Developers, Architects, Engineers and Contractors are demanding more from buildings today. In particular, they are demanding:
• Lower costs
• Flexible floor layouts: less columns and longer spans
• Unique designs: irregular shapes
• Faster construction
• Sustainable design
This has called for new and more efficient engineering solutions, hence the popularity of post tensioned concrete.
In traditional reinforced concrete, the steel reinforcement remains inactive until the formwork is removed. In post tensioned concrete, high tensile steel tendons are placed and stressed, making the reinforcing steel active.
This can also easily be observed when holding together several books and pressing them laterally. Under such pressure the whole row gains enough stiffness and strength to ensure its integrity.
The tendons are placed in a curved profile and in addition to the compression on the perimeters, an upward force is generated that will counteract the applied forces relieving the structure from the gravity effect. This is the reason why early demolding is possible within three days so that the formwork can be re-used.
Design Freedom
The introduction of Post-Tensioned slabs by Somers Engineering into East and Central African market is changing the way Architects, Engineers and developers design more innovative structures and with greater flexibility.
To maximize the benefits of post-tensioning at the building project level, the effects of reduced member sizing should be applied early in the design process.
Cost Comparison
Post-tensioning offers direct cost reduction over conventionally reinforced slabs primarily by reducing concrete and rebar material quantities as well as rebar installation labour. Typically, savings between 10% -20% in direct cost are achieved.
Factors contributing to direct cost reduction:
• Thinner slab (1/3 of RC alternative) with less reinforcement
• Reduction of material quantities and cost
• Reduction of labour and material handling costs
• Reduced total building height and cladding cost
• Reduction of beams and steps – simplified and cheaper formwork
• Rapid reuse of formwork – less formwork needed on site
Cost Structure of RC vs. PT Slabs
In a typical slab with spans over 7 meters, the net savings in material cost can range between 10% -20% of original RC alternative. This survey did not include other benefits such as time saving, cladding, plumbing, electrical, lift installation, painting and other finishes.
Design Solutions
Somers Engineering in partnership with Amsteele Systems SA and world leading post tensioning company Dywidag Systems International, Germany provides a complete design of the Post tensioning applications. Somers uses the latest software and up to date international practice in post tensioning.
For more information, please visit www.somerseng.com
