28 replies to this topic

[Peter]

The new Rampart lift at Summit East was hit by a tree on Sunday January 18th. This lift was just completed a few weeks ago. Snoqualmie has had a rough go lately...Hyak and Alpental still have not opened due to lack of snow.

From the Summit's Facebook page:

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Yesterday, Sunday, January 18th, an unfortunate incident occurred involving our new Rampart chairlift at Summit East. The strong windstorm yesterday morning blew a tree over onto the lower part of the slopes adjacent to the lift. It unfortunately struck the lift cable very close to tower 4 and some damage occurred to the lift tower. Summit East was closed as it is yet to open for the 2014/15 season. At this point, lift mechanics are assessing the lift, however, so far we’re happy to report that the damage seems to be contained to tower 4 and most other parts of the lift appear to be unaffected. We will know more once a full inspection is completed by our lift engineers. While this set-back is disappointing, we’re 100% committed to getting our new lift open soon as possible!

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[Peter Pitcher]

Quite a load test

[RibStaThiok]

Wow... Did it impact directly onto the tower? I don't recall anything like that happening on the destructive testing done on the Eskimo Riblet at Winter Park when they knocked a few trees down onto the lift, granted I don't think any of em hit the towers...

[liftinspect]

I can't tell from the picture, did the anchor bolts pull up through the concrete?.

[Allan]

liftinspect, on 21 January 2015 - 07:45 AM, said:

I can't tell from the picture, did the anchor bolts pull up through the concrete?.

Certainly does look that way in the middle picture.

[liftmech]

Wow.

[DonaldMReif]

Talk about bad luck.

[vons]

Another view of tower 4 base credit Facebook


Wow! the two corner bolts broke off in the threads, those are the leveling nuts in the picture.

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This post has been edited by vons: 21 January 2015 - 02:22 PM

[Lift Dinosaur]

vons, on 21 January 2015 - 02:08 PM, said:

Another view of tower 4 base credit Facebook


Wow! the two corner bolts broke off in the threads, those are the leveling nuts in the picture.

...and the leveling nuts should be at T.O.C.......
Dino

[cjb]

RibStaThiok, on 20 January 2015 - 10:39 PM, said:

Wow... Did it impact directly onto the tower? I don't recall anything like that happening on the destructive testing done on the Eskimo Riblet at Winter Park when they knocked a few trees down onto the lift, granted I don't think any of em hit the towers...

It has been a few years since I have watched that video but I seem to remember the trees being smaller that that one or at least the part of the tree falling on the line being more near the top. This tree looks pretty big.

[Peter]

News report about the downed lift and lack of snow at Snoqualmie: http://www.king5.com...eason/22297935/

It doesn't look like the tree hasn't even been removed yet.

[Peter]

Some more pictures from Flickr taken on 1/24

Source: https://www.flickr.com/photos/hyak/

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[teachme]

Have they given up on it for the season? With so little snow it seems possible. Slightly tangential, but how is the season for the coast resorts (Vancouver north shore and such as well?)

[Peter]

Update from The Summit's website:

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Rampart Chair at Summit East is under repair following a tree-fall during a violent wind storm in January. We began concrete work on February 4th and have completed the tower's foundation. We will also begin replacing parts from damaged chairs along with a complete MRT (Magnetic Resonance Test) of the haul rope.

In other news The Summit threw in the towel and closed due to lack of snow today.

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[shoemanII]

think i'd be pull-testing the remainder of the towers in both directions, 'cause somethin' ain't right. maybe these weren't poured in place anchor bolts, but anchor bolts inserted into drilled holes? (like rawl studs). somebody's got some 'splainin' to do.

[Razvan]

Don't look for rational explanations. David Lynch lurks there, shooting a Twin Peaks followup.

[vons]

shoemanII, on 01 March 2015 - 09:02 PM, said:

think i'd be pull-testing the remainder of the towers in both directions, 'cause somethin' ain't right. maybe these weren't poured in place anchor bolts, but anchor bolts inserted into drilled holes? (like rawl studs). somebody's got some 'splainin' to do.

Not sure there is anything wrong with the concrete anchor bolt connection. I think its a situation where leverage caused by the load application and dynamic nature of the loading was just right. I am impressed how little buckling was seen in the base connection suggesting the stiffness of the connection though. I have not crunched numbers but I am just looking at a 40+-ft lever vs a 8+-ft lever.

[Tramway Guy]

vons, on 02 March 2015 - 07:03 AM, said:

Not sure there is anything wrong with the concrete anchor bolt connection. I think its a situation where leverage caused by the load application and dynamic nature of the loading was just right. I am impressed how little buckling was seen in the base connection suggesting the stiffness of the connection though. I have not crunched numbers but I am just looking at a 40+-ft lever vs a 8+-ft lever.

The tower and footing are designed to withstand normally imposed loads with normal factors of safety. Once loads that exceed those amounts are imposed, failure will happen in unpredictable manners and degrees. In this case, it may be the anchor bolts. In another, the tower may buckle. That doesn't mean that the design of either was inadequate. That just happened to be the weakest link in each case. I recall an event back in late 1970's where a twin-engine hit a chairlift and bent (2) towers above the stiffeners. In that case the footings happened to be stouter than the tower. You cannot economically design to positively prevent damage in these cases!

This post has been edited by Tramway Guy: 02 March 2015 - 11:59 AM

[vons]

Tramway Guy, on 02 March 2015 - 11:50 AM, said:

The tower and footing are designed to withstand normally imposed loads with normal factors of safety. Once loads that exceed those amounts are imposed, failure will happen in unpredictable manners and degrees. In this case, it may be the anchor bolts. In another, the tower may buckle. That doesn't mean that the design of either was inadequate. That just happened to be the weakest link in each case. I recall an event back in late 1970's where a twin-engine hit a chairlift and bent (2) towers above the stiffeners. In that case the footings happened to be stouter than the tower. You cannot economically design to positively prevent damage in these cases!

There is nothing wrong with the design! read what I am saying, the conditions of this event were "Just Right" aka not normal nor predictable. The load application was dynamic and not typical so also not normally accounted for in design calculation. The moment arm comparison was just a way, without knowing actual loads, to compare the normal moment experienced at the base of the tower, to whatever happened during the event and was thought of because it looked in the picks like the tower acted like a hammer pulling a nail out of a board.

Just a note, by responding vs just adding on to the discussion it makes it difficult to tell (not a mind reader here) if you were reinforcing/simplifying my point or countering it...I also just go done with a hockey game so the blood is a little up. CVS

This post has been edited by vons: 02 March 2015 - 01:56 PM

[shoemanII]

here's an example, pulled out of thin air:

(one) 1 3/8 inch gr 8 bolt has a minimum tensile strength of 173 kips. times (four) failed bolts gives a minimum tensile strength of
692 kips.

assume the load is directly down the line and a rigid base connection

dividing 692 kips by 40ft tower gives 17,300 pounds of force acting at 90 degrees to the tower top. anything over that and the bolts fail. but the energy from a falling tree isn't pulling on the tower top, the line sheaves prevent this. the cable simply rotates the sheaves as it oscillates back and forth. maybe the tree landed on, or nearly on, the tower?

a tree falling on hauling rope is a very dynamic event, with the impact on the flexible cable being distributed up and downhill of the impact point in the form of energy waves. i've witnessed the aftermath of these events on 3 occasions, and in all the wave magnitude in the rope was such that all restraint bars proximate to the event were found in the "closed" position, and the cable deroped at the nearest tower. the pic above does not show restraint bars down. also, some energy is also absorbed by the tensioning system.

with the energy of a tree falling on a haul rope being absorbed thoughout the system (haul rope moving fore and aft, carriers moving vertically in both directions, carriage moving, bullwheels rotating, etc) it's hard to envision that there is still enough energy to pull the anchors out of the concrete (there's usually flat washers at the opposite end to prevent this), or have them fail in pure tension. .

food for thought, carry on! : )

This post has been edited by shoemanII: 02 March 2015 - 02:15 PM