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Technical highs

Construction of Bahrain’s largest ever precast concrete flyover called for some heavy duty shoring on site, which was taken on by falsework specialist RMD Kwikform, as NCE reports.

The Bahrain Isa Town Interchange was officially opened to traffic late last year, marking completion of one of Bahrain’s most ­complex road projects.

Few people would have been aware of technological challenges involved in building the three tier, Dinar 50M (£84M) structure that will see more than 6,000 cars per hour using it during peak times.

There were more than a few political challenges too: work on the project stopped temporarily after original contractor, Korea’s Sungwon Corporation, was axed in February 2010. It was retendered and awarded to local outfit Nass Corporation three months later. “This project is an engineering masterpiece,” says Bahrain works minister Esam Khalaf. “Three layers of traffic will move in different directions at the same time.”

Key to the project was the construction of Bahrain’s largest ever precast concrete flyover. Standing at 1.8km long, 733 segments each weighing up to 190t were needed to complete the flyover. These were erected in groups of three using a specialist launcher system supported by RMD Kwikform’s Megashor towers.

Megashor towers were needed to support both the weight of the launcher system at each pier point and the additional weight of the precast sections.

Precast sections

The precast sections were initially lifted horizontally by the launcher, before being moved vertically to meet the previously secured sections. Once all three sections were in place, they were secured and fixed together. In preparation for each of these sequence lifts, RMD Kwikform engineers operating from their Bahrain office worked with engineers from contractor Nass Contracting to determine the exact forces that would be placed on the Megashor support towers by each precast section.

Erected around the three piers to support the launcher, the tower systems are each made up of Megashor legs ranging in size from 500mm to 2.7m. Interlaced with Superslim soldiers for rigidity, the individual towers were connected together to form a rigid structure capable of supporting up to three precast sections.

With over 300t of RMD kit used on the site, the scale and complexity of the project was not missed by Nass Contracting contracts manager Ivan Pieterson. “To say the challenges on this project were complex is an understatement. We were dealing with the creation of the largest single flyover project in the country to date, using a method of construction that is completely new to Bahrain.

“The curvature of the structure itself is very eye-catching and therefore each precast section is unique. Couple this with the nature of constructing the flyover over and next to live traffic and you have a very interesting programme to manage.”

With pre-project planning restarting at the start of May 2010, the project construction phase began in June 2010 with the 1.8km flyover completed 24 days early in April 2011.

RMD Kwikform’s Bahrain technical manager Shekhar Sawant also found the experience revealing: “We are well known in the region for our involvement in cast in-situ structures. What is interesting about this project is that we are involved in supporting the country’s first precast bridge structure.”

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