Friday, July 31, 2015

Unbuilt Bridges (1)

I was reading a book, "AAD - Algorithm-Aided Design" by Arturo Tedeschi and on the last page was a computer generated drawing for a 'Cloud Bridge.'  This picture reminded me of the many other lovely bridge designs that were never built because they were too whimsical or too expensive.
For instance, the Ruck-A-Chucky Bridge was designed by TY Lin when he was working at Skidmore, Owings, and  Merrill. It was to go across the Middle Fork of the American River (in California) when the state was planning to built the Auburn Dam in the 1970s. Because the bridge was to be built in a steep canyon, it was thought that a curved superstructure hanging from cables anchored into the rocks above would be an economical alternative with the least environmental impact to the area. When it was decided not to build the dam, they also decided to abandon the bridge project.
Similarly, Frank Lloyd Wright had been interested in designing a bay crossing between the San Francisco to Oakland Bay Bridge and the San Mateo to Hayward Bay Bridge. His first drawings were made in 1949. The design had an sinuous, organic shape with 2000 ft long arch spans supporting a garden in the middle of the Bay. It was called the 'Butterfly Bridge,' perhaps because it resembled the flight of a butterfly. Several attempts were made to finance this 'Southern Crossing' but the state of California eventually rejected the idea as being too costly.

There are many other designs for bridges that were never built because they were perceived to be impractical for some reason. It seems like if you have a nice hand for drawing landscapes or for doing 3D computer graphics you can create something intriguing, but it requires something more to get your design built. We'll take a look at some more unbuilt bridge designs in my next post.

Wednesday, July 29, 2015

Strange Uses for Bridges (1)

There are a number of strange uses people put to bridges (other than crossing over a river). In the photo above Di Mainstone, a British artist, films Georgina Hampton Wale carrying a 'digibow' and electronic equipment to coax music out of the stays and suspension links of the Clifton Suspension Bridge in Bristol England. Mainstone has continued her experiments on the Bob Kerry Pedestrian Bridge in Omaha, Nebraska and on the Tower Bridge in London. I was going to provide a recording of her 'bridge' music but I couldn't figure out how to attach an audio file to my webpage. However, you can press on the link above to find her recording of the Brooklyn Bridge.
The Guardian had an article today about people hanging from the St John's Bridge over the Columbia River in Portland, Oregon to stop an ice cutter and other ships owned by Shell Oil from passing under the bridge on their way north to explore for oil in the Arctic. They are using the bridge to (hopefully) prevent global warming and environmental degradation of the Arctic.
Putting locks on bridge rails has become a popular way for couples to declare their eternal love for each other.  However, bridge owners have become concerned about the additional dead load on their bridges. The locks were particularly thick on the Pont de Arts in Paris and so the city eventually removed them.
Even more dramatic is the desire to end one's life by jumping off a bridge. I guess for some people, living becomes so intolerable that the thought of hurling themselves off a bridge deck (instead of making them terrified) makes them happy! In the photo of the Golden Gate Bridge above signs, counselors, and netting are all provided at considerable expense to try to prevent suicides. I previously wrote about a friend who worked the late night shift re-decking this bridge. He said about once a week, someone would slam on their brakes and throw themselves over the railing before anyone could stop them.

Tuesday, July 28, 2015

Los Angeles County, California Bridges

I thought I'd discuss some interesting new bridges that were recently built (or soon to be built) in the Los Angeles Area. The GoldLine Bridge (53 3068) shown above was built in 2012 and carries LA Metro tracks across State Route 210 in the City of Arcadia. The bridge cost $18.6 million and was designed by the artist Andrew Leicester. He said he wanted to pay homage to the past by designing the outrigger bent to look like two Native American woven baskets. Beneath the decorations is a prestressed concrete box girder bridge.
About 13 miles east of the GoldLine Bridge is the Los Angeles River beside Griffith Park, which is the site for the future North Atwater Park Equestrian Bridge. It will be a 302 ft long cable stayed bridge designed by Buro Happold, along with Fuscoe Engineering, Leighton Engineering, construction consultants Gardiner and Assoc., and landscape architects Mia Lehrer (with Tetra Tech). The tower will be over 200 ft tall to remind drivers on the nearby I-5 Expressway that the river (with its many recreational possibilities) is nearby.
Continuing east of the North Atwater Park Bridge is the Great Wall of Los Angeles, which shows the history of the area. Above the wall will be built the Green (Valley College) Pedestrian Bridge across Tujunga Wash that replaces a previous bridge at this site (that was removed last year). The new bridge is designed by Judy Baca, the Social and Public Art Research Center (SPARC), and wHY Architects. The bridge will be built out of recycled material (perhaps pulled out of the wash?) and lit by solar cells. Beneath the architectural features are steel plate girders supporting the deck and the roof.
We previously discussed the Sixth Street Viaduct Replacement Project across the Los Angeles River which is currently being designed for Downtown LA.

Sunday, July 26, 2015

Riverside County, California Bridges: I-10 Bridges across Tex Wash

July 20, 2015 (33.70467, -115.44221) Tex Wash Bridges
Last week a flash flood washed out the eastbound Tex Wash Bridge (56 0576L/R), which is one of two 3-span concrete slab bridges that carry I-10 across a desert wash near Desert Center, California. These bridges were built in 1967. Traffic was quickly diverted to the westbound bridge with one lane in each direction. A new eastbound bridge will be completed in September.
The one irritating thing about this story was how the news media reported it. They all said that the bridge had an 'A' rating and so officials are investigating why it collapsed. The news likes to make every natural disaster sound like negligence on the part of engineers. Bridges are designed for the 100 year flood, which was obviously exceeded by this event.

Thursday, July 23, 2015

Contra Costa County, California Bridges: Buchanan Field Viaduct across the Concord Fault

July 2015 (37.9810 Degrees, -122.0423 Degrees) Buchanan Field Viaduct
Since I haven't written in a while, I thought I'd take advantage of a recent field trip I made to the Buchanan Field Viaduct (28 0186) in Concord, California to write a new blog post. This structure was originally left and right bridges built in 1964 with a center and outside widening added in the 1990's. The bridge is on a high skew and so damage at the abutments was assumed to be a result of the tendency of skew bridges to rotate. However, when the environmental document for repairs went across our geologist's desk, she immediately recognized it as one of the fault crossings we were concerned about.
Most of the damage was at the southeast corner where creeping of the Concord Fault is pushing the abutment against the superstructure. The fault moves at about 4 mm a year, and so after many years, the wing wall/shear key is being crushed. California has a number of the bridges where an abutment is slowly moving due to a nearby fault. The question is how much should be spent due to serviceability problems from the creep and due to the fault eventually rupturing during a future earthquake.
Creative Commons License
Contra Costa County, California Bridges: Buchanan Field Viaduct across the Concord Fault by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.