Extradosed bridge

, Switzerland.Main span 174 m, 1980. , SwitzerlandMain spans 140 m, 1998 , New Haven, Connecticut, U.S.Main spans 157 m, 2012-2015 The earliest bridge known to incorporate some of the features of an extradosed design is Bridge in Rzuchów near Leżajsk, constructed in Poland in 1980. Next is the Ganter Bridge, constructed in Switzerland, designed by Christian Menn of Zurich, it preceded by several years the 1988 publication on the design philosophy of such bridges by Jacques Mathivat, who is credited with inventing the extradosed terminology and its design concepts. The Ganter Bridge is a modified prestressed concrete cantilever girder design, where the longitudinal "continuity" tendons are raised significantly above the deck height at the ends of each main span and supported on short towers. These tendons are encased in fin-like blade walls on each side of the towers for protection, a design arrangement now often referred to as a cable-panel bridge. at Camara de Lobos, Portugal, with a main span of . This was quickly followed by the Odawara Blueway Bridge on the Seisho Bypass, Japan, designed by Akio Kasuga and completed in 1994. These tendons pass over saddles at the top of each pylon, however it is unclear as to whether they form a continuous tendon between the two spans, as the designers' documentation refers to them being anchored outside each saddle to restrain slip. Numerous bridges have subsequently been constructed in Japan to similar designs, the twin, wide Ibigawa and Kisogawa "Twinkle" bridges, spanning and across the Ibi and Kiso Rivers respectively, and completed in 2001. Twinkle bridge was the longest extradosed bridge in the world until 2017, when the long Arrah-Chhapra Bridge in India became the longest bridge of this type. In 1996, a short span bridge of the extradosed style was constructed to pass the A43 Autoroute across the Maurienne River at Saint-Remy-de-Maurienne, France. This was followed in 1998 by the curved, multi-span Sunniberg Bridge in Switzerland, also designed by Christian Menn and utilising low, outward-leaning pylons to minimise its visual impact on the surroundings. In North America, a small fin-backed prestressed concrete bridge was built across Barton Creek near Austin, Texas in 1993 to service a private development. This is similar in concept to the original Ganter Bridge, except that the stay cables are encased within triangular blade walls connecting the deck to the towers. Since the mid-2000s, the style has grown appreciably in popularity with over fifty bridges with extradosed characteristics being recorded as of 2012. They have been constructed in many countries, although the significant majority of them are located in Japan and South Korea. The longest-span example remains the 2001 Kisogawa Bridge at . ==Design characteristics==

Visually, extradosed bridges typically have the appearance of a cable-stayed bridge with very short towers (pylons), with cable stays of shallow angle that may not extend along the full length of the deck, and (frequently) with a more substantial deck superstructure. Developed as a hybrid structure between the classic cable-stay and cantilever-girder bridge types, they can offer cost saving and aesthetic opportunities for medium-length bridges in the to span range. In comparison, extradosed bridges have towers with height:span ratios of between 1:8 and 1:15 (0.125 to 0.067), with around 1:10 (0.10) being most common. This lower tower height results in a much flatter cable angle, typically ~ 17° to the horizontal, and a correspondingly much higher axial compression force within the bridge superstructure due to the greater horizontal force component within each cable stay. From a structural perspective, the second extradosed characteristic is the reduced proportion of superstructure live load that is carried by the cables. On cable-stayed bridges, the stays commonly support at least 80% of the loading from vehicular traffic acting on the bridge superstructure, whereas on extradosed bridges, the stay cables typically support only between 20% and 60% of this load. In both cases, the remainder of the load is carried by the longitudinal girder element in spanning-action between the main bridge supports. This characteristic derives from the relative stiffnesses between the cable stays and the girder element. Cable-stay designs typically incorporate flexible deck structures without a stiff girder element, and such systems transfer the majority of any applied deck loads directly into the nearest stay cables. In comparison, extradosed designs utilise a substantially stiffer deck/girder structure, allowing the girder to support a significant proportion of any deck loads, and facilitating the distribution of the remaining load between a larger number of individual stay elements. Thirdly is the magnitude of fatigue loading experienced by the external cables, and their subsequent treatment by design codes. Unlike a bridge's near-constant dead load, its live load can be highly variable both in time and position, resulting in fluctuations in the stress level experienced by the bridge's structural elements as the live loading varies. The lower proportion of live load carried by the extradosed cables results in a reduced magnitude of stress fluctuations within the cables, down from typically or above for cable-stay bridges to around for extradosed designs. This has a direct benefit in reducing the detrimental effects of fatigue experienced by the stay cables and their end anchorages, and bridge design codes allow extradosed stay cables to operate at a significantly higher design stress level and therefore material efficiency level as a result. As a result of these characteristics, the "stay cables" on extradosed bridges are not treated as such by the design codes, but are instead considered as external post-tensioning tendons that have been deviated upwards from the deck to the towers to increase the superstructure's load capacity over the main supports. Extradosed bridges frequently extend this approach by making the extradosed tendons continuous over the towers via saddle supports and using anchorages only at the deck connections, significantly simplifying the tensioning operations. ==By country==

Australia The Fremantle Traffic Bridge is set to become Australia′s first extradosed bridge , located in Fremantle, Western Australia. Delivered as part of the Swan River Crossings project, this $400M+ project replaces an aging 1939 timber structure with a safer, more durable, 100-year-lifespan bridge that will improve marine, pedestrian, and traffic access. Much of the construction has occurred with the original bridge in service. The original bridge was closed to traffic in February 2026 to allow for its demolition, followed by the installation of deck girders and traffic surfaces. Completion of the bridge and reopening to the public is expected to be complete by Feb-2027. Bolivia The Triplets are the first three extradosed concrete bridges in Bolivia. The construction of a beltway allowing traffic decongestion in the city of La Paz was completed in 2010. The new elevated road crosses three parallel valleys with signature bridges. These three consecutive bridges have similar features and as a result are called the Triplets. All three-span structures are made of concrete, with maximum span of 113 metres, featuring extradosed pre-stressed concrete. The structures are built using balanced cantilever segmental construction. The elevation of the bridges reaches heights between 40 and 60 m above the bottom of the valley, which made a cable-stayed bridge option, with pylons higher than 25 m above the deck, inappropriate for the site. Therefore, it was proposed an extradosed bridge type, which reduces the height of the pylon, and a single plane of stays to allow a more transparent view. The bridges were designed by PEDELTA. Canada , Canada 2009 The North Arm Bridge is a transit-pedestrian bridge of SkyTrain Canada Line, connecting Vancouver with its suburb of Richmond crossing over the Fraser River. The bridge went into service on 17 August 2009, coinciding with the opening of the Canada Line. The Golden Ears Bridge, crosses the Fraser River between the municipalities of Pitt Meadows / Maple Ridge and Langley. It is the longest extradosed bridge in North America. The bridge opened to traffic on 16 June 2009. China Extradosed bridges are rare in China, while the first was Wuhu Yangtze River Bridge completed in 2000, One main span is long. Several bridges followed, including the recently opened Hongxi Bridge with long main span. India In 2006, Delhi Metro's Blue Line was extended to Indraprastha from Barakhamba Road. This section had a Extradosed Bridge between Supreme Court and Indraprastha Station. India's first extradosed bridge for road traffic, Nivedita Setu, was completed in 2007 by Larsen & Toubro Ltd. for the Second Vivekananda Bridge Toll corporation over river Hooghly, Kolkata. This bridge is long, with a span of . The 3rd Narmada Bridge, which bears a similarity to the Golden Ears Bridge in Vancouver, Canada, was completed March 2017 across Narmada River in Bharuch, Gujarat. It is the first extradosed bridge to be built in state of Gujarat and its span of is the longest in India. A few months later in June 2017, the Arrah–Chhapra Bridge opened across the Ganges river connecting Arrah and Chhapra in Bhojpur and Saran districts in the state of Bihar. It is the longest multi-span extradosed bridge in the world, with a main bridge length of . Norway The first extradosed bridge in Scandinavia is the Harpe Bridge crossing the Norwegian river Gudbrandsdalslågen as part of the highway E6. The bridge was opened for traffic 17 December 2016. It is 324 meters long and carries four lanes of traffic. one of the largest in the Europe, is the opened to traffic on 26 July 2013 over the Vistula River from Opalenie to Kwidzyn. The total length of the bridge is with the main span of 204 m. The bridge has been commissioned by General Directorate for National Roads and Highways, designed by Transprojekt Gdanski and is built by Budimex and Ferrovial Agroman at a cost of 90 million EUR. The widest extradosed bridge in the world is Most autostradowy w Mszanie (MA 532) on A1 autostrada (Poland). Sri Lanka Sri Lanka's Road Development Authority constructed the New Kelani river bridge, an extradosed bridge over the Kelani River, as part of a project aimed at improving traffic condition around the existing New Kelani Bridge. The total length of the bridge is 380m with a 180m main span and two 100m side spans. The project was completed in November 2021. Tanzania Tanzanite Bridge is the first extradosed bridge in United Republic of Tanzania. The 6.23-kilometre bridge will attempt to relieve the traffic bottleneck by connecting the area near Coco Beach and Agakan Hospital in Dar es Salaam with a four-lane bridge (1 km) on the sea. Construction is scheduled to start in the latter half of the year for completion in 2021. From the total length of 6.23 km, the length of the new bridge is 1.03 km. The main bridge itself is 670m long and is designed as an extradosed bridge with a maximum span of 125m. The road consists of a 4.52 km section where two lanes has been expanded to four lanes and a new 0.68 km section. Thailand Maha Chesadabodindranusorn Bridge is the first extradosed bridge in Thailand. The 4.3-kilometer Maha Chesadabodindranusorn Bridge links the western side (Bang Krang and Bang Sri Muang subdistricts) with the eastern part of the Nonthaburi province (Suan Yai and Talat Kwan subdistricts) and a new road connecting with Ratchaphruek Road. Turkey Çallı Bridge, in Antalya city center, is the first extradosed bridge designed and constructed in Turkey. The long bridge has an main span with side spans sustained by 2 x 4 sets of 4 extradosed cables (harp design) supported above the wide deck by two pylons canted away from the main span. The 6-lane bridge was opened to traffic for Expo 2016. United States The first extradosed bridge in the U.S. is the northbound span of the Pearl Harbor Memorial Bridge that carries Interstate 95 (Connecticut Turnpike) over the Quinnipiac River in New Haven, Connecticut, which opened to traffic on 22 June 2012. The southbound span opened on 19 August 2015, making it the fourth extradosed bridge in the U.S. The second and third extradosed bridges in the U.S. are Interstate 35 frontage road spans over the Brazos River in Waco, Texas. Construction began in July 2012 and the bridges were dedicated in July 2014. They are the first extradosed bridges to be constructed in Texas. The fifth extradosed bridge in the United States is the St. Croix Crossing, which crosses the St. Croix River between Oak Park Heights, Minnesota and St. Joseph, Wisconsin. Construction began on the bridge in 2014 and it was opened to traffic on 2 August 2017. The bridge replaced the older Stillwater Bridge in downtown Stillwater, Minnesota, which was functionally obsolete and deteriorating from its age. ==References==