118-667: Tilikum Crossing, Bridge of the People is a cable-stayed bridge across the Willamette River in Portland, Oregon , United States. It was designed by TriMet , the Portland metropolitan area 's regional transit authority, for its MAX Orange Line light rail passenger trains. The bridge also serves city buses and the Portland Streetcar , as well as bicycles, pedestrians, and emergency vehicles. Private cars and trucks are not permitted on
236-460: A 2-span or 3-span cable-stayed bridge, the loads from the main spans are normally anchored back near the end abutments by stays in the end spans. For more spans, this is not the case and the bridge structure is less stiff overall. This can create difficulties in both the design of the deck and the pylons. Examples of multiple-span structures in which this is the case include Ting Kau Bridge , where additional 'cross-bracing' stays are used to stabilise
354-486: A Maximum Credible Earthquake (MCE), estimated at 8.5 moment magnitude in a 1500-year time span. Rather than designing for rigidity, it is instead a flexible structure, with resonant motion absorbed by the plastic shear of sacrificial, replaceable components. Smaller earthquakes will impose mostly elastic stresses on components, with a higher proportion of plastic (and thus energy absorbing) stresses in larger earthquakes. This design philosophy extends to other metal components of
472-485: A book by Croatian - Venetian inventor Fausto Veranzio . Many early suspension bridges were cable-stayed construction, including the 1817 footbridge Dryburgh Abbey Bridge , James Dredge 's patented Victoria Bridge, Bath (1836), and the later Albert Bridge (1872) and Brooklyn Bridge (1883). Their designers found that the combination of technologies created a stiffer bridge. John A. Roebling took particular advantage of this to limit deformations due to railway loads in
590-473: A design tailored to the site. For ship channel clearance, the bridge would require at least one long span, while ready access to bedrock was found only close to Yerba Buena Island. A two tower cable-stayed design would require very deep tower footings, and a conventional two tower suspension bridge would additionally require a massive anchor to be built in deep bay mud. The curved nature of the approach and seismic safety criteria place additional constraints upon
708-420: A final price tag of $ 6.5 billion, a 2,500% increase from the original estimate of $ 250 million, which was an initial estimate for a seismic retrofit of the span, not the full span replacement ultimately completed. Originally scheduled to open in 2007, several problems delayed the opening until September 2, 2013. With a width of 258.33 ft (78.74 m), comprising 10 general-purpose lanes, it
826-415: A larger crane, were lifted and placed over the second set of columns. The tower now stood at an impressive height of 374 feet and was 71 percent complete. The erection process did not continue until the following year when the final set of tower columns finally arrived by Valentine's Day 2011. These four columns, each being 105.6 feet tall, were lifted in the week of February 28, 2011 and placed over
944-399: A light rail line to Milwaukie resumed, in the early 2000s, the bridge-alignment question was revisited, with a Hawthorne Bridge routing again among the options (because of its much lower cost) but with a new bridge having the widest support. In 2008, the earlier bridge routing choice was reaffirmed, except with the planned west end positioned farther south than previously, so as to better serve
1062-475: A result of the concurrent building boom in China, but also due to construction uncertainties owing to the innovative design. The entire project, requiring 100,000 tons of structural steel, was expected to cost $ 6.2 billion as of July 2005, up from a 1997 estimate of $ 1.1 billion (for a simple viaduct) and a March 2003 estimate of $ 2.6 billion that included a tower span. Despite the increase in costs, construction began on
1180-574: A signature span (a span with distinctive and dramatic appearance, unique to the site) by the Engineering and Design Advisory Panel (EDAP) of the Metropolitan Transportation Commission (MTC). A number of innovative proposals were examined until all but four proposals that were submitted by members of EDAP were selected as semi-finalists, and a winner was selected from this group. This posed a serious conflict of interest, as members of
1298-486: A single holiday closure, new temporary steelwork to route traffic around the location of the final approaches to the new bridge was put in place, and its connections to the tunnel exit and the existing bridge were completed, much as was done in September 2007. This bypass enabled the construction of the permanent transition structure between the double-deck tunnel exit and the new side-by-side bridge structure. Upon completion of
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#17328688451811416-553: A truss causeway. This part became the subject of concern after a section collapsed during the Loma Prieta earthquake on October 17, 1989. The replacement span is engineered to withstand the largest earthquake expected over a 1500-year period, and it is expected to last at least 150 years with proper maintenance. Bridge design experts had known for over 30 years that a major earthquake on either of two nearby faults (the San Andreas and
1534-497: A two-year delay and many hundred millions of dollars in additional costs. Various options were determined to be worthy of consideration and were carefully examined jointly by state and federal authorities, with input from the United States Coast Guard . Grade alternatives included: The last alternative was chosen because it was considered to have a superior visual effect and improved driving experience. The grade of
1652-509: A viaduct may not even be able to obtain Coast Guard approval, since the maximum width of the ship channel would be reduced by almost half. Local reaction to this announcement was intense, with most suggesting that the bridge be built to appear as proposed — either in the steel material as bid or using a reinforced concrete tower of similar appearance but of lower cost. The standpoint of pro-"signature bridge" activists and regional politicians
1770-647: Is a cable-stayed bridge with a more substantial bridge deck that, being stiffer and stronger, allows the cables to be omitted close to the tower and for the towers to be lower in proportion to the span. The first extradosed bridges were the Ganter Bridge and Sunniberg Bridge in Switzerland. The first extradosed bridge in the United States, the Pearl Harbor Memorial Bridge was built to carry I-95 across
1888-457: Is determined by the river's depth, that changes on the two towers and the suspension cables. The alignment was finalized in 2008, after consideration of several alternative alignments. However, some studies and public discussion had taken place more than a decade earlier, when a MAX light rail line to Milwaukie was part of the so-called "South/North MAX" project (Vancouver–Downtown Portland–Milwaukie–Clackamas Town Center) for which voters in
2006-406: Is done, the tension in the cables increases, as it does with the live load of traffic crossing the bridge. The tension on the main cables is transferred to the ground at the anchorages and by downwards compression on the towers. In cable-stayed bridges, the towers are the primary load-bearing structures that transmit the bridge loads to the ground. A cantilever approach is often used to support
2124-472: Is expected to save time in the total effort, speeding the completion of the span. The Oakland Touchdown was completed in March 2013. On the three-day weekend beginning 8:00 PM Friday, February 17, 2012, the westbound lanes were shut down to allow the connection of the approach roadbed with the new temporary structure. The execution of this task was dependent upon weather, dry conditions being required for re-striping
2242-524: Is midway between the Marquam and Ross Island Bridges , and the east landing is just north of Southeast Caruthers Street, with the east approach viaduct reaching the surface at the west end of Sherman Street, which the tracks follow to a new Oregon Museum of Science and Industry (OMSI) MAX station located near an existing Portland Streetcar station and the Oregon Rail Heritage Center . Although
2360-420: Is provided under the span owing mostly to the depth of the deck box structures. Alignment alternatives included (see image at right for details): The last alternative was selected, as it presents a superior view of San Francisco to the west compared to the others where views are obscured by Yerba Buena Island. Any more northerly track would encounter more difficult geotechnical circumstances. In December 2004,
2478-550: Is separated into a 31-foot-wide (9.4 m) transitway between the tower legs to accommodate two lanes of track and two flanking multi-use paths for pedestrians and cyclists. Cable saddles were incorporated in TYLI's bridge design to allow for more slender, solid towers and a cleaner bridge profile. Tilikum Crossing is the first bridge in the U.S. to use the Freyssinet multi-tube saddle design, which allows each cable to run continuously from
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#17328688451812596-485: Is the range within which cantilever bridges would rapidly grow heavier, and suspension bridge cabling would be more costly. Cable-stayed bridges were being designed and constructed by the late 16th century, and the form found wide use in the late 19th century. Early examples, including the Brooklyn Bridge , often combined features from both the cable-stayed and suspension designs. Cable-stayed designs fell from favor in
2714-452: Is the world's widest bridge according to Guinness World Records . The Bay Bridge has two major sections: the western suspension spans and their approach structures between San Francisco and Yerba Buena Island (YBI) and the structures between YBI and the eastern terminus in Oakland . The original eastern section was composed of a double balanced cantilever span, five through-truss spans, and
2832-466: The FX 2-Division , on September 18, 2022. City planners initially focused on three designs: cable-stayed , wave-frame girder , and through arch , but the design committee eventually recommended a hybrid suspension /cable-stayed design by architect, Miguel Rosales . Despite the recommendation, TriMet chose a cable-stayed option by MacDonald Architects in order to reduce cost. MacDonald had previously designed
2950-469: The Hayward ) could destroy the major cantilever span . Little was done to address this problem until the 1989 Loma Prieta earthquake. The earthquake measured 6.9 on the moment magnitude scale and while the epicenter was distant from the bridge, a 50-foot (15 m) section of the upper deck of the eastern truss viaduct portion of the bridge collapsed onto the deck below, indirectly resulting in one death at
3068-521: The Metro district approved funding in November 1994. Alternatives had included routing the proposed MAX line across the existing Hawthorne Bridge and, instead, building a new bridge on any of various alternative alignments, one of which was known as the "Caruthers Street bridge" alignment or simply "Caruthers Bridge" because its east end would roughly align with S.E. Caruthers Street. The "South/North" MAX project
3186-645: The Niagara Falls Suspension Bridge . The earliest known surviving example of a true cable-stayed bridge in the United States is E.E. Runyon's largely intact steel or iron Bluff Dale Suspension bridge with wooden stringers and decking in Bluff Dale, Texas (1890), or his weeks earlier but ruined Barton Creek Bridge between Huckabay, Texas and Gordon, Texas (1889 or 1890). In the twentieth century, early examples of cable-stayed bridges included A. Gisclard's unusual Cassagnes bridge (1899), in which
3304-593: The Penobscot Narrows Bridge , completed in 2006, and the Veterans' Glass City Skyway , completed in 2007. A self-anchored suspension bridge has some similarity in principle to the cable-stayed type in that tension forces that prevent the deck from dropping are converted into compression forces vertically in the tower and horizontally along the deck structure. It is also related to the suspension bridge in having arcuate main cables with suspender cables, although
3422-722: The San Francisco Board of Supervisors , in honor of Joshua A. Norton , passed a resolution "urging the California Department of Transportation and members of the California Assembly and Senate to name the new additions to the San Francisco Bay Bridge in honor of Emperor Norton I, Emperor of the United States and Protector of Mexico." The proposal was not supported by the Oakland City Council and
3540-567: The United States Geological Survey have cast doubt on the predictability of large earthquakes based upon the duration of preceding quiet periods. A more recent (2008) analysis asserts an increased probability of a major event on the Hayward Fault. The initial proposal for the eastern span involved the construction of substantial concrete columns to replace or supplement the existing supports. There would also be modifications to
3658-560: The 40 mph S-curve speed limit were installed following a major accident. The upper deck speed advisory at the curve was posted as 35 mph and an improved system of "rumble strips" was installed. The entire deck structure must be supported in precise alignment until: The falsework to perform this task is a pair of substantial truss bridges, prefabricated in segments, with columns and span segments lifted into place by barge cranes. The trusses are supported on foundations consisting of or built atop deeply driven piles. Upon completion of
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3776-591: The Alameda formation. Where long pilings were needed, segments were welded together as completed segments were installed. When all pilings were in place, a reinforced concrete pad was poured at the bottom of the cofferdam to form a footing for the column, subsequently cast in place around rebar using reusable metal formwork . A single viaduct segment located over each column was cast in place using forms. Pairs of precast span segments, fabricated in Stockton , were barged to
3894-495: The EDAP who were selecting the bridge design reviewed proposals by their own firms and rejected all proposals that did not have a representative on the EDAP. The design chosen was more expensive than the alternatives, because the primary structure cannot be self-supporting until it is structurally complete. This requires the building of two bridges, the first a falsework to support the final span, which would be removed upon completion of
4012-619: The Quinnipiac River in New Haven, Connecticut, opening in June 2012. A cradle system carries the strands within the stays from the bridge deck to bridge deck, as a continuous element, eliminating anchorages in the pylons. Each epoxy-coated steel strand is carried inside the cradle in a one-inch (2.54 cm) steel tube. Each strand acts independently, allowing for removal, inspection, and replacement of individual strands. The first two such bridges are
4130-479: The SAS section of the bridge was completed in early October 2011. On October 19, 2011, the small gap between the SAS deck and the curved skyway extension was finally closed for the east-bound side, and the west-bound gap was closed the following week. By November 2011, the deck placement of the SAS span was complete, making 1½ miles of continuous roadway. In July 2013, the entire SAS span was completed and asphalt paving for
4248-551: The Tilikum Crossing from the route's opening in September 2022. In August 2023, a fourth bus line began using the bridge, when TriMet route 19–Woodstock was moved to the Tilikum Crossing from the Ross Island Bridge . Cable-stayed bridge A cable-stayed bridge has one or more towers (or pylons ), from which cables support the bridge deck. A distinctive feature are the cables or stays , which run directly from
4366-598: The TriMet design was handled by the HNTB Corporation with primary contracting performed by Kiewit . Construction of the bridge was estimated to cost $ 134.6 million, to be paid for by federal grants, Oregon Lottery revenue and TriMet. Construction of the bridge began in June 2011, with a slow/no wake zone put in place to ensure the safety of river users and bridge construction workers. Beginning in July 2011, an exclusion area around
4484-631: The Willamette River in the Portland metropolitan area since the Fremont Bridge , in 1973. Tilikum Crossing has its western terminus in the city's South Waterfront area, and stretches across the river to the Central Eastside district. In the 21st century, these two industrial zones have been evolving into mixed residential and commercial neighborhoods, and new transit accommodations are required by
4602-410: The bridge deck near the towers, but lengths further from them are supported by cables running directly to the towers. That has the disadvantage, unlike for the suspension bridge, that the cables pull to the sides as opposed to directly up, which requires the bridge deck to be stronger to resist the resulting horizontal compression loads, but it has the advantage of not requiring firm anchorages to resist
4720-431: The bridge does not have an official name. Although it was somewhat controversial, authorities decided to allow bids to include major components and materials not made in the United States. This was partly due to the cost of materials, and especially due to the lack of suitable fabrication facilities within the United States, or even within the western hemisphere. In contrast, China, where the SAS deck components (including
4838-417: The bridge was built without such funds, for which it would otherwise qualify owing to its carriage of Interstate 80 . The authorities were shocked when they opened the bids on the proposed tower portion and only a single bid for US$ 1.4 billion was received, considerably more than their estimate of around $ 780 million. This was partially because of a rise in the cost of steel and concrete , particularly as
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4956-404: The bridge, another extended closure allowed the removal of the temporary structure and the completion of the road link. The S-curve became well known for accidents, from fender-benders to a fatal plunge. Wrecks typically occurred during non-commute times, when traffic flows faster, at or above the general bridge limit of 50 mph. Additional signage and visual and physical indicators indicating
5074-536: The bridge, including the sacrificial tubular end keys that align the self-anchored suspension with its approach structures at each end. The tower consists of four columns. Each roughly pentagonal column consists of four tapering and/or straight sections, joined end-to-end by external plates and internal stringer finger joints secured with fasteners. The columns are also joined horizontally by sacrificial box structures. These box joins are intended to absorb earthquake-induced motion by elastic and plastic shear deformation as
5192-560: The bridge, the entire falsework structure and all exposed underwater supports will be removed to make a safe channel for deep draft ships transiting to and from the Port of Oakland . By late August 2009, the temporary column work was complete, truss spans were in place and prefabricated sections were being placed upon it. A giant barge crane, the Left Coast Lifter , was used to place the 28 main deck box structures. Major segment placement on
5310-415: The bridge. It is the first major bridge in the U.S. that was designed to allow access to transit vehicles, cyclists and pedestrians but not cars. Construction began in 2011, and the bridge was officially opened on September 12, 2015. In homage to Native American civilizations, the bridge was named after the local Chinook word for people . The Tilikum Crossing was the first new bridge to be opened across
5428-613: The bridge. It was estimated that each turbine may generate up to 1,000 watts of electricity per hour, depending on the wind speed. They began operating in May 2019. In addition to their practical use in generating power, the turbines were described by the agency as supportive of the bridge's overall "sustainability" theme and "fun to look at", and were described by the Portland Tribune as "whimsical". TriMet's first Frequent Express route, FX2–Division, which uses articulated buses , began using
5546-403: The cables, towers, and underside of the deck. The USGS environmental data is translated by specialized software to a processor that issues cues programmed for each of the changing conditions. The base color is determined by the water's temperature. The timing and intensity of the base color's changes, moving the light across the bridge, are determined by the river's speed. A secondary color pattern
5664-437: The catwalks, eventually suspended by tensioning the strand. These strand bundles were then arranged to be finally compacted to form the completed main cable. Being asymmetrical, the shorter western span must be pulled down against the forces imposed by the longer eastern span. To avoid vertical uplift in the supporting columns (W2), the uplift at pier W2 is fully counterbalanced by a massive concrete end weight, which also carries
5782-422: The central span segments. The extreme deck segments on the eastern end are curved and tilted to fair into the curved portion of the skyway. These extreme segments are also beyond the main cable strand anchors and the eastern support columns and a substantial portion of the bridge joining the skyway is already in place (the grey portion seen above). The extreme east bound deck segments on the western end must fair with
5900-616: The collapse of a retrofitted overpass in the 1994 Northridge earthquake in Los Angeles, that structure having been modified in response to the San Fernando earthquake 23 years prior. Engineering and economic analysis in 1996 suggested that a replacement bridge would cost a few hundred million dollars more than a retrofit of the existing eastern span, would have a far longer expected useful life (perhaps 75 to 100 years rather than 30), and would require far less maintenance. Rather than retrofit
6018-533: The column. Eventually, the gap in spans between columns was closed, forming a tendon-reinforced beam. The Oakland Touchdown is a curved elevated roadway that connects the skyway to the Oakland shore (the beginning of the bridge). The curve is required to bring the alignment to that of the existing ground-level approach road. Like the Yerba Buena Island Transition Structure (YBITS) to the west of
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#17328688451816136-540: The connection of both to the regional MAX light rail system. The Orange Line continues south from OMSI to Milwaukie and northern Oak Grove and north from South Waterfront into downtown Portland . Two bus lines moved to the new bridge from the Ross Island Bridge on September 13, 2015: Lines 9-Powell and 17-Holgate/Broadway. Line 2-Division was moved to the new bridge from the Hawthorne Bridge when it became
6254-512: The deck, through the top of the tower and back down to the other side. Approximately 3.5 miles (5.6 km) of cables run continuously through the tower saddle, instead of terminating in each tower. A light art aesthetic lighting system, designed by installation artists Anna Valentina Murch and Doug Hollis, alters the bridge’s lighting effects based on the Willamette's speed, depth, and water temperature. It uses 178 LED modules to illuminate
6372-413: The delay and the cost of restarting the main span foundation work, an eventual toll of $ 5.00 is now expected. (The toll is only collected in the westbound direction.) The low bid by a joint venture of American Bridge and Fluor Corp. , named ' American Bridge-Fluor , was accepted on April 19, 2006. The skyway viaduct connects the SAS portion of the bridge with the Oakland shore. By 2007, 75 percent of
6490-478: The demolition of the old span. In January 2006, costs for the main structure steelwork were determined to be $ 400 million in excess of these expectations. New bids for the main span were opened on March 22, 2006, with two submissions at 1.43 and US$ 1.6 billion. Owing to reserves built up with a $ 3.00 toll during the delay, it was initially suggested by authorities that additional tolls exceeding $ 4.00 would not be required, but due to added costs in other portions due to
6608-568: The design, the columns may be vertical or angled or curved relative to the bridge deck. A side-spar cable-stayed bridge uses a central tower supported only on one side. This design allows the construction of a curved bridge. Far more radical in its structure, the Puente del Alamillo (1992) uses a single cantilever spar on one side of the span, with cables on one side only to support the bridge deck. Unlike other cable-stayed types, this bridge exerts considerable overturning force upon its foundation and
6726-411: The design, which set many firsts for a SAS bridge. While earlier bridges of this type use chain eyebars , the long span needed here uses wire cable, like other modern suspension bridges. Uniquely, this is a single loop of cable rather than the usual pair of cables, and, rather than being spun in place above the catwalks, substantial bundles of strands were dragged into place with temporary support above
6844-506: The early 20th century as larger gaps were bridged using pure suspension designs, and shorter ones using various systems built of reinforced concrete . It returned to prominence in the later 20th century when the combination of new materials, larger construction machinery, and the need to replace older bridges all lowered the relative price of these designs. Cable-stayed bridges date back to 1595, where designs were found in Machinae Novae ,
6962-402: The eastern end, with vertical supports driven to bedrock, is mostly contained within softer mud deposits, which respond much more actively to seismic shocks than does the shale. The intent is that the combination of the tensioned tendons and the compressive roadbed box structure will keep the two end caps in the same relative position. The bridge segments at each end are not simple repetitions of
7080-469: The entire day of May 19, 2011, operating engineers and ironworkers lifted and placed the 900,000-pound (410,000 kg) double cable saddle atop the SAS tower. While a large portion of the span was fabricated in China, this particular piece was made in Japan, as was the eastern and western deviation saddles and main cable hydraulic jacking saddle. This cable saddle guides and supports the mile-long main cable over
7198-471: The event completed by internal staff has shown that the bridge was close to a far more catastrophic failure in which either the through-truss or the causeway segment would have dropped from their common support structure. It was clear that the eastern span needed to be made more earthquake resistant. Estimates made in 1999 placed the probability of a major earthquake in the area within the following 30 years at 70%, although studies announced in September 2004 by
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#17328688451817316-405: The existing bridge, CalTrans (California Department of Transportation) decided to replace the entire eastern span due to cost savings of approximately $ 625 million, minimize scheduling impact to traffic, improved safety, and additional amenities compared to retrofit. The design proposed was an elevated viaduct consisting of reinforced concrete columns and precast concrete segment spans as seen in
7434-518: The existing span. Caltrans closed the Bay Bridge during the Labor Day weekend so crews could replace the old span. Once the old section was removed, the new span was rolled into place using a computer-guided system of hydraulic jacks and rollers. The new section was secured into place and the bridge re-opened 11 hours ahead of schedule, for the morning commute on September 4, 2007. In September 2009, during
7552-486: The expected cost (subsequently modified to $ 83 million in a December 2005 report). The design controversy continued for over six months. In essence, the governor believed that the entire state should not share in the costs of building the bridge, as he considered it to be a local problem. Northern Californians pointed out that when the southern portions of the state experienced disasters, the state supported rebuilding, especially as seen in earthquake rebuilding of freeways and
7670-400: The final span. It has also been criticized as both a less structurally robust design and with less predictable construction costs than other modern spans. In 1997, there was much political bickering over whether the bridge should be built to the north or to the south of the existing bridge, with the "Mayors Brown" (San Francisco's Willie Brown and Oakland's Jerry Brown ) on opposite sides of
7788-817: The first of the modern type, but had little influence on later development. The steel-decked Strömsund Bridge designed by Franz Dischinger (1955) is, therefore, more often cited as the first modern cable-stayed bridge. Other key pioneers included Fabrizio de Miranda , Riccardo Morandi , and Fritz Leonhardt . Early bridges from this period used very few stay cables, as in the Theodor Heuss Bridge (1958). However, this involves substantial erection costs, and more modern structures tend to use many more cables to ensure greater economy. Cable-stayed bridges may appear to be similar to suspension bridges , but they are quite different in principle and construction. In suspension bridges, large main cables (normally two) hang between
7906-552: The frequent trade interactions between pioneers and Native Americans. Before being named, the still-uncompleted bridge had usually been referred to as the Portland–Milwaukie Light Rail Bridge , or as Caruthers Crossing due to its proximity to Caruthers Street. After the public was invited to suggest names for the bridge in the summer of 2013, the favorite choice of participants was, by an overwhelming margin, street musician Kirk Reeves . However, TriMet rejected
8024-479: The governor on July 18, 2005. The compromise called for the state to contribute $ 630 million to help cover the $ 3.6 billion in cost overruns, and bridge tolls to be raised to $ 4 starting in 2007. At the time of the signing, the skyway portion of the bridge was 75 percent complete and the state was beginning to prepare to put the suspension span out for new bids. The entire project was then scheduled to be completed in 2013 at an estimated cost of $ 6.3 billion, not counting
8142-443: The governor's office announced that the signature span concept had been scrapped, with the bridge to be the simple viaduct originally proposed. The design, having gone full circle, remained expensive due to the continued high cost of materials. Many argued that there would be little difference in final cost with this lesser proposal since that concept required obtaining new permits, perhaps adding another two or three years; furthermore,
8260-477: The growing populations. Both districts, however, are limited by antiquated road infrastructure that was deemed incapable of handling the increased traffic that could be expected from a conventional automobile bridge. The primary rationale for the bridge was thus "first and foremost as a conduit for a light-rail line." The bridge is south of, and approximately parallel to, the Marquam Bridge . The west "landing"
8378-520: The horizontal eastbound portion of the YBITS connector, while the westbound (north side) segments begin a rise to the westbound YBITS, elevating traffic to the upper deck of the Yerba Buena tunnel. The old cantilever bridge was connected to the Yerba Buena tunnel with a double-deck truss causeway that included a curved section. As this structure occupied an area that must be clear for the new bridge approach, it
8496-511: The horizontal part of the cable forces is balanced by a separate horizontal tie cable, preventing significant compression in the deck, and G. Leinekugel le Coq's bridge at Lézardrieux in Brittany (1924). Eduardo Torroja designed a cable-stayed aqueduct at Tempul in 1926. Albert Caquot 's 1952 concrete-decked cable-stayed bridge over the Donzère-Mondragon canal at Pierrelatte is one of
8614-670: The horizontal pull of the main cables of the suspension bridge. By design, all static horizontal forces of the cable-stayed bridge are balanced so that the supporting towers do not tend to tilt or slide and so must only resist horizontal forces from the live loads. The following are key advantages of the cable-stayed form: There are four major classes of rigging on cable-stayed bridges: mono , harp , fan, and star . There are also seven main arrangements for support columns: single , double , portal , A-shaped , H-shaped , inverted Y and M-shaped . The last three are hybrid arrangements that combine two arrangements into one. Depending on
8732-399: The illustration at right. The design criterion was that the new bridge should survive an 8.5 magnitude earthquake on any of several faults in the region (particularly the nearby San Andreas and Hayward faults). The aesthetics of the proposal were not well received by either the public or their politicians, being characterized as a "freeway on stilts". After this, a design contest was held for
8850-406: The in-water bridge construction site went into effect. Construction of the bridge itself was scheduled for completion in 2014, followed by several months of work to install tracks and other infrastructure across the bridge. As part of testing the signaling and overhead catenary systems, MAX and streetcar vehicles first ran across the bridge under their own power on January 21, 2015. TriMet selected
8968-425: The issue. Yerba Buena Island is within the city limits of San Francisco and the proposed (and current) northern alignment would cast a shadow over certain prime development sites on the island's eastern shore. Even the U.S. Navy (at the time the controlling authority of the island) was involved at the behest of San Francisco in restricting Caltrans soil engineers' access to the proposed site . That may have caused up to
9086-452: The lanes, and it was not determined until a few days before that the work would be done on this weekend. Originally scheduled for completion by 5 A.M. on Tuesday, February 21, the work was completed 34 hours ahead of schedule, and opened to traffic at approximately 7:15 P.M. on Sunday, February 19. The principal span is of a seldom-built type, a self-anchored suspension (SAS) bridge . It is unique in being both single tower and asymmetrical ,
9204-419: The last phase was to lift the final top cap that will carry the crowning main cable saddle. On July 28, 2010, the first of four below-deck main tower pillars was erected, having arrived earlier in the month by barge from China. They were placed by lifting one end from a barge into a temporary scaffold, with a carriage on the barge to allow the lower end to move into place. After the columns were bolted into place,
9322-490: The lattice beams as are now complete for the western suspension spans. The original cost estimate for this refit was $ 200 million. The overall appearance would be little changed. Owing to the retention of the original structure, the bridge's ongoing maintenance costs would continue to be high. The robustness of a retrofit was called into question directly by the Army Corps of Engineers in a highly critical report and indirectly by
9440-415: The location and lifted into place with a specialized cantilever lift. (Cantilever lifts, counterweights and other equipment and materials were lifted either by a barge crane or by a jack-up crane located between adjacent columns.) Once in the proper location, the opposing segments could then be joined with through tendons (cables within conduits that are tensioned with jacks), forming a balanced cantilever over
9558-457: The main span, this section is also an end segment of the new bridge and is being constructed at the same pace as the YBITS. The construction process consists of two phases, the first phase already completed (westbound traffic side). The eastbound touchdown could not be completed until the existing roadway was out of the way. This was done by constructing a gentle swing to the south so that the touchdown may be completed. The first stage of this work
9676-505: The massive cable, key sections of the iconic tower and deck) were built by Shanghai Zhenhua Heavy Industries Company, has low cost materials producers. Other major components were produced in Japan, owing to the availability of large steel casting, welding, and machining capabilities. Suspender saddles were made in England. As Federal highway funds generally come with "Made in America" restrictions,
9794-570: The name of the bridge in April 2014 from a list of four finalists chosen by the public. Tilikum is a Chinook Jargon word meaning people, tribe, or family, and the name is intended to honor the Multnomah , Cascade, Clackamas , and other Chinookan peoples who lived in the area as long as 14,000 years ago. The Tilikum name also references the pervasive use of Chinook Jargon in Portland’s first half century in
9912-512: The new approach (estimated possible ranges of 1.710%-1.779%; vertically-curved suspension deck with crest, slightly different from what was chosen) to the channel span is somewhat less than that of the previous structure (exactly 4% for ground-upper deck connection; exactly 2.74% for deck trusses and east 2 through trusses; transition gradient for center through truss; exactly 1.3% for cantilever arms and west 2 through trusses; vertical curve with crest between cantilever towers) and less ship clearance
10030-522: The nomination of the recently deceased performer, and in January 2014, it chose four other, less popular finalists: Public commentary on the names was accepted until March 1 and TriMet chose the final name, Tilikum Crossing, Bridge of the People in April, using the spelling preferred by the Chinookan peoples . The crossing opened for general use on September 12, 2015, becoming the first new bridge built across
10148-513: The old curved connector. During replacement, the old section was jacked out of the way (to the north), and the new section jacked into place. On September 3, 2007, the first section associated with the construction of the new East Span, the 300-foot (91 m) temporary span connecting the main cantilever section to the Yerba Buena Island Tunnel, was put into service. Construction of the new connector span started in early 2007 alongside
10266-443: The pilings are founded in firm archaic mud below the soft mud deposited by distant placer mining in the late 19th century. Since even the archaic mud is too weak in this concentrated load application for conventional vertical friction piles, large diameter tubular piles were driven (inside the pumped-dry cofferdams) at angles, forming a "battered" (splayed) footing, through the archaic mud into the firm aggregated sand, mud, and gravel of
10384-483: The planned MAX Orange Line was the impetus for construction of the bridge, the structure also carries TriMet buses, the Portland Streetcar Loop Service and emergency vehicles, and is open for public use by bicyclists and pedestrians. Use by private motor vehicles (except emergency vehicles) is not permitted. Rerouting of TriMet bus routes onto the new bridge from more-congested crossings will shorten
10502-423: The point of collapse. The bridge was closed for a month as construction crews removed and reconstructed the fallen section. It reopened on November 18, 1989, with a new stronger retrofit in place. The failure was at the transition between the easternmost through-truss and the westernmost double-deck causeway segment, a location where the inertial response character of the structure makes an abrupt change. Analysis of
10620-539: The pylons; Millau Viaduct and Mezcala Bridge , where twin-legged towers are used; and General Rafael Urdaneta Bridge , where very stiff multi-legged frame towers were adopted. A similar situation with a suspension bridge is found at both the Great Seto Bridge and San Francisco–Oakland Bay Bridge where additional anchorage piers are required after every set of three suspension spans – this solution can also be adapted for cable-stayed bridges. An extradosed bridge
10738-501: The replacement on January 29, 2002, with completion originally slated for 2007. The span finally opened on September 2, 2013. On September 30, 2004, the office of Governor Arnold Schwarzenegger announced that, without sufficient funds authorized by the California Legislature , the bid must be allowed to expire. It was, at the time, unclear if this would require a redesign to obtain a less expensive span. On December 10, 2004,
10856-428: The river in the Portland metropolitan area since 1973. The first public access to the bridge was given on August 9, 2015, in the morning for the 20th annual Providence Bridge Pedal and in the afternoon with a three-hour period in which the bridge was open to everyone. In 2019, TriMet installed 12 vertical-axis wind turbines on the bridge, atop already existing lighting and overhead catenary poles near both ends of
10974-426: The roadway began. Each deck segment is paved with two single-inch layers of asphalt and concrete which should be very durable and last for the entire lifetime of the bridge. However, the rest of the bridge is not paved with asphalt but instead only received a protective coating finish. The design employs extensive energy absorbing techniques to enable survivability and immediate access for emergency vehicles following
11092-420: The scaffold and were placed over the first four columns that were placed earlier in the year. After the columns were set into place, they were bolted together with the first set of columns. After this second phase was complete, the tower was now about 51 percent completed and stood at a height of 272 feet. The third set of tower columns did not arrive until the week of December 15, 2010. The third set, now with
11210-408: The scaffolding was then extended upward to allow the next set of above deck columns to be erected, lifted, and translated into position, a process repeated for each of the remaining phases. Tower erection continued when the second set of columns finally arrived in the week of October 24, 2010, almost three months after the first set were placed. The second set of columns were erected by a gantry atop
11328-597: The self-anchored type lacks the heavy cable anchorages of the ordinary suspension bridge. Unlike either a cable-stayed bridge or a suspension bridge, the self-anchored suspension bridge must be supported by falsework during construction and so it is more expensive to construct. Eastern span replacement of the San Francisco%E2%80%93Oakland Bay Bridge The eastern span replacement of the San Francisco–Oakland Bay Bridge
11446-409: The signature span. Cost estimates of the contract deferral expenses and inflation range attributable to the delay have ranged up to $ 400 million. Direct costs due to cessation of work included some dismantling of temporary structures and their reconstruction upon the subsequent restart. After being approved by the legislature, the compromise legislation authored by Senator Loni Hancock was signed by
11564-483: The similar Eastern span replacement of the San Francisco–Oakland Bay Bridge . T.Y. Lin International (TYLI), Engineer of Record on the Tilikum Crossing project, designed the distinctive, 180-foot-tall (55 m), pentagonal shaped stay-cable towers as the bridge's focal point. The 1,720-foot-long (520 m) bridge also features two landside piers and two in-water piers. The 780-foot-long (240 m) main span deck
11682-400: The site the same day the fourth set of tower columns arrived. On April 15, 2011, the first part of the fifth and final phase began. The 500-ton grillage was lifted 500 feet in the air and was placed over the fourth set of columns. The tower then stood at a height of 495 feet and was 94 percent complete. It took about one day to lift and place the grillage on top of the tower. Working
11800-401: The skyway portion was completed. Since this section crosses the shallower portion of the bay, the foundations were constructed within sheet-pile cofferdams . By mid-2009, the final connection of the viaduct portion with ground level at the eastern end was being finished and the pedestrian walkway was being attached to the completed sections. Rather than set pilings deep enough to reach bedrock,
11918-512: The spar must resist the bending caused by the cables, as the cable forces are not balanced by opposing cables. The spar of this particular bridge forms the gnomon of a large garden sundial . Related bridges by the architect Santiago Calatrava include the Puente de la Mujer (2001), Sundial Bridge (2004), Chords Bridge (2008), and Assut de l'Or Bridge (2008). Cable-stayed bridges with more than three spans involve significantly more challenging designs than do 2-span or 3-span structures. In
12036-474: The subsequent seismic retrofit of state freeway structures and bridges. Since the objective of the replacement of the eastern span is to prevent the necessity of complete rebuilding after a large earthquake, Bay Area residents felt justified in their call for state support. A compromise was announced on June 24, 2005 by Governor Schwarzenegger. The governor said that he and State Senate President Pro Tempore Don Perata had reached agreement to resurrect plans for
12154-420: The suspended side-by-side roadways separated in the middle by fifty feet, with enough space between the tower and the roadways to allow swaying under severe earthquakes without collision. The process to build the SAS tower atop its foundation consisted of five phases. The first four phases each consisted of lifting segments of four similar columns and bolting them into place and to elements connecting them, while
12272-458: The then-new South Waterfront district, where major redevelopment had occurred in the several years since the "South/North" project's planning was undertaken. The project received required approval from both the Portland and Milwaukie city councils and Oregon's Metro regional governmental agency in 2008. TriMet approved a $ 127 million contract to build the bridge in December 2010. Onsite engineering of
12390-421: The third set of columns. The tower now stood at a height of 480 feet and was 91 percent complete. The fifth and final tower phase was to lift a grillage (a structure to join the columns, more commonly used as a foundation element) that weighs about 500 tons, lift the main 450-ton cable saddle, and finally lift the final tower head which completed the entire SAS tower. All of these final pieces arrived at
12508-416: The tower sways. Under a severe earthquake, this deformation absorbs energy that could otherwise lead to destructive tower motion, thus protecting the primary structure of the span. It is expected that this design will allow the immediate use of the bridge for emergency vehicles, with the joins being replaced as needed to restore the bridge to its original condition. Uniquely, the tower has no direct contact with
12626-428: The tower that was placed later in the year. In December 2011, the deck placement of the SAS span was completed and cable construction progress finally began. However, a few months before in July 2011, the tower head was lifted and placed over the saddle in a test fitting and was then removed to allow the laying of the cable. Later on in 2012, the cables were fully placed on the tower saddle and were then anchored throughout
12744-415: The tower to the deck, normally forming a fan-like pattern or a series of parallel lines. This is in contrast to the modern suspension bridge , where the cables supporting the deck are suspended vertically from the main cable, anchored at both ends of the bridge and running between the towers. The cable-stayed bridge is optimal for spans longer than cantilever bridges and shorter than suspension bridges. This
12862-419: The towers and are anchored at each end to the ground. This can be difficult to implement when ground conditions are poor. The main cables, which are free to move on bearings in the towers, bear the load of the bridge deck. Before the deck is installed, the cables are under tension from their own weight. Along the main cables smaller cables or rods connect to the bridge deck, which is lifted in sections. As this
12980-418: The travel time for riders on those routes. Bike and pedestrian paths line both sides of the bridge and are 14 feet (4.3 m) wide. The bridge connects a MAX station at OMSI on the east side of the river with a new OHSU /South Waterfront Campus MAX station on the west side. OHSU is the city's largest employer, while OMSI is one of the city's largest tourist and educational venues, and the new bridge facilitates
13098-433: The turning saddles for the main cables. As seen in the northwest corner image above, there is an upward component to the tension force provided by the main cable, and it is this component that removes most of the weight of the end cap from its columns. (The greater, horizontal, component is countered by the compressive forces exerted by the deck box girders, as is characteristic of this type of bridge.) The segments of each of
13216-400: The two deck spans will be retained in compression during a severe earthquake by post-tensioned internal tendons joining the extreme end caps, carried internally in cable trays. These tendons are required since the eastern end support is both much lighter than the western counterweight and the soil conditions are radically different at each end, the western end being founded in bedrock shale while
13334-413: The whole SAS span. The tower head was then permanently installed for the final time, along with aircraft warning beacons, completing the entire SAS tower at a final height of 525 feet (160 m). The tower saddle includes eyebars for the attachment of temporary cables that supported four walkways, each a simple suspension bridge (called a catwalk) that allowed access to the cable spinning mechanism and
13452-589: Was a construction project to replace a seismically unsound portion of the Bay Bridge with a new self-anchored suspension bridge (SAS) and a pair of viaducts . The bridge is in the U.S. state of California and crosses the San Francisco Bay between Yerba Buena Island and Oakland . The span replacement took place between 2002 and 2013, and is the most expensive public works project in California history, with
13570-441: Was necessary to construct an entirely new, temporary approach to the old bridge. This was required to swing to the south to clear the area for new construction, and then back to the north with a more severe curve to connect to the unilever. As there would only be a few days available during which the bridge could be shut to traffic, the curved portion was built adjacent to its final position on a trestle that extended beneath and beyond
13688-449: Was reinforced by a legislative analyst's report in late January 2005. The report indicated, due to additional time delays and all new permitting requirements, that the governor's viaduct proposal could likely cost additional funding and take longer to complete than the proposed signature span. This view was reinforced by a further report in March 2005 indicating that the delay imposed by the governor had already added at least $ 100 million to
13806-447: Was to move the eastbound traffic to the south was completed with only minor traffic delays during the 2011 Memorial Day holiday (May 28–30). The driving experience has been improved, without the problems that came with the infamous S-curve . A second stage to move the westbound traffic into the space made available required the construction of an elevated approach. This was completed on February 19, 2012. This recently designed procedure
13924-422: Was ultimately mothballed after Clark County voters rejected funding their share of the project in 1995 and subsequent efforts by TriMet and Portland officials to secure funding for a scaled-back Vancouver–Portland–Milwaukie MAX line were unsuccessful. However, the planning undertaken during that period included finalizing, by 1998, the choice of a 'Caruthers' alignment for the planned new bridge. After planning for
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