Canadian Pacific Railway installs country’s first hybrid-composite beam in 10 hours.

[Paul_D_North_Jr]

Notably, in several places on the HCB website - e.g., http://www.hcbridge.com/applications/railway - and http://www.hcbridge.com/case-studies/railway/ - is a quote / testimonial about the HCBs by John F. Unsworth, Deputy Chief Engineer Structures, Canadian Pacific Railway, British Columbia.

Mr. Unsworth is the author of the comparatively recent (2010) book, Design of Modern Steel Railway Bridges:

https://www.crcpress.com/Design-of-Modern-Steel-Railway-Bridges/Unsworth/978142008213 

For him endorse what is essentially a competing or superseding material and method is especially significant, and furnishes a lot of credibility (at least to me).

- Paul North. 

[rdamon]

I think the major “innovation” in this is that they were able to use a rail crane instead of bring track running cranes by truck due to the lower weight of the beam.

According to their website, BNSF will be able to replace bridges with less piers due to longer spans without special equipment.

 

I think this has significant applications on both rail and road bridges that need replacement or raising.

[Paul_D_North_Jr]

Murphy Siding

Thanks PDN and rdamon for the info.  It's been 34 years since I had a class in statics, but surprisingly, it comes back fast.  Now I see that it's a gift wrapped arch, it makes more sense.

    That being said, PDN mentioned, and the article too perhaps, that the existing piers could be reused with some modification.  Wouldn't the stress inputs at the piers change enough to warrant redesign?

Murphy, I figured you'd 'get it' after thinking about it a little bit.  

If you recall that statics class a little more, you'll realize that the loads from the girders onto the piers won't change much (as long as it's a "simple" beam configuration and not a "continuous" one, of course).  As long as the numbers of beams and their lengths don't change much, and the train loads are the same, then the loads onto the piers won't change much either.  Recall that the distribution of the proportions of those loads to each end is pretty much determined only by the geometry/ length of each beam and the point of application of the load (where the train is on the bridge), not the size or dimensions of the beam. 

Sure, the details of the bridge 'seats' and bearing connections would need to be changed.  That's because those bearings will be changed from the heavy steel "triangle" type "pins" at the fixed end and "rollers" at the expansion end to a flat, thick, and slightly flexible neoprene pad.  And if the new bridge has a different (most likely wider) beam-to-beam spacing than the old one, then the bridge seats will need to be shifted/ relocated accordingly as well.  But as long as the bearing location on the pier/ abutment doesn't change too much, it won't need much modification.  

Finally, the piers / bearings seats are likely stronger than you might think.  Even at a relatively low concrete compressive strength of 2,000 psi, an area about the size of a sheet of paper - 8-1/2" x 11" or 94 sq. inches - will then support a static load of 188,000 lbs., or about 1 end of a 263K car even allowing for some impact factor - and that's only for 1 of the 2 beams, and only 1 end of the bridge.  So a bridge of up to about 2 car-lengths long should have no trouble continuing to handle those kinds of loads.

- Paul North.     

[mudchicken]

Original design plans, annual steel bridge inspections, division bridge inspections and concrete coring in advance of the bridge program. There is a lot more going on than just switching spans.

[Murphy Siding]

mudchicken

 

 

Murphy Siding

    That being said, PDN mentioned, and the article too perhaps, that the existing piers could be reused with some modification.  Wouldn't the stress inputs at the piers change enough to warrant redesign?

 

 

Bridge seats and bearing surfaces are pretty robust. If you are dealing with the same bearing area and the concrete hasn't gone beyond the age fixable stage, not that much of a problem.

A couple years back, in eastern Wyoming, we helped Unca Pete replace an E-65 deck girder bridge (built 1903) with an E-85 reinforced concrete beam bridge of the same length. Bridge seats were fine, but the backwalls cracked and failed at the back edge of the seat. The few inches of clearance between the end of the beams and the backwalls disappeared as the backwall rotated. The backwalls were now canted inwards 3-4 inches instead of vertical.The 1903 hand made concrete had started to fail and crumble.  Repairing backwalls under traffic is no fun and the 10-Hour changeout window found itself postponed. No industrial bridge shoehorns happened to be handy to help place the new span. Railroad bridge people tend to be very resourcefull and industrious when fixing problems under traffic....something most of the public never see.

 

 Short of trial and error, how does one determine if 1903 infrastructure is up to carrying new 2015 bridgework above?

[blue streak 1]

rdamon

Hopefully PEX will do better than polybutylene did ...

It was interesting to read that the HCB could be shipped empty and filled with concrete onsite.

 

As someone who has worked with both PB & PEX there is no comparsion.  PEX has the ability to return to its former shape when stress is removed.  So if frozen it will expand but then return to original diameter when thawed.  Cannot do that with PB, galvanized, copper, or PVC.  As well you can bend it at about 12 times its outside diameter without crimping.  Connection methods have improved and are very easy now. Makes good outside installation although we always sleeve it inside some kind of conduit if possible.  PEX is a somewhat polyethylene product that has a special manufacturing method.

The Orange conduit often seen as underground conduit is PE ( polyethylene ) not PEX .  Often seen now around RR signal installations. Orange for electrical including low voltage, Yellow for natural gas, unknown for other applications. Both PE & PEX appear to have a 500+ year life.

Despised PB pipe as it seems to go bad over time.     

[mudchicken]

Murphy Siding

    That being said, PDN mentioned, and the article too perhaps, that the existing piers could be reused with some modification.  Wouldn't the stress inputs at the piers change enough to warrant redesign?

Bridge seats and bearing surfaces are pretty robust. If you are dealing with the same bearing area and the concrete hasn't gone beyond the age fixable stage, not that much of a problem.

A couple years back, in eastern Wyoming, we helped Unca Pete replace an E-65 deck girder bridge (built 1903) with an E-85 reinforced concrete beam bridge of the same length. Bridge seats were fine, but the backwalls cracked and failed at the back edge of the seat. The few inches of clearance between the end of the beams and the backwalls disappeared as the backwall rotated. The backwalls were now canted inwards 3-4 inches instead of vertical.The 1903 hand made concrete had started to fail and crumble.  Repairing backwalls under traffic is no fun and the 10-Hour changeout window found itself postponed. No industrial bridge shoehorns happened to be handy to help place the new span. Railroad bridge people tend to be very resourcefull and industrious when fixing problems under traffic....something most of the public never see.

[Paul_D_North_Jr]

Note that there are 2 aspects to the report excerpted and linked by the Original Poster:

1. The 10-hour replacement.  There's not much novel in that, although it's always an admirable achievement. 
2. The HCB.  That's new and different. 

Maybe more later.

- Paul North. 

[rdamon]

Hopefully PEX will do better than polybutylene did ...

It was interesting to read that the HCB could be shipped empty and filled with concrete onsite.

[ndbprr]

Like any new technology lets just wait and see if it lasts. I see pex piping being pushed for homes but nobody has any long term real world experience with it. Before we start accepting it as a solution we better be sure.

[Murphy Siding]

    Thanks PDN and rdamon for the info.  It's been 34 years since I had a class in statics, but surprisingly, it comes back fast.  Now I see that it's a gift wrapped arch, it makes more sense.

    That being said, PDN mentioned, and the article too perhaps, that the existing piers could be reused with some modification.  Wouldn't the stress inputs at the piers change enough to warrant redesign?

[rdamon]

Thanks guys ... I enjoy knocking the dust off of what I learned in statics a long time ago .. :)

 

I found this picture on the HCB site helpful.

[Paul_D_North_Jr]

Wizlish

See patent 7562499 for more on the structure.  Part of the story is that this is less a 'beam' structurally than a tied arch with 'covered bridge' protection. 

Pretty succinct description, close to how I was going to describe it.

A complicated subject, but:

• A tied arch is kind of like a beam, it's just that instead of being parallel all the way across, the tension and compression areas are spread out further in the middle than at the ends. 
• At the middle, a beam could be just a tension area in the bottom and a compression area at the top (see comment below on the near-zero shear at this location).  The rest of the beam section at the middle serves mainly to keep the tension and compression areas separated far enough apart, so it doesn't have to be real strong there.  And the farther apart the tension and compression areas are, the smaller each of them can be to resist the applied load.  Simplified, the strength of the beam - or the tied arch - at a particular point is the product of the tension or equal and opposite compression force, and the separation between them; increase the one and the other is reduced, and vice-versa.   
• The arch shape is inherently efficient because it changes beam-type bending/ sagging loads into mostly compression-type loads, and alters its shape at the ends to mirror the increasing compressive load there - a great example of "form following function".  The Romans figured that out about 20 centuries ago.  
• Many covered bridges are indeed tied arches - you can see that on the inside - but the rectangular covering fools people on the outside into thinking instead that they're squared off inside. 
• Murphy Siding (and some others) should consider the "bowstring trusses" that are often used for curved roofs, too.
• Shear is counter-intuitive.  It's near zero under the load(s), and highest at the supports.
• With the 'bending moment' (force that makes a beam tend to sag) near zero at the ends, the thicker part of the beam there to maintain parallelism there really doesn't serve much of a useful function other than to transfer the shear into the abutment/ pier, so reducing that is one way to save weight.  

Note that in these articles the abutments of the CP bridge could be reused with just minor adjustments/ repairs.  In many cases of work on existing bridges, the abutment/ pier / foundation conditions are the source of most of the biggest time-consuming, expensive, unforseeable, and unpreventable troubles.  

In his book The Nickel Plate Road, author John A. Rehor made the point that many of the NKP's high steel viaducts were strengthened by changing out the similar girder spans, even with heavy World War II traffic volumes on that line.

- Paul North.      

 

[Wizlish]

Convicted One

With the fibreglass shell handling the duties of resisting shear, much less concrete (mass) is needed.

See patent 7562499 for more on the structure.  Part of the story is that this is less a 'beam' structurally than a tied arch with 'covered bridge' protection.

[Electroliner 1935]

 whoops.

 

 

[Convicted One]

Murphy Siding

    
      Where does the weight saving come from? 

 

 

With the fibreglass shell handling the duties of resisting shear, much less concrete (mass)  is needed.

[rdamon]

jeffhergert

I guess concrete must shrink when left out in the open, because when the appointed day came to install them they were found to be about a foot shorter than expected. 

That also happens with my suit when it hangs in the closet.

[jeffhergert]

mudchicken

Measure/verify/check/confirm/ repeat twice....then go to work.

 

Back around 1999, the UP replaced a bridge over the Boyer River near Westside, Iowa.  At that location the title of river is generous, near the river's source it's more the size of a creek.  The bridge was just a tad larger than the one shown in the article.  The precast pieces had been out there for a while. 

I guess concrete must shrink when left out in the open, because when the appointed day came to install them they were found to be about a foot shorter than expected.  It took them an about an extra 12 hours to put everything in place.

Jeff 

[Paul of Covington]

   Murphy, the links didn't have much in the way of physical description to go by, but my guess from this part:

"The HCB is a structural member akin to a prestressed concrete or steel beam. The FRP outer shell provides shear strength and encapsulates the tension and compression elements. The compression element is a concrete arch. The tension element is steel reinforcement that runs longitudinally the length of the beam and ties the two ends of the concrete arch together."

is that it follows the same theory as pre-stressed concrete, but where the steel reinforcement in pre-stressed is inside the beam, in HCB it's outside the concrete arch except at the ends, much like a bow used in archery.   In other words, they took a thick pre-stressed beam and removed the bulk that does not contribute to the strength.   Then they enclosed the whole thing in a "fiberglass" box to protect it from the elements.   I'm sure Mudchicken or Paul North could enlighten us.

[Murphy Siding]

     The article says a concrete beam would weigh 60,000#, the HCB beam, 42,000#.  The article  explains that an HCB beam is similar to a concrete beam with steel tansion cables inside, but coated with fiber-reinforced polymer (FRP). It also says that the concrete and steel provide 90% of the strength.  
      Where does the weight saving come from?  Wouldn't an HCB beam still need 90% of the 60,000# of concrete and steel (=54,000#) to be as strong as a 60,000# concrete and steel beam?

[MikeF90]

For us non-civil engineers, an article on the inventor of the HCB: https://en.wikipedia.org/wiki/John_R._Hillman

FAQs on his companies website: http://www.hcbridge.com/faqs

These beams are about 1/3 the weight of a comparable prefab concrete beam, thus improving the likelihood of more rapid construction.

[mudchicken]

Measure/verify/check/confirm/ repeat twice....then go to work.

[Norm48327]

BaltACD

When the piers are in place, replacing the deck is a 'relative nothing' as long as the deck can be handled in one piece.

 

Six piece precast concrete deck. It went together as good as Lego.

[BaltACD]

When the piers are in place, replacing the deck is a 'relative nothing' as long as the deck can be handled in one piece.

[Norm48327]

I  watched, and photographed, that type of operation in 2007. All prep work was done while maintaining traffic flow and in one day the old bridge deck was removed and the new one set in place, track laid and ballasted. Traffic resumed late in the afternoon.

[rdamon]

http://cenews.com/article/10215/bridge-replacement-in-10-hours

On Oct. 22, 2014, and within a 10-hour traffic block, Canadian Pacific Railway crews replaced the existing bridge at a Fernie, B.C., location with the first-ever use of Hillman Composite Beam (HCB) technology for railroad-revenue service. Pioneers of bridge technology, the Class 1 railroads of North America recognize that their bridge assets have to be installed in one day yet be able to last for more than a century. As such, some of the earliest, most recent, and best innovations related to Accelerated Bridge Construction (ABC) originated in railroad applications. Canadian Pacific has furthered this legacy of innovation by bringing the first HCB bridge to Canada and the first revenue-service HCB railroad bridge in the world.....

[snip]