for increased column spacing and reduced total column quantity. Thinner slabs increase floor to floor height at each level and can increase the total number of floors for the same building height. Thinner slabs translate to reduced dead load weight of the base building and therefore smaller column sizes and foundation systems.
The use of PT reduces slab deflection. Flooring materials with stringent flatness requirements require less floor preparation and have less cracking/warping issues over time. PT slabs require significantly less reinforcing steel than conventionally reinforced slabs. The reduction in project concrete and steel reduces the embodied energy of the building and there are available LEED credits for material savings.
Reduced building heights can translate to less energy to heat and cool. The compression force from PT improves crack control and decreases water intrusion, thus reducing building maintenance and increasing durability.
As projects are in the developmental stages of design it’s important that developers understand all the potential initial and long-term cost savings for each element of their building. As we move forward with taller buildings the use of PT slabs should be considered as a viable construction method.