I can't see it being difficult to protect a chain-link fence from wind. Now if you have slats between each link or that tennis court stuff over all of it that would be different. That being said, I agree completely that a branch can take out a fence, and a falling church can take out an ASZ wall.

 

I'm too lazy to find the Mr. Spock meme where he says "Fascinating" and post it here. But yes, you are correct. No dispute from me. We are on the same page. Figuratively speaking of course. Literally speaking, you're post is on a prior page than mine. So technically, we're not really on the same page. Got me?

OMG! I'm gonna make you a STAR!!!!

 

That's not really the essence of what I was trying to get across though. I'm just saying that certain structures are designed to withstand certain types of stress better than others. My fence can obviously handle the enormous impact of a hurricane because of how it's designed. Whereas entire buildings can get ripped apart by that same force. Yet when something like a giant branch falls on top of my fence, it is clearly worthless. That same branch wouldn't do squat to my house, yet my house would be a hurricane's bitch. I understand the physics behind why that is the case for both, the ASZ wall, my fence and my house. I just also happen find it intriguing.

Now... no more discussion about my chain-link fence. I FORBID IT!!!

 

I'm throwing in another vote for that tower was definitely substantial enough to take down that fence.

 

That's pretty much what I was saying too. A flagpole can withstand a hurricane because it doesn't have much surface area and is anchored in concrete, so while the hurricane has tremendous force, it doesn't have as much over a very small area. A flagpole won't stand up to being hit by a truck because there's a lot more force/surface area. Same thing for getting a branch on someone else's fence or a steeple falling over on the top of the ASZ wall.

 

Technically, hurricanes produce high wind speeds. Wind speed (squared) produces pressure, and pressure times area equals force.

 

Yep, add a couple conversion factors and constants and this sums is up. We could calculate a rough estimate of the force on each panel for a given wind velocity.

To get pressure, we square the wind speed and multiply it by .0026, this is the conversion factor for speed to pressure.

So a 100 mph wind would be 26psf on fence surface. [100 x 100 x .0026]= 26.

Each fence panel is 15 feet tall by 12 feet wide to its surface area is 12 x 15 = 180 = area

Then there's a drag coefficient for each object depending on its shape and surface. As far as I can tell, a single fence panel would have a drag coefficient of about 1.4. I think taking the fence as a whole, making it a very long wall rather than single panel would make this coefficient higher.

So for one panel, F = Pressure x area x Coeff.

= 26psf x 180 sf x 1.4

= about 6,500 lbs of force on one panel at 100 mph winds.

I went through that fast, so it might be botched, but I think its about right. I realize that the fencing being corrugated instead of flat would change this somewhat, but to get a more accurate answer we'd probably have to actually measure the dimensions of the corrugations.

 

9216 lbf You should use the coefficent of 2 instead of 1.4. The wall would be considered a long flat plate. Also the the force added by the corrugations would be minimual because of the angles.

 

I figured the corrugations wouldnt' really change it much. I guessed that depending whether we use the coefficient of 1.4 vs. 2 would probably depend on how well each panel was secured to its neighbor. If the connections are a very weak spot, then 1.4, and if each connection is as strong as the steel in the panel itself, then use 2.

Judging by how relatively easily the panels seperated from each other in the fall, is why I used 1.4.

 

The coefficent relates to air drag. A taller surface has more air drag. Your reasoning would apply to the panels with the ribs running horizontal after they separated not before. Also I thought about it the area of corragated section would come into play for a wind not blowing perpendicular to the wall, but the force still wouldnt exceed the answer we got from this formula because the formula assumes
the wind is perpendicular to the structure.
Also kudos to you the method you used to come up with your answer,taking a section of the wall is how this would be done in the real world.

 

Yeah, I just figured the 1.4 coefficient was for flat plates that have a height fairly close to their width, and 2.0 was for plates with a width much longer than their height. So my reasoning was that if the connections between the plates was very weak, you could almost treat each plate individuallly, because they could fall independently of each other under a particular force. So you could almost treat them each as independently standing flat plates. Assuming the connections are very weak. No?

 

No, you have to consider a section as being continuous for this calculation. Connections have no bearing on this calculation. Connection sizes are partially based off this calculation which is considered the live load. Then you add the the dead load, the weight of the components of the wall, to get the total load.
To be able withstand the truck impact, this wall was extremely overbuilt as far as strength goes. The truck hit the wall with a force of approximately 160000 lbs. This is assuming 16000 lb truck, 200 ft from where the truck leaves road, and scene occurring in real time(2.5 seconds to reach wall and 0.5 seconds deacceleration. The truck's impact doesn't appear to separate any panels which implies those connections were strong enough. I think any separation in the panel during the collapse would be the heads of the bolts or rivets pulling thru the panels.

 

You do know what leverage is, right… it’s why a crowbar can be so powerful for being so small.

First of all, it wasn’t a shack. It was an entire two story+ watch tower. Yes it was made of wood. But even wood has weight, when aided by that little thing called ‘gravity’, it comes pounding down on the wall like a giant sledgehammer.

I have a co-worker who thinks the watch tower falling was some wolves conspiracy. It showed the watch tower structure cracking in several different episodes. Anyone being observant would have known this was coming. I have no idea why people are so confused over the watch tower coming down and why this was a trojan horse.

The question is why haven’t the done due diligence inside the walls and built trenches or morgan-inspired barriers to stop zombie hoardes or slow them down. Anyone with a large vehicle could ram through those walls at any time. They had all this time to prepare. We’re supposed to suddenly believe they lost the ability to think ahead?

 

Well, he hasn't read the comic

 

Won't matter come February.... ;P Oh, I mean. What?

 

The living have always been the problem. The dead are predictable and controllable.

 

Rick's group has never had the ability to think ahead. At the prison, they never had adequate look-outs, unless you count Glenn and Maggie sleeping in the watch tower as look-outs. They didn't deal with walkers crowding together outside the fences -- neither trying to investigate why or figuring out a counter-measure before the fences were about to fall. Even after the Governor's first assault, only Michonne looked for the Governor. They were so complacent that eve Darryl shamed Michonne out of scouting for him (unfortunately). After the epidemic, Michonne and Hershel jovially took bodies outside the fence to burn, without any look-outs or precautions. And here at Alexandria, Rick is so biased and prejudiced against the Alexandrians, he can't think or think ahead even when he's trying. And yes, they were trying to reinforce the walls, but there were a lot of other things they could have -- as you suggest trenches, etc. I am really beginning to wonder if human beings are as stupid and helpless as this last season of TWD as portrayed them to be.

Big, big Kudos to Rick for his plan to get the thousands of walkers away from Alexandria -- what happened may not be his fault. But it might help matters if he quits hating on the Alexandrians and giving speeches, and focuses on what the hell to do to survive -which he used to be so incredibly good at. It also might help if Rick would start treating other non-evil human beings as human beings, like he once used to. I truly hope Spencer, or some other "lowly Alexandrian" saves Rick's butt, or his family's, so that maybe Rick will come to his senses and stop being the major loser-jerk he has become and re-focus on survival and building a good life for all living humans. [But, I don't think that is Kirkman's world view]

 

They DID deal with walkers crowding outside the fences at the prison, we were shown different groups out there spiking them thru the fence. Also in theory a few walkers outside helps the perimeter defense. Note we've never viewed them 24/7 either. But anyone who thinks the tower falling wouldn't work, doesn't know much about construction. I though, think that Rick has trust issues, rightly so, and that's where they have problems. It's hard to implement a good plan of defense against unknown attackers while working on defending them from walkers at the same time. He has been trying to delegate some authority, but the Alexandrians are sheep, so how thin do you spread the core group? Carol is watching the internal stuff and distracted with Morgan. Daryl and Abraham's group are out of communication and Glenn doesn't count right now...Michonne and Carl have a place but it's not strategy foresite.... You don't understand or like Rick's actions? You seem to forget all the crap they've been thru. He's been right about the Alexadrians being weak and they're trying to teach them but it all takes time and He doesn't have time for the dumb shit.

 

The crap they have all been through is beside the point. That was then, this now. Get PTSD and die or get over and get on with the program of leading. That's what leaders, but not losers, do. Rick started thinking he was invincible hot stuff after he bit out Joe's jugular (granted, an amazingly admirable move). Since then, he has been intolerably arrogant and short-sighted. He has made mistake upon mistake upon mistake. He's been saved from many of mistakes by the actions of others like Carol, like Michonne knocking him out when he'd gone berserk, etc.

I agree they don't have much time -- but Rick's efforts at teaching the Alexandrians are pathetic and overshadowed by his arrogant, "F-them" , "I'm Mr. Know-It-All-God "attitude. He doesn't care if any one of them dies. You can't be a leader if you're viewing half (well more than half by the numbers) of the people you are trying lead as "inferior" and not worth saving.

He should have have made Aaron one of his major side-kicks by now because Aaron is smart, courageous and pretty competent with a rifle. But he hasn't. Why not? With his present attitudes, Rick is a mediocre to rotten leader -- but I am so, so hoping that changes.

 

"That was then" is a continuous thing for them. You judge him as the almighty viewer, but he or any of them, don't have the info you do, he hasn't seen shit from any of them. Except arguing he's too violent, even his own group have backslide some, and it proves Rick right when they fail at keeping the place safe. It's not just a lack of leadership, he only has the same people he can count on, but triple the number to try and protect. He didn't want any of them to help and knew when they did they'd die. That's not his fault, they should've stayed behind the walls. Bashing the one man that got them this far is stupid, it's exactly the attitude that has gotten the few Alexandrians dead, they didn't listen to or believe in Rick, they ran and died.