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.
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