Phase III Special Post Tensioned  Investigation

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The Malahide Viaduct  is a 12 span simply supported structure with deck formed from 4 longitudinally post‐tensioned main beams to each span. The viaduct  carries the main Belfast to Dublin railway line and in 2009 a 20m section of the viaduct collapsed shortly after a train had passed.

Emergency repairs were undertaken on this section but it was obviously essential to test the remainder of the viaduct.

HTS were selected for the task, because of their specialist knowledge of both the rail and marine environments.  The water here is tidal so it was essential to programme the works to fit in with the tidal movements, and to provide a safety boats to supervise all operations.

HTS undertook a Phase III special post-tensioned investigation of the  structure consisting of locating tendons, intrusive investigation of the lower row of the post-tensioned ducts, pressure testing of ducts where voiding was detected, and collection and laboratory analysis of grout samples from within the ducts.

HTS then produced a report on their findings and the client described the entire project as ‘delivered very efficiently’.