A question for the ENGINEERS!

[Jeff Lebowski]

DH, where do we send our invoices?

Ha. Like either of you have a PE license.

[FN Phat]

I am removed from my structural courses (and don't work as a structural), so this is basically from memory. Also, in your first paragraph you indicate a '200 lb force' but in the second you indicate '200 lb per square inch' you need to specify which you really mean.

Hypothetically, if a 201 lb person lifted themselves up on the rail on the palms of their hands, they are exerting a >200 lb downward (gravity) force on the rail, but only 200 lb/(whatever they square inch surface area of their palms is).

I am guessing that OSHA is using a point load, so the 200 lbs. Assuming this, an outward 200 lb would take person heavier than 200 lbs and depend on the angle of the force.

Also, I am assuming that the OSHA reg is based on a static load not an impact load. I don't think that the intent of the OSHA reg is to protect people from stupid recklessness, so if a 200 lb person ran at full speed and kicked the railing at full momentum, that would generate an impact load a lot higher than 200 lb.

Generally speaking, if your occupation takes you to places with guardrails, you should assume that they always rickety and never rely on them by leaning on them etc.

In the construction world, it is a 200 lbs force. Depending on the railing material, it takes a considerable force to achieve a 2" deflection.

[Uncle Ted]

In the construction world, it is a 200 lbs force. Depending on the railing material, it takes a considerable force to achieve a 2" deflection.

Watch out... JL is policing this thread and will asking for your PE license.

[Katy Lied]

Here is a probably dumb question for an electrical engineer, or electrician, or someone who has a modicum of electrical knowledge which is more than I have:

I have a surge protected power strip with a grounded plug and it provides grounded outlets in the strip. If I plug in an appliance which has an ungrounded plug, is it still protected by the surge protector? Do I need to use a grounded plug with the power strip to get the surge protection?

TIA.

[TripletDaddy]

lets get our English majors to weigh in. Surely they used electricity for illumination while composing essays, reading literature, and intuitively obeying rules of grammar, so they should be somewhat qualified to opine here.

[wally]

Ha. Like either of you have a PE license.

I just got my license renewal letter in the mail last week! Just the PE, though. I don't have an SE.

[Dwight Schr-ute]

I just got my license renewal letter in the mail last week! Just the PE, though. I don't have an SE.

It's okay, we can vote you in!

[Dwight Schr-ute]

Dear engineers.

If you started clearing a bunch of vegetation on some land that you did not own, while still waiting to receive your land owner authorization which is being held up by the Army Corps of Engineers concern regarding the recently listed yellow-billed cuckoo and some snot nosed biologist called you out on your stupidity and brought everything to a screeching halt, how pissed off do you think you'd be?

Asking for a friend.

[Katy Lied]

The friend is in much better shape than had he waited for authorization. He probably plowed under all yellow-billed cuckoo habitat, and a few families as well. Now he just needs to remove the trace evidence.

Now back to my question:

LEV_S2000-PS.jpg

[Jeff Lebowski]

The friend is in much better shape than had he waited for authorization. He probably plowed under all yellow-billed cuckoo habitat, and a few families as well. Now he just needs to remove the trace evidence.

Now back to my question:

[ATTACH=CONFIG]5415[/ATTACH]

I googled it for you.

http://ask.metafilter.com/146615/My-...rotector-be-OK

[Dwight Schr-ute]

I googled it for you.

http://ask.metafilter.com/146615/My-...rotector-be-OK

You P.E.s always know just what to do.

[Katy Lied]

hey thanks for your efforts!

[Donuthole]

I am removed from my structural courses (and don't work as a structural), so this is basically from memory. Also, in your first paragraph you indicate a '200 lb force' but in the second you indicate '200 lb per square inch' you need to specify which you really mean.

Hypothetically, if a 201 lb person lifted themselves up on the rail on the palms of their hands, they are exerting a >200 lb downward (gravity) force on the rail, but only 200 lb/(whatever they square inch surface area of their palms is).

I am guessing that OSHA is using a point load, so the 200 lbs. Assuming this, an outward 200 lb would take person heavier than 200 lbs and depend on the angle of the force.

Also, I am assuming that the OSHA reg is based on a static load not an impact load. I don't think that the intent of the OSHA reg is to protect people from stupid recklessness, so if a 200 lb person ran at full speed and kicked the railing at full momentum, that would generate an impact load a lot higher than 200 lb.

Generally speaking, if your occupation takes you to places with guardrails, you should assume that they always rickety and never rely on them by leaning on them etc.

Sorry, I posted my question yesterday and then was out of the office and without internet access for most of the afternoon. Yeah, scratch the PSI thing. That was me, not OSHA. Here is exactly what the applicable OSHA reg states:

Guardrail systems shall be capable of withstanding, without failure, a force of at least 200 pounds (890 N) applied within 2 inches (5.1 cm) of the top edge, in any outward or downward direction, at any point along the top edge.

The guardrail in question was temporary, as it was installed on a temporary walkway which was being used during some construction. After it was built, but before the walkway was put into use on the construction site, it was inspected by a 260-lb man who shook/wiggled it laterally and then leaned on it to make sure it was sturdy. So my question is, is 890N of force within a reasonable range of application for someone his size who admittedly did not exert his entire weight into the thing, but shook it, leaned against it, both laterally and downwardly.

I'm deposing an expert for the other side, and have a line of questions that I would like to ask, but, depending on the answer to my question, may not be as helpful as I'd like. I do not think the expert is particularly bright, and I think I can walk him into a pretty decent trap based on some of the comments in his reports.

[Walter Sobchak]

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.

[Omaha 680]

I just got my license renewal letter in the mail last week! Just the PE, though. I don't have an SE.

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.