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68-503: The San Diego–Coronado Bridge , commonly referred to as the Coronado Bridge , is a prestressed concrete / steel girder fixed-link bridge crossing over San Diego Bay , linking San Diego with Coronado, California . It is signed as part of State Route 75 . In 1926, John D. Spreckels recommended that a bridge be built between San Diego and Coronado , but voters dismissed the plan. The U.S. Navy initially did not support

136-467: A corrosion -inhibiting grease , usually lithium based. Anchorages at each end of the tendon transfer the tensioning force to the concrete, and are required to reliably perform this role for the life of the structure. Unbonded post-tensioning can take the form of: For individual strand tendons, no additional tendon ducting is used and no post-stressing grouting operation is required, unlike for bonded post-tensioning. Permanent corrosion protection of

204-403: A reversible lane in either direction in response to traffic volume. Before installation of the barrier, moveable cones were used to separate eastbound/westbound traffic. On December 7, 1981, Coronado resident Hal Willis was westbound when a drunk driver traveling eastbound at high speeds drove through the cones, hit him head-on, and caused his death. This incident began the process of implementing

272-428: A 25-degree angle (the “crab angle” ) along the barrier. Sophisticated models can be customized for their application and local road characteristics (grades, curves, etc.). Hydraulically adjustable units and computerized steering guidance systems in such models further aid in accurate transfer vehicle movement and barrier placement. Permanent, sophisticated units can cost around US$ 1 million each. Another variant of

340-568: A bridge that would span San Diego Bay to connect San Diego to Coronado. They feared a bridge could collapse due to an attack or an earthquake and trap the ships stationed at Naval Base San Diego . In 1935, an officer at the naval air station at North Island argued that if a bridge were built to cross the bay then the Navy would leave San Diego. In 1951–52, the Coronado City Council initiated plans for bridge feasibility studies. By 1964

408-508: A broad range of structural, aesthetic and economic requirements. Significant among these include: a minimum number of (intrusive) supporting walls or columns; low structural thickness (depth), allowing space for services, or for additional floors in high-rise construction; fast construction cycles, especially for multi-storey buildings; and a low cost-per-unit-area, to maximise the building owner's return on investment. The prestressing of concrete allows "load-balancing" forces to be introduced into

476-478: A feasibility study for suicide-dissuasion options for the bridge. Hueso stated, "The safety of residents and visitors traveling on the bridge, and those who gather below it in Chicano Park, is of the utmost importance." On March 26, 2018, Caltrans released its report; it outlined suicide-dissuasion options such as netting, fencing, and glass barriers. In 1972, three years after the bridge was opened to traffic,

544-679: A lane was opened to pedestrians for the Navy Bay Bridge Run/Walk, a fundraiser sponsored by and benefiting the Navy Morale, Welfare, and Recreation program. Beginning in 2008, cyclists have the once-a-year opportunity to ride over the bridge in the Bike the Bay "fun ride". The pillars supporting the bridge on the eastern end are painted with huge murals as part of Chicano Park , the most extensive collection of Chicano art murals in

612-592: A permanent barrier transfer system since 2000, when it was installed by the Delaware River Port Authority . A movable barrier system was introduced in Sydney, NSW, Australia, in 2012. The Golden Gate Bridge had a permanent 13,340-foot (4,070 m) movable barrier system installed in January 2015. The vehicle contains an S-shaped, inverted conveyor channel in its undercarriage which lifts

680-653: A prestressed concrete member, the internal stresses are introduced in a planned manner so that the stresses resulting from the imposed loads are counteracted to the desired degree. Prestressed concrete is used in a wide range of building and civil structures where its improved performance can allow for longer spans , reduced structural thicknesses, and material savings compared with simple reinforced concrete . Typical applications include high-rise buildings , residential concrete slabs , foundation systems , bridge and dam structures, silos and tanks , industrial pavements and nuclear containment structures . First used in

748-609: A proof-loaded, redundant and monitorable pressure-containment system. Nuclear reactor and containment vessels will commonly employ separate sets of post-tensioned tendons curved horizontally or vertically to completely envelop the reactor core. Blast containment walls, such as for liquid natural gas (LNG) tanks, will normally utilize layers of horizontally-curved hoop tendons for containment in combination with vertically looped tendons for axial wall pre-stressing. Heavily loaded concrete ground-slabs and pavements can be sensitive to cracking and subsequent traffic-driven deterioration. As

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816-419: A protective sleeve or duct which is either cast into the concrete structure or placed adjacent to it. At each end of a tendon is an anchorage assembly firmly fixed to the surrounding concrete. Once the concrete has been cast and set, the tendons are tensioned ("stressed") by pulling the tendon ends through the anchorages while pressing against the concrete. The large forces required to tension the tendons result in

884-626: A railway bridge constructed 1946 in the UK . By the 1960s, prestressed concrete largely superseded reinforced concrete bridges in the UK, with box girders being the dominant form. In short-span bridges of around 10 to 40 metres (30 to 130 ft), prestressing is commonly employed in the form of precast pre-tensioned girders or planks. Medium-length structures of around 40 to 200 metres (150 to 650 ft), typically use precast-segmental, in-situ balanced-cantilever and incrementally-launched designs . For

952-508: A result, prestressed concrete is regularly used in such structures as its pre-compression provides the concrete with the ability to resist the crack-inducing tensile stresses generated by in-service loading. This crack-resistance also allows individual slab sections to be constructed in larger pours than for conventionally reinforced concrete, resulting in wider joint spacings, reduced jointing costs and less long-term joint maintenance issues. Initial works have also been successfully conducted on

1020-532: A significant permanent compression being applied to the concrete once the tendon is "locked-off" at the anchorage. The method of locking the tendon-ends to the anchorage is dependent upon the tendon composition, with the most common systems being "button-head" anchoring (for wire tendons), split-wedge anchoring (for strand tendons), and threaded anchoring (for bar tendons). Tendon encapsulation systems are constructed from plastic or galvanised steel materials, and are classified into two main types: those where

1088-503: A single tendon duct, with the exception of bars which are mostly used unbundled. This bundling makes for more efficient tendon installation and grouting processes, since each complete tendon requires only one set of end-anchorages and one grouting operation. Ducting is fabricated from a durable and corrosion-resistant material such as plastic (e.g., polyethylene ) or galvanised steel, and can be either round or rectangular/oval in cross-section. The tendon sizes used are highly dependent upon

1156-407: A speed between 5 and 10 miles per hour (8.0 and 16.1 km/h). Some models of the machine hold 50 feet (15 m) of barrier at a time as they are engaged in transferring. The machine can transfer within the regular traffic flow without hindering other vehicles: Admirably engineered, the barrier-moving process does not compromise traffic flow in either direction, and the truck is shielded by

1224-660: A stiffening technique that was new to the United States; it increased the strength and resistance of the bridge. As a result, the bridge was strong and eliminated the need for additional superstructures over the deck to disperse weight. Construction on the San Diego–Coronado Bay Bridge started in February 1967. The bridge required 20,000 tons of steel (13,000 tons in structural steel and 7,000 in reinforcing steel) and 94,000 cubic yards of concrete. To add

1292-560: Is 100 feet (30 m). The length can vary based on application and the amount of barrier needed to effectively deflect an errant vehicle. Some barrier systems have four rubber feet on the bottom of each segment “to increase the coefficient of friction between the barrier element and the road surface”. This helps the barrier resist vehicle impact and keeps the barrier from moving significantly if struck. Barrier transfer machines can typically move their barrier segments anywhere between 4 and 24 feet (1.2 and 7.3 m) in one pass, usually at

1360-592: Is a highly versatile construction material as a result of it being an almost ideal combination of its two main constituents: high-strength steel, pre-stretched to allow its full strength to be easily realised; and modern concrete, pre-compressed to minimise cracking under tensile forces. Its wide range of application is reflected in its incorporation into the major design codes covering most areas of structural and civil engineering, including buildings, bridges, dams, foundations, pavements, piles, stadiums, silos, and tanks. Building structures are typically required to satisfy

1428-438: Is a type of heavy vehicle that is used to transfer concrete lane dividers, such as Jersey barriers , in order to relieve traffic congestion during rush hours. Many other cities use them temporarily during construction work. The lanes created by the machine are sometimes referred to as "zipper lanes". One advantage of barrier systems over other lane management treatments such as traffic cones or overhead directional lights

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1496-418: Is fed into a greasing chamber and then passed to an extrusion unit where molten plastic forms a continuous outer coating. Finished strands can be cut-to-length and fitted with "dead-end" anchor assemblies as required for the project. Both bonded and unbonded post-tensioning technologies are widely used around the world, and the choice of system is often dictated by regional preferences, contractor experience, or

1564-423: Is most commonly used for the fabrication of structural beams , floor slabs , hollow-core slabs, balconies , lintels , driven piles , water tanks and concrete pipes . Post-tensioned concrete is a variant of prestressed concrete where the tendons are tensioned after the surrounding concrete structure has been cast. The tendons are not placed in direct contact with the concrete, but are encapsulated within

1632-510: Is not sufficient for Nimitz -class nuclear aircraft carriers in light load condition. The principal architect was Robert Mosher . Mosher's job was to build a bridge that would provide transportation, allow ships access to the bay, and serve as an iconic landmark for San Diego. Mosher proposed a basic box and girder-style bridge for the framework, with a prestressed concrete and steel deck sitting atop steel girders and supported by towers. Mosher decided to make an orthotropic roadway, which used

1700-622: Is supported by 27 concrete girders, the longest ever made at construction time. In 1970, it won an award of merit for a long-span bridge from the American Institute of Steel Construction. The five-lane bridge featured the longest continuous box girder in the world until it was surpassed by the Shibanpo Yangtze River Bridge in Chongqing, China , in 2008. The bridge is the third largest orthogonal box in

1768-540: Is that a solid, positive barrier prevents vehicle collisions due to motorists crossing over into opposing traffic flow. A disadvantage is that lane widths can be slightly reduced. The Road Zipper variant has been in existence since 1984–1985. Auckland Harbour Bridge had its original moveable barrier system installed in 1990. The Hawaii Department of Transportation debuted a zipper Lane on Oahu on August 18, 1998. The Benjamin Franklin Bridge has had

1836-465: Is the most popular structural material for bridges, and prestressed concrete is frequently adopted. When investigated in the 1940s for use on heavy-duty bridges, the advantages of this type of bridge over more traditional designs was that it is quicker to install, more economical and longer-lasting with the bridge being less lively. One of the first bridges built in this way is the Adam Viaduct ,

1904-486: Is the protection afforded to the end-anchorage assemblies of unbonded tendons or cable-stay systems, as the anchorages of both of these are required to retain the prestressing forces. Failure of any of these components can result in the release of prestressing forces, or the physical rupture of stressing tendons. Modern prestressing systems deliver long-term durability by addressing the following areas: Several durability-related events are listed below: Prestressed concrete

1972-417: Is undertaken for three main purposes: to protect the tendons against corrosion ; to permanently "lock-in" the tendon pre-tension, thereby removing the long-term reliance upon the end-anchorage systems; and to improve certain structural behaviors of the final concrete structure. Bonded post-tensioning characteristically uses tendons each comprising bundles of elements (e.g., strands or wires) placed inside

2040-421: The Navy supported a bridge if there was at least 200 feet (61 m) of clearance for ships which operate out of the nearby Naval Base San Diego to pass underneath it. To achieve this clearance with a reasonable grade, the bridge length was increased by taking a curved path rather than a more direct path to Coronado. The clearance would allow an empty oil-fired aircraft carrier to pass beneath it – it

2108-405: The application, ranging from building works typically using between 2 and 6 strands per tendon, to specialized dam works using up to 91 strands per tendon. Fabrication of bonded tendons is generally undertaken on-site, commencing with the fitting of end-anchorages to formwork , placing the tendon ducting to the required curvature profiles, and reeving (or threading) the strands or wires through

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2176-459: The area. However, other systems simply park in a median between their movable barrier and an affixed barrier to keep them from impeding traffic flow. A barrier transfer machine that operates outside of Honolulu has its own garage in the space between viaducts. Moveable barriers are in permanent use in such cities as The Road Zipper brand movable barrier model is one vehicle, piloted by two operators located at opposite ends of it, typically at

2244-439: The authorities of building codes or standards, but rather exist to promote the understanding and development of prestressed concrete design, codes and best practices. Rules and requirements for the detailing of reinforcement and prestressing tendons are specified by individual national codes and standards such as: Barrier transfer machine A barrier transfer machine , also known as zipper machine or road zipper ,

2312-468: The availability of alternative systems. Either one is capable of delivering code-compliant, durable structures meeting the structural strength and serviceability requirements of the designer. The benefits that bonded post-tensioning can offer over unbonded systems are: The benefits that unbonded post-tensioning can offer over bonded systems are: Long-term durability is an essential requirement for prestressed concrete given its widespread use. Research on

2380-403: The barrier segments (which may weigh over 1,000 pounds (450 kg)) off the road surface and transfers them over to the other side of the lane, reallocating traffic lanes to accommodate increased traffic for the currently dominant (peak) direction. These barriers are linked together with steel connectors to create a sturdy but flexible safety barrier. The minimum length for some barrier systems

2448-413: The barrier solution. The eastern end of the bridge connects directly to a T interchange with Interstate 5 , just southeast of downtown San Diego . It is designated and signed as part of California State Highway 75. The bridge was designed entirely and exclusively for motor vehicle traffic; there are no pedestrian walkways , bike paths , or shoulders ("breakdown lanes"). Once a year, beginning in 1986,

2516-515: The blocks it's moving. If you're traveling in the same direction as the truck, the lane it's working behind is already blocked. And if you pass the vehicle at the speed limit, you can safely move into the lane ahead of it. Oncoming motorists, meanwhile, are prevented from entering the zipper's lane by the concrete barriers in front of it, and they can move into a lane after they have passed the truck. Upon completing its pass, some barrier transfer machines can be moved across outside traffic lanes away from

2584-502: The bridge urging potential suicides to call a hotline. However, call boxes are not provided. After an accident in 2016, where a drunk driver drove a pickup truck off the bridge and into Chicano Park , killing 4 and injuring 9, state senator Ben Hueso proposed a state funding bill to cover safety measures on the Coronado and require reports to the state legislature on progress. In February 2017, Caltrans announced its intent to perform

2652-421: The bridge's 50th anniversary. As of March 2014, the working target date was 2019. Three of the bridge's columns were illuminated from November 8 to November 14, 2020, as part of a lighting field test. A decades-old local urban legend claims the center span of the bridge was engineered to float in the event of collapse, allowing Naval ships to push the debris and clear the bay. The myth may have developed due to

2720-728: The bridge. In 2010, a London-based design group led by Peter Fink was chosen. The winning concept envisages illuminating the bridge with programmable LED lighting in an energy-neutral manner using electricity generated by wind turbines. In 2012, two years after choosing Fink's project, the Port of San Diego cut a check for $ 75,000 to initiate fundraising in concert with the San Diego Foundation. The Port of San Diego says no taxpayer dollars will be used. Instead, they are relying on grants and private donations to fund this lighting project, which will ideally be complete by 2019 to coincide with

2788-683: The concrete and is done to improve the performance of the concrete in service. Tendons may consist of single wires , multi-wire strands or threaded bars that are most commonly made from high-tensile steels , carbon fiber or aramid fiber . The essence of prestressed concrete is that once the initial compression has been applied, the resulting material has the characteristics of high-strength concrete when subject to any subsequent compression forces and of ductile high-strength steel when subject to tension forces . This can result in improved structural capacity and/or serviceability compared with conventionally reinforced concrete in many situations. In

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2856-430: The concrete girders, 900,000 cubic yards of fill were dredged, and the caissons for the towers were drilled and blasted 100 feet into the bed of the bay. The bridge opened to traffic on August 3, 1969, during the celebration of the 200th anniversary of the founding of San Diego. The 11,179-foot-long (3,407 m or 2.1 mi) bridge ascends from Coronado at a 4.67 percent grade before curving 80 degrees toward San Diego. It

2924-433: The concrete volume (internal prestressing) or wholly outside of it (external prestressing). While pre-tensioned concrete uses tendons directly bonded to the concrete, post-tensioned concrete can use either bonded or unbonded tendons. Pre-tensioned concrete is a variant of prestressed concrete where the tendons are tensioned prior to the concrete being cast. The concrete bonds to the tendons as it cures , following which

2992-404: The concrete wall to form a series of hoops, spaced vertically up the structure. When tensioned, these tendons exert both axial (compressive) and radial (inward) forces onto the structure, which can directly oppose the subsequent storage loadings. If the magnitude of the prestress is designed to always exceed the tensile stresses produced by the loadings, a permanent residual compression will exist in

3060-404: The country – the box is the center part of the bridge, between piers 18 and 21 over the main shipping channel. Originally, the toll was $ 0.60 in each direction. Several years later, this was changed to a $ 1.00 toll collected for westbound traffic to Coronado only. Although the bridge was supposed to become "toll-free" once the original bridge bond was paid (which occurred in 1986),

3128-979: The design and construction of prestressed concrete structures. In the United States, such organizations include the Post-Tensioning Institute (PTI) and the Precast/Prestressed Concrete Institute (PCI). Similar bodies include the Canadian Precast/Prestressed Concrete Institute (CPCI), the UK's Post-Tensioning Association, the Post Tensioning Institute of Australia and the South African Post Tensioning Association. Europe has similar country-based associations and institutions. These organizations are not

3196-413: The ducting. Following concreting and tensioning, the ducts are pressure-grouted and the tendon stressing-ends sealed against corrosion . Unbonded post-tensioning differs from bonded post-tensioning by allowing the tendons permanent freedom of longitudinal movement relative to the concrete. This is most commonly achieved by encasing each individual tendon element within a plastic sheathing filled with

3264-426: The durability performance of in-service prestressed structures has been undertaken since the 1960s, and anti-corrosion technologies for tendon protection have been continually improved since the earliest systems were developed. The durability of prestressed concrete is principally determined by the level of corrosion protection provided to any high-strength steel elements within the prestressing tendons. Also critical

3332-399: The end-anchoring of the tendons is released, and the tendon tension forces are transferred to the concrete as compression by static friction . Pre-tensioning is a common prefabrication technique, where the resulting concrete element is manufactured off-site from the final structure location and transported to site once cured. It requires strong, stable end-anchorage points between which

3400-521: The first "suicide" was recorded. It was subsequently reclassified as a murder after an investigation determined that Jewell P. Hutchings, 52, of Cerritos had been forced to jump at gunpoint. Her husband, James Albert Hutchings, was subsequently charged with murder and pleaded guilty to involuntary manslaughter. In April 1997, the Port of San Diego released an international call for artists seeking qualifications of artist-led teams interested in developing environmentally-friendly lighting concept proposals for

3468-451: The form of post-tensioned anchors drilled into the dam's concrete structure and/or the underlying rock strata. Such anchors typically comprise tendons of high-tensile bundled steel strands or individual threaded bars. Tendons are grouted to the concrete or rock at their far (internal) end, and have a significant "de-bonded" free-length at their external end which allows the tendon to stretch during tensioning. Tendons may be full-length bonded to

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3536-399: The hollow box design of the 1,880-foot center span, combined with the low-profile barges that made it appear to float on its own during construction. However, Caltrans and the bridge's principal architect, Robert Mosher , maintain that the legend is false. Prestressed concrete This compression is produced by the tensioning of high-strength "tendons" located within or adjacent to

3604-404: The late nineteenth century, prestressed concrete has developed beyond pre-tensioning to include post-tensioning , which occurs after the concrete is cast. Tensioning systems may be classed as either monostrand , where each tendon's strand or wire is stressed individually, or multi-strand , where all strands or wires in a tendon are stressed simultaneously. Tendons may be located either within

3672-432: The longest bridges, prestressed concrete deck structures often form an integral part of cable-stayed designs . Concrete dams have used prestressing to counter uplift and increase their overall stability since the mid-1930s. Prestressing is also frequently retro-fitted as part of dam remediation works, such as for structural strengthening, or when raising crest or spillway heights. Most commonly, dam prestressing takes

3740-697: The murals when permission for the park was finally granted in 1973. The Coronado Bridge is frequently used as a suicide bridge ; as of July 2017, at least 407 suicide deaths by bridge jumpers have occurred on the Coronado, trailing only the Golden Gate Bridge in San Francisco as the bridge most-often used for suicide in the United States. Solar-powered phones were once installed on the Skyway to offer direct help for those contemplating suicide, but have since been removed. Signs have been placed on

3808-553: The strands is provided by the combined layers of grease, plastic sheathing, and surrounding concrete. Where strands are bundled to form a single unbonded tendon, an enveloping duct of plastic or galvanised steel is used and its interior free-spaces grouted after stressing. In this way, additional corrosion protection is provided via the grease, plastic sheathing, grout, external sheathing, and surrounding concrete layers. Individually greased-and-sheathed tendons are usually fabricated off-site by an extrusion process. The bare steel strand

3876-579: The structure to counter in-service loadings. This provides many benefits to building structures: Some notable building structures constructed from prestressed concrete include: Sydney Opera House and World Tower , Sydney; St George Wharf Tower , London; CN Tower , Toronto; Kai Tak Cruise Terminal and International Commerce Centre , Hong Kong; Ocean Heights 2 , Dubai; Eureka Tower , Melbourne; Torre Espacio , Madrid; Guoco Tower (Tanjong Pagar Centre), Singapore; Zagreb International Airport , Croatia; and Capital Gate , Abu Dhabi UAE. Concrete

3944-475: The surface of the tendons is critical to the pre-tensioning process, as it determines when the tendon anchorages can be safely released. Higher bond strength in early-age concrete will speed production and allow more economical fabrication. To promote this, pre-tensioned tendons are usually composed of isolated single wires or strands, which provides a greater surface area for bonding than bundled-strand tendons. Unlike those of post-tensioned concrete (see below),

4012-432: The surrounding concrete or rock once tensioned, or (more commonly) have strands permanently encapsulated in corrosion-inhibiting grease over the free-length to permit long-term load monitoring and re-stressability. Circular storage structures such as silos and tanks can use prestressing forces to directly resist the outward pressures generated by stored liquids or bulk-solids. Horizontally curved tendons are installed within

4080-546: The tendon element is subsequently bonded to the surrounding concrete by internal grouting of the duct after stressing ( bonded post-tensioning); and those where the tendon element is permanently de bonded from the surrounding concrete, usually by means of a greased sheath over the tendon strands ( unbonded post-tensioning). Casting the tendon ducts/sleeves into the concrete before any tensioning occurs allows them to be readily "profiled" to any desired shape including incorporating vertical and/or horizontal curvature . When

4148-418: The tendons are stretched. These anchorages form the ends of a "casting bed" which may be many times the length of the concrete element being fabricated. This allows multiple elements to be constructed end-to-end in the one pre-tensioning operation, allowing significant productivity benefits and economies of scale to be realized. The amount of bond (or adhesion ) achievable between the freshly set concrete and

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4216-406: The tendons are tensioned, this profiling results in reaction forces being imparted onto the hardened concrete, and these can be beneficially used to counter any loadings subsequently applied to the structure. In bonded post-tensioning, tendons are permanently bonded to the surrounding concrete by the in situ grouting of their encapsulating ducting (after tendon tensioning). This grouting

4284-662: The tendons of pre-tensioned concrete elements generally form straight lines between end-anchorages. Where "profiled" or "harped" tendons are required, one or more intermediate deviators are located between the ends of the tendon to hold the tendon to the desired non-linear alignment during tensioning. Such deviators usually act against substantial forces, and hence require a robust casting-bed foundation system. Straight tendons are typically used in "linear" precast concrete elements, such as shallow beams, hollow-core slabs ; whereas profiled tendons are more commonly found in deeper precast bridge beams and girders. Pre-tensioned concrete

4352-545: The tolls continued for sixteen additional years. On June 27, 2002, it became the last toll bridge in Southern California to discontinue tolls, despite objections from some residents that traffic to the island would increase. The islands upon which the toll booths sat, as well as the canopy over the toll plaza area, are still intact, located at the western end of the bridge in the westbound lanes. Though tolls are no longer collected, beginning February 19, 2009, there

4420-677: The use of precast prestressed concrete for road pavements, where the speed and quality of the construction has been noted as being beneficial for this technique. Some notable civil structures constructed using prestressed concrete include: Gateway Bridge , Brisbane Australia; Incheon Bridge , South Korea; Roseires Dam , Sudan; Wanapum Dam , Washington, US; LNG tanks , South Hook, Wales; Cement silos , Brevik Norway; Autobahn A73 bridge , Itz Valley, Germany; Ostankino Tower , Moscow, Russia; CN Tower , Toronto, Canada; and Ringhals nuclear reactor , Videbergshamn Sweden. Worldwide, many professional organizations exist to promote best practices in

4488-491: The wall concrete, assisting in maintaining a watertight crack-free structure. Prestressed concrete has been established as a reliable construction material for high-pressure containment structures such as nuclear reactor vessels and containment buildings, and petrochemical tank blast-containment walls. Using pre-stressing to place such structures into an initial state of bi-axial or tri-axial compression increases their resistance to concrete cracking and leakage, while providing

4556-483: The world. This neighborhood park and mural display were created in response to a community uprising in 1970, which protested the adverse effects of the bridge and Interstate 5 on the Barrio Logan community. Local artist Salvador Torres proposed using the bridge and freeway pillars as a giant canvas for Chicano art at a time when urban wall murals were rare in the United States, and he and many other artists created

4624-406: Was talk of resuming westbound toll collection to fund major traffic solutions and a tunnel. However nothing came of the discussions, and more recently there have been discussions of removing the unused toll plaza completely. The bridge contains five lanes: two eastbound, two westbound, and a reversible middle lane with a barrier transfer machine system installed in 1993, which can be used to create

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