The Construction of the Humber Bridge - Essay Example

THE CONSTRUCTION OF THE HUMBER BRIDGE Background This paper aims to discuss the reasons for the construction of the Humber Bridge as well as how it was constructed whilst looking at environmental, social, health and safety issues upon its construction. The Humber Bridge is considered the world’s fifth largest single-span suspension bridge and connects the East Riding of Yorkshire and North Lincolnshire. It is a suspension bridge with the south tower sited in shallow water that measures 500 m from the ground and the north tower founded on the high water line (Humber Bridge Board, 2009). An average of 120,000 vehicles per week pass through the bridge whereby cars pay £2.70 each while commercial vehicles pay higher. It was in the 1930s that plans for the bridge were drawn up but only in 1972 did work finally begin. Before the construction was the passage of the Humber Bridge Act in 1959, establishing the Humber Bridge Board for raising funds (Humber Bridge Board, 2009). Reasons for Constructing the Humber Bridge There are two reasons for the construction of the Humber Bridge. The first of this is that a shifting bed and a navigable channel along which a craft can travel characterise the Humber, of which a suspension bridge without support piers in mid-stream allows no obstruction for the estuary. The second is that opting for a channel instead of a bridge (the Humber Bridge) would cost excessively due to the geology and topography of the area (Humber Bridge Board, 2009). The opportunity for commercial, industrial, and tourist development was given way through the construction of the Humber Bridge, which likewise saved several millions of vehicle miles between both sides of the Humber estuary (The Royal Academy of Engineering, 2003). These potential developments and financial savings serve as good justification for the construction of the Humber Bridge with huge cost investments, of which factored to such cost is the ongoing cost of maintenance and repair over the life span of the structure. It is important to mention that the Humber Estuary, across which now lies the Humber Bridge, had been a barrier to trade and development between the two banks whereby local interests were shown for over 100 years concerning the construction of either a bridge or a tunnel across it. It took eight years to finish work on the construction of the Humber Bridge project, during which several thousands of tons of steel and concrete were used with over a thousand of workers and staff working on peak activities (ibid). How the Humber Bridge was Constructed The structural type of the Humber bridge construction is suspension bridge that is gravity-anchored, asymmetric, and inclined-hanging with function/usage of a motorway or freeway bridge. The construction materials used were steel wires for the cables, steel for the deck, steel wires for suspenders, and reinforced concrete for the towers. The quantities used in construction were a concrete weight of 480,000 tonnes (Humber Bridge Board, 2009). On the north bank lies a a hard well-jointed bed of chalk that provided good foundations for both the anchorage and tower while on the south side were soft alluvium underlain by boulder lay, sand, and gravel. Below these beds is heavily fissured kimmeridge clay, serving as foundations for the tower and anchorage (ibid). After the passage of the Humber Bridge Act in 1959 serving as an enactment that establishes the construction of the bridge, construction work on the south approaches were started in July 1972. The substructure was then started in March 1973 while the superstructure was in April of that year. The north tower was completed in May 1974 while the south tower was in July 1976. From September 1977 to July 1979, cable spinning was worked on whilst the first body section of the superstructure was erected in October 1979. In July 1980, the closing of the superstructure was undertaken and later on June 24, 1981, the first traffic passes over the bridge took place. After over a month from the first traffic passes, Queen Elizabeth II officially opened the Humber Bridge, which signalled its operation. Further, in 1992, an installation of a dehumidification system for the cable saddles and the main girder was undertaken. It must be noted that there are 800 more wires for the cable carrying the shorter side span than the rest of the bridge. A main span length of 4,624 ft. comprises the bridge, making it the longest single span suspension bridge in the world (Humber Bridge Board, 2009). Below is a table showing the measurement of some of the areas of the Humber Bridge, serving as basis for its construction: Main Span 1,410 m Side Spans North Side South Side 280 m 530 m Length between anchorages 2,220 m Clearance over high water 30 m Deck width (including paths) 28.5 m Tower height above piers 155.5 m Diameter of main cables 0.68 m Total length of wire 71,000 km Load in each cable 19,400 tonnes Weight of Steel 27,500 tonnes Weight of concrete 480,000 tonnes Depth of Foundations, Anchorage North side South side 21 m 35 m Depth of Foundations, Towers North side South side 8 m 36 m (Source: http://www.humberbridge.co.uk/technical.php) In terms of carriageways, the Humber Bridge consists of dual two-lane carriageway alongside separate paths. It has two main cables, each measuring 14,948 wires of 5 mm diameter and 1,540 N/mm2 UTS of which the northern side span consists additional 800 similar wires in each cable (Humber Bridge Board, 2009). Techniques and Components Used for the Construction of the Humber Bridge It must be noted that the Humber Bridge was constructed with the application of the Global Positioning System (GPS) technique that aids in the measurement of movements of large structures such as the bridge. The finite-element modelling in the prediction of the behaviour of structures under a wide range of loading conditions was also used in the construction of the bridge (Brown, et al., 2004). Since its completion in 1981, the Humber Bridge has been operating successfully whereby continued in-service monitoring under increased traffic loads is carried out through the finite-element model applied to its construction. The deflections of the bridge were measured with the use of the Global Positioning System (GPS), which was able to determine the structure’s resonant frequency. Through the applied GPS, experimental data can be processed to give resonant frequencies of the Humber Bridge structure (ibid). Designed to cross the Humber estuary, the Humber Bridge consists of inclined hanger cables that support a continuously welded, closed-box road deck as well as reinforced concrete towers aerial-spun catenary cables (Humber Bridge Board, 2009). These allow suspension to be possible whilst ensuring strength of materials. Below is an engineering illustration of the structure of the bridge: (Source: http://www.humberbridge.co.uk/technical.php) The Humber Bridge, which has a design lifespan of 120 years, is considered an engineering masterpiece whose design was primarily developed for the Severn Bridge in England (Humber Bridge Board, 2009). The image below illustrates the measurement of the Humber Bridge used for its construction: (Source: http://www.humberbridge.co.uk/technical.php) The techniques in constructing the Humber Bridge follows certain rules for safety issues, such as the usage of appropriate sub-structural and superstructural materials to ensure safety. Safety is also seen in the fixed design lifespan of 120 years; long enough to ensure the public of the safety usage of the bridge based on the strength of materials used, such as 19, 400 tonnes of load in each cable, and 27,500 tonnes as weight of steel, 480,000 tonnes as weight of steel. Note that the depth of foundations and anchorage for the north side and south side are 21 m and 35 m respectively. For the towers, the depth of foundations for the north side and the south side are 8 m and 36 m respectively. The heaviness of load employed on the bridge indicates the magnitude of materials used in order to ensure its strength; thus, safety of usage and operational activities are ensured. Below is the Humber Bridge during its initial construction: (Source: http://www.freefoto.com/browse/11-35-0?ffid=11-35-0) In terms of environmental considerations, there were no hazardous chemicals or materials used in the project that may hamper the environment. Neither was the structure erected to damage certain parts of the ground between East Riding of Yorkshire and North Lincolnshire. The opportunity for commercial, industrial and tourist development that go alongside the construction of the bridge spell social considerations affecting the economic and social activities of people and businesses. There are corresponding impacts on the social behaviour of social groups concerning the commercial, industrial, and tourist development in the area. This is contrary to the social situation prior to the construction of the bridge, specifically on the aspect that the Humber Estuary, across which now lies the Humber Bridge, had been a barrier to trade and development between the two banks. Certainly, since more commercial and industrial businesses abound in the area near the bridge, the lifestyle of people – which is social in character – would be modified. The Bridge’s contribution to regional development also indicates some forms of social modifications in the way that people interact with one another. Below are images of the construction of the Humber Bridge: References Brown, C. J., Karunar, R., Ashkenzi, V., Roberts, G. W., and Evans, R. A. (2004) Monitoring of strictures using the global positioning system, Royaome-UNI. Humber Bridge Board (2009) Construction history, http://www.humberbridge.co.uk/explore.php, date accessed 11/11/09. The Royal Academy of Engineering (2003) The mathematics of framed bridge structures, http://www.raeng.org.uk/education/diploma/maths/pdf/exemplars_advanced/3_Frame.pdf, Date accessed 11/11/09. Read More