Thursday, August 24, 2017

Role of post tensioning in construction of efficient infrastructures

With the advancement in science, our world is evolving and so does the infrastructure. The demand of smart infrastructure has increased in recent decades which demand an upgraded quality of concrete so that the structure can support any load beyond its own dead weight. Many structures have collapsed in past because

• The concrete structure couldn’t bear the oversized load e.g. I-5 Skagit River Bridge accident in 2013

• It was structurally too rigid to withstand the damaging factors like strong winds e.g. I-35W Mississippi River Bridge collapse in 2007

• Frequent accidents where vehicles hit the supporting post like boat colliding with the foundation of the bridge e.g. 14th Street Bridge accident in 1982

• Design errors and material used in the construction e.g. Tacoma Narrows Bridge accident in 1940.

• Earthquakes causing damage to the structure e.g. San Francisco – Oakland Bay Bridge collapse in 1989

We have learned from these accidents that if the design and construction quality of any infrastructure is improved then accidents like bridge failures can be prevented. Post tensioning technique which uses prestressed post tensioned tendons to reinforce concrete structures has revolutionized the construction of infrastructures.  it offers many advantages over regular construction technique. Some of the features of post tensioning are following as

• It offers flexibility to the structure means if the structure tend to sag or deflect under the live load then also the concrete structure won’t crack.

• It has lowered down the material and maintenance cost

• It has also reduced the construction time because it allows longer spans in a structure without building supports.

• It increases the tensile strength and load bearing capacity of the structure thus making it durable and long lasting.

• It can also resist the environmental factors e.g. it can withstand stronger winds or earthquakes as it is structurally flexible.

How post tensioning improves the quality of concrete?

Post tension tendons made from high tensile steel, carbon fibre or aramid fibre is placed within or adjacent to concrete volume to provide flexibility to the concrete structure. When extra pressure is applied by the living load, the post tension tendons share the load and prevent cracking in the concrete member.

Once the concrete is stressed along with tendons, it becomes high strength concrete and can withstand tension forces. Post tension tendons and prestressed concrete is widely used in building huge structures like bridges, skyscrapers, dams, silos and tanks, nuclear containment structures and industrial pavement etc. Prestressed concrete with post tension tendons is much better option than the reinforced concrete because of its improved performance which allows reduced structural thickness and longer span which is essential for building complex structures.

What is the constraint while using post tension tendon in concrete structures?

The biggest advantage of post tensioning is lack of cracking and ability to span large spaces without any support. Post tension slabs can be placed or stamped just like reinforced concrete slab and the surface can be overlaid or stained. It is important to consider that the post tensioned concrete should not be cut or drilled because once a post tension tendon is cut down, it is difficult to repair or replace.

It is very difficult to find any damage to the post tension tendons from the surface as they are deeply embedded inside the concrete member. Infrastructure Preservation Corporation (IPC) provides the first post tension tendon scanning system which utilizes the Electrical Capacitance Tomography (ECT) to perform a MRI like assessment of the post tension tendons. This system is referred as “TendonScan” and it can provide accurate information about any deterioration or section loss like corrosions, voids, bleeding grout and any other problem caused to the tendons so that the decision makers can take appropriate action for repairs, in budget and on time.

To know more about TendonScan, our other products and services, you can visit our website or contact us at

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