POST TENSIONING TECHNOLOGY
Post Tensioning Technology has been used over the last three (3) decades in Trinidad & Tobago where it was introduced for the construction of Water Tanks, Beams, LNG Tanks etc.
CPML Contractors Limited recognized the benefits and potential of the system and took the decision to invest in Inventory and Personnel Training to ensure the wider availability of the Technology in Trinidad & Tobago.
Managing Director,Mr. Bill Ramrattan, a member of the Post Tensioning Institute is fully trained and certified by the Institute as an Installer / Inspector for the System. CPML has also available and Warehoused in Trinidad 60,000 Lf of Unbonded Monostrand Cable, Anchors and Wedges to undertake a Professional Installation immediately.
CPML Contractors Limited has the capacity to provide full Design Engineering Services using the Post Tensioning Technology by utilizing the expertise and services of Dr. Ian Khan Kernahan, a Structural Engineer and Lecturer at The University of the West Indies (UWI) Department of Civil Engineering, Mr Brendon Inniss, an experienced Civil Engineer who is a member of the Post Tensioning Institute and Mr Mark Francois, Director and Civil Engineer at Beston Engineering Ltd.
CPML Contractors Limited (CPML) has introduced Post Tensioning Concrete Technology as an economic alternative to Reinforced Precast Prestressed Concrete Construction as well as Structural Steel Systems. It allows for -:
a) Faster Construction
b) Efficient Members
c) Economic Advantages
WHAT IS POST TENSIONING TECHNOLOGY?
Post-tensioning is a method of reinforcing (strengthening) concrete or other materials with high-strength steel strands or bars, typically referred to as tendons.
Imagine a series of wooden blocks with holes drilled through them, into which a rubber band is threaded. If one holds the ends of the rubber band, the block will sag. Post-tensioning can be demonstrated by placing wing nuts on either ends of the rubber band and winding the rubber band so that the blocks are pushed tightly together. If one holds the wing nuts after winding, the blocks will remain straight. The tightened rubber band is comparable to a post-tensioning tendon that has been stretched by hydraulic jacks and is held in place by wedge-type anchoring devices.
BENEFITS OF POST TENSIONING TECHNOLOGY
Instead of using welded wire or conventional rebar to reinforce the slab-on-grade foundations, post-tensioning tendons are cast in the middle of the slab, running in both directions. The thickness of the slab and spacing of the tendons depends largely on the size of the structure and the type of soil the slab is built upon.
The embedded tendons are then stressed to an effective force of about 25,000 pounds with the use of hydraulic jacks. The internal compressive force thus generated in the concrete results in numerous advantages over conventional slab-on-grade construction, including:
Increased crack resistance under load
Decreased cracking due to temperature variations or concrete shrinkage
Reduced footing thickness resulting in reduced excavation, and less material costs
Fewer reinforcing elements result in faster installation
Reduced maintenance costs
In situations where the soils is medium expansive or higher (expansive index 50+) - Post Tensioned Slabs often become the construction method of choice for both quality and cost. In Trinidad & Tobago, we have a large percentage of expansive clays for which this method of construction is ideal.
As recommended for use in residential and commercial slabs, CPML Contractors Limited’s slab on grade post-tensioned system provides a simple and economical foundation, which has the following advantages over other reinforcing systems:
Require less concrete in slab
Ease of installation.
Speeds slab construction.
Improves control over project scheduling.
Reduced member size, cutting from cost.
Efficient long span design.
APPLICATIONS OF POST TENSIONING TECHNOLOGY
There are post-tensioning applications in almost all facets of construction. In building construction, post-tensioning allows longer clear spans, thinner slab, fewer beams and more slender, dramatic elements. Thinner slabs mean less concrete is required. In addition, it means lower overall building height for the same floor-to-floor height. Post-tensioning can thus allow a significant reduction in building weight versus a conventional concrete building with the same number of floors. This reduces the foundation load and can be a major advantage in seismic areas. A lower building height can also translate to considerable savings in mechanical systems and façade costs. Another advantage of post-tensioning is that beams and slabs can be continuous, i.e. a single beam can run continuously from one end of the building to the other.
Post Tensioned Slab Construction is used in:
Condominiums & Apartments
Warehouses & Industrial Floors
Tennis & Basketball Courts