Cable-Stayed Bridges - Sundial Bridge (8)

One last look at the Sundial Bridge. What I called a crackled glaze on the pedestal supporting the tower actually looks like broken pieces of white ceramic pottery grouted onto the surface. This was a technique used to great effect by Calatrava's countryman Antonio Gaudi in Park Guell (and in many other works).

This is a nice view of the bridge from under the deck, reinforcing yesterday's statement that you can't take a bad photo of this bridge.

The watercolor below must have been an early conceptual sketch Caltrava made to visualize the forces in his bridge. Writing this blog reminded me of some of the recent posts from the Tall Bridge Guy on painting, painted bridges, and on 3D computer graphics.

It's apparent that Calatrava is expert in all three forms of expression. His video of the Calgary Bridge was a thoughtful exploration of how the bridge would look at different times of day and at different times of the year. His roughest sketches are full of thought and feeling, And even though this bridge is painted white, it has elements of mosaic and sculpture.

Cable-Stayed Bridges - Sundial Bridge (8) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - Sundial Bridge (7)

The completed Sundial Bridge is very pretty, due to the perseverance of the investors, engineers, fabricators, builders, as well as due to Calatrava's design. It's hard to take an ugly photo of the bridge. This is largely because all the details and transitions have been carefully thought out.

Are all Calatrava's bridges white? It's a nice color for them since it accentuates the clean lines of the structure. Note how the end of the barrier rail has a crackle glaze, which is most often seen on Asian pottery. The tower supports have the same crackle texture.

The thin trapezoidal slots in the tower are repeated in the lights at the ends of the rails as well as in the metal railings. I like how the metal rails project outward from the deck before coming back in.

I wonder what it's like riding a bike on the glass surface? I don't like riding my bike on the metal grating of movable bridges, especially when it's wet. I imagine wet glass is even worse!

Cable-Stayed Bridges - Sundial Bridge (7) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - Sundial Bridge (5)

A composite view of the tower model, the tower during construction, and the tower on the completed bridge. I imagine the back bearings are in tension and the front bearing is in compression to resist the overturning force of the cables pulling on the tower. However, it's possible that since the tower leans backward and has such a heavy base that all three bearings stay in compression (and shear). Also the large tower base can resist the bending and shear from the cables pulling on the tower.

The cables are in a harp-arrangement. They are attached to steel arms on the side of the tower and to the vertical elements in the superstructure segments. They call this kind of bridge a 'cantilever spar' to differentiate it from cable-stayed bridges that support the superstructure by balancing the load on each side of the tower.

Note the vertical slots along the edge of the tower. Its possible they have a structural function, but I doubt it. They look more like ornamentation, like the openings they used to put in the sides of a Buick. Also, the glass deck looks nice on the bridge. However, at first, the tiles were prone to shattering whenever a hard object was accidentally dropped on them.

The tower points north and is used as a sundial in the park surrounding the bridge. The shadow moves fast enough so that you can perceive the Earth spinning on it's axis.

Cable-Stayed Bridges - Sundial Bridge (5) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridge - Sundial Bridge (4)

The superstructure that carries foot (and bicycle) traffic on the Sundial Bridge is built from triangular segments with a central spoke, similar to the vertebrae that supports human beings. Calatrava's work is often inspired by the human figure or by human structural elements.

In this photo we can see the unpainted tower behind the assembled superstructure with additional superstructure elements in the foreground. Cable stays are in rolled-up coils beside them. All that remains to do is put the remaining superstructure elements together and hang them from the tower.

Cable-Stayed Bridges - Sundial Bridge (4) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridge - Sundial Bridge (3)

A view under the tower of the Sundial Bridge. Note the concrete pedestals, which were used to jack the tower into place. Afterwards, the tower was painted and the columns were removed.

I was a little surprised that the tower sat on bearings. I imagined a strong earthquake could easily knock it over. Apparently its self-weight provides a sufficient restoring moment to keep it stable for seismic and wind loads.

Also note how the superstructure is attached to the tower at this location. To the west are cables that descend from the tower and support the superstructure. Unlike a conventional cable-stayed bridge, there is no back span to balance the tower and support the main span. Instead the tower slopes backward to support the main span.

Cable-Stayed Bridge - Sundial Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - Sundial Bridge (2)

Since we looked at a Calatrava-like bridge yesterday, I thought we might as well look at the real thing today.

I visited Calatrava's Sundial Bridge while it was being constructed (it's located on the Sacramento River just south of Redding in Turtle Bay). The engineer in charge felt that this project was different from a regular bridge construction project. For one thing, no one had any idea how much the bridge would cost. The owners just kept providing money until it got built. Also, the engineer complained that Calatrava provided very little engineering support for the project. Most of the details and much of the analysis was done by the project engineer. Finally, there were a lot of delays with the fabrication of the steel segments used to assemble the tower. The geometry of the sections and how they fit together must have been a matter of some concern since there were several models of the tower constructed of cardboard on the engineer's desk. I don't think Caltrava ever visited the site while the bridge was being constructed. Despite all of the problems, the owners were fortunate that they persevered and got an original Caltrava-designed bridge in the end.

In this photo, the tower is sitting on three bearings on the east side of the river while the skeletal superstructure is being assembled. Once the east side of the bridge was assembled, they had to take apart the crane and rebuild it on the west side of the river. We'll take another look at this interesting bridge tomorrow.

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

Movable Bridges - Meridian Bridge (2)

I'm standing on the deck of the Meridian Bridge. In the distance you can see the Sutter Buttes, which are the remains of some old volcanos.

The steel tower supporting the swing span is a model of simplicity. The tubular legs on each side of the deck come together at the top and are braced with a strut. The cables come up from two floor beams, through the top of the tower, and then are attached to two floor beams on the other side.

I often wondered why the swing span of this type of bridge doesn't bang into the corners of the side spans when it moves. I looked closely at the gap between them and saw that it was curved, probably to the circumference of the circle the swing span makes as it rotates about the pivot span.

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

Movable Bridges - Meridian Bridge

This is the last movable bridge I have photos of on the Sacramento River. However, there are a few more movable bridges up north that I hope to photograph (maybe during the summer).

Bridge engineers are faced with a challenge providing a big enough channel opening with a swing bridge. Because the support is in the center, it's difficult to make the cantilever spans on each side large enough for ships to pass. We saw that the Spokane Street Bridge (April 28th and 29th) has a swing span on each side of the channel so that a very large opening can be created. The other swing bridges we looked at had truss superstructures to provide long stiff cantilever spans. The Meridian Bridge solves the problem in a different way, with a central tower and a cable stays to support the cantilever spans.

This bridge carries State Route 20 across the Sacramento River a little south of Colusa and a little west of Marysville. It was built in the 1970s (and along with the Spokane Street Bridge) provides a good example of how engineers can develop new solutions to address some of the disadvantages inherent with swing bridges. The tower is 50 ft tall and the leaves are about 180 ft long, providing a suitable opening for ships to pass.

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

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

Movable Bridges - Knights Landing Bridge (3)

A last look at the Knights Landing Bridge. Its a double leaf simple trunnion bascule bridge that carries State Route 113 over the Sacramento River. The counterweights are enclosed in the large bin-type abutments.

Balancing the bridge leafs with the counterweight requires careful planning. Because traffic travels on approach spans rather than directly on the counterweights, this bridge is more stable in the closed position. When the locks are opened at midspan, the bridge can be raised with a smaller motor than would be needed if the deck had been made heavier to resist the counterweight and live load behind the trunnion.

I believe this bridge can still be operated. At least, it looks in good shape. Perhaps it is only opened when a request is made to the U.S. Coast Guard several days in advance.

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

Movable Bridges - Knights Landing Bridge (2)

A view from the deck of the Knights Landing Bridge. In this view, we can see the top chord of the bascule span going through a slotted hole in the approach slab.  The trunnion must be a little bit in front of the approach slab, the counterweight sits below the slab, and it descends into the bin-like abutment when the operator raises the bridge.

This area has changed a lot over the years. When Dr. Knight first came here, this was a meeting place of Native Americans living along the Sacramento River and Cache Creek. A town and ferry were built to handle all the traffic moving along the river, but now its like a ghost town.

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

Movable Bridges - Knights Landing Bridge (1)

North of Sacramento are several interesting movable bridges across the Sacramento River.

The Knights Landing Bridge is the first double leaf bascule bridge across the river that isn't a through truss. I'm actually not sure what kind of structure it is. Are those pony girders with rectangular openings or is it some kind of Vierendeel truss?

I'm also not sure what kind of bascule bridge it is. Is it a double leaf simple trunnion bridge or is it a Scherzer rolling lift double leaf bascule bridge? I vote for the latter since the bridge is high up with counterweights that can pivot into the concrete boxes at the far ends.

The bridge carries State Route 113 over the Sacramento River in the town named after Dr. William Knight, a physician who founded the town of Knights Landing on an ancient Native American mound in 1842.

We'll take another look at this unusual bridge tomorrow.

Movable Bridges - Knights Landing Bridge (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Movable Bridges - I Street Bridge (2)

A closer look at the I Street Bridge. A swing railroad bridge has stood at this site since 1858. The current double-deck bridge was built in 1911. Note the round pivot pier supporting the swing span.

This bridge is 840 ft long with a 340 ft long swing span.A 34 ft tall boat can pass under it at low tide. Otherwise, the captain must signal to the bridge operator to get through. Boaters need to check with the US Coast Guard when planning a trip to find out the bridge's hours of operation,

Swing bridges, and especially swing railroad bridges are more complicated than bascule or lift bridges. Not only do they need locking devices that open and close, but the railroad tracks need to be retracted to open the bridge and extended for trains to pass. There are also devices to help the bridge resist wind (and seismic) loads.

This is one of the largest center bearing swing bridges ever built. It weighs about 6800 kips. At the turn of the 19th century, such big swing bridges had rim bearings with rollers along the perimeter. When this large bridge was successfully built and operated with a center bearing, no one wanted to go through the trouble of fabricating the conical rollers that supported a rim bearing swing bridge and they were no longer built.

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

Movable Bridges - Tower Bridge (2)

The Tower Bridge spans the Sacramento River on a straight line from the state capitol on M Street into West Sacramento. My feeling is that Sacramento has changed a lot since the bridge was built.

For instance, at the turn of the 19th century, Sacramento was a railroad town and a swing bridge carrying the Sacramento Northern (SN) Railroad was built at this site in 1912.  The Tower Bridge replaced the swing bridge in the early 1930s but continued to carry the SNRR (along with cars and pedestrians) until 1962.

In this photo you can see the cables attached to the lift span (and counterweights). The total bridge length is 737 ft, the roadway is 52 ft wide, the lift span is 209 ft long, and the towers are 160 ft tall (and supported by 50 ft deep caissons).

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

Movable Bridges - Freeport Bridge (2)

A view from the east side of the Freeport Bridge. Movable bridges often have open grid decks to reduce their weight. However they can be scary if you are riding across them on a motorcycle or a bicycle.

The east side of the bridge has a pony truss approach span, a through truss span, and then the bascule spans. The west side has a steel stringer approach, so it must be slightly shorter.

North of Freeport, State Route 160 ends, the road becomes Freeport Boulevard, and highway traffic switches to nearby I-5 into the City of Sacramento.

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

Movable Bridges - Freeport Bridge

Just south of Sacramento in the tiny town of Freeport is another bascule bridge across the Sacramento River. It's nearly identical to the Paintersville Bridge, only painted green instead of yellow.

The Freeport Bridge was built in 1930 and carries traffic between SR160 on the east side of the river and SR E9 on the west side. It has more elaborate fenders protecting the piers on each side of the 200 ft channel opening, perhaps because it sits next to a dock lined with weekend pleasure craft.

The spaces around the huge counterweights are so tight, that its remarkable that the truss members never get hit as the weights swing past. There must a large industry of mechanics and engineers whose job is to constantly maintain these massive machines. Movable bridges are much more dangerous than fixed structures. Every year people in a hurry or who aren't paying sufficient attention die while trying to cross a bridge that is moving or open.  There's hundreds of these bridges in California and thousands of them in the U.S. However, my feeling is that it's cheaper to build a long tall bridge over a river, rather than to put up with all the problems of owning a movable bridge.

We'll take one more look at the Freeport Bridge tomorrow and then continue up river into the City of Sacramento and beyond to study a few more movable bridges.

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

Movable Bridges - Sutter Slough Bridge

Like the previously studied Steamboat Slough and Three Mile Slough Bridges, the Sutter Slough Bridge crosses a tributary flowing into the Sacramento River. Movable Bridge Engineering lists Sutter Slough as a fixed swing bridge (by which I assume it means it no longer can move). There's a lot of old bridges that can't move, probably because no ships or barges travel past anymore.

I believe swing bridges were more popular before WWII when they were thought to be economical and there was less objection to having a pier in the middle of the waterway. After the war, the US government would help pay the cost of replacing or removing obstructions in waterways. Most of these obstructions were old swing bridges.

Sutter Slough Bridge was built in 1939 in Courtland California. The swing mechanism sits on a three column bent. The bridge carries two-way traffic (on two lanes), it has a total length of 397 ft, and it carries an average of 6020 vehicles a day.

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

Movable Bridges - Paintersville Bridge

In the late 1910s, Sacramento County improved the road between Isleton and Paintersville and provided free ferry service across the river at these two towns. The ferries were replaced with bascule bridges in the early 1920s. The two bridges are almost identical, except the Isleton Bridge has tied arch approaches and the Paintersville Bridge has through truss approaches. They both have the Joseph Strauss patented heel trunnion double leaf spans for a 200 ft channel opening. They are both on concrete piers with timber piles protecting the piers at the channel opening. The two bridges are about 20 miles apart. Thirty years later the bridge at Walnut Grove was built between the older bridges.

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

Movable Bridges - Three Mile Slough Bridge

I found that I skipped an attractive vertical lift bridge on my march up the Sacramento River. I thought we might as well go back and take a look at it as a break from all the bascule bridges. Actually, I've learned quite a bit about bascule bridges by reading Movable Bridge Engineering by Terry L. Koglin. I think they are more complicated and interesting than the generally simpler lift and swing bridges, but still its nice to enjoy a change.

The Three Mile Slough Bridge is actually a little south of the Rio Vista Bridge, across one of the sloughs that twist and turn in California's Inland Delta. I imagine it's easy to get lost, even with a GPS device, when traveling by boat through the hundreds of islands.

At one time Three Mile Slough must have been an important waterway to have merited such a big bridge. Perhaps the slough is still used to carry ships and barges into Stockton. I like the counterweights with their unusual shapes. I also like the chains hanging from the counterweights, although I'm not sure what they're for. This bridge is much simpler than the Rio Vista Bridge with its parabolic-shaped top chord. It looks like the operator's house sits on top of the lift span!

The Three Mile Slough Bridge was built in 1949. It's 750 ft long and provides 105 ft of vertical clearance and 150 ft of channel width. Apparently the bridge is in poor shape although (or because) it carries about 1000 vehicles a day. It's a steel, vertical lift, through truss bridge with long approaches and a 175 ft long lift span.

I realized that the reason I see so few big ships on the Sacramento River these days is because they built a shipping channel just west of the river. The channel is straight and wide compared to the meandering Sacramento River.

Movable Bridges - Three Mile Slough Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Movable Bridges - Steamboat Slough Bridge

All the bridges at the southern end of the Sacramento River (north of the Rio Vista lift bridge) are heel trunnion double leaf bascule structures. They must have put a half dozen of these movable bridges between Sacramento and Rio Vista during the 1920s. Perhaps there was more ship traffic in those days. Riding my bike along the river today, all I see are a few speedboats. I wonder if a bridge operator is always on duty just in case?

Steamboat Slough Bridge doesn't actually cross the Sacramento River. It carries State Route 160 traffic over Steamboat Slough on the west side of the river. It's a 68.9 m long bridge that was built in 1924.

All of these bridges have height restrictions due to the huge, concrete counterweights (and low cross-beams). The bridges are almost identical with short spans to support the counterweights and long through truss movable spans. They just have different approach spans when a longer bridge is needed.

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

Movable Bridges - Walnut Grove Bridge

Continuing upstream along the Sacramento River we come to another double leaf bascule bridge. It is much like the previously viewed Isleton bridge, but without the tied arch eastern approach. The river has narrowed slightly where two branches come together in Walnut Grove. The bridge was built in 1952.

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