As part of the scope of the main works for the Erskine Bridge Lighting and Electrical Refurbishment Contract we replaced the network cabling supplying the high mast lighting units at the Dalnottar Interchange as well as the control pillars and panels. We also replaced the existing SON luminaires with new LED luminaires.
We were subsequently issued with a Variation to the Contract to replace all 16 No. 30m high mast lighting units which were located on dual-carriageway trunk road and single carriageway local authority road. All works were to be undertaken at night time during the hours of 8pm – 6am to minimise disruption to traffic and other road users.
The new masts were to be sited on the existing reinforced concrete foundation plinth and use the existing holding down bolts. The masts had to be design checked and certified to confirm by calculation and maximum overturning moments that the new high mast lighting units did not impart more onerous loads onto the foundation than the existing.
The pull out resistance of the bolts was tested to ensure that the existing anchors were undamaged and could accommodate the design forces from the new column.
Each mast location was assessed and a specific traffic management layout and lift plan was formulated for each mast / location.
Several mast locations were in difficult locations remote from the carriageway and therefore required additional measures to gain access for the crane. At these locations we used temporary trackway and / or reinforced steel mats and a larger crane where required. The temporary trackway was installed by a specialist sub-contractor. At another location, sections of the vehicle restraint barrier were required to be removed and reinstalled on completion to allow access for the crane, again this operation was undertaken by a specialist and Sector Scheme approved Contractor.
Programme, RAMS, lift plans and traffic management layout drawings were submitted to Client for approval prior to works commencement.
The new masts were assembled within the administration building compound area and transported to each location on site by trailer with escort vehicles.
At each location the existing mast was removed and laid down, the recently installed LED luminaires were removed (to be transferred to new mast) and the mast cut into sections and transported off site. The existing grout around the base was removed and the holdings down bolts were pull-out resistance tested. The luminaires were transferred to the new mast, new mast lifted into position and holding down bolts tightened to correct torque and denso tape installed. The existing bases were shuttered and a layer of epicon grout applied leaving an air gap between the existing foundations and base of newly installed mast. The operation of the cradle was testing by lowering and re-docking and all electrical connection completed.
The works were completed in 8 nights between 3rd March 2017 and 10th March 2017.