Thoughts on the Engineering Industry

A blog covering engineering, technology and business topics

Archive for the month “August, 2013”

Basic Overview of the Hyperloop

Hello everyone, I hope y’all are doing well.  I’ve taken a bit of a vacation, both literally for a weekend, and then for longer in regards to my blog.  I feel guilty but it just felt like the right time to do something like this.  Nothing else new has really been going on with me – still just looking for work as an engineer and keeping my resume up to date.  I have taken the time to really learn Revit which should help me and my next big to do list in regards to personal learning is getting sharp on AutoCAD again.  One fun thing is that I’m also working harder on getting my Spanish to a conversational level, it would really be nice if I could put that on my resume too although not as important.  I will also start working as a substitute teacher again and I hope that won’t cut into my job hunt and personal job training right now.  We’ll see how that goes.  Anyways, that’s about all as far as updates go – today, I want to talk about the recent Hyperloop Alpha Proposal published by Elon Musk (founder of Paypal, SpaceX and Tesla Motors).  It has created quite the stir in the engineering community and I thought it would be a good topic to come back on. For this blog post, I am going to reference Elon Musk’s Hyperloop Alpha Proposal (http://bit.ly/16LCXwt).  However, this is a complex enough idea with enough attention that I might do some more detailed analysis in another blog post.

The hyperloop is a combination of a maglev and vacuum tube system.  Similar concepts have been proposed by Rand Corporation and ET3.  The main difference is that the previous designs involve using a hard or near hard vacuum in the tube; however, the Hyperloop uses a low pressure system.  The low pressure system is supposed to be much easier to maintain using standard pumps and maintenance than a hard vacuum.  The propulsion system involves a combination of air pumps and magnetic levitation.  An air pump will be put in the front of the train and will pump air below and behind the train.  This will accomplish several things: reduce air pressure in front of the train, create a buffer of air below the train, and reduce drag behind the train.  A pump will also be used directly below the train to reinforce the buffer of air as needed.  The maglev system will propel the train forward and will be powered by a battery similar to the battery found in the Tesla Model S.  There are two options for the size and purpose of the train: one is a smaller passenger train and one that is a larger passenger train that can also carry several vehicles.  The Hyperloop is theoretically designed to travel at 700 mph according to the proposal.  However, the critical part of this design not the propulsion system but the tube system.  The proposal suggests a tube system that is supported above ground using precast reinforced concrete columns that would take up no more room than a power line pole would require.  The track would follow the I-5 Highway and only deviate from the highway when necessary.  Also, due to changes in elevation, it is estimated that the tube would occasionally have to be placed at or below grade.  The track would be stabilized using dampers and minor adjustments would be allowed for to account for foundation settlement.  The different sections track would be connected using expansion and contraction joints that would help account for lateral loads due to earthquakes and other lateral vibrations.  The rest of the report is numbers and calculations used for estimation and comparison in regards to other systems.  The specific numbers and calculations read like a rough estimate and aren’t worth discussing in this post in my opinion; however, I would recommend quickly browsing the numbers and calculations just to get a quick idea about the comparisons to other modes of transportation.  Elon Musk in closing goes on to list the critical issues that need to be considered to implement the idea:

“The authors recognize the need for additional work, including but not limited to:

1. More expansion on the control mechanism for Hyperloop capsules, including attitude thruster or control moment gyros.

2. Detailed station designs with loading and unloading of both passenger and passenger plus vehicle versions of the Hyperloop capsules.

3. Trades comparing the costs and benefits of Hyperloop with more conventional magnetic levitation systems.

4. Sub-scale testing based on a further optimized design to demonstrate the physics of Hyperloop.

Engineering News Record wrote an article (http://bit.ly/1a7MWQQ) recently sharing some professional critiques.  The first one is a quote from an unnamed source:

“Many media sources offer commentary from professors about the impossibility of the hyperloop. One of those same sources told ENR off the record that “the idea of building a $68-billion rail line that takes 25 to 30 years to complete is just as absurd.””

They go on to say that Elon Musk has addressed the issue that testing and further research is required, but that some blow back has come his way for that.

“Other media critique Musk for being only an idea man who is hiding behind his massive business responsibilities and not moving toward implementation of the hyperloop. Musk admits as much in his proposal and, noting that the hyperloop idea is not complete, asks for help from “all members of the community.””

The article then goes on to share some thoughts Ted Zoli of HNTB, National Chief Bridge Engineer.

““Just the substructure costs alone for elevated structure over the entire length of the alignment is enormous,” says Ted Zoli, national bridge chief engineer at HNTB. The hyperloop’s proposed design requires elevated piers every 100 ft. Zoli says if the structure was built instead at grade, the construction costs could be “sharply reduced.” He adds that it conceivably could be built at grade for much of the route, “particularly if it is in the median of I-5,” which is where Musk envisions much of the transit tube being placed.

Zoli suggested that, given the hyperloop’s 88-in.-dia passenger pipe, any necessary tunneling could be done with horizontal directional drilling (HDD), “an inexpensive pipe installation technique.” Zoli adds that the largest HDD done now is 56 in. in dia, but he thinks custom HDD equipment readily could be developed, given the size of the hyperloop project.””

In closing, a final addition to the list of concerns is added in reference to another comment by Ted Zoli.

“5. A closer look at expansion joints.

“The expansion joints have not been figured in, in any meaningful way, and would be required much more often than at the terminal stations [as the current proposal outlines]. I would expect something on the order of every mile or thereabouts, even with a telescoping connection. Bearings would also have to accommodate relatively large relative movements for this distance between expansion joints,” says Zoli.”

In my opinion, there will be several critical issues if this is pursued.  The main one is the tube system in regards to column supports or on grade and expansion and contraction joints.  Given the high portion of the budget it involves, the high maintenance cost, even if it is designed well, could make it infeasible.  That combined with the earthquake and dynamics issues make that the most critical issue.  Another possible issue is testing – this is a system that has never been used on this scale before and would need significantly more testing and research to make a final decision, both of which cost money and won’t magically happen overnight.  And the final issue I see that has not been mentioned in the article at all is the reticence of the government to use unproven systems.  Take a look at how long it has taken to get high speed rail going in California and that is a system that has been proven to work for a couple decades in other countries.

Well this post got longer than I expected for my first post back in a while but thanks for reading if you got to this point.  What are your thoughts on the Hyperloop?  Do you have any concerns about the hyperloop?  Do you think this system can realistically be designed and implemented?  Thanks for your time and have a good week.

New Landmark Bridge for Downtown Fort Worth

Hello everyone, I hope y’all are doing well.  Not much has changed with me…still looking for work and I am also making a solid effort to brush up on some structural engineering programs like Revit, SAP, and AutoCAD.  Today I want to share my opinion on a new bridge that is going up in my hometown of Fort Worth, TX.  Part of it is for selfish reasons –  it is my hometown and I am glad we are getting a fancy new bridge for an up and coming area of town.  However, it also uses a unique combination of bridge design concepts I would like to discuss.

The design of the bridge is a combination of two common bridge design concepts – a network-arch bridge and a precast concrete bridge.  The city wanted a network-arch bridge to add aesthetic appeal to the design.  However, they wanted minimal disruption in regards to traffic – hence application of precast concrete principals.  The article gives the following specifications for the bridge: “The bridge is a series of 12 post-tensioned concrete arches, six on each side, which are the main structural elements. Each arch is 163 feet long and over 23 feet tall. While the new bridge will remain with four traffic lanes, it will be much wider to incorporate lanes outside the arches for pedestrians and cyclists.”  The goal was to reduce the on site construction site down to 150 days.

To do this, the arches were cast on their side for efficiency.  Post tensioning was applied in three stages.  The arch was cast sideways and post tensioning was applied, the the arch tilted up right and another round of post tensioning was done.  Then the arch was moved into storage and a final round of post tensioning was done.  The casting process took between 3 to 6 weeks; while this was being done, the foundation and columns were constructed on site.  Transport and installation of the arches started in July and will finish by October.

Personally speaking, I like the bridge design and location.  The bridge will connect the up and coming West 7th District with downtown Fort Worth which should guarantee good visibility.  Along with that, the creative design process and improved construction time is also impressive.  This should make the bridge a good icon that can be advertised for the Fort Worth area.  The only drawback I could see is that the new combination of design concepts may not work as well as expected.  I trust that it can initially handle the dead loads and traffic live loads adequately so safety isn’t a major concern for me.  However, the lifetime demands like fatigue, deflection over time, etc. are more difficult to predict and can’t be tested as accurately – especially with uncommon designs like this.

What are your thoughts on the bridge?  Do you think the design will be effective?  And on a personal note, if you have been to downtown Fort Worth or West 7th Street district, do you think the bridge will be a good addition to the area?  Thanks for your time and have a good weekend.

Source:

Nancy S. Giges, “World’s First Precast Network-Arch Bridge”, www.asme.org, http://tinyurl.com/n7wblwa

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