Tree fail as it happens

Birdyman88

Well-Known Member
Location
Arlington
Tree across the street from me survives a nighttime storm. On the following calm, sunny morning, a third of the tree splits off and falls on a car.
Cycles to failure. Weak area cycled all night continually separating wood fibers and just on verge of failing. Add some extra water weight from saturated ground all night and she finally fails. Easier to conceptualize when visible defect present and obvious cycling occurring (like wind). Harder to conceptualize when defect may be at molecular level, cycling is not currently present, and stressor is not easily visible.
 

Richard Mumford-yoyoman

Well-Known Member
Location
Atlanta GA
.
In my perticularlar case max wind speed for the 7 day period, (I have an anemometer 10' above a nearby pine at about 100') was 15 mph.
No other leaves or debris present
 
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Richard Mumford-yoyoman

Well-Known Member
Location
Atlanta GA
I don't discount LC complex abnormalities being a or the root cause. I guess I'm more curious about proximate causes.

Tree across the street from me survives a nighttime storm. On the following calm, sunny morning, a third of the tree splits off and falls on a car. A structural abnormality can explain where it split, but that doesn't answer the question of why it survived a storm and fails hours later when it's calm. Seems that if the failure point could withstand an appreciable increase over the static load, cellular changes would not occur rapidly enough to have a failure under static conditions the next morning.
You mean after dissecting this branch with my bandsaw I now have to start splitting individual atoms?
Seriously, this is I believe the root hypothesis.
(Also why I believe in a doubled and sustained load test of climbing anchors)
 

Richard Mumford-yoyoman

Well-Known Member
Location
Atlanta GA
That is my understanding too, no sign or cause of failure, lack of decay and defects.
But I’ve heard second hand even Shigo dismissed SLD stating something along the lines of “no matter how small, there is always a defect present” (@KTSmith ?)

but, if something is going to break, it’s always at the weakest point… so who in the hell knows?
Just like accident investigation, the thing that started the chain of events may have occurred days prior and is not even visible at the scene.
 

Richard Mumford-yoyoman

Well-Known Member
Location
Atlanta GA
Please tell me m
Much of the discussion of SLD focuses on the stressors. Sort of like saying the reason the building in Miami failed was because there were too many people and too much furniture inside. Like that condo, the limb has a built in safety factor that allows it to take on extra weight, like water, glucose, or climbers. And like that condo, the limb must have some sort of abnormality.

Since its strength comes from the lignin cellulose complex, that must be where the abnormality is. When an obvious defect is present, then it's likely that is the root cause of the weakened structure, as well as the likely failure point. When no obvious defect is present, then you must still look at the L-C complex, just at the cellular and molecular level. What happens here could be many things. Maybe just good old fashioned cladoptosis, maybe a genetic defect affecting the chirality or geometry of the molecules and thus bonding, maybe there were stressed points where the complex was interupted at some point prior, maybe there is higher production of peroxidases breaking down the lignin. The stressors just exploited this, but the root cause for the sudden weakness must be in the L-C complex.
Please tell me more, start a specific thread or point me where I can read more on the L-C complex.
 

Richard Mumford-yoyoman

Well-Known Member
Location
Atlanta GA
A little light reading.

Did not know, "Lignin is used for producing carbon fibers..."

 

moss

Well-Known Member
That's the part that doesn't add up for me. Seems like the failure should occur during a stress cycle instead of well after the cycling has ceased unless other factor(s) are in play.
Exactly. If the failure doesn't occur at the "end point" of cycles to failure then it wasn't enough. Other processes were required to finish it off. I suspect that is rare for a "cycles to failure" situation.
-AJ
 

Richard Mumford-yoyoman

Well-Known Member
Location
Atlanta GA
Can't help it...
Because we are talking about living tissue I don't know that cycles to failure have much to contribute when the stress that has caused the cycles is no longer present. We have all seen trees build back better. No example is perfect but Just like someone that works lifting weights, there are those cycles that tear down the tissue which causes the body to react by building better. Sure, hand that person the barbell soon after a good workout and they may tip over but soon be back to the gym for more punishment.
 

Graeme McMahon

Active Member
Location
Cockatoo
The reason for failure might be the same as in all our many "sudden limb drop" incidents, but I believe the mystery is when they have no internal decay or obvious ddefects?

@Graeme McMahon has been working on a study to look into a theory he has about predicting them before they happen. Very interesting stuff!
Mark, thanks for the heads up.
I am interested in the conditions leading up to the event to see if it fits to my model. I wanted to have the work published first but am so time poor after this storm time there isn't a spare moment. May not be back to normal work for months yet. Even William Ricketts Sanctuary has had sections destroyed.

I used to contribute for many years to a Mr. Laurance Costello who built a data base of tree failures in the US. That project would also have interesting data.
 

Bart_

Well-Known Member
Location
GTA
Later, seemingly sudden failure could just be the end point of slow fiber crush failure cascading stress buildup into nearby material, that previously was loaded staticly below its failure point. Envision the deformations of a normal hinge bending plus failure, then apply that to a union, trunk bend or codom crack etc. trying to imagine the pre-failure stress distributions and how they could focus or amplify at a weak spot post "trigger" where trigger could be e.g. one too many/too hard wind gust during a storm initiating some fiber crushing. Just a thought.

Plain old change in material properties due to biology of course also makes sense too, explaining cases with no known load change. Research measurements should be in order by interested parties, perhaps.
 

Birdyman88

Well-Known Member
Location
Arlington
Later, seemingly sudden failure could just be the end point of slow fiber crush failure cascading stress buildup into nearby material, that previously was loaded staticly below its failure point. Envision the deformations of a normal hinge bending plus failure, then apply that to a union, trunk bend or codom crack etc. trying to imagine the pre-failure stress distributions and how they could focus or amplify at a weak spot post "trigger" where trigger could be e.g. one too many/too hard wind gust during a storm initiating some fiber crushing. Just a thought.

Plain old change in material properties due to biology of course also makes sense too, explaining cases with no known load change. Research measurements should be in order by interested parties, perhaps.
Exactly. A tree could be in failure right in front of you and the separation process happening so slowly that you would think it's fine. I define failure as when the holding force on the piece of interest is less than the force on that piece due to gravity or other stress. Failure could have happened long before you even noticed anything. Like @Bart_ alluded to, the separation process could be very slow in an area of stronger fibers, but next you could get quick failure while the fibers in a weak area separate.
 

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