5. Design, Needs

Design Process

The initial briefing process of the Humber Bridge was to design a bridge to span the Humber estuary, capable of dealing with the increasing levels of traffic requiring transit over the river. The idea was to allow for increases of traffic from the 90,000 vehicles a year which used the Humber ferries to an estimated capacity of around 6,000,000 vehicles, which is still roughly the same amount of traffic flow per year to this day. The bridge was designed very effectively in this functional aspect as it still today copes easily with the mass increase of vehicles on the road since the bridge opened in June 1981. The method used to come to the final design of the bridge was purely to meet this function. After many schemes to cross the estuary were proposed, including various types of bridge design, one of which was a scheme not dissimilar to the Tyne bridge in Newcastle, a suspension bridge seemed the most efficient and practical form of bridge design to use in order to span the Humber, with it being a river more than a mile wide. In itself not a hugely inspired design, as  with many similar bridges around the world such as the Golden Gate Bridge in San Francisco, it, like the Golden Gate, is subjectively an inspiring design, with many companies copying the style of the Humber bridge, mainly in countries like Japan, an example being Pearl Harbor Bridge on the Japanese Awaji Island. This is because the Humber Bridge has proven and still is proving to be a well-designed bridge, standing the test of time and offering simplicity of maintenance.

The elegance of the bridge is also a compliment to the designers, as a structure weighing in at 526,900 tonnes of concrete and steel appears to float on the air. Other features are impressive, such as the bridge deck being designed like an aeroplane’s wing to pull the deck down in high winds to maintain stability in extremely strong wind loads up to 48/meters per second at bridge deck height, as well as coping with other adverse weather  conditions. Thanks to the bridge’s sheer size, the bridge deck, especially from a distance, looks thin and in some respects, at 4.5 meters thick, this isn’t a great depth where the bridge deck is concerned. Also, the bridge cables look incredibly inadequate to deal with the wind loads, live loads and dead loads of supporting the bridge deck. However, the fact that the cables are made up of 14,948 smaller cables of 5mm thick which individually span the bridge 4 times weighing in at 11,000 tonnes which are in turn anchored at either side by a total of 490,000 tonnes of concrete, means that, despite their dainty looks, they can cope with a load up to 19,400 tonnes per main cable. However, on the bridge itself the cables do look thicker.

Needs

The Humber Bridge is needed by approximately 120,000 vehicles per week and performs a vital role in the area offering the chance to transport business goods, emergency services and families across the river. This saves a great deal of travel time by avoiding having to go right around the river to the Ouse bridge which could be, in some cases, a life saving amount of time for an ambulance. The reduced distance can also help businesses to keep transport costs down. Additionally, the bridge attracts visitors from Lincolnshire to Yorkshire and vice versa. Construction on the Humber Bridge started in July 1972 and was officially opened by the Queen on the 24th of June 1981, remaining open ever since despite the extreme conditions of adverse weather, such as high gales when it is closed to high sided vehicles.

The main image surrounding the Humber Bridge is primarily a functional one, the main reason being that the primary activity the bridge is the carriage of vehicles from one side of the estuary to the other. This function, however, has not been compromised due to cost. When the Humber Bridge was built it was at the forefront of British engineering and still performs a great function and service to this day.

The structure was designed to account for the difficult ground conditions of the Humber’s geology, being primarily made from clay, sand and chalk with a bedrock of kimmeridge clay. As a result, the design called for the towers to be placed in positions of the most stability, namely the Hessle bank where the tower stands on chalk bedrock and an area of firmer clay which was used for the tower on the south side of the estuary. This results in the Humber Bridge being a very solid and permanent structure.

The materials used in the Humber bridge and the way it was constructed led to a fairly fast build time for such a large scale project of just 9 years. This time could have been reduced further if not for the frequent industrial action and also adverse weather conditions slowing the process. The towers took the least time to construct once the foundations were in place and spanning the bridge with the supporting cables was also done fairly quickly. However, hanging the deck from the cables and fastening each modular steel deck section together took the longest, due mainly to wind. The lifespan of the Humber Bridge, which is being maintained constantly, could be indefinite, as elements in the bridge can be replaced once they have come to the end of their life span. However, going by other suspension bridges in the UK such as the Forth Bridge, which is being replaced due to the extent and cost of constant maintenance, the Humber Bridge could be expected to remain viable for at least 50 years until it may have to be replaced. However, construction technologies and material use had advanced in the 10 years between the two bridges being built which may see the Humber bridge last far longer.