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Ok, admitedlly pure speculation on may part but I've zoomed in on the picture of the SFSJ River bridge and to me, it looks like the bridge is still suspended well above the river. From the overhead shot it looks to be sitting in the river itself but look at the shadow of the bridge and it appears that is not the case. Anyone else come to the same conclusion? Did just the downstream sided railing fail? Certainly it's gonna take folks getting in there to know for sure, and perhaps its in a precarious condition regardless, but perhaps a ray of hope?
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Chris, Some people know how to look at pics ! I didn’t notice the shadow :) you are right that it doesn’t look sitting in the river ? Karina Bezkrovnaia
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On Apr 22, 2023, at 18:18, Chris Armstrong <sacarmstrong@...> wrote:
? Ok, admitedlly pure speculation on may part but I've zoomed in on the picture of the SFSJ River bridge and to me, it looks like the bridge is still suspended well above the river. From the overhead shot it looks to be sitting in the river itself but look at the shadow of the bridge and it appears that is not the case. Anyone else come to the same conclusion? Did just the downstream sided railing fail? Certainly it's gonna take folks getting in there to know for sure, and perhaps its in a precarious condition regardless, but perhaps a ray of hope?<Screenshot_20230422_173511_Facebook.jpg>
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I'm reading the photo as:
-right (downstream) handrail buckled and kinked outwards severely, twisting the bridge
-left handrail rotated about 45 degrees in the middle, with perhaps a kink in the middle of the deck (seen in the shadow in the river)
-seems still anchored on both abutments.
I agree that it still seems quite above the river. I doubt it is safe to cross. Restoring steel that has been severely kinked like this seems like quite a challenge, especially in the backcountry.
I'm quite curious how such a seemingly robust bridge could fail like this; it seemed to be in good shape when I crossed it last summer. Does anybody have any ideas on if/when/where an official report might be published? If this could fail, what about the other bridges that have similar designs?
Luckily, failed steel bridges often retain clues that allow reconstruction of the collapse. Such was the case in 2007 when the I35 bridge here in Minneapolis dropped into the Mississippi river.
Mike Sherman
On 04/22/2023 7:54 PM Chris Armstrong <sacarmstrong@...> wrote:
Ok, admitedlly pure speculation on may part but I've zoomed in on the picture of the SFSJ River bridge and to me, it looks like the bridge is still suspended well above the river. From the overhead shot it looks to be sitting in the river itself but look at the shadow of the bridge and it appears that is not the case. Anyone else come to the same conclusion? Did just the downstream sided railing fail? Certainly it's gonna take folks getting in there to know for sure, and perhaps its in a precarious condition regardless, but perhaps a ray of hope?
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An older and longer bridge on the MFSJ failed back in 1997, they managed to get it back into service the next year before proper repairs could be made. While I don't know if the failure this year bridge is in good enough condition for
temporary repairs it is at least an interesting read. Click on the photos for... more photos
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I'm reading the photo as:
-right (downstream) handrail buckled and kinked outwards severely, twisting the bridge
-left handrail rotated about 45 degrees in the middle, with perhaps a kink in the middle of the deck (seen in the shadow in the river)
-seems still anchored on both abutments.
I agree that it still seems quite above the river. I doubt it is safe to cross. Restoring steel that has been severely kinked like this seems like quite a challenge, especially in the backcountry.
I'm quite curious how such a seemingly robust bridge could fail like this; it seemed to be in good shape when I crossed it last summer. Does anybody have any ideas on if/when/where an official report might
be published? If this could fail, what about the other bridges that have similar designs?
Luckily, failed steel bridges often retain clues that allow reconstruction of the collapse. Such was the case in 2007 when the I35 bridge here in Minneapolis dropped into the Mississippi river.
Mike Sherman
On 04/22/2023 7:54 PM Chris Armstrong <sacarmstrong@...> wrote:
Ok, admitedlly pure speculation on may part but I've zoomed in on the picture of the SFSJ River bridge and to me, it looks
like the bridge is still suspended well above the river. From the overhead shot it looks to be sitting in the river itself but look at the shadow of the bridge and it appears that is not the case. Anyone else come to the same conclusion? Did just the downstream
sided railing fail? Certainly it's gonna take folks getting in there to know for sure, and
perhaps its in a precarious condition regardless, but perhaps a ray of hope?
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I would guess dynamic forces (like an avalanche) would be the culprit - seems like a bridge like this would be designed to manage a winter snow load, even a big one.
I’ll be curious to see how close the bridge is to the water when the river rises, especially when logs get washed down the river. If that sag mid-span is severe enough, a log jam could damage it further, or just finish the job altogether.
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On 23 Apr 2023, at 12:02 pm, Mike Sherman <msherman55@...> wrote:
?
I'm reading the photo as:
-right (downstream) handrail buckled and kinked outwards severely, twisting the bridge
-left handrail rotated about 45 degrees in the middle, with perhaps a kink in the middle of the deck (seen in the shadow in the river)
-seems still anchored on both abutments.
I agree that it still seems quite above the river. I doubt it is safe to cross. Restoring steel that has been severely kinked like this seems like quite a challenge, especially in the backcountry.
I'm quite curious how such a seemingly robust bridge could fail like this; it seemed to be in good shape when I crossed it last summer. Does anybody have any ideas on if/when/where an official report might be published? If this could fail, what about the other bridges that have similar designs?
Luckily, failed steel bridges often retain clues that allow reconstruction of the collapse. Such was the case in 2007 when the I35 bridge here in Minneapolis dropped into the Mississippi river.
Mike Sherman
On 04/22/2023 7:54 PM Chris Armstrong <sacarmstrong@...> wrote:
Ok, admitedlly pure speculation on may part but I've zoomed in on the picture of the SFSJ River bridge and to me, it looks like the bridge is still suspended well above the river. From the overhead shot it looks to be sitting in the river itself but look at the shadow of the bridge and it appears that is not the case. Anyone else come to the same conclusion? Did just the downstream sided railing fail? Certainly it's gonna take folks getting in there to know for sure, and perhaps its in a precarious condition regardless, but perhaps a ray of hope?
<Screenshot_20230422_173511_Facebook.jpg>
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Seems plausible some dynamic force is the cause but hard to imagine an avalanche was the culprit as there is no damage to even the smallest of trees in the photos.?
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Most plausible failure mechanism to me is an extremely heavy, wet snow load that got lopsided as the upstream side melted, twisting the bridge until it buckled. Might have been aided by a strong wind coming downstream.
But I'd love to hear what the pros say when they get in there!
Mike Sherman
On 04/22/2023 10:11 PM Chris Armstrong <sacarmstrong@...> wrote:
Seems plausible some dynamic force is the cause but hard to imagine an avalanche was the culprit as there is no damage to even the smallest of trees in the photos.?
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This bridge of similar construction over Dusy branch shows a minor twist on the upstream side, since quite some years. Possibly caused by logs?
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Gesendet:?Sonntag, 23. April 2023 um 14:26 Uhr
Von:?"Mike Sherman" <msherman55@...>
An:[email protected]
Betreff:?Re: [JMT-groups.io] Speculating on the SFSJ bridge
Most plausible failure mechanism to me is an extremely heavy, wet snow load that got lopsided as the upstream side melted, twisting the bridge until it buckled. Might have been aided by a strong wind coming downstream.
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But I'd love to hear what the pros say when they get in there!
Mike Sherman
On 04/22/2023 10:11 PM Chris Armstrong <sacarmstrong@...> wrote:
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Seems plausible some dynamic force is the cause but hard to imagine an avalanche was the culprit as there is no damage to even the smallest of trees in the photos.?
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This was a VERY high snow year. I’m “assuming” (an engineering term [ ;) ]) that the snow load exceeded the design load for the deck. The right beam simply failed and buckled and relieved the stress by dumping the snow.
One of my degrees is in engineering, but P.E. In my case means pseudo-engineer.
Tim
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If you take a cross section through the bridge, you get a U shape. U shapes are not very good at handling twisting (torsion). That's why I think a lopsided load (heavy snow on one side, missing snow on the other where it melted) created a twisting load could well have caused the bridge to buckle.
Not something that I would have thought about at all if I had been the one designing the bridge. And this bridge's orientation of east to west would make it more susceptible to the snow melting on one side than, say, the bridges immediately up and down stream of it.
Mike Sherman
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On 04/23/2023 11:15 AM Tim Mulholland <tim@...> wrote:
This was a VERY high snow year. I’m “assuming” (an engineering term [ ;) ]) that the snow load exceeded the design load for the deck. The right beam simply failed and buckled and relieved the stress by dumping the snow.
One of my degrees is in engineering, but P.E. In my case means pseudo-engineer.
Tim
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I don't take much hope from the fact that it is not in the River:? it looks that way to me from the start.? But if you carefully identify which bars are where in the structure of the bridge, and match them up with their shadows, and add in the fact that the edges of the snowbanks on both sides of the river are also a few feet above the stream, you can conclude that the bridge is not nearly as distorted as the shadow makes it look.? The downstream handrail is certainly a mess, but the rest?? Maybe not so much.
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On Sun, Apr 23, 2023 at 02:45 PM, Peter Hirst wrote:
The downstream handrail is certainly a mess, bust the rest?? Maybe not so much.
Yeah, it's hard to gauge from an aerial shot and with the snow. Comparing that photo to the photos I took of that bridge in 2020, It doesn't look like it was pushed off the foundations (again, hard to say for sure with the snow).
If it's not wobbling and didn't slide completely off one or both of the foundations, I can see someone (not me :) ) trying to climb horizontally across it using any parts still there.
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Here is my prediction. The PCTA will post alternative routes. ?Most likely exit over bishop pass to south lake and enter via Paiute pass. ?This approach will be completely legal with a PCTA pass. ?It seems highly likely that crossing the bridge will not be allowed. The early season PCT hikers will probably try many of the options previously discussed. ? No doubt some will try and use the bridge. ?They will report back on “Far Out” and the herd will follow. ?? If you follow NOBO hiker social media you should be able to glean direct observer information from those folks. ?What you do with that information is up to you to decide. Good luck to all that face difficult choices. ?Even with intact bridges this year is gonna be one to remember.
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On Apr 23, 2023, at 2:45 PM, Peter Hirst <peter.p.hirst@...> wrote:
?I don't take much hope from the fact that it is not in the River:? it looks that way to me from the start.? But if you carefully identify which bars are ahere in the structure of the bridge, and match them up with their shadows, and add in the fact that the edges of the snowbanks on both sides of the river are also a few feet above the stream, you can conclude that the bridge is not nearly as distorted as the shadow makes it look.? The downstream handrail is certainly a mess, bust the rest?? Maybe not so much.
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I agree with Mike.? I don't see any evidence of avalanche or other catastrophic event, and relatively little deformation on the upstream side.? Would like to see a lower angle shot, but from the available view, it looks like the upstream railing is evenly bowed and the lower beam on the same side is straight.? It is all still bhigh above the water, so little buckling over all.? But time and better photos will tell
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Karina Bezkrovnaia
Lange Jorstad
Henning Rech
Tim Mulholland
WanderingJim