Cable-Stayed Bridges - North Arm Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Wednesday, June 30, 2010
Tuesday, June 29, 2010
Cable-Stayed Bridges - North Arm Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Monday, June 28, 2010
This is another composite steel and concrete bridge designed by Buckland and Taylor. They must feel they have a competitive edge on this kind of structure (it was completed in only 31 months). It was built as two balanced cantilevers in 30 ft increments until the two structures became one. The cables are distributed along the arms of the 'H' shaped towers and support the superstructure in a semi-fan arrangement. The cables support the 6.6 ft deep steel frame with precast deck slabs placed on the flanges and made continuous with a closure pour.
I heard that this bridge was having maintenance problems. I hope the deterioration is minor or that it can be repaired. It is a very elegant looking structure and you can see it for miles above the surrounding landscape.
Cable-Stayed Bridges - Alex Fraser Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Sunday, June 27, 2010
The bridge cables are in an unusual fan arrangement with five cables attached to special anchors at the ends of the back spans. Perhaps the extra cables are needed to balance the long main span? At the top of the towers the cables are attached to diaphragms between the pylons. The girders on the approaches look very deep (or the girders on the cable-stayed bridge look very small).
On the Buckland and Taylor Website, they mentioned that they were underbid by 0.5% on the project but later came in to evaluate whether the bridge was capable of carrying heavier trains. Information on this bridge is limited but I noticed that some websites say the bridge was completed in 1986 (in time for Expo86) while others say the bridge wasn't completed until 1990. Also I saw a couple of reports stating that chunks of concrete were falling from the bridge but that the bridge owner (Translink) assured reporters that there was no cause for alarm.
Cable-Stayed Bridges - Skytrain Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Saturday, June 26, 2010
The new bridge will be supported by towers between the decks with big blocks on top with anchors for four planes of cables.
The government is attempting to make the new bridge more palatable to environmentalists by including bicycle and HOV lanes.
The Fraser is an odd sort of river. Freshly cut timber is still transported downstream through the city. Bridges on the Fraser must be well-protected to handle constant collisions with log booms and other river debris. An odd aspect of Vancouver is that virgin forests are just outside an expanding metropolis of about 3 million people.
There is a four mile gap between the Port Mann Bridge to the west and the Skytrain Cable-Stayed Bridge to the east across the Fraser River (see below). The river widens appreciably just before bending to the south. Perhaps the river is too wide to cross at this location with another cable-stayed bridge?
Cable-Stayed Bridges - New Port Mann Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Friday, June 25, 2010
Cable-Stayed Bridges - New Port Mann Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Thursday, June 24, 2010
Cable-Stayed Bridges - New Port Mann Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Wednesday, June 23, 2010
I've been taking bridge photos recently with a Canon SD780 IS that fits in the palm of my hand. I used to carry an SLR camera and a tripod on my trips, but lately I've been traveling lighter. The Canon takes good photos for such a tiny camera.
I think this photo has a painterly quality due to the distortion from the bus window. We can see the grassy bridge embankment but not the Pitt River. The steel girders are haunched and framed into the towers. There's no sign of the swing bridges, which must already have been removed.
I read that the toll revenues on the Golden Ears Bridge have been disappointing (and drivers have to pay for both directions of travel). I haven't read about the toll revenue on the Pitt River Bridge or if they've even started collecting tolls as yet (perhaps toll collection is automated). Traffic looks busy though moving east from Vancouver in the afternoon.
In the Google Earth photo below, we can see construction on the Pitt River Bridge near the top of the picture, the Golden Ears Bridge on the bottom right, and the Port Mann Bridge (which we'll be visiting tomorrow) on the left. This photo gives a good sense of the many waterways that residents must cross to get around the region. By the way, a good article on the Pitt River Bridge is in Issue Number 54 (March 2009) of the excellent journal Bridge Design and Engineering.
Cable-Stayed Bridge - Pitt River Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Tuesday, June 22, 2010
In contrast to the four, two legged towers on the Golden Ears Bridge are the two, three legged towers on the nearby Pitt River Bridge. There were two existing swing span bridges that were far enough apart to allow an eight lane bridge to be built between them (see Google Earth photo below). I wonder if the swing bridges were able to open and close while the new bridge was being built?
The new, three span Pitt River Bridge has one tower in the river while the other tower sits on the east bank. It has a main span length of 640 ft and back spans of 320 ft. This seems short for a cable-stayed bridge, but there were apparently enough cost savings in the design to make it worthwhile to Kiewit (the prime contractor).
In some ways, this bridge is similar to the Golden Ears Bridge. They both have steel girder superstructures that frame into the tower with a composite deck. They both are supported on pile caps in weak soil. They were both design-build projects.
We'll take another look at this interesting bridge tomorrow.
Cable-Stayed Bridges - Pitt River Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Monday, June 21, 2010
For today's photo, I provided a view of the bridge deck of the Golden Ears Bridge, You can see eagles flying next to the pylons on the first tower. I'm not sure what the golden cylinders on the sides are meant to be (perhaps golden ears of corn?). Also, I'm surprised there are no cross-braces at the tops of the towers to improve the bridge's seismic behavior.
The pylons were quickly assembled out of steel boxes stacked together with a crane. The boxes alternate with anchor sections. Stay-in-place forms allowed the exterior concrete to be quickly poured. After each anchor section went up and the concrete was poured, the next steel girder and floor beam section could be hung from the towers.
Cable-Stayed Bridges - Golden Ears Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Sunday, June 20, 2010
Don said the bridge owner was concerned about excessive settlement and so they provided openings in the pedestals for jacking the towers (the pile caps are supported by 12 - 8 ft diameter pile shafts). Above the pedestals at stiff Pier M2 (in the foreground) are steel plates that can form plastic hinges and give the bridge a more balanced response during earthquakes.
Note the complicated connection where the steel girders, towers, and tower struts meet. Also note the steel fairings on the outside of the main spans to control wind vibrations. The bridge has six lanes supported by two steel girders connected to long floor beams and a composite concrete deck. The deck is made of precast concrete segments laid on the floor beams and made composite with closure pours. Pedestrian/bike lanes are on the overhangs outside of the cable-stays.
The cables are parallel, at an extremely flat angle, and are distributed from the top to the bottom of the short towers. Don said the cables are composed of 7 galvanized wires per strand. Each strand is sheathed in polyethylene and placed parallel to the other strands. The interstices between the strands are filled with corrosion resistant material and the cable is wrapped in a polyethylene. Dampers control vibrations at the bottom of the stays.
This long bridge with its short towers is a very economical design. The superstructure is light and requires a minimum of support from towers and cables. Its not a very dramatic structure, but not every bridge needs to be dramatic. Its about 8000 ft long and 100 ft wide and cost $800 million CAD, which gives a unit cost of about $1000 per square ft.
We'll take one more look at the bridge (at one of its approaches) tomorrow.
Cable-Stayed Bridges - Golden Ears Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Saturday, June 19, 2010
The City of Vancouver is laced with waterways and so there is a need to connect the bodies of land between them. Consequently, Vancouver has a lot of bridges and probably more cable-stayed bridges than any other city.
The Golden Ears Bridge is a five span hybrid cable-stayed structure. Some have called it an extradosed bridge, but a true extradosed bridge carries dead load with its cables and live load with deeper girders.
This bridge was designed by Buckland and Taylor and completed in 2009. It has a continuous, 2370 ft long composite steel girder superstructure. There are three equal main spans of 800 ft and two side spans of 400 ft. It crosses the Fraser River just east of Barnston Island. It's name is taken from the twin peaks of Mount Blanshard (seen in the background) which apparently has a golden glow at sunset. It also comes from 'Golden Eyries' and so the bridge towers are decorated with eagles.
We'll take a closer look at this interesting bridge tomorrow.
Cable-Stayed Bridges - Golden Ears Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.Publish Post
Friday, June 18, 2010
I came upon this bridge by chance while driving from Pennsylvania to Michigan. I wasn't even aware that the Maumee River was flowing under the bridge. Only later did it occur to me that this was the cable-stayed bridge my friend in Toledo was talking about.
A single tower cable-stayed bridge is a good solution when you need to span a 500 to 1000 ft river or other obstacle (the longest single tower cable-stayed bridge is the Surgut Bridge in Russia with a 1339 ft span).
The Veteran's Glass City Skyway includes a 612 ft span over the Maumee River. It replaced the movable Craig Memorial Bridge, which was named after a Medal of Honor winner. It was initially named the Maumee River Crossing, which created some controversy until it was renamed.
There are several unusual things about this bridge. It is one of the few cable-stayed bridges where the cables go through the tower (on saddles) to support the span on both sides. The 400 ft tall tower includes 384 light emitting diodes that provide displays that can be seen three miles away. It was designed by Figg Bridge Engineering, which was founded by one of the two designers of the Sunshine Skyway.
Cable-Stayed Bridges - Veteran's Glass City Skyway by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License
Thursday, June 17, 2010
We are continuing to study different aspects of the Cooper River Bridge.
The cables are arranged in what's called a semi-fan arrangement around the towers.
In a harp arrangement, all of the cable are parallel. In a fan, the cable on one side of the tower has the same angle on the other side and they are all congregated near the top of the tower.
This bridge has a semi-fan arrangement which means each cable has the same angle on both sides of the tower, but the cables are spread along the top of the tower.
Since the cables become less effective at carrying vertical load as their angle becomes less steep, the semi-fan arrangement seems optimal. More cables can be directed to the center of the span where because they are less effective at lifting while fewer cables can be used to support the span by the towers where they are more effective.
Apparently, the towers were quickly constructed using self-climbing forms and the lowest cables were hung and began supporting deck segments before the tower was even completed.
Cable-Stayed Bridges - Cooper River Bridge (4) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Wednesday, June 16, 2010
It began to rain softly as we walked along the deck of the new Cooper River Bridge. I can see several raindrops on the camera lens obscuring this photo.
The new bridge has four lanes in each direction. In some of the computer graphics they showed an asphalt deck, but in this photo it looks like a reinforced concrete deck. I would be surprised if asphalt was used since it weighs so much. In California, an acrylic or polymer coating is often used for deck protection.
The 1929 bridge had two 10 ft lanes and the 1966 bridge had three 12 ft lanes, and the third lane was made reversable resulting in several head-on collisions. Maintenance wasn't being performed regularly on the bridges and traffic loads had to be reduced. Also, modern container ships couldn't go under the existing bridges. All of these problems were solved with the construction of the New Cooper River Bridge.
Cable-Stayed Bridges - Cooper River Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Tuesday, June 15, 2010
I must be standing on a platform extending out from the strut past the bridge tower. In this photo we have a nice view of one of the gravel islands built to protect the towers from ship impacts. The theory is that ships will run aground before they strike the tower. However, it looks to me that if the ship had a projecting element, it could still strike the tower. Look at that barge carrying the crane. If it was a container ship with a large prow, I could easily strike the tower.
This is another all concrete bridge like the previously studied Sunshine Skyway Bridge. However it appears that we've learned a few things about cable-stayed bridges in the intervening twenty years. The towers now have a more harmonious transition from under the deck to over the deck (if you don't mind the tower swelling around the deck). I also feel more comfortable with two planes of cable stays to support the superstructure (the bridge is designed for a M7.4 earthquake a few miles from the bridge site). And look at the fancy dampers and anchors that connect the cables to the deck. Also, the main span is somewhat longer (although still dwarfed by China's and Japan's cable-stayed bridges). The prestressed concrete superstructure is not directly supported by the towers (rubber snubbers prevent the superstructure from smashing into the tower legs during earthquakes and wind storms).
I have had nothing but trouble with design-build contracts. I don't know anyone who likes them. Usually the contractor goes broke, and the owner loses control of the project (the contractor is waiting for the owner to make a change so they can recompense their losses). I don't know if this contract was a happier experience. A friend at SCDOT told me they weren't specific enough in requiring on and off ramps at both ends of the bridge and paid dearly for that change order.
Note the bike lane sitting outside the cables. I believe this was also added after the contract began (hopefully without a painfully expensive change order). Bicyclists and pedestrians have to share this space.
Cable-Stayed Bridges - Cooper River Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Monday, June 14, 2010
Ports can have a big impact on bridges. The new Cooper River Bridge replaced the 1929 Grace Memorial Bridge and the 1966 Silas Pearman Bridge with a structure that provides 58 meters of vertical clearance for ships heading up the Cooper River to the Port of Charleston. Although this is less than the 70 meters required by the largest container ships, it was sufficient incentive for the Port to put $50 million into the fund to replace the cantilever truss structures. Of course, that was a small fraction of the $700 million cost of this design-build project.
The truss bridges in the photo (taken while construction was being completed in 2005) are now gone. If you look closely you can see the concrete roadway suspended inside the diamond-shaped towers (and crossing over the old bridges). The Cooper River (or U. S. Senator Arthur Ravenel Jr) Bridge currently is the longest cable-stayed span in the U. S. at 471 m (1546 ft). We'll take a closer look at this interesting bridge tomorrow.
Cable-Stayed Bridges - Cooper River Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Sunday, June 13, 2010
One last photo of the Sunshine Skyway Bridge. It's composed of two long approaches that suddenly rise up on sculpted piers 193 ft above mean sea level for the cable-stayed channel crossing.
As you can see in the photo, the approaches are squat pier walls supporting precast I girders and a concrete deck. The entire bridge is 5.5 miles long and crosses Tampa Bay just east of the Gulf of Mexico.
It's not apparent why these approach structures would perform any better than similar bridges we saw destroyed by Hurricane Katrina. I wonder if they've ever been tested by 200 mph storm surges? The girders sit in recesses in the bent caps that must act like shear keys, but they don't seem like they could resist a hurricane. Probably, the Florida DOT is content to protect the cable-stayed portion and can quickly rebuild the approaches after a big storm.
Cable-Stayed Bridges - Sunshine Skyway Bridge (4) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Saturday, June 12, 2010
A single plane of cables supports the main and side spans of the Sunshine Skyway Bridge along the center of the deck. Twenty one cables in a fan arrangement descend from each 240 ft tower (above the deck). The cables vary from 38 to 80 strands and are housed in nine inch diameter steel pipes.
The deck is 94 ft wide and so the precast single cell box girder superstructure must be pretty rigid to be supported only at the center. The main span is 1200 ft long, which is only 1/3 the length of the Sutong Bridge in China.
I can see a lot of cracking on the bridge deck. Hopefully the reinforcement remains in good shape in this marine environment. Deck replacement remains a big issue for cable-stayed bridges. Since the cables put the deck into compression, replacing the deck is difficult. Even when corrosion is not an issue, the deck is the most critical element since it is quickly worn down over time. It seems a shame if the bridge has to be replaced when the deck wears out.
Cable-Stayed Bridges - Sunshine Skyway Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Friday, June 11, 2010
I like the shape of the piers below the bridge deck but I have trouble with the stick-like appearance of the towers above the deck. Of course, they couldn't continue that shape above the deck without blocking the roadway. Still, they could have made the transition a little more attractive (there was no architect).
This is a completely concrete bridge and the superstructure is state-of-the-art (for the 1980s). This is one of the first bridges that used match cast construction of precast girders. The girders were gantry-launched and post tensioned after they were in place. The stiff concrete box girder main and side spans helps to stabilize the bridge against wind loads up to 240 mph and gusts up to 290 mph.
We'll take a closer look at this interesting bridge tomorrow.
Cable-Stayed Bridges - Sunshine Skyway Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Thursday, June 10, 2010
The center spans were later demolished with dynamite, which can be seen on a beautiful YouTube video. One of the damaged bridges is in the foreground of today's photo still in use as a fishing pier (for people and pelicans).
The new bridge was designed by Jean Muller and Eugene Figg. It was built to be extremely tall for it's time (193 ft) to allow the passage of container ships into Tampa Bay. The dolphins that surround the two towers were designed to resist the impact of a ship bigger than the ones that damaged the older bridges.
There's a lot of good information available on this handsome bridge and so we'll take another look at it tomorrow.
Cable-Stayed Bridges - Sunshine Skyway Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Wednesday, June 9, 2010
The Brickell Avenue Bridge actually crosses over the Miami River just before it empties into the Intercoastal Waterway in Miami Beach, Florida. The bridge is decorated with sculptures, sconces, and a pretty tender house. It's a bascule bridge built in 1995 that replaced a 64 year old structure. It was recently widened to three lanes in each direction but it still gets backed up with traffic during rush hour. The bridge has a higher vertical clearance and the river was dredged so it doesn't have to open quite so often.
Movable Bridges - Brickell Avenue Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Tuesday, June 8, 2010
Continuing our travels westward, we come to the Biloxi Bay Railroad Bridge. New ties and rails were just placed on the deck when I took this photo and they are waiting for the ballast to be poured. This bridge must have been less damaged than most of bridges along the coast of Mississippi, if they just needed to replace the rail that got knocked off by Hurricane Katrina.
The swing span can be seen in the distance. It provides a clear span of 132 ft for ships to enter and leave Biloxi Back Bay. The bridge was built in 1978, perhaps replacing an earlier bridge. I've seen photos of a wooden trestle bridge with a steam locomotive crossing Biloxi Bay from 1901.
The Sunset Limited ran from Los Angeles to Orlando Florida until Hurricane Katrina took it out of service and it has never been fully restored.
Movable Bridges - Biloxi Bay Railroad Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
Monday, June 7, 2010
It seems like bridges along the Gulf Coast are in a constant state of disrepair. In this photo the bridge is being put back together after Hurricane Katrina came through (in August 2005). I was reviewing my trip on Google Earth and found a photo of the bridge being repaired again after being hit by a tugboat pulling eight barges in 2009. The bridge tender opened the double-leaf bascule spans for the tugboat, but the operator must have had trouble with the current because he knocked out a bridge span instead. If it's not hurricanes, or errant vessels, its oil spills for the ill-fated residents of Biloxi's Back Bay.
The Popps Ferry Bridge has long and short precast I girder approaches and a 180 ft wide channel opening. The bridge was originally built in 1979 but its been rebuilt several times.
I'm afraid we are going to see a lot more damaged movable bridges before we get out of the Gulf. We estimated there was over $2 billion in bridge damage from Hurricane Katrina and many of these bridges have movable spans.
Movable Bridges - Popps Ferry Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.