A question for the ENGINEERS!

[wally]

The guardrail in question was temporary, as it was installed on a temporary walkway which was being used during some construction.

Was the rail one of those 2x4 constructed jobs? I see those on construction sites all the time and assume that their major utility is in serving as a physical reminder of where the edge of the platform/walkway when guys bump their hips into it while working and not so much as a guardrail. I really wouldn't think that they would be OSHA compliant.

Find a 260lb man. Attach a bathroom scale to a wall at the height of the guardrail and have the man push on the scale. Record the result.

I like this. I think that the OSHA reg is rather vague. There is no practical discussion about the requirement at all. If you do Walter's suggestion, and the 260 lb man can get the needle past 200, for even an instant, who's to say that he didn't adequately test it?

I have an SE. But only in Utah . But I do also have PEs in NY/NJ/PA

[Donuthole]

Was the rail one of those 2x4 constructed jobs? I see those on construction sites all the time and assume that their major utility is in serving as a physical reminder of where the edge of the platform/walkway when guys bump their hips into it while working and not so much as a guardrail. I really wouldn't think that they would be OSHA compliant.

You are a smart man. That is a part of my expert's opinion, along with the fact that the walkway was only 12" off the ground, and thus not high enough to invoke the OSHA guardrail standard. However, it is the Plaintiff's expert who insists that any rails put up anywhere near a construction site must meet the 200-lb force requirement set forth in OSHA. There is no in between, he says.

That said, he was too lazy to re-construct a sample walkway and test the strength, and he doesn't offer any evidence that the rails would not have supported 200 lbs of force, other than the fact that the 180-lb plaintiff, carrying a 50-lb bag of salt, stumbled and fell through them.

[Jeff Lebowski]

I have an SE. But only in Utah . But I do also have PEs in NY/NJ/PA

Anyway, Wally got it right. It would be nearly impossible for a man of any size to generate a 200 lb force on a railing by pushing on it. The controlling direction of the force for sizing of the posts will be parallel to the ground (with the force applied right at the top of the post. No matter how strong someone was pushing out on the post, the amount of force he could exert parallel to the ground would be controlled by the slip of his feet against the walking surface. For rubber on concrete, you are looking at a coefficient of friction in the 0.6 range, which means a 200 lb man would max out his lateral force on the railing and his shoes would slip once he applied about 120 lb to the railing. And this is assuming 100% of his weight is on his feet, which is likely not the case when pushing against the railing. If there were a block or curb to brace your feet on, you could likely apply 200 lb, but I wouldn't want to be the one who performed that test if the post failed.

The above is for post sizing. The controlling direction for the rail sizing will depend on the cross section of the rail member. If it is doubly symmetric, hanging a known weight of 200 lb on top of the rail midway between the posts would be sufficient to demonstrate adequate strength. For the post you are better off having someone just run the numbers on the chosen post members.

WTH? For some reason I thought you were a lawyer.

[FN Phat]

You are a smart man. That is a part of my expert's opinion, along with the fact that the walkway was only 12" off the ground, and thus not high enough to invoke the OSHA guardrail standard. However, it is the Plaintiff's expert who insists that any rails put up anywhere near a construction site must meet the 200-lb force requirement set forth in OSHA. There is no in between, he says.

That said, he was too lazy to re-construct a sample walkway and test the strength, and he doesn't offer any evidence that the rails would not have supported 200 lbs of force, other than the fact that the 180-lb plaintiff, carrying a 50-lb bag of salt, stumbled and fell through them.

The handrail is required to withstand a 200-lb force or less than a 2" deflection when in place as a barrier to protect a leading edge of a fall of 6' or more. If the barrier is not protecting a leading edge of 6' or more it is not held to the same standard. It is simply a barricade and not used as a fall protection.

[Donuthole]

The handrail is required to withstand a 200-lb force or less than a 2" deflection when in place as a barrier to protect a leading edge of a fall of 6' or more. If the barrier is not protecting a leading edge of 6' or more it is not held to the same standard. It is simply a barricade and not used as a fall protection.

Or at any height if there is dangerous equipment adjacent to the runway, right? (There wasn't, btw.)

[Omaha 680]

Was the rail one of those 2x4 constructed jobs? I see those on construction sites all the time and assume that their major utility is in serving as a physical reminder of where the edge of the platform/walkway when guys bump their hips into it while working and not so much as a guardrail. I really wouldn't think that they would be OSHA compliant.

The handrail is required to withstand a 200-lb force or less than a 2" deflection when in place as a barrier to protect a leading edge of a fall of 6' or more. If the barrier is not protecting a leading edge of 6' or more it is not held to the same standard. It is simply a barricade and not used as a fall protection.

FN is correct. Anything 6' and over needs to provide the protection rated for the 200 lb force, unless there is alternate fall protection schemes such as nets or personal harnesses. So theoretically those 2x4 railings you see on bridges and other construction sites should be strong enough to resist the OSHA force. I'm sure there are frequent violations. Just like I don't always put on my fall protection harness when I'm required by OSHA regs.

WTH? For some reason I thought you were a lawyer.

Probably because of my many well reasoned arguments on the board.

You are a smart man. That is a part of my expert's opinion, along with the fact that the walkway was only 12" off the ground, and thus not high enough to invoke the OSHA guardrail standard. However, it is the Plaintiff's expert who insists that any rails put up anywhere near a construction site must meet the 200-lb force requirement set forth in OSHA. There is no in between, he says.

That said, he was too lazy to re-construct a sample walkway and test the strength, and he doesn't offer any evidence that the rails would not have supported 200 lbs of force, other than the fact that the 180-lb plaintiff, carrying a 50-lb bag of salt, stumbled and fell through them.

As FN said, the out is the height off the ground, not the flimsy construction of the barrier. If the edge had been over 6' tall and someone fell through the railing, he would have a pretty good case. Although I suppose in court it's less about the intent of the regulations and more about which side has the more convincing expert witness.

[Katy Lied]

It would be nearly impossible for a man of any size to generate a 200 lb force on a railing by pushing on it. The controlling direction of the force for sizing of the posts will be parallel to the ground (with the force applied right at the top of the post. No matter how strong someone was pushing out on the post, the amount of force he could exert parallel to the ground would be controlled by the slip of his feet against the walking surface. For rubber on concrete, you are looking at a coefficient of friction in the 0.6 range, which means a 200 lb man would max out his lateral force on the railing and his shoes would slip once he applied about 120 lb to the railing. And this is assuming 100% of his weight is on his feet, which is likely not the case when pushing against the railing. If there were a block or curb to brace your feet on, you could likely apply 200 lb, but I wouldn't want to be the one who performed that test if the post failed.

The above is for post sizing. The controlling direction for the rail sizing will depend on the cross section of the rail member. If it is doubly symmetric, hanging a known weight of 200 lb on top of the rail midway between the posts would be sufficient to demonstrate adequate strength. For the post you are better off having someone just run the numbers on the chosen post members.

This is hawt.

[Omaha 680]

This is hawt.

Yeah. I'm only an engineer because it gets chicks.

[Bo Diddley]

I have an SE. But only in Utah . But I do also have PEs in NY/NJ/PA

Anyway, Wally got it right. It would be nearly impossible for a man of any size to generate a 200 lb force on a railing by pushing on it. The controlling direction of the force for sizing of the posts will be parallel to the ground (with the force applied right at the top of the post. No matter how strong someone was pushing out on the post, the amount of force he could exert parallel to the ground would be controlled by the slip of his feet against the walking surface. For rubber on concrete, you are looking at a coefficient of friction in the 0.6 range, which means a 200 lb man would max out his lateral force on the railing and his shoes would slip once he applied about 120 lb to the railing. And this is assuming 100% of his weight is on his feet, which is likely not the case when pushing against the railing. If there were a block or curb to brace your feet on, you could likely apply 200 lb, but I wouldn't want to be the one who performed that test if the post failed.

The above is for post sizing. The controlling direction for the rail sizing will depend on the cross section of the rail member. If it is doubly symmetric, hanging a known weight of 200 lb on top of the rail midway between the posts would be sufficient to demonstrate adequate strength. For the post you are better off having someone just run the numbers on the chosen post members.

This is while he's at rest right? What if he's moving? How does speed and inertia factor into the equation?

[Omaha 680]

This is while he's at rest right? What if he's moving? How does speed and inertia factor into the equation?

I'm just talking about standing there and pushing on the railing because the question was can someone exert 200 pounds of force on the railing by pushing. As Wally mentioned, impact forces can be much higher. So if someone ran and jumped into the railing they could probably exert 200 lb of force or more. That's where acceleration would factor into the force applied. But that wouldn't be a very safe method of testing the railing.

The criteria is 200 lb to begin with because it is meant to simulate impact loads of someone falling into the railing. Most codes don't require an actual dynamic analysis to design for impact loads in simple structures. They just substitute a static analysis that has been determined to be equivalent because static analyses are much simpler.

[Harry Tic]

Probably not the right thread, but there you go.

Question, on behalf of Harry Tic Jr., for anyone that knows the engineering culture on campus at the U (he hasn't decided yet between the U, USU, and BYU): he's interested in both Materials Science (in the College of Engineering) and Metallurgical Engineering (in the College of Mines and Earth Sciences) and could go either way. A degree in either might open up the right kinds of doors for him. Talking to folks in both departments, it seems that there's a bit of rivalry between the two. Has anyone on the board had experience with either of them?

Okay, I realize that posting a question like that on a site like CS is not exactly a ringing endorsement of my intelligence. But let it never be said I lack a sense of iron-y.

[Jeff Lebowski]

Probably not the right thread, but there you go.

Question, on behalf of Harry Tic Jr., for anyone that knows the engineering culture on campus at the U (he hasn't decided yet between the U, USU, and BYU): he's interested in both Materials Science (in the College of Engineering) and Metallurgical Engineering (in the College of Mines and Earth Sciences) and could go either way. A degree in either might open up the right kinds of doors for him. Talking to folks in both departments, it seems that there's a bit of rivalry between the two. Has anyone on the board had experience with either of them?

Okay, I realize that posting a question like that on a site like CS is not exactly a ringing endorsement of my intelligence. But let it never be said I lack a sense of iron-y.

Those are fine majors, but they are both rather obscure* and specialized. If he were my son, I would encourage him to consider a degree in mechanical or chemical engineering and then a master's degree in metallurgy or materials science if the interest is still there. I think that would open up the broadest array of career opportunities.

*These degrees are only offered at a handful of schools. Utah has both programs most likely due to sponsorship from Kennecott. Neither degree is offered at BYU or USU.

[Harry Tic]

Those are fine majors, but they are both rather obscure* and specialized. If he were my son, I would encourage him to consider a degree in mechanical or chemical engineering and then a master's degree in metallurgy or materials science if the interest is still there. I think that would open up the broadest array of career opportunities.

*These degrees are only offered at a handful of schools. Utah has both programs most likely due to sponsorship from Kennecott. Neither degree is offered at BYU or USU.

Thanks, JL. ME's a definite possibility as well. Hadn't thought of saving the more specialized interest for the MS degree but that's pretty sound advice. My sense is that the Mines college at the U is flush with $$$, so that does make it pretty appealing, especially since the U is more expensive than the other options.

Good heavens, I only wish that my own interests had been half as well defined when I was still in high school. Took me years to find my way and some days I'm not sure that I'm there even now.

[wuapinmon]

Can someone explain what happens to this paper near the end?

[mtnbiker]

Can someone explain what happens to this paper near the end?

The high pressure and associated heat fused the paper. I'd guess some residual moisture in the paper had an effect as well. If you watch some of the other videos, he mentions the heat left in the things he crushes. The blue gumby at the end of this video is hilarious as it melts and flows. Watch the one where he crushes a Barbie. It makes the doll look like a drunk pole dancer as the body is smashed flat and the legs snap off.