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Top trends within the GCC’s post-tensioning sector

by CW Guest Columnist on Mar 6, 2016

From large-scale infrastructure projects to residential developments, business has been good during recent years for post-tensioning (PT) firms of all sizes in the Middle East. Increasingly, GCC clients are registering their interest in the benefits that PT has to offer, says Rachmad Irwanto, CEO of Ichsan. Mohammed Zaid, design director for e-solution Construction and Engineering, agrees, adding that the sector is developing “every day”.

Innovation within the field is also moving at pace, with Stephen Burke, deputy general manager for VSL Middle East, citing the example of PT bridge structures that are now seeing “designers looking to promote the use of external PT tendons”. These tendons are accessible within the box cell of the bridge, rather than the conventional type, which are encapsulated.

“They can be readily monitored and inspected during their lifetime,” Burke continues. “Another advantage is that should the carrying capacity of the bridge deck need to be increased in the future, this is readily achievable by the addition of further tendons at a later stage.”

Accessibility and monitoring also make life easier for companies that focus on PT repairs. But with new techniques come new challenges, as Structural’s division manager, Chris Hill explains.

“We are starting to see a lot more PT slabs with increasingly thinner sections and with a lot less mild steel reinforcement located in the remainder of the slab,” he notes. “In some of the older structures, there would be a significant amount of reserve capacity with the mild steel and the thickened sections. But with a lot of the ‘tighter’ PT designs that have become more popular recently in the region, there is less room for error – and any minor changes in the element have larger implications on the safety of the structure.”

Although these designs meet all international codes, the loss in concrete cover to the PT strands and the complete reliance on them for structural stability are only now starting to have an impact, Hill asserts. Another challenge is to convince owners to “utilise a similar PT method in the final repair solution”, he adds.

“This can be the most efficient means of repair, but the hesitance from a system that has had issues forces the repairs to other methods such as carbon-fibre strengthening, pressurised form and pump concrete enlargements, or a redesign of the section to conventional reinforced concrete elements.”

Furthermore, the regional picture isn’t a coherent one, with each GCC country exhibiting its own issues and strategies. Zaid confirms that e-solution Construction and Engineering has noted a number of hurdles in Saudi Arabia.

“We faced a big issue in megaprojects where the main designer designed the flat slabs ignoring the long-term deflection calculations,” he explains.

In this instance, flat slabs were designed to be the same thickness as the post tension slab, 80mm thinner than required. Thankfully, e-solution’s design team identified the discrepancy, which would have had major structural and financial implications had it not been spotted.