Post Tensioning
As an undisputed pioneer, STRANDS POST TENSION EXPERTS offers a complete range of strand and bar post-tensioning systems (PT systems), covering all possible applications in the civil engineering and building sectors. Our in-house teams ensure professional execution of PT work, handling all stages of design, installation, stressing and grouting.
STRANDS manages the entire PT process, including:
● Design
● Installation
● Stressing
● Grouting
The post-tensioning technique involves installing and tensioning tendons in a concrete element, thereby applying compressive stress to the material. This compensates for the tensile stress that the concrete may undergo as a result of
external loads and reduces or eliminates deformation and cracking.
A revolution in the art of construction:
Post-tensioning has revolutionised the design and construction of concrete structures, allowing thinner concrete sections, longer spans and more durable concrete structures. It also paved the way for the development of new construction methods, making bridge construction simpler, faster, and more cost-effective.
Greater architectural and design freedom:
The use of post-tensioning opens up a wide range of geometric and architectural possibilities. In particular, it allows complex curves, variable elevations, and long free spans without support.
Lower construction cost, faster construction:
Post-tensioning significantly reduces the amount of concrete and steel required for the structure and the foundation work. It allows for the rapid assembly of precast elements using industrialized methods, allowing the site to progress quickly and efficiently.
Greater architectural and design freedom:
The use of post-tensioning opens up a wide range of geometric and architectural possibilities. In particular, it allows complex curves, variable elevations, and long free spans without support.
Lower construction cost, faster construction:
Post-tensioning significantly reduces the amount of concrete and steel required for the structure and the foundation work. It allows for the rapid assembly of precast elements using industrialized methods, allowing the site to progress quickly and efficiently.
Increased durability, reduced maintenance cost:
A post-tensioning solution reduces the need for joints, which in turn reduces joint maintenance. For tanks, silos, and reservoirs, post-tensioning results in concrete that is virtually free of cracks and therefore less prone to corrosion problems.
Reduced environmental impact:
Post-tensioned structures require less construction material, such as steel reinforcement and concrete, and therefore generate fewer greenhouse gas emissions for their production and transportation. The carbon savings are usually between 20 and 30%.
Composite Structure with PT:
PT is sometimes introduced in steel or composite design due to its excellent tensile capacity.
It is usually introduced at the members which experience high tensile stresses (e.g. bottom chord of a simply supported steel truss).
The benefits of introducing PT in such structures are as follows:
To reduce the overall steel sections required to satisfy the required tensile forces by replacing them with PT tendons, which can be installed and stressed after the erection of the steel truss.
This will help to reduce the overall handling weight of the steel truss, which could greatly benefit the builder on site.
PT tendons could also be used to moderate the overall deflections of the composite structure.
Flat Slab / Flat Plate:
These are generally 2-way spanning slabs.
They are most ideal for grids with an aspect ratio (X & Y direction) of up to 1.4.
Flat plate design is generally governed by its punching shear capacity, so it is usually suitable for light loading (~ 5 kPa) and small span structures (<12m).
Flat slab design with a drop panel can be designed for live loads exceeding 30 kPa and for spans greater than 15m.
Tendons run in both directions in clear column and middle strips, making it perfect.
Banded Slab / Beam & Slab:
The distinction between a “banded slab” and “beam & slab” system is that the former permits the transfer of moments into columns in the slab design, while the latter does not.
As a guide, a banded slab is used when the aspect ratio of grids (between X and Y direction) is less than 1.5.
PT beams are generally much wider compared to conventional RC beams for the following reasons:
To optimise slab direction design
To allow for installation of tendons and anchorages beside columns at the end of the building