- Letchworth Garden City, Hertfordshire
We are an innovative, robust and fast growing business, whose main focus is to deliver continues improvement to existing products and offer new sol..
- Recruiter: Helmet Integrated Systems / Gentex Corporation
- Cumbernauld, Glasgow
- Grade: 6/7* £26,537 - £37,768*
Work as part of a growing dynamic team on a wide range of technical projects with particular emphasis on experimental validation and testing
- Recruiter: University of Strathclyde
- Hatfield, Hertfordshire
Responsible for updating and writing electrical engineering standards, approved codes of practice and safe systems of work
- Recruiter: Affinity Water
- York, North Yorkshire
Senior electronics engineer to work as part of a team developing an MEG imaging system; working with the engineering team and external contractors.
- Recruiter: York Instruments
- Lostock Junction
- Competitive Salary & Benefits
Whats the opportunity? Manufacturing UK is an integral part of the Operations Directorate whose principal mission is to ensure that MBDAs deliverable commitments are met...
- Recruiter: MBDA
- Great Dunmow, Essex
This High Voltage Engineer will provide design leadership for high voltage cable assemblies up to one megavolt.
- Recruiter: Essex X-Ray & Medical Equipment
- Barrow-In-Furness, Cumbria, England
Team Leader - Flank Arrays Would you like to work in a unique role within the construction of the Astute Class submarines? We currently have a vacancy for a Team Leader - Flank Arrays at our site in Barrow-in-Furness. As a Team Leader - Flank Arrays, you
- Recruiter: BAE Systems
- circa £35,000 per annum + bonus
Develop new test equipment for the pharmaceutical industry. Good opportunities to grow and develop. Successful family-owned and managed business.
- Recruiter: Copley Scientific Ltd
- Birmingham, West Midlands
Our transport technology team in Birmingham is currently growing a highly skilled and customer-focused team to...
- Recruiter: Mott MacDonald
- Southampton, Hampshire
- £45,271 to £49,207 per annum
Responsible for technical oversight and project management of internally and externally funded innovation centre projects.
- Recruiter: National Oceanographic Centre
Classic Projects: Second Severn Crossing
Find out about the River Severn’s most southerly bridge
Three decades after the opening of the original Severn Bridge a second crossing was opened to alleviate congestion caused the huge growth in traffic streaming into Wales.
The Second Severn Crossing (SSC) is the most recently constructed bridge over the estuary separating England and Wales. Five miles downstream from the original motorway link, which was constructed in the 1960s, the SSC closely follows the line of the Severn rail tunnel that has been in place for more than a century. It is also close to a ferry route that dates from the days of the Roman Empire, which illustrates how few crossing points there are at this point in the river.
The need for a second crossing arose from the increase in motorway traffic across the Severn Bridge in the 1980s. A rise of 63 per cent in traffic flow, along with repeated closures due to high winds and congestion, meant that the M4 and M5 network could no longer cope. After a period of consultation and tendering, the Secretary of State for Transport selected a bid from John Laing and GTM-Entrepose that led to the formation of Severn River Crossing PLC, which was to design, build, finance, maintain and operate the new bridge.
The second crossing was not to be simply an enlarged version of the original, which is a combination of a suspension bridge, two viaducts and a cable-stayed bridge. The SSC, although bigger in scope, was less complex architecturally, being essentially an enormous viaduct with a central cable-stayed span over the Shoots channel at its centre. Because of its location, local geology and other environmental factors associated with the point where the lower reaches of the River Severn meet the Severn Estuary, the task of construction was complex.
The SSC connects Sudbrook, Monmouthshire, with Severn Beach in South Gloucestershire. At this point on the river there is a tidal range of 14.5m and notorious currents. This meant that the bridge needed to be prefabricated wherever possible and put in place using a fleet of 10 floating craft and seven back-up barges, often working within a two-hour tidal window. The first job was to get the foundations in place, requiring the placing of 37 precast caissons weighing 2,000 tonnes apiece. These were then filled with concrete that took up to 20 weeks to cast.
The caissons were positioned using a computer-controlled dynamic positioning system that could hold the modified barge on station to within a tolerance of half a metre. Once the tide had gone out the construction area was left dry and the caissons could be sealed around their 300m perimeter.
Pier construction and movement of viaduct and pylon segments relied on floating precast sections into place. Much of the bridge deck was moved into place from the construction yard by road, having been 'match bolted' prior to dissassembly and transportation to ensure a perfect fit.
The construction phase took four years and came in at a cost of £330m, compared with the £8m of the original motorway crossing three decades earlier.
But improvements were significant, especially in the way in which the new bridge coped with lateral winds. Its sides are fitted with baffles that improve stability, especially for high-sided vehicles. This means that speed restrictions in windy conditions that were a common feature of the Severn Bridge are now less frequent, while the overall design of the bridge makes it more resistant.
The SSC carries three lanes in both directions as well as a hard shoulder (compared with the Severn Bridge's two lanes) and so handles volume well. It is able to accommodate 75 per cent of traffic across the river with comparative ease.
NEXT MONTH: The manual typewriter
1,000 construction workers employed
Construction period 1992-1996
Opened on 5 June 1996 by HRH Prince of Wales
Toll booths on Welsh side
Pay to get into Wales – no exit charge
60,000 vehicles use crossing per day
Carries six-lane M4 motorway
The SSC is a cable-stayed bridge with approaching viaducts
Seen from above the bridge is a slight 'S' shape
Volume of concrete 320,000m3
Weight of reinforcing steel 30,000 tonnes
Total length of pre-stressing steel 150,000m
Number of concrete deck units: 2,434
|To start a discussion topic about this article, please log in or register.|
"We visit Barcelona, one of the smartest cities in the world, to find out what makes it so special. What does it look like and what is the future?"
- HS2 to cost 'five times as much as TGV', study finds
- Turning sunlight into heat doubles solar cell efficiency
- Apple investigating electric vehicle charging stations
- Heart-monitoring tablet named best tech innovation for Africa
- Nasa inflates Bigelow space station module
- X-ray laser reveals first of a kind images of exploding water droplets