Sydney Harbour Bridge - Research Paper Example

?Sydney Harbour Bridge Bridges are historically known to shape and influence the social and cultural environment and contribute in the advancement of human civilizations, by enabling communication and interaction between the two masses of land separated by water bodies. They are the physical manifestation of a giant leap of imagination translated into engineering marvels. With the development of techniques and craftsmanship, these engineering feats began to become more and more sophisticated and complicated, over the years from its humble beginnings of tree barks used for connecting land masses, to more sophisticated suspension, cantilever and arch bridges. These pieces of construction not only add to the visual imagery of a geographical location, but also bear testimony to the imagination, craftsmanship and engineering accomplishment of mankind, as represented by the Sydney Harbour. Introduction: “Of all the inventions, the alphabet and the printing press alone excepted, those inventions which abridge distance have done the most for the civilization of our species” Thomas B. Macaulay, 2010: 290 Bridges have historically, played a key role in the development of human civilizations. This unique piece of construction and sheer engineering marvel has contributed to the development and flourishing of human civilizations, since time immemorial. It is on account of this very reason, that bridges have been featured prominently in the development of some of the most affluent cultures and cities around the globe - including the likes of London on the river Thames, Brooklyn bridge in the city of New York; the various artistic bridges on the Seine river in the city of Paris; Howrah bridge in Kolkata etc., among many others. Not only do they add a sense of artistic imagery and beauty to the city, but also help accelerate the mobility and access to various key locations in and around the area, thus enhancing the overall vitality of the cities they are built in, ultimately contributing to the social, economical as well as cultural development (John, 2000). This paper on the Sydney Harbour Bridge, aims to discuss the various factors critical to this unique and historical piece of construction, such as the history behind its construction, the various materials used, the materials used for its construction; the various equipments used; the availability and use of labour force used during construction; the civilizations and culture that flourished in that era etc. It also includes a brief discussion and analysis on the type of structure it would have been, if it was built in present times. The history of the Sydney Harbour Bridge: The Sydney Harbour Bridge, is one of Australia's most prominent landmarks, was open to the public on 19th March, 1932. The bridge, which is also popularly known as the “Coathanger” by the locals, is the largest (although not the longest) bridge in the world. It is not only a great engineering feat but also revered as one of the greatest economic accomplishments of the century, especially considering the fact that it was built after the world war, during the years of the Great Depression. The bridge was built using extensive labour, which included as many as 1400 men, and took almost eight years to complete (from 1925 to 1932), with an investment of six million pounds (Lalor, 2006; Sharpe, 2001; Langmead and Garnaut, 2001). It was designed by a British firm Dorman Long and Co Ltd, under the directions of Dr. J. J. C. Bradfield along with other officers of the NSW Department of Public Works. The design of this bridge was inspired by the Hell Gate Bridge in New York (Sydney Harbour Bridge, 2012). Although the construction of the bridge began in the year 1925, the foundations for the same were laid decades ago, which is evident from the various historical events that took place, as is described in the following sections. Brief Background: Events that led to the construction of the Bridge Prior to the construction of the Sydney Harbour Bridge, the city was divided into two, but the monumental arch helped in merging the two and changed the iconography of the city for the better. The bridge helped join the vast mass of land, about 300,000 on the north and 600,000 in the south and facilitated exchange of and access to facilities which were previously restricted or rendered inaccessible. Captain Arthur Phillip was one of the very few people who recognized an opportunity to use this harbour for marine parking, due to the security it offered. Prior to the construction of the bridge, for thousands of years, the local Aboriginals used it for fishing and travelled to the other end by building bark rafts held together by twines. The people on both the sides of the river remained separated, until things began to change. On the 26th of January, 1788 Phillip, spotted a real estate opportunity and things began to change, after people began migrating to settle on the banks of the river. Over time, millions of people migrated and settled in the surrounding areas, settling in a pecking order - with the rich living near the water's edge and the poor in distant locales. Various bridges were constructed over the years, which sought to unite the north and the south, but were destroyed by floods or were rendered dysfunctional due to various other reasons (Lalor, 2006). During the year 1815, Francis Greenway proposed the construction of a bridge which would help connecting the northern and southern shores of the harbour, although the actual realization of this project took several decades, and it was only during the early 1900s that serious considerations were given to the plan, proposed by Greenway (Harbour Bridge, 2012). In the year 1912, Dr. J. J. C. Bradfield was appointed as the Chief Engineer for the Sydney Metropolitan Railways Construction and Harbour Bridge project, and was transferred to Europe and North America in the year 1914 to study the modern practices associated with the construction of underground railways and other techniques related to the construction of long span bridges. The government then invited worldwide tenders on December 8, 1921 and Dr. Bradfield was again sent to North America and Europe to select and negotiate with prospective tenders, on March 16, 1922. On the closing date of the tender, on January 16th, 1924, as many as twenty four tenders were received by the NSW Government. The design submitted by the British Firm Dorman Long and Co., of Middlesbrough, was finally selected, which led to the awarding of a contract to them, on the March 24, 1924 (Ghassemi and White, 2007). It took a lot of time for the construction of the bridge to commence, since it involved demolishing of the existing houses on and around the proposed site. Hence, approximately 438 houses were bought and demolished and finally on March 26, 1925, the foundation stone was laid at the southern abutment tower by the Minister of Public Works and Railways (Ghassemi and White, 2007). Prior to the construction of this bridge, various temporary constructions / bridges were made, by the civilizations that thrived along the river basin, including the Aboriginals, but all of them were either destroyed or rendered dysfunctional due to natural calamities and other technical setbacks. The successful completion of the bridge, and its grand opening on the 19th of March, 1932 indicated a historical moment for the people of Australia, and particularly the locals in the city of Sydney. Construction and Engineering: The Sydney Harbour Bridge is a two-hinged 503- meter span arch bridge. It is a two hinged trussed arch made primarily of steel with a span of 1650 ft. and constructed using temporary cantilever methods at each end (Troyano, 2003). Figure 1: The Sydney Harbour Bridge Source: Flaxman, 1967: 33 The NSW Government was largely in favour of constructing a cantilever bridge, however since the selected tender proposed a steel bridge, it was finalized since it was estimated to cost much less as compared to the cantilever bridge, and the arch bridge looked visually appealing. The topmost point of the arch is estimated to be about 440 ft. above the high-water level and provides a clearance of 173 ft. 6 in. max., at the centre of the span. The erection of the arch took two years to complete costing over 2.5 million pounds (Flaxman, 1967). Materials used: The following is the list of materials used for the construction of this bridge: Concrete: The Sydney Harbour Bridge is largely constructed using steel. However according to available statistics, approximately 95,000 cubic meters of concrete was used for the construction of this bridge. The choice of material used for the construction of this bridge, is attributed to the fact that during that era, the use of reinforced concrete was in its infancy. (Harbour Bridge, 2012). Although steel is relatively more expensive than concrete it is also lighter than concrete constructions, and easier to repair. Steel: The principles of engineering advocate the use of steel for constructing the strongest parts of a bridge. Hence the arches of the Sydney Harbour Bridge were made largely out of steel. Also the use of steel is justified, since it is lighter as compared to other metals such as iron, and used in making arches, girders as well as trusses (Larsen and Tyas, 2004). The Sydney Harbour Bridge used approximately 53,000 tonnes of steel (Sydney Harbour Bridge, 2012). Cable sockets: The arch of the bridge was made of two separate constructions, and hence each of the arches was required to be supported by using some material, that would prevent it from falling apart. For this purpose cable sockets were used, to link these two arches, which were made to pass through the 'U' shaped tunnels underground. A total of 128 cables were used to fix the arch on the south-eastern corner of arch, and similar process was repeated on the north shore of the construction as well. The position of the arch had to be controlled, and this required the cables to be adjustable / flexible, especially when the arches were lowered at the time of joining them together. In order to facilitate this action, each of the two cables was fixed into a steel socket (Sydney Harbour Bridge, 2012). Rivets: Most of the riveted bridges were commonly constructed during the early 20th century between the period beginning from 1900s to the early 1960s (Mahmood, 2003). Steel structures during this period were assembled using rivets although it is rare in present times (Wilson, 2005). Over 6,000,000 rivets were used for assembling the various plates on the Harbour Bridge (Sydney Harbour Bridge, 2012). Construction techniques: The following construction techniques were used for the construction of the bridge: Cantilevering method: This method is used in case of structures which require very large spans. In this method, the erection of the structures beginning from the abutment end and the members ahead is done by using cranes, which travels on the top boom of a previously erected part, in this case the arch (Ponnuswamy, 2008). Arch Construction: The Sydney Harbour Bridge is a fine example of an arch bridge. It is one of the most exquisite structures built of steel arches, and represents the artistic masonry extensively used during the 18th to early 20th century. This method of constructing bridges was first introduced by the Romans, which continued through the middle ages (Megson, 2005). Hangers and Deck and trusses: The decks of the bridge are supported by hangers which in turn are suspended from the arches. Trusses are built by fastening beams together in a triangular shape. This type of framework helps in distributing the load of the bridge, in a way that the weight of the bridge is distributed and shared by the three beams. This method of constructions helps in reducing the overall weight of the bridge, and reduces the cost. Furthermore, it enables the bridge to carry more weight and heavy loads (Megson, 2005). Constructing the harbour bridge in 21st century: The construction of bridges and the technology used for the same, during the 20th century, was largely influenced by the industrial revolution. The techniques used during the construction of bridges in the previous century, hence differed greatly with those which can be and are used in present times. For instance, the method of riveting used for construction in the Sydney Harbour Bridge, is almost outdated now. Also, the concrete bridges were cast on the site of the construction rather than pre-casting them, as is done in contemporary times. Furthermore, a lot of materials used in present times, were not even invented back then, for instance, plastic. Most importantly, the method of surveying the site was done mechanically and the entire process was labour intensive in nature and approach. With the turn of the century, and the range of technological advancements that took place over the years, novel and innovative means of construction have evolved and applied today. Also, various new issues and concerns have emerged along with the benefits brought about by the technological advancements, such as concerns related to managing heavy inflow of traffic; strategies to manage congestion – both after and during the construction of the bridge etc., among many others. Construction times have significantly reduced over the years. The Sydney Harbour Bridge which roughly took eight years to complete would have been completed much earlier if it were built today. Also, the loss of lives during the construction of the bridge, which is believed to have claimed 16 lives on site; would have reduced to nil, due to the rise in safety measures and equipments which are readily available for the workers. Also, the availability and easy accessibility of technology, novel equipments and enhanced working conditions, is likely to have increased productivity, thus reducing the construction time significantly. The advances in construction technology would allow for better quality control, and help in enhancing the designing of the bridges. The construction industry today is more environmentally conscious hence, the approach to constructing huge structures, is highly likely to attract stricter rules and accountability. Also, the problems encountered during the construction, which could have led to a complete halt in the construction process, would be resolved immediately thus preventing any loss of time, and hence preventing from adding to the existing cost of the project. Innovative tools and equipments such as GPS (Global Positioning Systems) would be used to help the workers work more effectively; and the engineers would be able to locate plans and make changes with immediate effect. The use of video cameras to computers would help in interacting with people located in distant locations. The use of materials used for construction during the 20th century will be replaced with new and environmentally friendly material, especially components which are easier to maintain and repair, would find greater acceptance. Materials such as plastic, high performance concrete etc., will be used for repair and maintenance work. The use of cutting edge technology will aid in research purposes, thus leading to better designs, lighter weights of material used and improved quality. The 21st century offers an amazing opportunity for an amalgamation of technology, engineering and aesthetics and an increased opportunity for structural integrity of the bridges than never before. References: Flaxman, E., (1967). Great feats of engineering, Ayer Publishing, pp. 33 Ghassemi, F., White, I., (2007). Inter-basin water transfer: Case studies from Australia, United States, Canada, China and India. Cambridge University Press, pp. 362-63 John, N., (2000). Building the Sydney Harbour Bridge, St. Leonards: Allen and Unwin Lalor, P., (2006). The Bridge: The epic story of an Australian icon - The Sydney Harbour Bridge. Allen & Unwin Publication, pp. 32-38 Langmead, D., Garnaut, C., (2001). Encyclopedia of architectural and engineering feats. ABC-CLIO Publishers, pp. 323-325 Larsen, O. P., Tyas, A., (2004). Conceptual Structural Design: Bridging the Gap Between Architects and Engineers. Thomas Telford Publishers, pp. 51-52 Macaulay, T. B., (2010). The history of England from the Accession of James II. Cosimo Inc. Publication, pp. 290 Mahmoud, K. L., (2003). Recent developments in bridge engineering. Taylor & Francis Publication, pp. 194 Megson, T. H. G., (2005). Structural and stress analysis. Butterworth-Heinemann Publication, pp. 133 Ponnuswamy, K. N., (2008). Bridge engineering, McGraw-Hill Publication, pp. 511 Sharpe, A., (2001). Pictorial history: the City of Sydney. Kingsclear Books Ptv Ltd., pp. 23-27 Troyano, L. F., (2003). Bridge engineering: A global perspective. Thomas Telford Publishing, pp. 286-87 Primary Sources Harbour Bridge (2012). History of the Sydney Harbour Bridge [Online] Available at: http://www.harbourbridge.com.au/hbpages/historycontent.html [Accessed: April 16, 2012] Sydney Harbour Bridge (2012). Bridge Design [Online] Available at: http://sydney-harbour-bridge.bos.nsw.edu.au/engineering-studies/bridge-design.php [Accessed: April 17, 2012] Wilson, J., (2005). The model railroader's guide to bridges, trestles and tunnels. Kalmbach Publishing, pp. 38-41 Appendix: Table 1: Facts about the Sydney Harbour Bridge: Source: http://www.sydneyharbourbridge.info/ Read More