Demolition of covered birth and module hall at BAE Systems Surface Ships Ltd, South Street, Scotstoun, Glasgow G14 0XN.

The Phase 8 works at BAE Scotstoun, was one of several phases of demolition carried out by TDS.

Each steel structure was an ad hoc constructed steel framed building, the maximum height from floor to ridge level was 55m & approximately 5000t of steel was used in the construction of the building.

Client: BAE Systems Surface Ships Ltd

Contract: Demolition of Covered Berth & Module Hall

Contract Start/End: 2014 – 2015

Total Project Value: £3,000,000.00

Description

The machines allocated to the project included a 67m super high reach excavator, 37m high reach excavator, & boom machines, these were fitted with a combination of attachments such as selector grabs, cutting shears, magnets etc.

The basic principles for the demolition of the entire structure, was that the roof structure & roof sheeting was to be removed by the super high reach & high reach machines.

The steelwork on the side elevations were heavy gauge, these were removed using a combination of conventional boom demolition machines, attached with large cutting shears, we then safety attached wire ropes to all the remaining columns, this was then attached to an excavator, columns were then pre-weakened using flame cutting, then pulled down slowly by our machine for a controlled collapse.

There were several overhead cranes on site that needed removing with limited available space, the safest way to do this was to remove the end stops/buffers or a section of crane rail from each side, depending on where the drop zone was needed, they were then simply pulled using an excavator machine & steel connecting rope as we did with the columns, for a controlled collapse on to a hardcore bed for subsequent sectioning up & removal of scrap.

South gable demolition above tidal gate phase

For the demolition of the last structural bay which was situated above the tidal gate to the river, high reach machine demolition would of caused damage to the tidal gate, so the safest method was to do a full dismantle, this required the use of a mobile crane/man basket which was used for access & cutting, we then used a mobile crane for hoisting down the cut sections, this involved a lot of working at height by operatives.

To reduce & minimize the risks of working at height, a hinge-over method was selected, we used supporting imagery for the operatives who were carrying out the flame cutting & attaching of steel pull cables to ensure

they had a full understanding of the method that was undertaken so that works were safety carried out.

A consulting structural engineer was engaged by TDS Ltd, to inspect the structure & review the RAMS before the hinge-over operation proceeded, a notice to mariners was also requested by TDS from the local Port Authority, to keep any boats/ships away from the structure while work was commencing.

The weight of the structure being hinged-over was approximately 170t as determined when it was subsequently processed & removed for scrap recycling.

North gable demolition & electric fence adjacent to busy street phase

We had to take into consideration a busy street approximately 5m away from a 45m high gable on the North side of the site, road closures were arranged to coincide with the timing of the required operations.

Our client required the use of electrified fences as opposed to barb wire for their security measures, this was challenging not only because the electrification posed a serious risk to our operatives, but the downtime involved & associated financial costs of repairing any potential damage.

As with the South gable, demolition by high reach machines would almost certainly of caused damage to the electrified fence, so again we dismantled the structure using a mobile crane for access & mobile crane for hoisting down the cut free sections.

During one weekend closure, the cladding & sheeting were removed by MEWP access in a controlled & precise manner to the predetermined separation points for each gable section, as well as attaching steel pull cables. This enabled all structural steelwork at these points to be exposed & thus minimized the extent of exposing operatives to working at height risk.

During a second weekend road closure, our high reach machine cut away all the remaining connecting steelwork between the first section, to allow for flame hinge-cutting at the base of the structural columns, this was then pulled inwards to the building footprint & away from the electrified fence.

Demolition to the north west adjacent to a six-story office block being retained by the client:

This roof structure involved the removal of 3 substantially constructed flat lattice roof trusses, much of the steel work was too heavy for the use of high reach so this was again dismantled.

This part of the works was intentionally left as the last section to be demolished, this was because it was fairly large in size, also not unsubstantial in weight, approximately 550t as determined when it was subsequently processed & removed for scrap recycling. It required a large area for it to land after the hinge-over method & the direction of hinge-over was not as precise as the previous hinge-

overs, because of the angle of the columns constructed, they were not consistent with all the other columns meaning that it would possibly fall slightly to one side.

Completion Report

As with any contract completed, the project manager will issue the client with all the relevant documentation:

  • Demolition drawings, which were superimposed over footprints of the sites
  • All service capping locations
  • All services that remained in the ground on completion of the project
  • Other uncovered structures/ apparatus discovered during foundation removal
  • Location of adjoining structures
  • Completed construction phase plan
  • Copies of all risk assessments & method statements as well as final revisions