Sunday, May 28, 2017

Russian Federation Bridges: Bridges across the Strait of Kerch

Strait of Kerch Bridge
Bridge building is a political act that confers considerable power to the bridge owner. I was reading in this week's New Yorker that Vladimir Putin is building a bridge across the Kerch Strait (between Russia and Crimea) to increase the Russian Federation's power over it's newly conquered peninsula.

This is not the first attempt to build a bridge across the Strait of Kerch. When the British Empire was still expanding, an attempt was made to build a bridge from England to India across the Strait of Kerch, but it was determined to be too expensive. Russia's first attempt to build the bridge was at the beginning of the 20th century before the revolution put an end to their plans. The Russians got another chance at the end of WWII but the bridge was soon destroyed by ice floes across the Strait.
The latest attempt to build the Kerch Strait Bridge began in May of 2015. The projected budget is $4 billion (228 billion rubles). The alignment crosses Tusla Island to reduce the amount of bridge that is required (see above map). Construction of the bridge was awarded to Arkady Rotenberg's SGM Group who also built the facilities for the 2014 Sochi, Winter Olympics. That project had huge cost over-runs, which is apparently part of doing business in Russia.

Rotenberg is Putin's childhood friend. Putin apparently only trusts his friends to run Russian industries. According to the New Yorker article, the Russian economy is a form of feudalism where all the chiefs of industry are one step away from the seat of power.
Actually, it looks like two bridges are being constructed, a four lane roadway bridge and a parallel two track railway bridge. The bridges will have three segments, from Taman Peninsula to Tusla Split is 7 km, from the Split to Tusla Island is 6.5 km, and continuing to Crimea is another 5.5 km for 19 km total.

Large diameter steel pipe piles were driven into the sea bed and two column bents were cast on top. Big steel truss superstructure spans were built on land, carried to their location by barge, and lifted onto the bents. What bothers me from looking at the top photo is that there are no bent caps or lateral bracing between the columns to provide lateral strength and resistance to the structure. Hopefully, they are going to be built later. A pair of steel arch spans will eventually be built over the shipping channel, as shown in the computer generated image below.
The bridge is supposed to open at the end of 2018 and be fully operational by June 2019. Trestle bridges were constructed at both ends to move material and as a base for pile driving. It was reported that 200 WWII era bombs were found while the site was being prepared for construction. The photo below (showing the pile driving off of the trestle structure) was taken with a drone operated camera by the Russian News Service, RUPTLY. Several excellent videos and other information can be found on the Internet, unfortunately mostly in Russian.
There is considerable conjecture about whether the bridges will be completed on time and at cost. My feeling is that Rotenberg will do whatever it takes to keep his boss happy.

Sunday, May 21, 2017

California's Bridges: Recent Books about the East Bay Bridge across San Francisco Bay

Books on the New East Bay Bridge
After the Loma Prieta Earthquake in 1989 caused damage to the San Francisco - Oakland Bay Bridge, Caltrans engineers spent many months analyzing the structure before coming to the conclusion that the West Bay Crossing (a suspension bridge) could be retrofitted but the East Bay Crossing (a long steel truss bridge) needed to be replaced. The decision to retrofit or replace a seismically vulnerable structure, repeated countless times during the big retrofit program in the 1990s, only resulted in controversy on the East Bay Crossing Project.

Two recent books shed light on this project.  'Bay Bridge, History and Design of a New Icon' was written by an architect involved in the project (Donald MacDonald) with help from the writer Ira Nadel.  'Remaking the San Francisco - Oakland Bay Bridge' was written by an adjunct professor at the University of California at Berkeley in Transportation Planning (Karen Trapenberg Frick) who explores the rebuilding of the bridge as a 'MegaProject,' a strange creature that needs to be better understood.
Caltrans engineers tried to make reasonable decisions for the design of this bridge but everything was amplified by the many people and groups who had an interest in the project.  There were professors and consultants eager to have their ideas considered, government agencies moving the project in different directions, politicians trying to make the project benefit their constituents, and reporters looking for a big story.

The original plan was to build a simple skyway, two miles of prestressed concrete box girder spans that provided a seismically safe structure to resist the next big earthquake (see figure above by MacDonald for his book). However, all of the different groups were pushing for a signature span for this important structure. Perhaps if Caltrans had been allowed to build their 'plain vanilla' bridge, billions of dollars could have been saved.

Readers interested in studying how big bridge projects can take on a life of their own are encouraged to read these interesting books.

Sunday, May 14, 2017

Sacramento County, California Bridges: Curtis Park Pedestrian Overcrossing over the Union Pacific Railroad

May 2017 (38.5428 Degrees, -121.4838 Degrees) Curtis Park POC
There's a great deal of interest by bridge engineers in developing Accelerated Bridge Construction (ABC) techniques to minimize the time working in the right-of-way of railways and roadways. A good example of these techniques was in the construction of the Curtis Park POC over the Sacramento Regional Transit Light Rail and Union Pacific Railroad tracks. A 174 ft long tied arch was chosen because it could be picked up and placed on its piers in just a few minutes and because it was long enough to span over the Union Pacific Railroad Yard (the Sacramento Light Rail tracks were spanned by the adjacent precast concrete slab).
As can be seen in the photos above and below the 50 ton arch, which was sitting on the ground on 10th Avenue, was picked up at the top of the arch ribs and swung 180 degrees onto the piers.
A tied arch is a good choice for this project. Steel girders would have been too deep and would have interfered with the 23.5 ft vertical clearance required by the railroad. A tied arch has its supporting members above the deck where it doesn't interfere with traffic below.
Note the long ramps that zigzag along the sides of the bridge to carry pedestrians and bicyclists onto the arch structure. In the United States the Americans with Disabilities Act (ADA) is taken very seriously. I noticed a lot of grinding of the ramps to meet ADA requirements on the grades.
This $6 million bridge opened in April and allows pedestrians and cyclists on the east side of the tracks to get to Sacramento Light Rail, Sacramento City College, and Freeport Blvd. 

Note that the arch ribs support the deck with steel cables attached to the ties (in the photo below). After the arch was placed on its supports a concrete deck was poured, cured, and the bridge was then opened to the public.
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Sunday, May 7, 2017

Yolo County, California Bridges: Yolo Causeway Viaducts

Yolo Causeway Viaduct
We've visited the Yolo Causeway several times before because it crosses over the main flood protection for Sacramento (Yolo Bypass) and because it has an interesting seismic retrofit (pile wraps at lap splices for liquefaction) but we are revisiting it today because it is home to 300,000 bats.  Every evening at around 8 PM the bats drop out of their resting place (between the precast girder segments), fly around a big oak tree (on the left), and spend the night flying many miles in search of insects.
The Mexican Free-Tailed Bat is a remarkably evolved creature. It flies from sunset to sunrise and catches its weight in insects (using its wings and a catcher's mitt of a tail to funnel them in). The male sings to win a mate, the female has one child a year, and they emit a high pitched series of sounds to locate their prey.
Bats love bridges but bridge inspectors don't love bats. Their excretions are the source of the debilitating Hantavirus.  However, California State environmental planners require any bats removed from a bridge to be given a new home near their preferred habitat. In the photo below a zoologist is taking visitors on a tour of Yolo Causeway (at sunset) to witness the daily exodus of the bats.

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.