At the beginning of the bridge construction, most of the riveted grids were replaced by bolted steel plates, thus transforming the original grid beams into box beams. The replacement project also includes adding panels to the large inclined beam on the outer layer of the cable tower to make the appearance more beautiful.
Box-shaped inclined beams are also set on both sides of the upper and lower decks of the West Bridge to reduce the relative motion amplitude of the upper and lower decks during the earthquake and reduce the probability of deck damage.
It is pointed out that the giant concrete bearing of the west bridge may break under certain pressure, which needs special reinforcement and a new reinforced concrete structure is added to the bearing surface. The first step of the project is to locate the reinforcement in the concrete bearing by magnetic technology. Then, drill a hole between each steel bar, insert L-shaped steel bars into it, and use high-strength epoxy glue. The newly inserted L-shaped rebar extends out of the concrete bearing surface 15 to 25 cm, so as to weld the new rebar horizontally and vertically on the bearing surface. After the welding of steel bars is completed, a template is placed on the steel bar structure, and then high-strength concrete is poured into the gap of the mold. After removing the mold, the surface looks the same as the original support. This advanced repair technology was later applied to the repair and reconstruction of piers and central column bases of other elevated highways in California, especially irregular bases. The old East Bridge was seriously damaged in the 1989 San Francisco earthquake. The authorities decided to build a new bridge next to it and demolish the old one after completion. Among them, the front section is a self-anchored suspension bridge and the back section is a viaduct.
The design schemes of the East Bridge and the New Bridge have been revised many times, both positive and negative, and the budget figures and bid prices have soared. The most striking visual feature of the East Bridge and the New Bridge is the emergence of an independent and safe bicycle lane in the south of the New Bridge. This bicycle lane can be used by cyclists from Caofang Island and Treasure Island to Auckland. It can be used by office workers during busy hours and can also be used by other citizens for entertainment. Take a look at the scenery in San Francisco Bay. You can kill two birds with one stone. On June 27, 2009, during the evening commute, a section of steel beam and two steel tie rods installed during the bridge repair during the Labor Day holiday suddenly broke and fell to the upper floor of the East Bridge. According to the investigation, the falling event may be caused by the vibration caused by the traffic on the bridge and the wind speed as high as 88 kilometers per hour on the bridge, which caused one of the tie rods to break and caused a part of the metal structure connected with it to fall. Three cars were hit by falling debris in the incident, but no one was injured. On June 1 65438+1October1day, California Department of Transportation announced that the bridge will be closed until the commuting time on Monday1October 2. During the closure of the bridge, the San Francisco Bay Area Rapid Transit System (BART) and the Golden Gate Ferry Passenger Transport System increased flights to increase passenger flow. 165438+1October 2, the bridge was opened to traffic as scheduled.
What fell on September 27th was a joist, a cross beam and two tie rods. There are two design defects in the failure of early maintenance: first, the pull rod passes through the through holes of the beam above the joist, and these through holes are too small, which leads to the direct contact between the pull rod and the beam; Secondly, the vibration of the tie rod caused by strong wind will not only lead to the fracture of the tie rod, but also lead to the wear and bending of the beam. As for the joint of the beam falling off, it is because it is only connected with the upper beam by spot welding and fixed by the friction and tension of the pull rod, so the beam will inevitably fall off after the pull rod breaks.
During the restoration, six effective improvements were made in the design:
1. Weld the structure between the beam and joist to prevent the beam from falling;
4. Enlarge the through hole to avoid contact with the pull rod;
3. Install a ball seat and tension nut to avoid excessive load bending of the crossbar;
4. Place sleepers at three different positions between the tie rod and the eye rod to prevent the tie rod from falling directly after breaking;
5. Install a protective sleeve to prevent the pull rod from directly contacting other parts and causing wear;
6. Install a strain gauge and auxiliary instruments to continuously monitor the stress of the assembly.
Since then, California Department of Transportation has completely repaired this broken eye pole from June 5438 to February 2009, completely cutting off the broken end of the eye pole, connecting new fittings with bolts, and then reinforcing it with a pair of reinforcing plates. Engineers from California Department of Transportation and Federal Highway Administration supervised and overhauled the overhaul. After completion, the two parts temporarily repaired during the Labor Day holiday and at the end of 10 will be dismantled together. On the afternoon of September 2, 2065438+03, the steel bridge of the world's largest single-tower self-anchored seismic suspension bridge and the new bridge in the east section of the San Francisco Bay Bridge in the United States were opened to traffic on Labor Day. After waiting for 24 years, this famous bridge damaged in the 1989 earthquake will be opened to traffic that night. The new bridge, the most important part of which was built by China Shanghai Zhenhua Heavy Industry Co., Ltd. with a cost of 6.4 billion US dollars, connects San Francisco and Oakland, and can resist the strong earthquake that occurred in 1500.
The eastern section of this bridge is made in China.
The investment of $7.2 billion makes the reconstruction project of the San Francisco-Oakland Bay Bridge one of the most expensive projects in California history. The rebuilt new bridge will become another new landmark in America. What is particularly striking is that the eastern section of this new bridge is "Made in China".
China built a bridge for the United States, which was called by the media as "China's manufacturing industry entered the world's large steel structure market for the first time".
The most important part of the new bridge project-single tower column and all steel products, was completed by China Shanghai Zhenhua Heavy Industry. California Department of Transportation told the media in August of 20 1 1 that the choice of Zhenhua Heavy Industry saved 400 million dollars for the new bridge. In addition, Japan, Britain and Canada also participated in the construction of the bridge, adding the color of international cooperation to the steel structure bridge of the world's largest span single-tower self-anchored seismic suspension bridge.