Misplaced Pages

#688311

31-607: The Lewisville Lake Toll Bridge ( LLTB ) is a 1.7-mile (2.7 km) tied arch bridge crossing Lewisville Lake in Denton County, Texas , USA. Operated by North Texas Tollway Authority (NTTA), the four-lane toll bridge connects Swisher Road in Lake Dallas to Eldorado Parkway in Little Elm . It is one segment of the 13-mile (21 km) Lewisville Lake Corridor, which connects Interstate 35E and Dallas North Tollway . The bridge

62-445: A through-type arch bridge , is a bridge that is made from materials such as steel or reinforced concrete, in which the base of an arch structure is below the deck but the top rises above it. It can either be lower bearing or mid-bearing . Thus, the deck is within the arch, and cables or beams that are in tension suspend the central part of the deck from the arch. For a specific construction method, especially for masonry arches,

93-523: A single span, two tied-arches are placed in parallel alongside the deck, so the deck lies in between the arches. Axial tied-arch or single tied-arch bridges have at most one tied-arch per span that is usually centered in the middle of the bridge deck. An example for this is Hoge Brug in Maastricht. Since it has hinged hangers it might also classify as a Nielsen bridge who held a patent on tied-arch bridges with hinged hangers from 1926. Some designs tilt

124-467: A through arch does not change the proportions or size of the arch: a large span will still require a tall arch, although this can now reach any height above the deck without obstructing traffic. The arch may also reach downwards at its sides, to either reach strong foundations or to place the roadway at a convenient height for spanning a deep valley from a plateau above. The Tyne Bridge demonstrates both of these advantages. A well-known example of this type

155-520: A tied-arch; however, the bowstring truss behaves as truss , not an arch . The visual distinction is a tied-arch bridge will not have substantial diagonal members between the vertical members. In a 1978 advisory issued by the Federal Highway Administration (FHWA), the FHWA noted that tied-arch bridges are susceptible to problems caused by poor welds at the connection between the arch rib and

186-413: A vital transportation link between Lake Dallas and Little Elm. On August 1, 2009, a 5K charity run crossing the completed bridge was held. The run, which served as a fundraiser for local food banks, was the only time pedestrians will ever be allowed to cross the bridge. The bridge opened to vehicular traffic after the event was completed. The Lewisville Lake Corridor is approximately 13.8 miles long and

217-511: Is also called a bowstring-arch or bowstring-girder bridge . The elimination of horizontal forces at the abutments allows tied-arch bridges to be constructed with less robust foundations; thus they can be situated atop elevated piers or in areas of unstable soil . In addition, since they do not depend on horizontal compression forces for their integrity, tied-arch bridges can be prefabricated offsite, and subsequently floated, hauled or lifted into place. Notable bridges of this type include

248-509: Is constructed in place or lifted into position. In some cases, this type of arch has been created by constructing cantilevers from each side, with the shoreside ends bolted securely down into heavy piers. The incomplete channel ends are then constructed toward each other and either filled by construction or by lifting a prefabricated center section. This type of construction was used in the Sydney Harbour Bridge illustrated above, with

279-483: Is divided into eight sections constructed by Denton County, NTTA, the Texas Department of Transportation , Little Elm, and Frisco . NTTA funded and constructed the toll bridge, while the other partners funded improvements to the roadways approaching the bridge. Only the bridge itself is tolled. Tied arch bridge Thrusts downwards on a tied-arch bridge deck are translated, as tension, by vertical ties between

310-399: Is not practical to support the arch from beneath during construction. In modern construction, temporary towers are erected and supported by cables anchored in the ground. Temporary cables fly from each side to support arch segments as they are constructed. When the arches are almost complete a jacking bridge is placed over or beneath the gap to force the arches apart, whence the final section

341-632: Is the Fremont Bridge in Portland, Oregon which is the second-longest tied-arch bridge in the world and also classifies as a through arch bridge . The Chaotianmen Bridge in Chongqing is a tied-arch, through arch and a truss arch bridge . Contrarily, the Hart Bridge uses a cantilevered trussed arch, it is self-anchored , but its arch is non-tied. In particular the bridge deck is suspended, but does not tie

SECTION 10

#1733085006689

372-968: Is the Sydney Harbour Bridge in Australia, which is based on the Hell Gate Bridge in New York City . Other bridges include the Chaotianmen Bridge in China, the world's longest through arch bridge; Tyne Bridge of Newcastle upon Tyne ; the Bayonne Bridge that connects New York City to New Jersey , which is longer than the Sydney Harbour Bridge; the Ahwaz White Bridge ; the Bourne Bridge and Sagamore Bridge , smaller, near-twin bridges over

403-573: Is the second-longest bridge in the North Texas area. Only the State Highway 66 bridge over Lake Ray Hubbard , which connects Rowlett and Rockwall , is longer. Toll rates across the bridge are $ 1.32 for TollTag customers and $ 1.98 for ZipCash drivers. The bridge is 60 feet (18 m) above the normal water level to allow clearance for sailboats. At the center of the bridge is a 360-foot (110 m) steel arch that rises 60 feet (18 m) above

434-797: The Cape Cod Canal ; the Pennybacker Bridge in Austin , Texas and as the Hernando de Soto Bridge in Memphis, Tennessee . Wylam Railway Bridge is an early through arch bridge upstream of the Tyne Bridge. The through arch bridge usually consists of two ribs, although there are examples like the Hulme Arch Bridge of through arches with a single rib. When the two arches are built in parallel planes,

465-585: The Fremont Bridge in Portland, Oregon and the first "computer-designed" bridge of this type, the Fort Pitt Bridge in Pittsburgh, Pennsylvania . Both the tied-arch bridge and the self-anchored suspension bridge place only vertical loads on the anchorage, and so are suitable where large horizontal forces are difficult to anchor. Some tied-arch bridges only tie a segment of the main arch directly and prolong

496-494: The foundations for the bridge. Arch bridges generate large side thrusts on their footings and so may require a solid bedrock foundation. Flattening the arch shape to avoid the humpback problem, such as for Brunel's Maidenhead bridge , increases this side thrust. It is often impossible to achieve a flat enough arch, simply owing to the limitations of the foundations – particularly in flat country. Historically, such bridges often became viaducts of multiple small arches. With

527-666: The arch ends. Tied arch bridges may consist of successively lined up tied arches in places where a single span is not sufficient. An example for this is the Godavari Arch Bridge in Rajahmundry, India. It has four separate supports on each pier and carries the South Central Railway Line of India. It was designed for 250 km/h rail services. Like for multi-span continuous beam bridges the tying chord continually spans over all piers. The arches feet coincide (fuse) at

558-413: The arches outward or inward with respect to the axis running along the bridge deck. In analogy to twin bridges , two tied arch bridges erected side by side to increase traffic capacity, but structurally independent, may be referred to by tied arch twin bridges . Each in return may use a single- or multi-span, discrete or continuous tied-arch design. A bowstring truss bridge is similar in appearance to

589-413: The arches. Contrarily each abutment on the riverbanks supports a single arch end only, in the middle of the deck. The tying chord(s) consist of a composite deck structure. Four post tensioned coil steel cables, two to each side of the walking deck, are locked in place by orthogonally run steel beams every 7.5 meters. The hangers are joined to each of these beams between each cable pair. Since the beams extend

620-493: The availability of iron or concrete as structural materials, it became possible to construct a through arch bridge : a bridge where the deck does not have to be carried over the top of the arch. This requires a structure that can both support the deck from the arch by tension rods, chains or cables and allow a gap in the arch, so the deck can pass through it. The first of these in particular cannot be achieved with masonry construction and requires wrought iron or steel. The use of

651-458: The bridge piers. A good visual indication are shared supports at the piers. Dynamic loads are distributed between spans. This type may be combined with the shouldered tied-arch design discussed above. An example for this is Dashengguan Bridge in Nanjing, China. Its two main arches are shouldered by short auxiliary arches. It is both, a (rigid) tied-arch and a cantilevered trussed arch design. Because

SECTION 20

#1733085006689

682-400: The deck and the arch, tending to flatten it and thereby to push its tips outward into the abutments, like for other arch bridges. However, in a tied-arch or bowstring bridge, these movements are restrained not by the abutments but by the strengthened chord, which ties these tips together, taking the thrusts as tension, rather like the string of a bow that is being flattened. Therefore, the design

713-481: The deliberate tension member that is the key to a tied-arch. Although visually similar, tied- and untied- through-arch bridges are quite distinct structurally and are unrelated in how they distribute their loads. In particular, cast iron bridges such as the Stanley Ferry Aqueduct may resemble tied-arch bridges, but as cast iron is weak in tension they are not structurally a tied arch. In some locations it

744-432: The proportions of the arch remain similar no matter what the size: wider arches are thus required to be taller arches. For a semi-circular arch, the height is half of the span. Bridges across deep, narrow gorges can have their arch placed entirely beneath a flat roadway, but bridges in flatter country rise above their road approaches. A wide bridge may require an arch so tall as to become a significant obstacle and incline for

775-469: The road deck. The arch's design resembles the arch on the Pennybacker Bridge in Austin . At night, the arch is illuminated using LEDs , making the structure visible from the surrounding shores of the lake. A bridge previously connected Little Elm and Lake Dallas, but it was removed in the 1950s when the United States Army Corps of Engineers expanded Lewisville Lake . The old bridge provided

806-488: The roadway. Small bridges can be hump-backed , but larger bridges such as the Old Bridge, Pontypridd may become so steep as to require steps, making their use for wheeled traffic difficult. Railways also find arched bridges difficult as they are even less tolerant of inclines. Where simple arched bridges are used for railways on flat terrain the cost of building long approach embankments may be considerable. Further issues are

837-467: The strengthened chord to tie to the top ends of auxiliary (half-)arches . The latter usually support the deck from below and join their bottom feet to those of the main arch(es). The supporting piers at this point may be slender, because the outward-directed horizontal forces of main and auxiliary arch ends counterbalance. The whole structure is self-anchored . Like the simple case it exclusively places vertical loads on all ground-bound supports. An example

868-502: The structure is a parallel rib arch bridge. When the two arch ribs lean together and shorten the distance between the arches near the top, the span is a basket handle arch bridge. Many tied-arch bridges are also through-arch bridges. As well as tying the side-loads of the arch, the tension member is also at a convenient height to form the bridge deck, as for a through-arch. The converse is not true: through-arch bridges do not imply that they are tied-arch bridges, unless they also provide

899-446: The tie girders, and at the connection between the arch and vertical ties. In addition, problems with electroslag welds , while not isolated to tied-arch bridges, resulted in costly, time-consuming and inconveniencing repairs. The structure as a whole was described as nonredundant : failure of either of the two tie girders would result in failure of the entire structure. Through arch bridge A through arch bridge , also known as

930-471: The traffic runs through the structural envelope, it is also a through arch bridge. Guandu Bridge in New Taipei, Taiwan is a non-trussed example with three main arches augmented by two auxiliary arch segments at the bridge portals. The Infinity Bridge uses two arches of different height and span length that both bifurcate before their apex. Above its single, middle-displaced river pier the deck lies between

961-474: The width of the post-tensioned concrete deck, the tensing cable pairs remain visible. A close-up of the river pier shows that the structural dead load is tied per span: The larger arch span uses thicker tensing cables and the reflex segments are not suspended from, but supported by steel beams, essentially completing the arches at the river pier. However, for dynamic and non-uniform loads the visually defining arch continuations must not be neglected. Usually, for

Lewisville Lake Toll Bridge - Misplaced Pages Continue

#688311