NASC YEARBOOK 2012 | PROJECT NEWS


39


OVERHEAD POWER LINES NEED EXPERT HAND


Norwich Overhead Line


Refurbishment NASC member: Dixon Scaffolding (Transmission) Ltd Main contractor: Electricity Alliance East


comprehensive refurbishment of a major National Grid overhead line facility – running between Norwich and Wisbech – has gained from the scaffold protection experience of specialist contractor, Dixon Scaffolding. Work has been carried out on


two parallel power circuits over nearly eight months. Eleven scaffold towers and protective netting had to be set up in the


area of Thickthorn Services at the busy junction of the A47 and the A11 on the outskirts of Norwich. This was typical of the project. Here, a 350-metre run has seen tower installations accommodate a variety of locations and terrains, including a traffic roundabout, service station slip roads and car park areas. “We work closely with our customer, Electricity Alliance East, who are undertaking the overall project for the National Grid, and also the local authority and traffic management specialists in order to erect the scaffold towers most effectively,” explains Dixon Scaffolding project manager, Andy Boaz. “This is an area in which we have specialised for many years so have an excellent understanding of the particular considerations that need to be applied. The towers, for example, have to be designed to minimise the potential for the protective


RAIL LINE PROVES CHALLENGE FOR BLOCK OF FLATS


Rainbow House, Watford NASC member: MPT Scaffolding Ltd Main contractor: Willmott Dixon*


rainbow house is an eight-storey block of flats consisting of a semi-basement car park and plant rooms. The construction is a


reinforced concrete frame with a rendered and rainscreen cladding façade. There is also a large amount of glazing which is predominately of curtain wall design. There is also an atrium to the full height of the building which includes a corridor running around it for access and egress to the dwellings on each floor. The seventh level is closed in with a fully-glazed roof. The site is situated off Water


Lane in Watford: a ‘no through road’ for heavy goods vehicles. This has led to all deliveries having to be planned as ‘just in time’.


One of the major safety considerations has been the close proximity of an overground/underground rail line that runs adjacent to the eastern elevation of the building. The scaffolding has had to be designed to actually oversail the northbound line. To achieve this, MPT and its designers, Optima Scaffold Designs, came up with the solution of a truss out scaffold on one elevation and, on the other elevation, an RSJ cantilevered 8m from the building as the bank could not support the weight of


net to sag while maintaining a minimum clearance of 6.1m above the highway, with weather and, of course, potential line loading taken into account,” Andy continues. “They also have to provide consistent access and inspection points at the highest lift level whilst reflecting the variety of ground conditions underneath.” He explains that tower stability was achieved via kentledge – in the form of 1.5 tonne concrete blocks – and a system of guy-ropes.


He also points out that the Layher Allround® scaffold system is being used throughout the project for reasons of safety, speed, tidiness and, importantly, minimum number of components. “This dramatically reduces the risk of material being accidentally left on site, whilst the welded connections at the heart of the design minimise potential slippage, which has a direct bearing on the loadings that can be designed into each structure,” concludes Andy.


the scaffold. A fully cantilevered scaffold has been erected; this had to be put in place at night. MPT and its operatives achieved


this ahead of the schedule and saved the contractor two further possessions. * This contractor has a ‘NASC only’ policy


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