Britain’s national railway network has evolved over the last 150 years plus. The network has over 40,000 bridges and tunnels that have to be inspected and maintained. Many of the structures are as diverse in size and complexity as they are almost inaccessible in the British countryside. Normal inspection techniques cannot be used in many cases and this is where the Bridgeway Consulting Infrastructure Services team has provided innovative techniques to gain access.
Specialist access inspections
The specialist access inspections team of Bridgeway Consulting presents its examiners and engineering staff new challenges to face every day, by carrying out the very important job of establishing the current condition of each of these structures.
All bridges, tunnels, retaining walls, culverts and sea defences require at least a visual examination every year, and then at different intervals, a full detailed (tactile) examination which requires access to every part of the structure.
The use of specialist access techniques for the examination of these structures requires an in-depth knowledge of roped access, diving and confined spaces to ensure that all examiners can safely gain access to parts of the structure. All examiners and engineers carrying out these works are multi-skilled so that they not only have the competency to carry work out as trained structural examiners but, in addition, are HSE qualified divers, IRATA roped access trained and/or confined spaces trained.
Bridgeway has successfully examined some of the difficult access structures around Britain including Dinting, Mottram, Arnside and Leven Viaducts. To add to this, the company has examined a raft of famous structures on the River Thames (both above and below water) including the Hungerford, Richmond, Barnes and Kew bridges.
Hungerford Bridge, London
After a previous successful inspection of the Hungerford Bridge, Bridgeway has again been appointed to carry out a detailed examination both above and below the River Thames.
In the interests of offering a value engineering solution to Network Rail, they suggested that a combined detailed and underwater examination would provide the client with better value for money.
This meant a realignment of the anniversary dates for examinations but provided substantial reductions in the mobilisation costs for Port of London Authority permits, installation of span closure signs to the River Thames, dive platforms and safety boats in attendance for works.
The works involved the use of a self-propelled working platform vessel with a Spudpole that can anchor the vessel in effectively any location within the river to allow the greatest flexibility in access to the extensive bridge deck and superstructure.
In addition, this platform had a cherry picker (MEWP) mounted to the deck to allow the examining engineers access to as much of the bridge deck as possible and could also be used as a dive platform for the underwater examination team.
Much consultation and detailed planning with the Port of London Authority was required, to establish ‘span closures’ for the bridge, in one of the busiest navigable rivers in Europe.
Dinting and Mottram Viaducts, Derbyshire
The task of tackling the detailed examination of these structures was formidable, from planning stages to the delivery of physical works on site, and in converting all the information into a single condition report.
Due to the complex nature of the bridge, the project and roped access managers were tasked with the problem of gaining safe access to the structures to maximise daylight working during the early stages of the summer months and longer days.
Following a site visit, the responsible managers established safe access both from above and below the deck providing a number of options for the site teams. Works commenced in May 2015 for both structures and involved the use of experienced IRATA Level 3, Level 2 and a number of Level 1 STE4 examiners.
The IRATA Level 3 Supervisors have extensive knowledge of advanced rigging and rescue techniques and implement a safe system of work for all roped access works. The Level 1 operatives have carried out extensive training that qualifies them to work at height, however, under strict supervision of the Level 3 Supervisor.
Bridgeway’s team was prepared for the challenges on both structures, not only the obvious physical demands but also the entry to the confined spaces within the two outer main external girders.
The team held numerous competencies including confined spaces training that allowed them to gain access to the part of the structures that may otherwise remain unseen, or at the very least not have had a ‘tactile’ examination carried out. All these hazards and risks were identified at the site visit stage and the project team were able to implement the appropriate control measures and ensure that the correct staff were available when necessary.
Both structures span a watercourse, and Bridgeway was able to use its internal diving and underwater department to mitigate with the risks of working at height and working over water! A safety boat and qualified HSE III diver/RYA Level II boat operative were on standby at all times below the roped access team to enable a rescue.
Dinting Viaduct, the larger of the two, posed additional challenges that required road closures with access to the deck via a MEWP, and some of the masonry spans examined with the assistance of a mobile aluminium scaffold tower.