The first commercial application of a unique, flexible, unreinforced, pre-cast concrete arch bridge design – the FlexiArch – developed by Queen’s University Belfast in conjunction with the award winning County Antrim firm, Macrete Ireland Ltd was installed in Monaghan on 23 May 2007.

This bridge was constructed to afford a water course crossing of 6.5m span on the newly built property of a well known local businessman and was erected in a single day.

The 4m wide arch bridge follows the classical principles of accurately angled masonry blocks or voussoirs for its construction. The individual voussoirs are high precision pre-cast and connected using a bonded flexible polymer membrane system. Precision lifting of the line allows it to descend into the correct arch shape and dimension for the required span.

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Four FlexiArch units were used and each was craned from the flat bed transporter and lowered onto prepared pre-cast seating. Each arch is entirely self-supporting by virtue of its construction geometry. The bridge was completed with the addition of spandrel walls – also pre-cast concrete units, made to the precise curve of the created arch, and craned into situ in four quarters. Spandrel walls were laterally secured by steel tie bars. Erection was completed in one day.

A 500mm thick 25N concrete saddle was then applied to the back of the FlexiArch units and the spandrels decoratively finished with stone cladding in keeping with the architectural style of the new dwelling house/home.

The FlexiArch Bridge is the result of extensive research, design and collaboration and is the subject of a number of patent applications.

It is believed there are many opportunities for the installation of rapid FlexiArch system in both arch bridge construction and as an alternative to box culvert installation.

There is no requirement for river diversion and a typical bridge can be erected and backfilled within a week. The system can comfortably support full highway loading. Macrete are currently working on increasing spans up to 10m and on a skewed system. Macrete is sole licensee and manufacturer of the system.

(JM/SP)