Load Bearing
Created | Updated Mar 19, 2003
This entry is not complete!
I thought I would make my first contribution to the H2G2 on the exciting world of load distribution. I am one of those people that think sarcasm is a valid substitute for wit - just thought I would warn you before I carry on. Once I have mastered the art of GuideML I'll come back and tidy this up.
This is where you will need to start if you want to work out if the floor will hold the large piece of equipment you are going to place on it.
Let's discuss the units.
We are going to be using the following SI base and derived units (See A471476 for units of measurements):
The kilogram, kg (little k little g), which is the unit of mass
The metre, m (little m), the unit of length
The second, s (little s), the unit of time
The newton, N (big N), the unit of force, measured in kgms^-2
I'll briefly explain the kgms^-2 bit here.
Longhand Newtons are kg x m x 1/s^2, ^ means raised to the power, i.e. 2^2 is two squared. For those that maths is not your strongest point the s^-2 mean 1 divided by seconds squared.
From a practical point of view - combined with the metres - it gives s^-2, metres per second per second, or acceleration. With the kilograms it gives kilogram metres (don't get confused with kilograms per metre) per second per second.
1 kilogram under the influence of the earth's gravity at sea level will exert a force of 1kg x 9.81ms^-2. 9.81ms^-2 is a useful figure to know, this is the acceleration due to gravity at sea level in a vacuum. For practical purposes this can be though of as 10ms^-2. The effects of air resistance and experimental error make an accuracy of two decimal places pointless.
Now that I've got you interested I'm going to bore you a bit here. Under no circumstances am I to be held responsible for collapsing buildings. If you are stupid enough to do something that big from reading an entry on the Internet then I cannot be held responsible. However if you do use this information and something goes horribly wrong please tell me - I am never one to turn down a good laugh.
Right, back to the plot.
UDLs and Point Loads
For the purposes of simplicity I will not cover point loads and load deflection in this entry. All loads are assumed to be uniformly distributed - UDL uniform distributed load.
Building Regulations
In the City of London the building regulations state the load on the floor must not exceed 3.5kN per m^2. Little k in front of the big N for Newtons means kilo or 1000. So the load on the floor must not be greater than 3500N per square metre. This does not mean that you can put a four tonne fire-safe in the middle of a floor and leave the rest unoccupied, it is not an 'on average' measurement.
If your building was built within the last 15 years you should be able to find out what the maximum loading is by contacting the architect and/or the structural engineers.
Test Scenario
You need to put a new server in the comms room of your London office.
The building regs state that the load imposed on the floor must not exceed 3.5kNm^-2.
The server weighs 550kg and covers an area of 1m^2.
The loading on the raised floor must not exceed 5kNm^-2.
The loading on the concrete slab must not exceed 8kNm^-2
As you must comply to the building regs - these are available from Her Majesty’s Stationary Office http://www.hmso.gov.uk. I wonder is HRH steals as many pens from her stationary cupboard as I do from my departments? Getting back to it. As you must comply to the building regs and the test case is in the CoL the maximum load is 3.5kN.
Ok we have the following:
The acceleration due to gravity is 9.81ms^-2
The unit weighs 550kg
The unit covers and area of 1m
So we have metres per second per second, metres and kilos.
We want to end up with Newtons which are kgms^-2.
The imposed load is 550kg x (9.81ms^-2 / 1m)
Giving us: ~5.5kN.
This is too high for both the raised floor and the building regs.
We have three choices here:
1) Tell them they can't have their server. This looks like the easiest option but then they'll tell you they've already bought it and it sitting in the basement waiting to be commissioned.
2) Ignore the building regulations. Again this looks like fun but the nice people at the CoL have the power to shut down your building and take custody of your first born son.
3) Spread the load.
Option 3 is the only one I can say any more about so I'll ramble on about that one.
Load spreading
The usual MO here is to cut a hole in, or remove the raised floor. This will mean that you will mount directly on the slab beneath. This is good for two reasons
Here's a few handy (HA!) facts and figures:
Excuse the formatting - see note on GuideML
Material Unit Weights (kN/m^3)
Bleach, in barrels 5.02
Concrete, breeze 15.09
Potatoes, piled 7.07
Water, fresh 9.81
Water, sea 10.05
For those of you who are paying attention: How much does one litre of fresh water weigh?
Floor type Max. Loading (kN/m^2)
Links:
http://www.bau.tugraz.at/ibb/hartl/3Dconcrete.html
I thought I would make my first contribution to the H2G2 on the exciting world of load distribution. I am one of those people that think sarcasm is a valid substitute for wit - just thought I would warn you before I carry on. Once I have mastered the art of GuideML I'll come back and tidy this up.
This is where you will need to start if you want to work out if the floor will hold the large piece of equipment you are going to place on it.
Let's discuss the units.
We are going to be using the following SI base and derived units (See A471476 for units of measurements):
The kilogram, kg (little k little g), which is the unit of mass
The metre, m (little m), the unit of length
The second, s (little s), the unit of time
The newton, N (big N), the unit of force, measured in kgms^-2
I'll briefly explain the kgms^-2 bit here.
Longhand Newtons are kg x m x 1/s^2, ^ means raised to the power, i.e. 2^2 is two squared. For those that maths is not your strongest point the s^-2 mean 1 divided by seconds squared.
From a practical point of view - combined with the metres - it gives s^-2, metres per second per second, or acceleration. With the kilograms it gives kilogram metres (don't get confused with kilograms per metre) per second per second.
1 kilogram under the influence of the earth's gravity at sea level will exert a force of 1kg x 9.81ms^-2. 9.81ms^-2 is a useful figure to know, this is the acceleration due to gravity at sea level in a vacuum. For practical purposes this can be though of as 10ms^-2. The effects of air resistance and experimental error make an accuracy of two decimal places pointless.
Now that I've got you interested I'm going to bore you a bit here. Under no circumstances am I to be held responsible for collapsing buildings. If you are stupid enough to do something that big from reading an entry on the Internet then I cannot be held responsible. However if you do use this information and something goes horribly wrong please tell me - I am never one to turn down a good laugh.
Right, back to the plot.
UDLs and Point Loads
For the purposes of simplicity I will not cover point loads and load deflection in this entry. All loads are assumed to be uniformly distributed - UDL uniform distributed load.
Building Regulations
In the City of London the building regulations state the load on the floor must not exceed 3.5kN per m^2. Little k in front of the big N for Newtons means kilo or 1000. So the load on the floor must not be greater than 3500N per square metre. This does not mean that you can put a four tonne fire-safe in the middle of a floor and leave the rest unoccupied, it is not an 'on average' measurement.
If your building was built within the last 15 years you should be able to find out what the maximum loading is by contacting the architect and/or the structural engineers.
Test Scenario
You need to put a new server in the comms room of your London office.
The building regs state that the load imposed on the floor must not exceed 3.5kNm^-2.
The server weighs 550kg and covers an area of 1m^2.
The loading on the raised floor must not exceed 5kNm^-2.
The loading on the concrete slab must not exceed 8kNm^-2
As you must comply to the building regs - these are available from Her Majesty’s Stationary Office http://www.hmso.gov.uk. I wonder is HRH steals as many pens from her stationary cupboard as I do from my departments? Getting back to it. As you must comply to the building regs and the test case is in the CoL the maximum load is 3.5kN.
Ok we have the following:
The acceleration due to gravity is 9.81ms^-2
The unit weighs 550kg
The unit covers and area of 1m
So we have metres per second per second, metres and kilos.
We want to end up with Newtons which are kgms^-2.
The imposed load is 550kg x (9.81ms^-2 / 1m)
Giving us: ~5.5kN.
This is too high for both the raised floor and the building regs.
We have three choices here:
1) Tell them they can't have their server. This looks like the easiest option but then they'll tell you they've already bought it and it sitting in the basement waiting to be commissioned.
2) Ignore the building regulations. Again this looks like fun but the nice people at the CoL have the power to shut down your building and take custody of your first born son.
3) Spread the load.
Option 3 is the only one I can say any more about so I'll ramble on about that one.
Load spreading
The usual MO here is to cut a hole in, or remove the raised floor. This will mean that you will mount directly on the slab beneath. This is good for two reasons
Here's a few handy (HA!) facts and figures:
Excuse the formatting - see note on GuideML
Material Unit Weights (kN/m^3)
Bleach, in barrels 5.02
Concrete, breeze 15.09
Potatoes, piled 7.07
Water, fresh 9.81
Water, sea 10.05
For those of you who are paying attention: How much does one litre of fresh water weigh?
Floor type Max. Loading (kN/m^2)
Links:
http://www.bau.tugraz.at/ibb/hartl/3Dconcrete.html
