Movable Bridges - Spokane Street Swing Bridge (2)

Another view of the Spokane Street Bridge. Note the old bascule railroad bridge in the background. This area is part of a huge port. The Spokane Bridge carries container trucks into the harbor while also allowing container ships through the channel.


The previous bridge restricted access to the channel and so it was replaced with a double leaf swing bridge that can rotate completely out of the way. Each leaf is 450 ft from end to end and the bridge  provides about 350 ft  of channel clearance.


The tower that controls the bridge can be seen on the right side of the photo. Each leaf rests on a 103 inch diameter steel piston. To move the bridge the operator disengages locks that hold the two leafs in place, turns on a pump that raises the two pistons on hydraulic fluid, and then activates two arms that turn the leaves in opposite directions. That was the case until after the 2001 earthquake when one piston was found to be damaged. The City of Seattle had more pistons sitting on the site and replaced the damaged cylinder in a few days. Eventually KPFF, who acted as a sub-consultant to URS, designed a new cylinder that was less likely to suffer fatigue.


A concrete swing bridge is an innovative idea and this attractive bridge won a number of awards.

Movable Bridges - Spokane Street Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Movable Bridges - Spokane Street Swing Bridge

This is our second look at these bridges (first shown in my May 20, 2009 blog). This is a more detailed examination of the lower, double leaf swing bridge that crosses the Duwamish River and carries traffic between Harbor Island and West Seattle.

I find it strange that the two leafs can swing past each other without touching. The two (7500 ton) leafs are supported on hydraulic cylinders that lift them up an inch and then swing them out of the way. The operation is performed eight times a day and takes ten minutes.

I'm standing in the control tower where a bridge operator moves the bridge. I was there to inspect bridge damage after the 2001 Nisqually earthquake. However, it was never clear whether one of the cylinders became damaged from the earthquake or because of the strain of lifting such a heavy structure. The bridge was quickly repaired and put back in service. We'll take another look at this structure tomorrow.

Movable Bridges - Spokane Street Swing Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Painted Bridges - Atlantic Avenue Bridge

Atlantic Avenue crosses the Los Angeles River at a sharp angle a little south of the Century Freeway in Los Angeles. The bridge has extremely long cutwaters to protect it from all the debris that the river carries at flood-stage (the river can't carry all the water that accumulates during heavy rains).

I believe that the graffiti painted on one of the cutwaters says Feyiro, who was a character in the novel Wicked. The novel was a re-imagining of The Wizard of Oz from the wicked witch's point of view. Perhaps it is also be the nom de plume of the artist?

I like how the painter went through the trouble of copyrighting the painting (just like I do on my blog). He or she must be very optimistic that it wouldn't be immediately covered by the city (or by another artist). I also like the flat surface of the letters that are also deeply creased with a colorful grain. The letters in the center have a different color and texture just like the graffiti yesterday, which was painted 400 miles away in Crockett, California. Apparently there must be different periods and movements in graffiti just like in paintings on canvas.

Painted Bridges - Atlantic Avenue Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Painted Bridges - The Carquinez Bridge

We'll look at just a couple of graffiti paintings on bridges. This one is on the pile cap of the 1950s era Carquinez Truss Bridge. I wonder if the gray paint behind the graffiti was applied by the artist or by Caltrans to remove an earlier painting?

This is a common style of graffiti in which the artist's name is embellished in text so intricate that I cannot read it (If you know what it says, please let me know). What I like is how the image starts out rather benign, but grows progressively more savage and bloody before returning to civility.

Painted Bridges - The Carquinez Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Painted Bridges - Los Angeles River Bridge

An under-appreciated class of painted bridges are structures covered with graffiti. In fact, bridge owners often pay to have graffiti removed! That's unfortunate since the best graffiti is a highly accomplished and beautiful folk art that enhances a bridge's appearance.

Few graffiti artists have the resources to cover an entire bridge with a single painting. Therefore, graffiti-embellished bridges have two appearances. From a distance we get a pointillistic impression of patterns and colors that remain indistinct while a closer look reveals individual works of art. For instance, looking at this railroad bridge across the Los Angeles River, we get an impression of a variety of colors representing a kind of collage on the steel through girder.

It's amazing how these artists manage to put their paintings on the outside of bridges. On this bridge they might have stood on the deck and painted their image while bending upside down over the girder. On taller structures they might have used rope climbing gear!

Please feel free to send your own favorite photos of graffiti-embellished bridges or your comments on the controversy of allowing graffiti to remain on bridges. Tomorrow, we'll take a closer look at individual works of bridge graffiti.

Painted Bridges - Los Angeles River Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Painted Bridges - Alkaff Bridge (3)

One last photo of the Alkaff Bridge. I really like tubular members for steel bridges. They have good performance well beyond the elastic range and they're more attractive than the I girders and other members usually chosen for steel bridges.

If you look closely, you can see steel caps at the ends of the members. The caps look like they have vents on the end, but that must be an artistic embellishment by the artist (Pacita Abad). I like her signature near the end of the bottom chord. We should all get to sign our bridges with such panache!

On the far side of the river are bridge workers (perhaps the PIRAS rope climbing crew) touching up Pacita's handiwork. They're wearing harnesses and hanging from static lines in a similar fashion to bridge inspectors in California.

Painted Bridges - Alkaff Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Painted Bridges - Alkaff Bridge (2)

After the historical/political paintings on the Coronado Bridge, it's refreshing to look at the purely abstract and sensory art on the Alkaff Bridge. I think the smaller hand painted circles on the blue and red rails make a nice contrast to the larger, more detailed circles on the structural elements. Pacita's art reminds me of Larry Poons and the Color Field Artists of the 1960s and 1970s. There may also be a Filipino element to her work although she was hardly a folk artist.

This bridge has an interesting structure.  Four parabolic-shaped members descend at midspan to support the deck and then ascend to form triangles with diagonal elements at the supports. There is also a bottom chord along the sides of the deck that ascends slightly at midspan. The diagonals and the bottom chord are in compression and the parabolic elements are in tension. I think the structure is a kind of truss, although it also reminds me of a suspension bridge with it's parabolic shape. We'll take another look at this interesting structure tomorrow.

Painted Bridges - Alkaff Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Painted Bridges - Alkaff Bridge

Singapore has some of the prettiest bridges in the world, including the Alkaff Bridge. It was built in 1997 as part of an effort to improve accessibility to the walkways on each side of Singapore River. The bridge is near where the Alkaff Quay once stood and where Robertson Quay still stands.

The bridge was built to resemble a tongkang (a lightweight boat that was once was a common sight along the river). It's a 180 ft long single span steel through truss pedestrian bridge.

The bridge was painted in 2004 by Pacita Abad, a famous Fillipino artist. She came to Singapore in 2003 and somehow convinced officials to support her plan to paint the bridge. She got Visual Media Works to turn her hand sketches into bridge plans, Nippon Paint to provide 56 different colored paints for the project, and PIRAS rope climbing workers to clean, prime, and paint the bridge. Pacita completed the job (almost a year later) by hand painting the railings. Unfortunately, she died soon after completing this project.

We'll take a closer look at this bridge tomorrow.

Painted Bridges - Alkaff Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Painted Bridges - Coronado Bridge Approach (2)

The paintings on the Coronado Bridge columns have long been a source of controversy. Before the land was seized as 'Chicano Park,' artists may have felt greater freedom to express themselves on bridge columns. After the park became managed by the neighborhood, there was more control over what was painted.

Caltrans also felt uncomfortable with images of Ho Chi Minh, Che Guevara, Fidel Castro, Salvadore Allende and other revolutionaries on it's bridges. Caltrans District Director Pedro Orso eventually met with civil rights leaders, and decided that free expression was more important than who was painted on the columns and he even gave some money to help renovate the park.

Groups taking land under a bridge and turning it into a place to practice their cultural activities is fairly common in California. I had a bridge in Oakland and the ground underneath was used by teenagers who turned it into a skateboard park. I protested that the concrete poured around the columns was reducing their effective length and making them unsafe (with higher shear) during earthquakes. Although California politicians listened to my arguments, they sided with the teenagers.

An even more common occurrence is poor people who turn the underside of bridges into their homes. On a positive note, its nice that our bridges fill so many peoples' needs.

Painted Bridges - Coronado Bridge Approaches (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Painted Bridges - Coronado Bridge Approach

The northeastern approach to San Diego's Coronado Bridge (see Google Earth Map below) is beautifully painted with images that reflect the cultural heritage of the Hispanic community. The land under the bridge became Chicano Park through the efforts of the Mexican-American population around Barrio Logan. Almost every vertical surface in the park has been decorated with political, religious, and historical images.

The park and the paintings are so important to the community that Caltrans had many meetings in the neighborhood when they had to retrofit the seismically vulnerable approach structures. All of the murals were carefully protected while the bridge was being retrofit, the murals were examined afterwards, and any damage was repaired.

Sensitivity to a community's wishes is generally a good idea. However, it can sometimes be taken to extremes. The new East Bay Bridge in San Francisco Bay is an example where a community's desires turned a simple bridge replacement into a very expensive and decades long construction project.

Painted Bridges - Coronado Bridge Approach by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Painted Bridges - Posuwaegeh Overcrossing

Posuwaegeh is Towa for "place to drink." The Pojoaque Pueblo owns a market, restaurants, casinos, a hotel, and even an 18 hole golf course just to the east of the Posuwaegeh Overcrossing. This is a single-span reinforced concrete box girder bridge. The outside of the box girder is painted with symbols for mountains, clouds, and (maybe) water. Large 'whirling logs' (a symbol for the infinite) were painted on the walls extending up from the abutments.

Painted Bridges - Posuwaegeh Overcrossing by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Painted Bridges - K'uuyemugeh Overcrossing

The next overcrossing has 'K'uuyemugeh'  painted on its exterior steel girders. It translates as "(I am told) the place of the falling rock" in the Tewa language spoken by the Pojoaque Pueblo people (and others).

Deer with their heartlines are on the abutment wingwalls. Corn Maidens and other images common to the pueblos of the region are shown. Perhaps these images tell one of the sad stories about Corn Maiden, which are told from Canada south to the West Indies.

As I mentioned, this painted bridge is part of a program begun by the New Mexico Department of Transportation (NMDOT) to give recognition to the Native American people. The Google Earth Map below shows the location of the thirteen mile stretch of Highway 285/84 where many of the highway structures have been decorated with images from the native culture. There's nothing very interesting about these structures but by using them as a canvas they give voice to the state's indigenous people.

This area was home to the Anasazi people who moved here about 10,000 years ago. Their descendants may continue to live in the area although it is commonly thought that they left thousands of years ago. There's a beautiful book by Tony Hillerman (The Great Taos Bank Robbery) about the various cultures and peoples who moved into New Mexico and created the unique culture that is contemporary New Mexico.

The region is between the Painted Desert, the Chihuahuan Desert, and Sonoran Desert. It is part of the Rio Grande River Basin, which is slightly smaller than the adjacent Colorado River Basin. We'll look at one more bridge decorated by the Pueblo people tomorrow.

Painted Bridges - K'uuyemugeh Overcrossing by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Painted Bridges - Tano Road/Circle Drive Overcrossing

Since many bridges are painted, a better description for this series might be 'beautifully' painted bridges.

All of the retaining walls and bridges on US 84/285 (north of Santa Fe, New Mexico) between the NM-599 turnoff north to Pojoaque (a distance of 13 miles) are painted with traditional images executed by native artists.

The first bridge is an overcrossing just north of the Route 599 turnoff from I-84. On the north barrier it says 'Tierra Sagrada' (the sacred land) and the south side it says 'Paz' (peace). This bridge is an 150 ft long single span precast I girder bridge with magenta girders and pink wingwalls decorated with ears of corn. The pink and aquamarine railings are decorated with triangles and diamonds. Nearby are elaborate brick and concrete retaining walls with inset decorative panels.

In the next couple of days we'll look at a few more New Mexican bridges decorated by the native people of the region. More information on this project can be found on several websites including high plains traveler and the cultured traveler.

Painted Bridges - Tano Road/Circle Drive Overcrossing by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

California Bridges - Route 105/110 Separation (2)

We've spent the last week looking at unusual supports for freeway interchanges in California. We've studied the use of outriggers (on the 880/980/24 Interchange in Oakland), bridges on bridges (on the 5/110 Interchange in Los Angeles), and holes in bridge decks (on the 405/90 Interchange in Los Angeles). However, if we get really desperate, we can always use a C-bent like the one I designed for the 105/110 Interchange (shown in the photo).

There's no room for a column under the deck and no room for a second column on the right side of the bridge. So at this location the column is offset several feet from the center of the superstructure. These C-bents have to be designed for the large moments and shears due to the eccentric loads they carry. This is difficult for dead and live load, but it can be extremely problematic for earthquake loads.

Architects typically design a special look for freeways and interchanges. On this interchange the columns have a special shape and the outside of the barrier rails have a texture that we called fish scales (although the architect probably wasn't thinking about fishes).

California Bridges - Route 105/110 Separation (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

California Bridges - The Distribution Structure

Another bridge on bridge, this one part of the Distribution Structure that connects traffic to I-80, I-580, and I-880 just east of San Francisco Bay (see Google Earth Map below). The bridges were built in the 1950s, but one structure was replaced after the Cypress Viaduct collapse and the rest have been retrofitted. Because of the large traffic volume, no one is eager to replace the entire interchange. Its at the other end of the Cypress Viaduct Replacement from the Stack. The interchange is also called the MacArthur Maze and a section of it was replaced after a tanker truck crashed and burned on it a couple of years ago.

The photo shows another situation where a support was required over a river channel. Therefore, a small bridge was built over the channel to support the column. We can see the railroad tracks in the foreground that prevented the designer from placing the column beyond the channel. Bridges are built to carry people and goods over obstacles. Sometimes the bridge's supports also need bridges when there are a variety of obstacles to be avoided.

California Bridges - The Distribution Structure by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

California Bridges - Northwest Connector

I've mentioned bridges on bridges but I also wanted to show bridges through bridges. The Northwest Connector is a continuous 13 span RC box girder (except for two precast box girder spans over I-405) on single column bents (and end diaphragm abutments). This bridge is just a little east of Venice, California.

This long connector spans over I-405, State Route 90, Slauson Avenue, and Jefferson Boulevard (see figure above). Because of all the bridges underneath, one of the columns  on the Northwest Connector pierces the deck of a lower structure. Although this idea may seem clever, it looks dangerous to drivers, especially during earthquakes. Unless the opening is large, the two bridges (with different periods) will move in different directions during earthquakes, possibly damaging the column and possibly both bridges.

California Bridges - Northwest Connector OC by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

California Bridges - Elysian Viaduct

The Elysian Park Viaduct is a long steel girder and RC box girder (4 cell) bridge on multicolumn and single column bents and pile foundations. Its part of a network of connectors between I-5 and I-110 in Los Angeles. I've written about how hard it is to find a place to put your columns in urban interchanges. At the Elysian Park Viaduct the engineers had to design a bridge to support one of the single column bents over the Arroyo Seco Flood Control Channel.

I like the somewhat paradoxical concept of a bridge supporting a bridge. When the science writer Douglas Hofsteader has a group of people at his disposal, he likes to have them sit on each other's laps in a ring. There's something odd about the fact that the entire group is self-supporting. Can a bridge superstructure support some of its columns? A special prize for the best self-supporting bridge drawing sent to this blog!

I have a few more bridge on bridge photos to share. I also have several photos of a bridge column going through a hole in one bridge deck to support a higher level bridge. I always wondered what would happen when the two bridges start moving out-of-phase during an earthquake? Can you think of any other odd alignments between bridges in an interchange?

You can spot the Elysian Viaduct on the southwest side of the interchange shown in the Google Earth Map below (Bridge #53-1424). Like many of the bridges in Los Angeles at the time of the Northridge earthquake, the columns on Elysian Viaduct had been encased in steel shells and the bridge had almost no damage.

In Greek mythology, the Elysian Fields are the final resting place for the souls of heroes. Of course, there are Elysian Parks all over the world including one just west of this interchange (and north of Dodger Stadium).

California Bridges - Elysian Viaduct by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

California Bridges - Oakland Stack (3)

One last look at the Stack in Oakland California. I was wrong when I wrote that this interchange was part of the 'modern' aesthetic of the 1950s. The I-980 was a segment built in the 1980s to connect I-24 to I-880. When a mile of the I-880 collapsed during the Loma Prieta earthquake, the I-980 was used to divert traffic.

Although the interchange is only 20 years old, there is something 'modern' about its lines and contours. I've always been fond of the textured concrete forms used on the columns and bent caps. I also like the incongruent white column casings that give the interchange the look of a collage by Braque or of a tubular painting by Leger.
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California Bridges - Oakland Stack (3) by Mark Yashinsky is licensed under a Creative Commons Attribution 3.0 United States License.

California Bridges - Oakland Stack (2)

Another photo of the Stack. These interchanges may not be art, but I enjoy the sense of freedom and spaciousness of these long curved connectors. I like the white steel casings like band-aids on some of the gray concrete columns. I even like the horizontal sign structure in the middle of this photo.

Note the nice job of designing the green landscapes around the structures by Caltrans' landscape architects. These 1960s era interchanges express a modern aesthetic with their trim lines, parabolic curves, and effective use of light and shadow.

California Bridges - Oakland Stack (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

California Bridges - The Oakland Stack

We are currently looking at complicated urban interchanges in California. There are a number of themes I want to explore. Can a connector or ramp on a busy urban freeway ever be a work of art? Is there something pleasing about the connectors as they step around each other? Does the subsequent seismic retrofit to these structures add or detract from their appearance?

Three routes (I-980, I-880, and I-24) come together in Oakland, California as 'The Stack.' During the Loma Prieta Earthquake this interchange, which looks like a big 'X' from the air, had similar damage to the four ends: crumbled interior diaphragms from too many cable restrainers holding the superstructures together at the hinges.

The concrete barrier rail had to be isolated from the columns to prevent a smaller effective column length and subsequently larger shear forces. I wonder if those knee joints have to carry the column plastic moment? Probably the columns are pinned to the bent caps, which became standard policy after Loma Prieta.

We'll continue looking at urban interchanges over the next week to see if we can learn anything important through the process.

California Bridges - The Oakland Stack by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

California Bridges - Mulholland Drive Overcrossing

When I first saw this bridge high above the  San Diego Freeway, I thought it was really great. The tall columns and haunched girders make for a dramatic entrance into Los Angeles. The Santa Monica Mountains are covered in a sunburnt chaparral with no sign of human habitation.

Mulholland Drive Overcrossing has a three span, reinforced concrete box girder superstructure on three column bents. It was built in 1959 and it has been designated as a historic structure.

I was less pleased by its appearance after we encased the concrete columns with steel shells in the aftermath of the 1994 Northridge earthquake. However, I was really displeased upon attending a meeting last month (on the widening of I-405 to ten lanes) to discover they are now going to remove this historic landmark! The people of Los Angeles must take an unsentimental attitude towards their bridges.

California Bridges - Mulholland Drive Overcrossing by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

California Bridges - Route 105/110 Interchange

I don't know if these bridges are particularly attractive, but I like this photo as a composition. This is part of a complicated interchange where the Harbor and Century Expressways (along with light rail bridges, city streets, and HOV ramps) come together.

I sometimes feel the Tall Bridge Guy and the Happy Pontist live in a different world where aesthetics still plays a role while my biggest problem is trying to find an unoccupied place in crowded interchanges to put my columns.

These bridges were designed before the Loma Prieta earthquake taught us about problems with outrigger bents. I think I put as much longitudinal steel as possible in the columns, not realizing I was actually putting larger demands on the knee joints and  bent caps if there was a large earthquake.

We'll take a look at a few more of these crowded California expressways during the next few days.

California Bridges - Route 105110 Interchange by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

California Bridges - San Mateo Creek Bridge

San Mateo Creek Bridge (also called the Eugene A. Doran Memorial Bridge)is a five span continuous steel girder bridge on sculptural, two column bents. The bridge spans over the creek, over Crystal Springs Road, and over a lot of valley oaks.

This bridge was designed in 1970 by Bob Cassano who was a Caltrans engineer and a really nice guy. I remember when he retired (as Caltrans Chief Bridge Engineer) in 1988, he went around the design floor, shaking everybody's hand, and saying a personal goodbye.

In those days Caltrans had a dozen design branches and a half dozen architects to help the engineers work on their bridges' appearance. As I've mentioned before, I really like unusual bridge supports and these bents are exceedingly strange, like four pairs of woolen dress slacks.  They don't seem to have any relationship to the girders or the bridge deck, but that's okay. They're like giant non sequiturs, making the landscape come alive with comical possibilities.

California Bridges - San Mateo Creek Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.