Alaskan Way Viaduct – Earthquake Simulation – from U-Tube. Could this be deja vu for SkyTrain?

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The following video from the Washington State Department of Transportation (WSDOT), showing the effects of a 7.0 earthquake in Seattle is telling and is very much worth a watch. Even though Seattle’s Alaskan Way Viaduct is long past its prime and not designed for catastrophic earthquakes, it’s collapse plus the failure of other aged infrastructure is chilling.

The late transit expert, Des Turner, was always concerned about the effects of a large earthquake and on the mostly elevated Expo and Millennium light-metro lines. In theory, the SkyTrain viaducts should survive an earthquake measuring 6 on the Richter Scale with minimal damage, with few exceptions, such as if a support column fails due to local soil liquefaction or earth movement.

Unlike at-street/at-grade light rail, failure on any section of viaduct would mean several months of disrupted service on the metro until new columns and guide-ways could be rebuilt and emplaced. Large scale failure of the SkyTrain viaduct may even lead to line abandonment.

In summer 1995, a letter from a US engineer specializing in earthquake resistant design to Mr. Turner, expressed a worry that if a 7+ earthquake were to hit Vancouver, the elevated SkyTrain guide-way would fail in several sections, just like what happened in Kobe Japan in 1995, where once thought earthquake resistant viaduct design failed, with devastating consequences.

3 kobe

Vancouver doesn’t have 60 year old decaying elevated double-deck highway viaduct to worry about, but it does have a large elevated light-metro network, which some sections are now approaching some 30 years old and one wonders that TransLink has an earthquake plan, if and when the unthinkable happens.

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7 Responses to “Alaskan Way Viaduct – Earthquake Simulation – from U-Tube. Could this be deja vu for SkyTrain?”

  1. mrjauk Says:

    All the more reason for the Millennium Line extension westward to UBC to be built underground.

    Zweisystem replies: Tunnels also pose hazards during earthquakes and have to be specially designed to withstand seismic forces. This may increase the cost of subway construction by a factor of 2. This means a $4 billion subway to UBC may cost as much as $8 billion! I doubt any politicians will OK that.

  2. mezzanine Says:

    http://en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake

    “The BART rail system, which hauled commuters between the East Bay and San Francisco via the Transbay Tube, was virtually undamaged and only closed for post-earthquake inspection. With the Bay Bridge closed because of its damage, the Transbay Tube became the quickest way into San Francisco via Oakland for a month.”

    Zweisystem replies: Yes BART was in operation, because the Transbay tube cost about three times more to build than a standard subway. The tunnel tubes are so constructed to act as a piston. The wrong type of quake, there would have been a different story. All it takes is one failure in an under-water subway tube and it will be closed for months, if not years.

    Up to $8 billion for a UBC quake resistant subway: who is going to pay?

  3. David Says:

    When Sam Sullivan’s group first asked about Millennium extensions I said stick it underground. I didn’t think about cost of construction, cost of operation or the ability to attract passengers from cars. In short I didn’t think. I gave a straight forward “I don’t want it running past my window” response.

    I should have known better. I travelled in Europe and Asia as a student and even took some courses on urban planning once long ago, but had forgotten that the point is to move people rather than vehicles. I’d forgotten that people who move slowly are more likely to contribute to their environment than those zipping past quickly. What had stuck in my brain was the course on traffic flows and how best to move large numbers of vehicles. I’d been sucked into believing some of the pro-SkyTrain propaganda and hadn’t stopped to question whether the costs we’re given are true or not.

    When I did start questioning I found the answers I was given to be entirely unsatisfactory. In fact some appeared to be outright lies intended to fulfill some political rather than practical purpose.

    I’ve discovered that things are done differently elsewhere and almost without exception differently means better. Nobody builds light metro for objective reasons because any objective analysis shows that it provides poor value for the money. Even in France, where building with VAL was seen as a way of supporting jobs for French people, few systems were built. In Canada SkyTrain is seen the same way and has been given the cold shoulder everywhere except BC, a place long known throughout the country for its wacky politics. The only other Canadian line is the despised Scarborough RT: the original SkyTrain boondoggle.

    Ridership on SkyTrain has been growing for the past 24 years, but the number of registered vehicles has been growing faster. SkyTrain isn’t solving our transportation problems. Because it has cost so much and been so ineffective at getting people out of cars, SkyTrain has actually made the problems it was intended to solve worse.

    It’s time to say “No” to more SkyTrain. Extensions to the existing lines, currently served by buses, should use standard at-grade LRT. It would be a dramatic improvement over diesel buses and in the long run will cost less than the no rail option of simply adding more and more buses or, worse, adding more road capacity for single occupancy vehicles.

    Over time the extensions would grow in both directions replacing SkyTrain in the middle. When combined with LRT on new routes it would become a network that would serve more customers, but cost less to operate than the current metro plus bus solution.

    I’m sure some readers fear LRT wouldn’t be capable of handling demand between Broadway/Commercial and Downtown, but LRT can move a lot more people than local officials want you to believe and the crowding on the current system is caused by the lack of alternatives. TransLink forces as many people as they can onto a single path in an effort to justify the enormous cost of SkyTrain.

    Putting tram services on Broadway, Hastings, Commercial/Victoria, etc. and long distance LRT onto existing railroad tracks would not only service a lot more people more efficiently it would spread out the demand so no single section would be overburdened like it is today.

    Talking about extending the Millennium Line, whether to Olympic Village to connect with Canada Line and the Vancouver Streetcar, or all the way to UBC is simply an excuse to avoid getting on the with job of building a more cost effective network.

  4. zweisystem Says:

    A note from Zweisystem.

    I wrote this post to underline a problem SkyTrain may have with its pre Kobe designed viaducts. In Seattle, it took the Nisqually earthquake to ram home the fact that the Alaskan Way viaduct would not survive a 6.5+ quake and that it was living on borrowed time!

    We have not even thought about the kilometres of elevated guide-way with SkyTrain and the viaducts have not been tested at all in quake. This is pure negligence on the part of TransLink and METRO Vancouver.

    God forbid an earthquake topples the viaduct, but such an event must be planned for.

    Some years ago on a radio talk in show, there was a long program on “if” there was a major quake (7+) in Vancouver and one of the guests mentioned substantial damage on many bridges and stated: “It maybe that SkyTrain would be the only way to move for some day.”

    Zwei phoned and stated the obvious: “What happens if just one section of viaduct collapses, the SkyTrain system is effectively closed down, what then?”

    After a long silence, the guest blurted out: “SkyTrain will survive a 7 quake…….”. to which zwei responded: “Yes and the Titanic was unsinkable and oh by the way, has anyone factored in the prospect of SkyTrain out of operation after a quake event?”

    The silence and the fumbling of the moderator, going to another caller said it all – no one has.

    A very sad state of affairs, that by pretending nothing will happen, nothing will. It is a recipe for disaster.

  5. David Says:

    The most common reason for bridge and viaduct collapse during an earthquake is not structural failure of members, but movement of one member relative to another.

    The Oakland Bay bridge disaster was caused by one chunk of bridge deck shifting just enough during the earthquake to fall off its support. The Embarcadero freeway experienced the same thing. A lot of old bridges sit atop their supports with nothing more than gravity and static friction holding them there. Move the post a little too far and the piece on top falls to the ground.

    It’s also common for structures to experience resonant vibrations during earthquakes. In Kobe a lot of 5-10 storey buildings looked remarkably intact after the quake until you took a closer look and realized that they were about 8 feet shorter than they should be, that part way up the building there were two floor slabs directly on top of each other.

    Earthquakes tend to have long periods so harmonics are unlikely in SkyTrain support columns, but primary resonance would tend to cause the guideway to swing rather wildly back and forth. In soft soil the force could cause a sideways collapse like the one pictured above. The Expo Line from Clark to Stadium, the Millenium Line at VCC Clark, Expo at Scott Road and Millennium around Gilmore are probably most at risk of a collapse from loss of soil stability. The rest of the elevated Expo line has the highest risk of movement causing the guideway to shift relative to its supports.

    It would take a pretty big shift to cause a section to fall, but even a small relative shift from one piece of guideway to the next would bend the track and derail trains.

    Vancouver has experienced major quakes in the past and will experience them again. It’s only a matter of time.

  6. David Says:

    I completely forgot about Canada Line. The Richmond/Sea Island sections are almost guaranteed to fail in a significant quake.

  7. allan Says:

    A few years ago, a newspaper story about a threatened bus drivers’ strike made some interesting points about Sky Train, although this was probably unintentional. It mentioned that the buses were responsible for some 80% of the passenger/miles in the metro system, all on about 20% of Trans-Link’s overall operating budget.
    Which means, reading between the lines, that Sky Train/Sea Bus is responsible for the other 20% of the passenger/miles — but on the remaining 80% of the operating budget.

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