The Arch bridges and Cantilever Bridges
Table of Contents
Arch Bridges:
The arch form is best suited to deep gorges with steep rocky banks which furnish efficient natural abutments to receive the heavy threat exerted by the ribs. In the absence of these natural conditions, the arch usually suffers a disadvantage, because the construction of suitable abutment is expensive and time-consuming.
The arch form is aesthetically the most pleasing and has been used in steel bridges in open range of 100 to 250 m. Typical steel arch bridges are shown in Fig.
Deck-type spandrel arches can be particularly attractive as in the case of the Rainbow Bridge across the Niagara River at Niagara Falls. The arch profile is intended to reduce bending moments in the superstructure and will be economical in the material when compared with an equivalent site simply supported girder or truss. The efficiency is made possible by the horizontal beams provided by the supports and hence the site has to be suitable.
The fabrication and reactions of an arch bridge would pose a more difficult problem than a girder bridge and should be properly taken into account by the designer. Arch ribe can be hingeless as in the case of the Rainbow Bridge; or may have one, or two
The famous steel arch bridges include the Kade Bridge in St. Louis, Missouri (1874) Garabit Viaduct in France (188),
The Hell Gate Bridge in New York (1017),
The Bayonne Bridge oven Kill Van Kull in New York (1931),
Sydney Harbour Bridge in Sydney, Australia (1932). Eada bridge. designed by d 15. Enda consisted of three spana of 153 m, 168 m, and 153 m. Thin bridge in ales historically important because this was the first bridge in America whore;
- Steel was used extensively in bridge construction:
- Steel material was tested for strong conformity to specified strength;
- Prismatic caissons were used for foundation work,
- The Cantilever method of erection was used
Guesbit viaduct, designed by Gustay Biffel is a magnificent two-hinged arch bridge that tapers to the springings, providing increased internal Suffocas. Lindenthala Hell Gate bridge Tas a two-hinged arch span of 298m and is one of the longest steel bridges in the world having a cuerall length between abutmente of 5571 m.
It Is also the most heavily loaded long spar bridge in the world carrying four ballasted railway tracks upon a nolid deck floor. Ralph Freeman designed the Bydney Harbour bridge with a two-hinged arch apon of 503 m and the bridge was compiled in 1032 Dageoc Iodee designed by O.11. Amman, with a two-binged arch span of 504 m, Han boon a record bridge till 1977.
The New River Gorge bridge in West Virginia completed in 1977 with a span of 510 m using weathering steel has been the world’s largest span arch bridge till recently. Currently, the title for the world’s longest-span arch bridge is held by the Lupu Bridge in Shanghai, China, built in 2004 with a main span of 550 m.
The arch form is likely to go out of adoption for new steel bridges in the near future, in favor of the cable-stayed form of construction, as the latter tends to be more economical and aesthetically pleasing.
Cantilever Bridges
A cantilever bridge with a single main span consists of an anchor arm at either end between the abutment and the pier, a cantilever arm from either pier to both a suspended span and its terminus are present. A large unobstructed span for navigation is made possible by this configuration, which also makes it easier to install steelwork without the requirement for supporting centering from below.
Due to their increased rigidity over suspension bridges, steel cantilever bridges became the standard for long-span railway bridges. Three well-known examples are shown In Fig. When the Firth of Forth bridge was completed in 1889, its two main spans, measuring 521 meters each, became a significant landmark in the history of bridge building. In order for the arch ribs to endure wind pressures of 2.68 kN/m, the designers, John Fowler and Benjamin Baker, used tubular components of a rather considerable size with riveted construction. Despite the massive size of the tubes, the bridge’s weight per linear meter was still lower than that of the Quebec bridge.
The design of the Quebec bridge was first entrusted to Theodore Cooper, who was then well-known for his specifications for railway bridges.
The plan envisaged a main span of 549 m with anchor spans of 157 m each, making this bridge the longest span in the world. 75 men were killed when the south arm of the bridge collapsed completely during the first effort to build it (1907). The failure was due to a miscalculation of dead load and the wrong design of compression members, which errors were not noticed in time. The design was revised by H.A. Voutelet and the structure was reconstructed in 1917 with the same main span.
Howrah Bridge with a main span of 457 m was the third-longest-span cantilever bridge in the world at the time of its construction (1943). Creeper cranes were used to build the bridge, starting at the two anchor spans and working their way down the upper chord toward the middle. The closure at the middle was obtained by means of sixteen hydraulic Jacks of 800 t capacity each. The construction was successfully completed with very close precision.
The Arch bridges and Cantilever Bridges
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