Bridges of Mexico: Pedestrian Overcrossing across Blvd. Adolfo Ruiz Continues in Mexico City

September 2017 (19.2913, -99.1105)

There were just a couple of bridge collapses during the 9/19/2017 Mexico Earthquake. A Pedestrian Overcrossing across Blvd. Adolfo Ruiz Cortines (taken from Google Earth) is shown before the earthquake. The supports are slender single column bents with slotted bent caps to support the single girder spans.

The superstructure must have been made up of simple spans supported on a narrow seat. This allowed the bridge to come apart when it was shaken during the earthquake, unfortunately landing on a passing cab. Bridge designers must provide continuity or very large seats in order to protect human lives at locations where earthquakes can occur.

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.

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

Monterey County, California Bridge: Mazda Raceway Pedestrian Overcrossing

July 2016 (36.5859, -121.7495) Mazda Raceway POC

A modern timber bowstring truss carries pedestrians over the Mazda Raceway in the Laguna Seca Recreation Area. This interesting structure is almost hidden behind all the advertisements on display.

The top and bottom chords of the bridge are glulam members secured to the diagonal truss members with metal plates and bolts (shown below). The walkway is housed within a plywood structure built on the inside of the truss. 

Pedestrian overcrossings built over freeways usually have a fencing on the inside to prevent people from throwing things onto the cars below. Maybe the plywood serves a similar purpose?

A few bracing members on the inside completes the job of securing the structure's shape.

Google Earth provides an excellent view of the racecourse in 3D with our bowstring truss bridge in the foreground (the raceway looks more painterly than photographic!). We had to pay $8 to gain admission to the park so we could photograph the bridge.

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

Santa Clara County, California Bridges: College Drive POC across I-280

May 2014 (37.31667 Degrees,  -121.91920 Degrees) College Drive POC

Back on the freeway I noticed that many of the bridges had been retrofitted in anticipation of the next big earthquake. The population of Santa Clara County resides in a central valley between two mountain ranges formed by two fault zones (see Google earth photo below). This makes the area at a high risk for large earthquakes. 

Driving west on I-280 I photographed the College Drive Pedestrian Overcrossing (37 0322). These types of bridges have skinny single column bents and can be highly excited during earthquakes. A popular retrofit strategy has been to strengthen and stiffen the columns by surrounding them with shear walls. 

Santa Clara County, California Bridges: College Drive POC across I-280 by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Contra Costa County, California Bridges: Iron Horse Trail POC across Ygnacio Valley Road

February 2014 (37.90707 Degrees, -122.05778 Degrees) Ygnacio Valley Road POC

The next bridge on the Iron Horse Hiking Trail is a more traditional steel arch. The Ygnacio Valley Road Pedestrian Overcrossing is a 550 ft long viaduct with a 136 ft long tied arch main span and with truncated deck arches for the side spans.

This bridge was built in 1998 by C. A. Rasmussen and designed by Santina and Thompson. However, unlike yesterday's Treat Blvd OC, there are few postings on the internet other than the always reliable Bridgehunter Website with photos by Craig Philpott.   

Today's bridge is more utilitarian than the Treat Blvd POC. The arch ribs are parallel steel box girders with lots of tubular steel cross-braces between the ribs.  The deck is wider but it's hanging from steel rods with turnbuckles. The dark fence imparts a feeling of claustrophobia while crossing over the bridge.

Contra Costa County, California Bridges: Iron Horse Trail POC across Ygnacio Valley Road by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Contra Costa County, California Bridges: Robert I. Schroder Pedestrian Overcrossing across Treat Blvd

February 2014 (37.92655 Degrees, -122.0546 Degrees) Iron Horse Trail Bridge

One of the nicest bridges on the Iron Horse Hiking Trail is the Robert I. Schroder Pedestrian Overcrossing in Pleasant Hill. This tied arch bridge was designed by Arup of San Francisco, it cost $6.8 million, and it was completed in October of 2010. It's an 800 ft long steel structure with a concrete substructure and a 10 ft wide deck. The bridge has a steel box girder superstructure supported by outward-inclining steel arches that rise 42 ft above Treat Blvd. 

Each arch rib is composed of three steel pipes bolted to wedge-shaped steel diaphragms. The ends of the steel arch ribs are connected with a steel cross brace and anchored into cylindrical reinforced concrete legs that are part of a single large foundation. The main span is 240 ft long and supported by pairs of crossed cables (40 ft apart) hanging from the wedge-shaped steel diaphragms.

This is an efficiently designed structure. A cylindrical concrete column is placed squarely between the concrete legs of the arch ribs. The steel diaphragms brace the pipe elements of the arch ribs and also carry the weight of the deck. In the past arch ribs were parallel or inclined together into a basket-handle shape but now outward inclining arch ribs seem to be popular.

My friend Richard Hartzell mentioned that the bridge is on a horizontal curve and so each arch rib has a different slope to accommodate the curve, which must have been difficult to analyze and design. More information about this bridge can be found on the Arup website.

Contra Costa County, California Bridges: Robert I. Schroder Pedestrian Overcrossing across Treat Blvd by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Tokyo Prefecture. Japan Bridges; Shinagawa Station Pedestrian Overcrossing

November 2013 (35.62933 Degrees, 139.73755 Degrees) Shinagawa Station POC

Greetings from Tokyo. I just had time to photograph a wraparound pedestrian overcrossing (POC) at Shinagawa Train Station before the start of our tour of the Honshu Shikoku Bridges far to the southwest.

The POC has a steel box girder span across Daichi Keihin Road and steel stringer spans across the side streets. The complicated structure is supported on steel columns (and adjacent buildings?). This POC is old and not particularly attractive, but it does show the willingness of Tokyo to spend money on infrastructure to protect its citizens.

Tokyo Prefecture. Japan Bridges; Shinagawa Station Pedestrian Overcrossing by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Ibaraki Prefecture, Japan Bridges: Kenkyugakuen Pedestrian Overcrossing across Route 19

November 2013 (36.08203, 140.08385) Kenkyugakuen POC

Next to the Kenkyu-Gakuen railroad station is a pedestrian overcrossing. It's a one span bridge with long approaches on retaining walls to raise it over Route 19 in Tsukuba.

The retaining walls look like mechanically-stabilized earth (MSE) walls with attractively-textured panels.

The single span is a reinforced concrete box girder on seat-type abutments. I was surprised to see that the abutment had a sign warning people to watch out for robots!

Ibaraki Prefecture, Japan Bridges: Kenkyugakuen Pedestrian Overcrossing across Route 19 by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Tokyo, Japan's Bridges: Salt Road Bridge across the Onagi Gawa

March 2012 (35.686 Degrees, 139.839 Degrees) Salt Road Bridge

The next bridge has ramps along the canal that carry people up and over the Onagi Canal. The bridge is 120.7 meters long, and varies (2.4 to 4 meters) in width. It was built in 2008 and it was named in a contest by the local school children based on the long history of this canal in bringing salt from Chiba to Edo (there's a nearby bridge called Sand Island for similar reasons). Both bridges are part of evacuation routes for the school children during disasters. The bridge is supported on single column bents. One ramp stretches out a long distance while the other snakes back and forth as it gains in elevation.

Tokyo, Japan's Bridges: Salt Road Bridge across the Onagi Gawa by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Tokyo, Japan's Bridges: Kita Jikkengawa POC

March 2012 (35.707 Degrees, 139.820 Degrees) Kita Jikken Gawa POC

The next bridge over the Kita Jikkengawa is a steel pedestrian overcrossing (POC) with long ramps parallel to the river and to the road (Asakusa Dori) south of the river. It's similar to a POC built in the U.S. with landings to give people a chance to rest on their way up.

The road is above the river and so the POC is high above the river to provide vertical clearance above the road. Just beyond the POC is the confluence of the Yoko Jikkengawa where we are going to turn south (instead of continuing to the Sumida River). We can now see the Sky Tree Tower through the clouds.

Tokyo, Japan's Bridges: Kita Jikkengawa POC by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Japan's Bridges: Sendai Station POC in Miyagi Prefecture

June 2011 (38.260 Degrees, 140.880 Degrees) Sendai Station POC

There are many elaborate pedestrian overcrossings in Sendai, but this structure around Sendai Station is easily the biggest. It's about six blocks long and carries passengers above city's streets to public parking and to the many station platforms.

I've recently started taking GPS cameras on my journeys. I just take a lot of photos without paying much attention to where I am. When I get back home, I load the photos onto my iMac. iPhoto turns the photos into little red dots on a map. Picasa provides the latitude and longitude of each photo. I type these coordinates in Google Earth to see where I was. For instance, when I typed today's latitude and longitude into Google Earth, I saw this enormous structure wrapping around the buildings in downtown Sendai.

Japan's Bridges: Sendai Station POC in Miyagi Prefecture by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.