Bay Bridge

San Francisco-Oakland Bay Bridge
Official name	Eastern section: James "Sunny Jim" Rolph Bridge ; Western section: Willie L. Brown Jr. Bridge
use	Motor vehicles only. Pedestrian and bicycle path over the eastern section between Oakland and Yerba Buena
Crossing of	San Francisco Bay
construction	two-story two suspension bridges, one-hip suspension bridge and a tunnel
overall length	8320 m
width	five lanes
Longest span	Suspension bridges: 704 m single-hip suspension bridge: 385 m
building-costs	77.6 million US dollars
start of building	July 9, 1933
opening	November 12, 1936
toll	$ 2.50 to $ 6 (two-axle vehicles from east to west)
	location
	The course of the Bay Bridge and its new section

37.816666666667 -122.35194444444Coordinates: 37 ° 49 ′ 0 ″ N , 122 ° 21 ′ 7 ″ W.

The San Francisco-Oakland Bay Bridge , mostly just called the Bay Bridge or Oakland Bay Bridge , spans the Bay of San Francisco and connects the two Californian cities of Oakland and San Francisco , USA .

The bridge consists of two bridges; in between lies Yerba Buena Island . The western section connects this island with San Francisco and consists of two individual suspension bridges , each with two pylons , which meet at a central concrete anchor block. The eastern segment connects Oakland with that island and consists of two parallel ramp bridges and finally a large one-hip suspension bridge. The latter replaced the original bridge, a steel framework construction, in 2013. The traffic in the western part is routed on two levels; the upper deck faces San Francisco, the lower one faces Oakland. Around 274,000 vehicles drive over the bridge every day.

The original bridges were designed by Charles H. Purcell . The bridge opened on November 12, 1936, six months before San Francisco's second famous bridge, the Golden Gate Bridge .

history

The bridges in the San Francisco Bay Area

San Francisco lies at the mouth of the bay of the same name; this location made the city thrive during the gold rush . Almost all goods that could not be produced locally came by ship. But after the first transcontinental railroad was completed in May 1869, San Francisco was on the wrong side of the bay because the railroad ended in Oakland. Many citizens feared that the city could lose its position as a central trading and trading center. The concept of a bridge came about during the gold rush. Various newspaper articles dealt with this idea as early as the early 1870s. In 1872 a bridge building committee ( Bay Bridge Committee ) began to plan the railway bridge. The April 1872 edition of the San Francisco Real Estate Circular featured an article on the Building Committee:

"The Bay Bridge Committee lately submitted its report to the Board of Supervisors, in which compromise with the Central Pacific was recommended; Also the bridging of the bay at Ravenswood and the granting of railroad facilities at Mission Bay and on the water front. Wm. C. Ralston, ex-Mayor Selby and James Otis were on this committee. A daily newspaper attempts to account for the advice of these gentlemen to the city by hinting that they were afraid of the railroad company, and therefore made their recommendations to suit its interests. "

“The Bay Bridge Committee presents its report to the city's clients recommending a compromise with the Central Pacific Railway Company ; this includes a bridge on Ravenswood Bay and the granting of railroad facilities in Mission Bay and on the coast. Wm. C. Ralston, Former Mayor Selby, and James Otis are members of the committee. A daily newspaper stated that the result of these gentlemen's reports for the city was based on their fear of the railway company, and therefore they had made their recommendations as the interests of the railway company approve. '"

- San Francisco Real Estate Circular, April 1872

Joshua Abraham Norton, called Norton I.

The self-proclaimed Emperor Norton I considered a decree necessary that a suspension bridge had to be built to connect Oakland with San Francisco. Later in 1872, after nothing happened, he decreed in frustration:

“Whereas, we issued our decree ordering the citizens of San Francisco and Oakland to appropriate funds for the survey of a suspension bridge from Oakland Point via Goat Island; also for a tunnel; and to ascertain which is the best project; and whereas the said citizens have hitherto neglected to notice our said decree; and whereas we are determined our authority shall be fully respected; now, therefore, we do hereby command the arrest by the army of both the Boards of City Fathers if they persist in neglecting our decrees. Given under our royal hand and seal at San Francisco, this 17th day of September, 1872 "

"On the matter of we issued an order that the citizens of San Francisco should provide funding to study the Oakland Bridge Project and a tunneling project, and see which project is better; and because the aforementioned citizens have so far ignored the aforementioned order; and because we are determined to put pressure on our authority; therefore we hereby order the arrest of both councilors of the city fathers by the army if they continue to oppose us. With a royal-imperial seal, San Francisco on September 17th, 1872. "

- Emperor Norton I, 1872

Contrary to many eccentric ideas of Norton I, his decree to build such a bridge received a lot of public and political attention. But the task seemed too daunting considering the breadth and depth of the bay. In 1921, 40 years after Norton's death, an underwater tube was considered, but it quickly became clear that such a tube would not be suitable for vehicles. In the course of the 1920s - due to the increase in motor vehicle traffic - the demand for a way to cross the bay became louder and louder. In 1926, the California government handed over responsibility for building a bridge between San Francisco and Alameda County to the Ferry and Bridge Authority.

In 1929, the US President Hoover and the California Governor Young set up a commission to examine the technical feasibility and develop recommendations. The investigations were led by Charles H. Purcell, who was subsequently appointed chief engineer responsible for the design and construction of the bridge. The commission included Ralph Modjeski , Leon S. Moisseiff , who was involved in almost all suspension bridges of the time, and Charles Derleth, Jr.

In order to make the bridge construction feasible, it was decided to include the Yerba Buena Island and thus reduce the cost of materials compared to a one-piece bay bridge. At that time, this island was the base of the US Navy , so that the approval of the US Congress in Washington was necessary for the bridge to be built. Only after many years of extensive lobbying did Congress give its approval on February 20, 1931.

The Bay Bridge under construction over Yerba Buena Island (1935)

The 3.2 km of the western section between the island and San Francisco was an enormous challenge for engineering . The bay is 30 m deep in places and the building ground required new foundation and foundation techniques . Suspension bridges with more than two pylons are very difficult to implement for reasons of stability, and a single suspension bridge with only two pylons was not possible at the time due to the large span. The solution consisted of a large concrete anchor block halfway between San Francisco and the island and the construction of two separate, complete suspension bridges.

The eastern segment was no less expensive. The distance between Yerba Buena Island and Oakland is 3.1 km and was spanned with a combination of one large and 19 smaller steel truss bridges; overall this made the longest bridge of its kind.

Tunnel exit to the west

A tunnel 165 m long connects the halves of the entire structure on the Yerba Buena Island . Rock and rubble from the tunneling was partly used to fill the new Treasure Island .

Most of the truss bridge is built on wooden foundations. Because of the very deep mud at the bottom of the bay, it did not seem possible to base on rock. Because the deeper layers of the mud are relatively solid, long stakes were driven from old Douglas firs into these layers.

The construction of the entire structure began with the groundbreaking ceremony by Herbert C. Hoover and California's Governor Frank Merriam on July 9, 1933 shortly after the Golden Gate Bridge ; The bridge was opened on Thursday, November 12, 1936 at 12:30 p.m., six months before the Golden Gate Bridge. 24 workers were killed during construction. The total cost amounted to 77.6 million US dollars . At the time of completion, it was the longest suspension bridge and also the longest truss bridge in the world. Since there are ultimately two bridges, the western part of the suspension bridge was declared the second and the eastern part the third longest suspension bridge in the world. Only the George Washington Bridge in New York had a larger span between the pylons.

Fairy lights on the west crossing since 1987

The bridge was part of US Highways 40 and 50 until 1964; since then it has belonged to Interstate 80 and is a key link in the motor vehicle network. It is used extensively and is so prone to traffic jams that traffic accidents often paralyze traffic for several hours, even if the scene of the accident can be cleared quickly. The traffic then also puts a massive strain on the alternative routes.

The Bay Bridge was added to the List of Historic Civil Engineering Landmarks by the American Society of Civil Engineers in 1986 .

The fairy lights on the load-bearing ropes of the suspension bridge were installed in 1987 as part of the celebrations for the 50th anniversary of the Bay Bridge.

Bridge name

The official name of the bridge is James "Sunny Jim" Rolph Bridge , but the name is rarely used and it wasn't until 1986 that the bridge's 50th anniversary celebrations began to attract attention. The appropriate name has always been San Francisco-Oakland Bay Bridge .

James Rolph Jr. was Mayor of San Francisco and Governor of California when construction began on the bridge . He died in office two years before the bridge opened, and to show his respect it was named after him. Due to political rivalries with the editor of the Oakland Tribune , Joseph Knowland, this naming was withheld by the press.

The early sponsorship of a bridge between San Francisco and Alameda County by Emperor Norton I was honored on Thursday, December 14, 2004; the San Francisco Board of Supervisors advocated naming the new eastern segment after Norton.

There are plaques in favor of the support of both Governor Rolph and Emperor Norton. The panel for Rolph was originally placed at the west end of the bridge in San Francisco and has been hanging on Fifth and Bryant Streets since 1986. The plaque honoring Emperor Norton for his original idea adorns the western arch of the Transbay Terminal, the toll station and greyhound bus depot at the western end of the downtown San Francisco bridge.

It is popularly known as the Bay Bridge .

Finances

When it opened in 1936, the toll was 65 cents . Within a few months it was reduced to 50 cents to stay competitive with the ferry system , and eventually it was reduced to 25 cents after that amount was found to be enough to pay off the loans.

Then again, fees were levied in order to be able to maintain and maintain the bridges and to strengthen local public transport . Since there was an interest in keeping the effort for toll collection and the costs for toll stations low, as with all bridges in the region, the move was made to levy the toll as a double amount in only one direction of travel. In order to cover the costs of the new construction and further road construction projects, the toll for journeys in the west was initially increased from 1 to 2 dollars and in July 2004 to 3 dollars. The same amounts apply to other bridges in the region. As of January 1, 2007, the toll increased to $ 4 to cover an increase in the cost of replacing the eastern structure. The traffic in the east direction remains toll-free. Most recently, the fees were increased in July 2010. The toll is now $ 6 during rush hour, $ 4 outside of these hours during the week, and $ 5 at the weekend. There is a reduced fee of $ 2.50 for car pooling.

panorama

The bridge from the air from the south, San Francisco on the left, Oakland on the right. The two suspension bridges with a concrete connecting pillar can be seen on the left of the island and the half-timbered construction on the right of the island

Construction 1936

The bridge consists of four sections. It begins in San Francisco with an access ramp bridge to which the actual West Bay Bridge connects. The third section is the crossing of the Yerba Buena Island; the East Bay Bridge follows.

San Francisco driveway

The Bay Bridge begins in San Francisco with a 1130 m long ramp bridge. This consists of a 1031 m long viaduct with an overhead deck. The cross- section of the bridge is a T-beam made of reinforced concrete with a tapered construction height ; the standard spans are 20.7 m. On the subsequent 99 m to the suspension bridge, the structure is designed as a double-decker bridge.

Crossing West Bay

Pylon, suspension cable, hanger stiffening beam

East Bay Old Main Bridge

The West Bay Bridge is a twin suspension bridge anchored in the ground , starting with an approximately 47 m long anchor block and a 263 m long edge section. The suspension bridge that follows has spans of 357 m - 704 m - 354 m. The 52 m long central anchor block is followed by the second suspension bridge with spans of 354 m - 704 m - 354 m as well as an approximately 40 m long anchor block. The suspension cables have a sag of 70.4 m with a center distance of 20 m and a diameter of 73 cm. The stiffening beams are attached to these with four hangers at a distance of 9.25 m. The stiffening girders are designed as lattice girders with a construction height of 9.0 m and connected at the top and bottom by cross girders that support the 18 m wide upper and lower deck lanes. The steel pylons are 158 m above sea level. In contrast to the Golden Gate Bridge , the pylon stems are connected to each other by crossing diagonals in order to achieve sufficient transverse rigidity. The maximum clearance for ships is 69 m. The common central anchor block between the two suspension bridges is founded as a caisson on rock at a depth of 70 m and has a height of 85 m above the water. It has a floor area of 28 m × 52 m and was dimensioned so that a suspension bridge could also be demolished.

Yerba Buena crossing

The road structures on the island of Yerba Buena have a total length of 860 m. They consist of a 98 m long reinforced concrete viaduct with standard support widths of 14.1 m. This supports the upper carriageway, while the lower one is at ground level. This is followed by the 165 m long, two-storey tunnel with a width of 23 m and a maximum height of around 18 m as well as another 244 m long reinforced concrete bridge. The transition to the East Bay Bridge is formed by four double-storey steel truss bridges with a curved floor plan with a total length of 353 m. The road decks are at the top, the spans are between 85 m and 91 m.

East Bay crossing

The original East Bay Bridge had 38 bridges and was 3,101 meters long. The 119 m high two-storey main bridge in front of the island of Yerba Buena was striking, a steel truss bridge with spans of 155 m - 427 m - 156 m. It was a cantilever bridge with the Gerber girder as a construction element. In the main opening, the 125 m long cantilever arms on both sides received the 177 m long suspension beam . The bridge ends of the side panels were secured against lifting by anchors back in the pillars. The construction height of the bridge varied between 58.5 m above the main pillars and 29 m in the field. The maximum headroom for ships was 58 m. Five truss bridges with 155 m span and 27 m construction height were connected to the main bridge. The single-span girders had decks below. This was followed by 14 truss bridges with 89 m standard support width and overhead road decks. The bridge was completed by a 327 m long reinforced concrete viaduct. The first two pillars of the cantilever bridge could be founded on rock. However, since the rock horizon plunges steeply, the next three pillars had to be founded on caissons 70 m deep. The following 17 pillars had a pile foundation . For this purpose, wooden piles up to 26 m long were driven into the building site.

Reconstruction in 1957

Western segment from San Francisco; consisting of two suspension bridges, each with two pylons and a central connecting pillar made of concrete

When the bridge reopened, the upper deck consisted of three lanes for each direction; On the lower deck, the trucks drove with one lane in each direction and a common middle lane for overtaking maneuvers. This was a very dangerous division. On the lower deck there were also the rails for the tram with one lane for each direction of travel. In the decades that followed, motor vehicle traffic increased dramatically and tram use decreased. In 1957, five lanes were set up on the upper deck to the west and five lanes on the lower deck to the east; the rails of the tram were dismantled. Trucks were allowed on both decks. However, since the clearance height for trucks on the upper deck was too low in the tunnel on Yerba Buena Island, the upper deck had to be lowered and the tunnel was dug deeper to achieve the necessary height on the lower deck guarantee. The tunnel was in operation during construction; the traffic ran over a movable bridge in the tunnel, under which each one was dug. At the lower deck of the tunnel and at the viaduct into which the eastern end of the tunnel merges, elementary load-bearing parts had to be removed and rebuilt; the load-bearing structure of the viaduct had to be doubled in order to take the weight of the traffic. These alterations can still be seen today.

Renovation and new construction after the earthquake of 1989

Part of the East Bay Bridge demolished as a result of the Loma Prieta earthquake in 1989

It has been known since the 1960s that an earthquake in the San Andreas Fault or in the Hayward Trench could seriously damage the bridges; Initially, however, politicians saw no reason to act. It wasn't until the Loma Prieta earthquake on October 17, 1989 that people started to think differently. The earthquake, which reached a magnitude of 7.1 on the Richter scale , caused a 15 m long section of the upper deck of the East Bay Bridge to tumble down onto the lower deck. The bridge was closed for over a month; it reopened on November 18 of the same year.

Given the relatively distant epicenter (110 kilometers south of San Francisco), the extent of the damage in the San Francisco Bay area was surprisingly high. The analysis of the quake showed that the seismic waves had been reflected on irregularities in deep layers of the earth's crust. Damage occurred mainly where construction had been carried out on soft earth or on small bays that had been piled up, or on sand and rubble that had fallen in the San Francisco earthquake of 1906 and had been saturated with water and softened. The only exception was the collapse of the Cypress Viaduct in Oakland, which was not built stable enough and collapsed due to resonance .

With the stipulation that the San Francisco-Oakland Bay Bridge is a lifeline, i.e. that it must be fully functional for the rescue units even after an earthquake, the bridge was statically examined in the 1990s and the necessary reinforcement measures were carried out.

Crossing West Bay

The western suspension bridges have therefore been subject to major retrofitting, to an extent that has not significantly damaged the appearance and appearance of the bridge, and has even improved it in some details.

Rivets were used as fasteners throughout the bridge , the steel of which could not be hardened at the time. Research showed that these rivets failed at relatively low shear forces . That is why almost all the rivets were burned out with cutting torches , the holes were precisely drilled and replaced with threaded bolts and nuts made of high-strength steel.

Most of the larger girders originally consisted of two I-profiles (double-T-girders) that were connected with cross struts. In these constructions, the gusset plates were exchanged and the rivets were replaced by high-strength screws. In the strut constructions, square tubes were installed as an alternative. This work included large diagonal girders on the pylons.

In addition, diagonal struts were added on both decks of the western part. These stiffen the bridge in such a way that lateral vibrations in the event of an earthquake are dampened. The analyzes also showed that the massive concrete support structures could fail early, which is why the western supports were extensively rebuilt.

Work started in 1999 and was completed in 2003. The construction cost was $ 170 million.

New construction of the East Bay link

Eastern segment with the first extensions for the conversion (red cranes in the background), September 2004

Status of construction work in May 2008

Demolition work on the old Bay Bridge, June 2015

Completed suspension bridge with steel cables, June 2015

planning

With the large truss bridge, a decision had to be made between elaborate reinforcement or a new construction.

The first planning involved the construction of concrete columns ; The struts and girders were also to be reinforced, as was done in the western segment of the bridge. The cost of this project were to 200 million US dollars announced. The appearance of the bridge would have remained largely the same.

Technical as well as economic studies in 1999 showed that a new bridge would be only a few hundred million dollars more expensive, but would last much longer - possibly 75 or 100 years instead of just 30 years if refurbished - and would also be much cheaper to maintain. The public authorities therefore decided to replace the entire eastern segment except for the main bridge - a prestressed concrete structure - with a new building.

An architectural competition was announced for a "remarkable bridge", a bridge with a distinctive and impressive, unique appearance. The authorities were surprised when the competition ended because only one design had been submitted for the tower of the new bridge, and that design was significantly more expensive than expected. The projected total cost of the project was now (July 2005) at 6.2 billion dollars, after 1.1 billion dollars in 1997 (for a simple viaduct) and 2.6 billion dollars in March 2003 (bridge with a tall tower).

After more than a decade, detailed planning for the replacement of the East Bay Bridge began on January 29, 2002; completion was scheduled for 2007.

In December 2004, the California Governor's Office announced that the original project for an impressive bridge would be overturned; instead, a simpler construction, as originally planned, should now be built. The design, although again greatly simplified, remained expensive enough in view of the high material costs.

Construction was further delayed by an input from fifteen previous welders and foremen who had worked on the construction of the new eastern segment. They claimed that due to the high work pressure, one third of the welds were certainly not good enough and that workers had been instructed to correct the surface of defective welds. However, detailed investigations by independent experts could not confirm this.

The clashes continued in the first half of 2005. The governor did not want to see that the entire cost of the project would be borne by the State of California alone; he viewed the project as a local one in the Bay Area. In June 2005 a compromise was negotiated between the authorities, politicians and companies concerned; the bridge is being built, and it will be new, but a toll of $ 4 will be levied as early as 2007. The governor signed this compromise on July 18, 2005; By this time, 75 percent of the bridge's shell had already been completed, and the state was preparing another tender for the suspension bridge that was now planned. The total costs are calculated at $ 6.3 billion by the time the project is completed in 2012.

The new building in detail

New construction of the East Bay Bridge

Construction status of the new suspension bridge on October 1st, 2011

The new East Bay Bridge is north of the old bridge. It no longer has a two-story cross-section, but has two adjacent superstructures for the two 24-meter-wide carriageways. A self -anchored (fake) , single-hip suspension bridge made of steel was used as the main bridge, a construction built for the first time in this shape and size with a length of 614 meters. The horizontal component of the tensile forces in the suspension cables is not introduced into anchor blocks, but anchored back in the bridge superstructure.

The two 28.5 m wide and 5.5 m high superstructures were designed as steel box girders with an orthotropic deck . They are attached to the 78 cm thick suspension cable on the outside every 10 meters with hangers and connected to each other every 30 meters by 10 m wide and 5.5 m high cross members. The steel bridge pylon, consisting of four shafts, is arranged between the two 28.5 m wide superstructures and is 160 meters high.

The access ramp bridge to the approximately 55 m high main bridge, the so-called Skyway, is a 2100 meter long prestressed concrete structure with spans of 160 meters. The construction of the box girder bridge, 5.5 meters high in the field and 9.9 meters above the piers, was carried out using cantilevered cantilevering with precast segments. The superstructures are fixed in box-girder piers with pile foundations. Mockers call the ramp bridge a motorway on stilts . In order to thread the two parallel carriageways into the existing double-storey structure, elaborate 500-meter-long overpass structures were also built on the island of Yerba Buena.

In addition, an approximately 5 m wide strip was reserved for pedestrians and cyclists.

The opening

Immediately after the closure of the old part of the bridge on August 28, 2013 at 8:00 p.m., work began on connecting the new bridge to the existing traffic routes. The East Bay Bridge was opened on the evening of September 2, 2013. Following the commissioning, demolition work on the old bridge began. This should take about three years.

Repair after traffic accident in 2007

On April 29, 2007, a driveway to the bridge on the Oakland side was so badly damaged by the fire of a tanker truck with 32,000 liters of gasoline that the bridge had to be closed. A section over seventy meters long fell on the road below. The repair costs were over ten million US dollar appreciated. Since it was an important access road, Governor Arnold Schwarzenegger temporarily declared a state of emergency for California in order to acquire federal funds and repair the bridge as quickly as possible. The repair work was then completed in record time in 27 days, so that the governor was able to reopen the bridge section at the end of May.

Light show "The Bay Lights" 2013

The eastern section of the bridge from Yerba Buena Island to Oakland in September 2013. The new bridge on the left, the old bridge on the right.

Since March 2013 the Bay Bridge has been shining with a light show The Bay Lights over the Bay of San Francisco. This will initially remain for two years and will attract many visitors to San Francisco as a new tourist magnet. Over 25,000 LEDs were attached to the steel cables of the western span of the Bay Bridge over a length of 1.8 miles. Every evening at dusk, the bay is illuminated by this light show. The New York artist Leo Villareal planned and installed the light installation on the vertical lines of the San Francisco-Oakland Bay Bridge. The privately financed project cost around eight million dollars.

reception

The Bay Bridge appears in numerous writings and films. In William Gibson's futuristic Idoru trilogy , the bridge is closed after an earthquake and taken over by the homeless; a small town of the dispossessed is created. In the novel Little Brother by Cory Doctorow , its demolition by Islamic terrorists is the starting point for the plot in which San Francisco is gradually transformed into a surveillance state. In the film The Maturity Exam , Dustin Hoffman drives over the upper deck in the direction of Berkeley , even if the upper deck actually leads in the other direction, towards the west, i.e. San Francisco. The bridge appears in many other films, such as The Thin Man , Born to Kill , Vertigo , George of the Jungle , Made in America , Basic Instinct , Sudden Impact , The Dead Pool and Sid & Nancy .