An overview

Post tensioned design and construction methods have become more popular lately. Better construction techniques and simplified design methods have fueled the growth of P-T in construction industry ever since. By the early 1990’s the popularity of P-T increased with further refinements to the tensioning process, the development of corrosion-resistant anchorages and availability of design software. P-T has become a preferred method for reinforcing concrete today.

Product

There are two types of P-T systems: bonded and unbonded. Unbonded systems use strands surrounded with special corrosion-inhibiting grease and encased in waterproof plastic sheaths. Concrete is placed around the cable assembly, similar to standard reinforced concrete. In a bonded system, steel or plastic ducts are placed in the formed area. After concrete is placed and gains strength, P-T strands are threaded through the ducts and tensioned. The ducts are subsequently grouted to prevent corrosion. Unbonded systems are nearly always used for building and slab construction, while bonded systems are mostly used in bridge construction.

The advantages of P-T concrete over reinforced concrete are far too many to be overlooked in the design and construction of concrete structures. Since the reinforcement is protected, P-T reinforced structures have lower annual maintenance costs. Another reason for lower maintenance is that P-T systems have fewer joints. When owners consider maintenance costs over time (life-cycle costs), they realize the significant benefits of P-T systems.

Reasons to consider P-T include the following:

Concrete slabs are thinner, and consequently and less costly. Slabs reinforced with P-T have less deflection. Joints in a P-T slab are minimized or eliminated. Curling in slabs is greatly reduced or eliminated. P-T system often costs less and is much faster to than standard rebar systems. P-T is an effective way to design shallow foundation systems. P-T improves the long-term durability of structure. Span lengths can be greatly increased.

Advantages of P-T Technology

• Due to this technology, complexes are facilitated with better parking area
• Clear span areas with less obstruction of beams and columns facilitates better interior arrangements
• It facilitates less air conditioning cost