Will triple bunk beds cause a bedroom floor to collapse? 7

[DurableEfficientGood]

The main thing I want to know is whether heavy-duty tri-level bunk beds will overload the floor. There is currently a severe housing shortage in a not-insignificant part of the country and worldwide.

Let's say in a hypothetical (and slightly somewhat realistic) scenario that the housing shortage gets so severe that people have to sleep in any indoor dry room (including living rooms, dining rooms that are not part of the kitchen, and foyers) they can find. Since all the dry rooms have already been occupied by multiple other sleepers each, they now have to resort to having only bunk beds in all bedrooms. Of course, having that many of people in any property unit is currently illegal due to timely evacuation under current fire laws, but let's say that it's been waived for this scenario. Let's also say that none of the buildings have been reinforced for this, but meet all other codes and are maintained in great condition.

The minimum load (unknown if that means rated or design limit) for "sleeping rooms" (according to the IBC) is 30 psf. Let's say that the weight of the heavy-duty steel king-size triple bunk bed is 400 lbs (very high estimate), all 3 king-size mattresses are each 180 lbs (highest amount for commercially produced ones), and that all 3 mattress topping sets are comprehensive and are each 30 pounds (extremely high estimate). This means that the bed setup has an overall empty operating weight of 1030 pounds, which is the same as the curb weight of a 4-seater golf cart. A king size bed has dimensions of 76 inches by 80 inches.

Let's also give an aisle on one side of the bed so that people can get on without passing through other beds. Let's make the aisle have the width as that in a school bus, which is 12 inches. However, the aisle is shared between facing beds, so that the aisle width per unit cell is only half that. Assume that each bed corner support post is 2 inches by 2 inches (fairly small estimate). That gives a bedset unit cell of 86 inches by 84 inches, which is an area of 7,224 in^2 = 50.16667 sqft.

Let's say that everyone who sleeps in the bed is the heaviest person who is healthy. The tallest height for a healthy person is 6'6", the heaviest sex for any given height is male, and the heaviest weight for 6'6" is 230 pounds. That means everyone sleeping in the bed is an extremely muscular (but not insanely, because being too muscular is unhealthy) 6'6" tall male. 2 of these men are able to fit with plenty of space remaining in a queen size bed, while 3 of them cannot fit in it without one turning his body or sleeping on top. So, 3 of these men sleeping on every king-size mattress was chosen because they give the greatest density within a standard size while being able to totally fit inside. The weight of clothing and shoes are insignificant, so they will be ignored here. The total weight of all men on the bed is 2070 lbs. This gives a total system bed weight of 3100 pounds, which is the heavy-duty bed can definitely support. This means each unit cell has a night average load concentration of 61.794 psf. Let's also say that they do not have to work and genuinely enjoy sleeping with each other during free time (and they all rapidly become best friends forever within a week from that), so they spend an average of 20 hours laying in bed, 12 cumulative of them being sleep, for every calendar day including weekends and holidays.

If all dry rooms (including bedrooms) were loaded to a 20-hour average of 61.794 psf and all wet rooms loaded to a 24-hour average of 40 psf, both in every calendar day, in a well-maintained, light wooden-framed multi-storey building that was built to the minimum standard (30 psf for bedrooms and 40 psf for other dry rooms) in a location that is seismically stable, has little wind, and has little snow, will it have a not-insignificant chance (e.g., greater than one in a million chance of collapsing within any given year) by itself of causing the bedroom floors to pancake on top of each other? Will it even have a not-insignificant chance of causing the entire building to collapse? Given that it's well maintained and located in a geographically easy place, external factors such as natural disasters, water damage, erosion, and termite damage will not be a thing here. The only factor remaining will be structural. Also, this is way different from college students crowding together and dancing in a room because there are severe impact loads and significant resonance there but no impact loads here.

 

[Tomfh]

Your assumptions seem fairly pessimistic. A 1000 lb bed? Every occupant 230 lbs?

But assuming a final load of 61psf then absolutely this could potentially collapse a floor designed for 30 psf.

Could it result in progressive collapse? Seems a bit far fetched…..

 

[LittleInch]

I think the bed post will go through the floor first...

but this is all fantasy - There might be a housing shortage, but triple king size bunks of 3 big blokes per bed - come on.

you didn't mention any areas whereby they would pass by the end of the bed?

I think if you're in a situation this bad, then the floor would be the least of your worries. Food, sanitation, ventilation, cooling, heating etc are far harder to solve.

but what's with all these vague "What happens if..." posts? Is this a research project or something?
You need to come clean about why you're asking all these off the wall questions or no one will answer.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DurableEfficientGood]

@LittleInch But what happens after the post goes into the floor? Anyway, such heavy duty beds will definitely have widened bases to make the load concentration only a small fraction of what it would be otherwise because the designers know about the problems that it would cause. People pass by the end of the bed by passing into the adjacent unit cell's half-aisle. Also, how would there be problems such as food, sanitation, and HVAC? Those housing units will still have all the wet rooms unaltered and fully functional. For cooking, they would just use a huge pot for every dish during every meal (prepared for the entire day) and all eat the same food just like a restaurant, exponentially simplifying the task and making it similarly more efficient. To shower, they would just take turns on a routine schedule and take several hours between the first and the last person, maximizing the utilization rate without overloading that one. Also, since they are so close together anyway, the shower stall will be widened and each mattress-mate will shower 3 together, dividing the time in 3. When they're sleeping so close together and are such close friends anyway, they'll almost certainly sleep naked together at least ocassionally, and the 9 men within each shared bed will soon become gay and decide to call themselves a family.

 

[DurableEfficientGood]

@Tomfh Also, what if the bed were instead 200 pounds, each mattress 130 pounds, and each bedding set just 10 pounds (these are all typical values) meaning that the bed operating empty weight is 620 pounds? This gives a total loaded load at 2,690 pounds, which gives a load concentration of 53.62 psf. Will that then likely lead to a collapse or not?

 

[Tomfh]

Loading of 1x design load will not cause collapse of a properly designed and built structure.

Loads close to 2x design load could potentially cause failure. Some code compliant structures will fail by this point.

What are these questions about? What are you trying to understand.

 

[BAretired]

I'm feeling a lot of empathy for the person who has to make those beds every morning.

BA

 

[Brad805]

If designing a bldg for the beds below you need to discuss that in design phase. It will be a localized problem for sure, but averaging the load as you did does not tell you much.

 

[XR250]

Wood structures are pretty damn resilient. I doubt the hypothetical 61 psf would cause a collapse. You would have a fair bit warning regardless.

 

[IRstuff]

3 houses with Cal King waterbed at 45 lb/sf without collapse.

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[DurableEfficientGood]

But is the entire room filled with Cal King waterbeds or is it just a concentrated load in one corner? In my hypothetical scenario, the entire room is filled with king size triple bunk beds, only leaving a 1-foot aisle in between facing beds.

 

[Tomfh]

Why are you asking these questions? What are you trying to understand?

 

[DurableEfficientGood]

I'm trying to understand if all of the dry rooms in a building built to the minimum code but well-maintained are packed for sustained periods of time for all of its life with as many people as possible (who are relatively stationary, and never jump up and down, so no impact/dynamic loads or resonance) while still giving them enough room to pass each other, will it (being overloaded to 2.06 times the rated amount for the average of all bedrooms, and around 1.86 times the rated amount for the average of all floor space) have a non-negligible chance of causing the structure to fail, either shortly or prematurely over the long run?

 

[DurableEfficientGood]

In other words, I'm trying to know whether or not a light wooden-framed building in good condition, without structural defects, and having dynamic loads below 20% of that of static loads, being sustained statically overloaded to 2.06 times the rated load for all bedrooms and being sustained statically overloaded to around 1.86 times the rated load for the average among all floor space will have a greater than negligible chance of collapsing, either over the the short run of a week or over the building's design life of 30+ years.

 

[DurableEfficientGood]

In other words, I'm trying to know whether or not a light wooden-framed building in good condition, built to the minimum factor of safety allowed by the most lax manual (probably the International Residential Code) of the International Code Council, without structural defects, and having dynamic loads below 20% of that of static loads, being sustained statically overloaded to 2.06 times the rated load for all bedrooms and being sustained statically overloaded to around 1.86 times the rated load for the average among all floor space will have a greater than negligible chance of collapsing, either over the the short run of a week or over the building's design life of 30+ years.

 

[Tomfh]

will ... overloaded to 2.06 times .. have a non-negligible chance of causing the structure to fail, either shortly or prematurely over the long run?

Yes. There is a non-negligible chance.

A structure designed to code minimum has a negligible chance of collapse when loaded to its design load. Loading 2x the design load the chance of collapse is well past "negligible". More like 50/50 for a structure that has been designed to code minimum.

But why are you really asking these questions?

 

[3DDave]

"A light wooden-framed building" doesn't mean that any specific building will. They are supposed to be well enough built, but any particular one might not be.

Proof load the installation to 1.5X the expected load case you are confirming and see if anything deforms too much. Include that they might stack the rest of the room to the top with books or heavy equipment as the most typical situation will be construction workers with tools they need to keep safe.

 

[DurableEfficientGood]

Loading 2x the design load the chance of collapse is well past "negligible". More like 50/50 for a structure that has been designed to code minimum.

But I mean at 2.06 times the rated load, not at 2.06 times the design limit load. I couldn't find the minimum factor of safety that the IBC or IRC specifies for floors, so I don't know how much it is over the design limit for a minimum code building. I actually want to know how much over the design limit it is, and I mainly wanted to actually know how much over the design limit would have a non-negligible chance of causing a collapse. Asking about how much over the rated amount is way less accurate because the designer could set an arbritrarily high factor of safety. So, can anyone tell me the minimum factor of safety that the IBC and IRC separately specifies for floors, and how much over load at the upper limit of the factor of safety (design limit) that will increase the chances of causing the floor to collapse to a marginal level, say 1 in 1,000,000 in any given year that the building is structurally in great condition (so there wouldn't even be a single crack larger than a hairline in any structural component at that time, and as soon as one larger than that appears, it'll be replaced as part of standard maintenance like parts on a vehicle)?

 

[hokie66]

In what part of the world would these sleeping rooms be used?

 

[DurableEfficientGood]

They would be used in the US and Canada, just that it is a hypothetical in which the population is much larger, cellular agriculture gets perfected so everyone has plenty of food despite limited farmland, there is net zero GHG emissions, there is no crime and everyone is friendly, people are immortal, and everyone is a huge healthy, strong, and handsome white male, but everything else stays the same.