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Phanatic posted:Yeah, it's just odd-seeming, is all. If I'm building a raised floor for a server room and I use stuff that's rated to load limit of 1500lbs per square foot, it doesn't mean that my 1000-square-foot server room's floor can support 1.5 million pounds. There is a general 'x pounds per square foot', which is used for general loading of lighter stuff, office furniture, people, refrigerators, etc. There is also a point loading spec 'do not exceed y pounds per 10 foot span' or whatever for things like 1500 pound server racks full of UPS batteries, or machine tools. And yes, technically you could put that much crap on top of the floor.
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Jun 17, 2015 17:42
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kastein posted:Well, those are two completely different problems. I know. Which is why using psf for both of them is weird; in one, the psf is the maximum load a unit area of surface can support, in the other the psf is something you multiply by the area of the surface to find the load the entire surface has to support. Yes, given the context, people should know which is which, but from an engineering perspective using the same units of measure two mean two different things in two different situations is undesirable. It's why we like using Newtons and kilograms instead of pounds-force and pounds-mass. Methylethylaldehyde posted:And yes, technically you could put that much crap on top of the floor. Assuming you equally distribute it and don't load any of your panels greater than the load rating.
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Jun 17, 2015 17:48
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How the gently caress is it confusing? When would you need to specify the pressure rating of a balcony? It's not a goddamn submarine. The reason the unit is the same is because they have the same dimensional units And I hate English units, but pounds-force and pounds-mass are different units. lb vs. lbm. This is not a point of confusion to engineers, because they have different dimensional units Slanderer fucked around with this message at 18:14 on Jun 17, 2015 |
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Jun 17, 2015 18:11
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Slanderer posted:How the gently caress is it confusing? When would you need to specify the pressure rating of a balcony? It's not a goddamn submarine. what about a 400 lbm block of concrete
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Jun 17, 2015 18:14
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Bad Munki posted:what about a 400 lbm block of concrete My balcony isn't rated for that.
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Jun 17, 2015 18:15
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Phanatic posted:but from an engineering perspective using the same units of measure two mean two different things in two different situations is undesirable. It's why we like using Newtons and kilograms instead of pounds-force and pounds-mass. It doesn't work that way sometimes, for instance engine torque is measured in foot pounds and so is rifle round muzzle energy. Hell, if you want to play with units you can really confuse people, for instance I walk at a speed of around 3 cubits per ohm-farad. Spec stuff in the units that it makes the most sense in. In this case, 60psf or 100psf makes perfect sense. These assholes realized the sills in the house were rotten and sistered a 2x8 against them on the inside so they could put new joists in, completely hiding the rotten sills since they were behind sheathing on the outside. Thanks for making me think everything was fine, dickheads.  (that's not the worst one, which came out with a garden trowel not a prybar.)
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Jun 17, 2015 18:15
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Methylethylaldehyde posted:There is a general 'x pounds per square foot', which is used for general loading of lighter stuff, office furniture, people, refrigerators, etc. There is also a point loading spec 'do not exceed y pounds per 10 foot span' or whatever for things like 1500 pound server racks full of UPS batteries, or machine tools. I work for a manufacturing company. One of the factories had to receive a new tool/piece of equipment that was too heavy for the floor. In preparation, they reinforced the floor only in the path leading from the dock to where the tool would eventually end up. They taped off the floor on delivery day to show the safe path. Move 2 feet to the left or right, and you might punch through the floor
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Jun 17, 2015 18:38
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Stormangel posted:The difference is total load vs footprint load. Are there engineering terms used to differentiate these cases? By footprint, I believe you mean people, which would be under live load. Live load would be a load which is dynamic and not permanent. The opposite would be dead load, which is the weight of the structure and any fixed loads like a large air conditioner. But these are minimum standards and accidents like this are what cause them to be reevaluated and hopefully improved.
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Jun 17, 2015 19:51
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How does "load" relate to force, when we're discussing engineering standards? For example, if the maximum "load" of my surface is enough for three 250lb people to stand on it safely, fine, but if they all jump into the air and land, the force they're applying on landing is way more than the static 750lb load. Similarly, if I'm driving my vehicle onto a ramp, even if the ramp is (just barely) strong enough to support the whole vehicle, if I hit the ramp at speed and then stomp on the brakes, I may apply force under my front wheels far higher than the total weight of my vehicle at rest would apply. Seems to me like engineers should be more concerned about maximum applied force than static load?
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Jun 17, 2015 20:09
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Jun 17, 2015 20:18
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What is this block I keep seeing references to.
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Jun 17, 2015 20:25
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Most of the others I can excuse as temporary patch jobs and/or make-dos because of poverty, but what on Earth did the person who taped up this crack expect it would accomplish?
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Jun 17, 2015 20:32
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TooMuchAbstraction posted:
A funny picture on the internet
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Jun 17, 2015 20:35
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Presumably it was done as a joke? I hope? It is funny.
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Jun 17, 2015 20:35
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The Gardenator posted:By footprint, I believe you mean people, which would be under live load. Live load would be a load which is dynamic and not permanent. Okay, here we go. I'm a registered civil PE in California, and a structural engineer by discipline so I am familiar with the process of live and dead load evaluations. Basically, you have the dead loads, as described above, as well as live loads which are transient, not dynamic, as well as special load cases (dynamic loads like earthquake and possibly wind), and deflection limits for how much movement the structure can move. Often, in light construction, designs are stronger than needed in order to meet the deflection requirements. Cantilevers like balconies are often deflection controlled from the ones I have designed, at least. The design process goes kind of like this: 1) You estimate the dead load based on the plans and confirm the estimate bounds your as-built condition at the end. Typically it is a smeared load assumption over the surface of your balcony and maybe linear load patterns for railings. Call this D. 2) You look up the prescribed live and special load cases for your structure, in this case it was 60psf. So any combination of loads using live will assumes smeared load of 60psf across the balcony surface. However, ASCE-7, the structural engineering standard the building code adopts, advises engineers to consider that people congregate at the edge of balconies so line loads may be more appropriate. Call this L. 3) Special load cases are also quantified such as seismic, wind, and snow. These are E, W, and S. Again, typically a smeared load assumption for calculation purposes. 4) Now you create load combinations. All of them include dead loads, most include live loads. Special load cases are not concurrent and use a fraction of the live load since multiple worse cases are unlikely. It is either wind, snow, or seismic, plus dead and some or no live load. Depending on the methodolgy there are factors applied to multiply these forces. I will use load resistance factor design as an example, but allowable stress design is another valid methodology that is functionally equivalent. The maximum case here would look like this: 1.2*D+1.6*L+0.5*(live roof load, S, or rain load) So already you have 20% margin in dead, 60% in live load, and assuming rain or snow. Statistically this is huge. Then you do an analysis, by hand or computer, and the strength of components are reduced by factors based on how catastrophic a failure would be. For bending it is typically 90% strength, shear is 60-85% strength except for steel, which is 90%. You can either explicitly design the structure or, for wood especially, consult design tables which add even more conservatism. Combined, the idea is for a given structure a collapse like this has a 0.01% probability over its design lifetime. On top of all that, you check cases like 1.0*D+1.0*L and each load separately to see how much a structure deflects. Too much is unnerving or causes facade cracking and so you might add more strength in order to add more stiffness. This is not explicitly a safety consideration but it often adds margin. A note about point loads: there is some guidance but typically you have to make separate checks to design for this. Not all engineers think this part through but normally this does not end in catastrophe as much as embrassment and damage. This was shoddy construction or a massive design failure, in my opinion. The place was built at the height of the housing bubble (2006-2007) so I suspect a rush job. Leperflesh posted:How does "load" relate to force, when we're discussing engineering standards? For example, if the maximum "load" of my surface is enough for three 250lb people to stand on it safely, fine, but if they all jump into the air and land, the force they're applying on landing is way more than the static 750lb load. All loads are forces, and for cases like yours they are typically covered under load factoring. For example, machine equipment or elevators that can have sudden stops have required dynamic amplification factors for their loads. In some cases the dynamic response is explicitly calculated. AASHTO I believe has similar considerations for ramps. Blindeye fucked around with this message at 23:31 on Jun 17, 2015 |
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Jun 17, 2015 20:36
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Phone posing so no link, but I saw a report today that said the balcony was "for decorative purposes" and was pretty much explicitly never supposed to have more than one person ducking out for a quick smoke break on it.
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Jun 17, 2015 20:40
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Four times the heads, four times the power, right?TooMuchAbstraction posted:
Possibly shaming a city department/ city council into actually doing something about the issue? But probably just for comedy. ColHannibal posted:What is this block I keep seeing references to. It's a secret. We can't tell you. Sorry. 
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Jun 17, 2015 21:40
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The only thing I can tell you is that it probably isn't 400lbs.
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Jun 17, 2015 21:54
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Thanks for posting the long writeup about load and strength calculations. In rope work there's a ton of those rules of thumb built into what's considered a safe working load. Introducing a bend to nylon rope by running it over a cliff or by tying a knot reduces the strength. You see it when some cheap newbie asks an online forum "Can I rappel off 6mm accessory cord for $0.36/foot rather than 9mm rope for $1/foot? The cord is so much cheaper, lighter, and has a breaking strength of 1,200 lbs! I only weigh 1/6th of that, so I'll never need something with a breaking strength of 6,000 lbs!" But then you get it wet. Or tie a knot in it. Or run it over an edge at a 90 degree angle. Or put something on the end of it that isn't a perfectly static load (like a living human). Then whoopsie, you're dead, but at least you saved $150!
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Jun 17, 2015 21:54
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TooMuchAbstraction posted:
For the same reason as this guy:
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Jun 18, 2015 00:51
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Slanderer posted:Not really. Dry rot is just a weird outdated term for wood decay due to certain types of fungi. TooMuchAbstraction posted:
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Jun 18, 2015 02:16
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Jun 19, 2015 05:54
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 took me a second
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Jun 19, 2015 06:42
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 Good god it must take an hour to get the temperature just right.
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Jun 19, 2015 16:20
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What the hell is going on there?
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Jun 19, 2015 18:25
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Well for starters, they're using magnetic hot instead of true hot.
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Jun 19, 2015 18:28
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Arrath posted:
Hot water, cold water, bath oil, beer, and whiskey, all from the same tap. Bathtime rocks.
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Jun 19, 2015 18:42
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kid sinister posted:What the hell is going on there? It's a hotel shower.
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Jun 19, 2015 18:48
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Arrath posted:
I really hope one of those is "magic" and another "more magic." AMISH FRIED PIES fucked around with this message at 18:58 on Jun 19, 2015 |
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Jun 19, 2015 18:51
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You turn one to flush the toilet, and you turn it more to flush the toilet harder.
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Jun 19, 2015 18:57
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Arrath posted:
Maybe multiple shower heads? Or 2 for faucet... 2 for shower... and 1 for switching back and forth between faucet and shower?
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Jun 19, 2015 19:00
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My guess is it's a hotel shower, yeah. Saw one once which had separate knobs for three different horizontal streams from the front, one stream from the top, and two streams from the sides -- so six altogether. And it was a lovely shower too.
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Jun 19, 2015 19:09
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Maybe water is expensive there and it's some sort of combination lock.
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Jun 19, 2015 19:11
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TooMuchAbstraction posted:My guess is it's a hotel shower, yeah. That's pretty filthy for a hotel shower.
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Jun 19, 2015 19:13
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Motronic posted:That's pretty filthy for a hotel shower. So not a hotel, how about a motel or a holiday innnnnnnnn
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Jun 19, 2015 19:32
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Arrath posted:
Bad Munki posted:Well for starters, they're using magnetic hot instead of true hot. 
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Jun 19, 2015 19:50
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I've heard of ouija boards, but I've never seen an ouija shower before.
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Jun 19, 2015 20:23
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We had one at one house that had two for the tub, two for the shower, one to mix the water, and one to close the drain. That way you could set the temperature and leave it there, and just turn the water full on or off. Of course it was an antique when my grandparents bought the house.
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Jun 19, 2015 20:45
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The top 3 valves are symmetrical. What about the other 2?
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Jun 19, 2015 22:46
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One Legged Ninja posted:That way you could set the temperature and leave it there, and just turn the water full on or off. This is the only correct way to dispense cleaning water, and it's a goddamned shame that the practice is so rare.
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Jun 21, 2015 09:24
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