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Case Studies - Rail & Bridge Works
Over the years HRS have inspected literally 1000's of rail structures. Bridges, shafts, station roofs, culverts down to lowly cattle creeps; confined spaces under platforms upto spaces the size of cathedrals in bridge abutments have all been accessed safely and works carried out.
Numerous consulting engineers have drawn on our wide range of skills to extend their project capability. Centred on difficult access, HRS Services can support inspection, surveying, testing and sampling and maintenance jobs as required. We effectively co-ordinate and manage all aspects of the access and site works freeing up engineers to carry out their contracts, more cost effectively.
Major Structures worked on have included bridges-Forth, Tay, Tamar, Newcastle High Level; stations - Kings Cross, Liverpool Street
Merstham Cutting posed particularly difficult access problems as access at the top and bottom was extremely limited and from either end. This restricted works greatly and meant transfer of men, materials and equipment was very awkward on this large scale contract. After large scale concrete beams were installed HRS had to install a system of ground anchors and netting to ensure no debris could work loose and fall onto the track.
However, HRS managed to complete their contract in a period of 8 weeks and were also awarded a much greater scope or works and extras.
Using rope access techniques allowed HRS to measure up and install a new set of cradle rails to the underside of a rail bridge, during a series of short possessions.
Other more conventional systems of access were not suitable as there was not the room to keep the track open.
Lime Street cutting had heavy vegetation growing along it which needed to be removed as the risk of root damage and 'jacking' was considerable. However, the cutting was large and possessions short.
HRS were able to provide 20 operatives every week for a single shift early on Sunday mornings to remove the vegetation.
HRS Services have inspected literally 1000's of Network Rail structures but probably the most challenging and famous structure worked on was the Forth Bridge. HRS had to put forward an extremely well thought out Method and Risk Assessment to inspect 12% of the overall structure to gain an indicative condition report. Given the exposed nature of the bridge itself and the fact that the lattice structure itself is massive and complicated HRS's work was cut out!! However over a period of 3 months working alongside other consultants and contractors HRS successfully completed the works.
Other notable rail bridges worked on include the Britannia Bridge, Royal Albert Tamar Bridge, Newcastle (High Level) Tyne Bridge, Britannia Bridge (Menai Straits)
A condition survey of the concrete deck, piers and cable stays of the Flintshire Bridge in North Wales has recently been completed by consulting engineer Pell Frischmann in conjunction with roped access specialist HRS Services. The bridge carries a dual two-lane highway over the navigation channel of the Dee estuary.
The structure has approach viaducts totalling 660m in length, and a 118m high inverted Y-shaped tower supporting the 194m-long main span and 100m of back spans. The tender for the principal inspection of the bridge was put out by Gifford on behalf of Flintshire County Council.
The shape and location of the bridge poses particular problems for inspections, and Pell Frischmann engineers trained in roped-access worked with HRS to access all areas of the structure.
The arrangement allowed Pell Frischmann to concentrate on the engineering aspects of the contract, leaving HRS to manage the access arrangements and proposals. The contract was won on the strength of the detailed proposal and method statement. All parts of the bridge had to be inspected hands-on, so a range of access equipment and methods was required.
These included 20m mobile access platforms for reaching the soffits and access hatches to the internal confined space deck voids; a 54m platform for the lower part of the main tower and roped-access techniques for the upper tower and cable stays. In order to inspect the underside of the deck above the river, HRS fabricated a lightweight aluminium movable truss which was sequentially moved under the 30m-wide deck in a longitudinal direction.
This provided a stable basis for inspection whilst imparting manageable loads on the delicate parapet detail and producing benefits in time, quality of inspection, cost and flexibility.
Westminster Bridge in London is one of the best known bridges in the UK that HRS have worked on. Prior to strengthening works HRS won a contract to carry out a very detailed condition and measurement survey using rope access techniques. Using rope access meant no scaffold had to be erected which meant that boat traffic could still gain access past the bridge.
Over a period of 2 months HRS carried out the site works which meant taking over 60,000 on site measurements. The contract was completed successfully without a hitch enabling the on going strengthening and alteration works to proceed.
Over the last twenty years HRS have had a close working relationship with the Humber Bridge Board and contracts have included various inspections, concrete coring and maintenance tasks. However over three summers in the mid 1990s HRS Services working with the Humber Bridge Board replaced all the main hanger cable clamp bolts on the main catenary cables.
In total on the bridge there are over 2000 bolts, each over 600 mm long and weighing 5 kgs. HRS designed and fabricated special cradles which could be broken down into small sections to enable them to be transported inside the bridge tower lifts! Over the summer HRS erected and moved cradles then working in with an operative from the Humber Bridge Board to removed, re-placed and torque set the new bolts. Over the three summers all works were carried out safely and no item were dropped which a matter of great import as the road crossing the bridge was at times over 100m below the cradles
HRS Services have carried out works on the QE II Bridge at Dartford from the day the concrete piers were coming out of the ground and to date over £1M of works have been successfully completed. Recent contracts have included inspections to bearings; structural inspections to concrete piers; and painting to anchor boxes and fences. No doubt with our experience of pricing and successfully completing contracts there, will mean we will be back again.