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Cairnhill Structures were originally tasked to fabricate a new signal gantry for the Glasgow Queen Street refurbishment project which is part of the EGIP works.(Edinburgh Glasgow Improvement Project) Queen Street station was closed to the public for 20 weeks in order to allow for major upgrades which would allow full fit out of Overhead Line Equipment within the station. Cairnhill completed the 26t gantry plus all associated OLE equipment and small part steelwork throughout the station during the blockade.
Our original scope of works was to supply small wall supporting brackets on either abutment, central A frame support plus two gantry sections. Once Cairnhill were awarded the contract it became apparent that the original contract scope was not erectable due to site constraints.
Existing abutment walls were orientated in three opposite plains which required full 3d surveying of both abutments. Our proposed signal gantry was situated over 60 metres away from the nearest crane laydown area which prevented the structure erection in two sections due to weight restrictions. Cairnhill assisted Jacobs & Morgan Sindall with the revised design of the structure to take into account the abutment faces, plus the erectability of the final fabricated structure.
Our project team agreed to fabricate the structure in six number sections which would be spliced on site to create the original two sections of gantry each in excess of 25m in length. Individual sections had to be loaded from Cathedral Street bridge utilising specialist road protection mats plus low ground pressure 360° tele handler complete with specialised lifting mechanism onto rail bogeys situated at track level. Once each section was loaded from above onto the rail bogeys Cairnhill operatives were required to move the three rail bogeys each unit were landed on to a pre-determined location on the track directly in front of Queen Street tunnel. Once we had lifted the first three sections of the gantry down to track level, plus moved the individual sections into the correct location we had 12 hours to complete splices on site plus complete the fit out of the gantry at ground level.
Please see a picture which highlights the complexity of the abutment support frames due to the geometry of the masonry abutment. Within the picture below you will note at the rear of each of the 1500mm embedded rods is a individual fabricated support bracket which takes into account the geometry of the existing abutment. Each fabrication was individually surveyed by our site team to ensure compliance with the drawing office requirements. If we were to set the support frames off by half a degree we would end up almost 50mm short or over 70mm long .
Cairnhill erected the signal gantry utilising Babcock Rails Kirow crane during a restricted ten hour window due to the extremely tight program available for the overall station refurbishment project. In order to reduce down time during the installation phase Cairnhill designed suitable temporary lifting beams to suit the Kirow cranes lifting beam which reduced overall slinging time required for each of the two main sections of gantry. Pictures below shows the first of the two sections being lifted in preparation for final erection.
Cairnhill had previously erected the wall mounted support brackets on each abutment, plus installed the central A frame. We had also completed an as built survey of the three support structures and checked these against the trial erection completed within our workshops prior to the galvanising process. Due to the nature of the project, we had no margin for error, if our structure did not go in first time, then the complete project would have suffered and failed as a direct consequence of this. Cairnhill’s design team, drawing office, production team, installation squads and project managers worked as one in order to erect this challenging structure. Margins
Cairnhill have been privileged to be asked to complete such a demanding structure. It is testament to our team that we are again working in partnership with Jacobs and Morgan Sindall on a further project of a similar nature.
Please see below a few pictures which show the second span being erected 3 hours ahead of our anticipated completion slot. All members of our team breathed a huge sigh of relief when we landed the second span. Even with all the checks available and completed we still had doubts over the structure landing first time due to the very small margin of error available to us.
Cairnhill would like to note our thanks to John Fraser of Jacob’s for his tremendous effort and help throughout the Glasgow Queen Street project. We would also note without Morgan Sindall’s Neal McKenzie this structure would not have been erected on time and to correct specification, his help was invaluable.