Floor loading is a badly understood issue in Data Centers. Not just in the place where the equipment eventually ends up but also en-route from the loading bay to the final resting place.
OK, so lets start looking at the problem. Most data centers have a raised floor made of specialist tiles held up on struts and a tile mounting framework pushing down on the underlying slab and fabric of the building. Each of these elements must be strong enough to withstand the weight of the equipment to be installed. In addition, the floor must be strong enough to deal with carrying it’s design weight with a number of the tiles removed for maintenance. The photograph above shows very bad practice where too many tiles have been lifted compromising the load bearing capacity of the floor.
Typically a data center floor will have a loading capability measured in Kilo Pascals (kPa) aka Kilograms per square meter (Kg/m2) or Pounds per square foot (lbs/ft2) depending on your preferred units of measure.
There are three kinds of load that we need to take into account:
- Static Load – the load a stationary object places on the floor (kg/sq m)
- Concentrated Load – The point load transferred directly to the floor from a wheel or foot support (kg/sq cm)
- Rolling or Dynamic Load – The load placed on the floor as the object is pushed through the data center into it’s final location (kg/Tile)
Discontinuities in the floor, such as the steps in the photograph above, can reduce lateral strength and impact the floor’s capability to deal with rolling loads. Perforated and vented tiles as well as damaged tiles and tiles with holes for cables (particularly on the edge of the tile rather than in the middle) are significantly weaker than complete tiles.
The table below shows the types of tiles available and their load bearing characteristics.
|Panel Type||Common Name – Construction||Tile Weight (lbs/ft2) (kg/m2)||Concentrated Load (lbs/in2) (kg/cm2)||Static Load (lbs/ft2) (kg/m2)|
|1.1″ thick steel encapsulated wood core||5.75 / 28.07||1000 / 70.31||250 / 1221|
|Steel||Type 1 – Steel top sheet welded to a formed steel bottom pan||6 / 29.29||1000 / 70.31||250 / 1221|
|Type 2||7 / 33.18||1250 / 87.88||313 / 1528|
|Type 3||8.5 / 41.5||1500 / 105.46||375 / 1831|
|Concrete Filled||Type 1 – Steel welding pan filled with lightweight cement material||9 / 43.94||1000 / 70.31||250 / 1221|
|Type 2||9.5 / 46.38||1250 / 87.88||313 / 1528|
|Type 3||10.5 / 51.27||1500 / 105.46||375 / 1831|
|Type 4||11.5 / 56.15||2000 / 140.61||500 / 2441|
|Type 5||12 / 58.59||2500 / 175.77||625 / 3052|
|Heavy Duty||2.15″ all steel construction||16.5 / 80.56||3000 / 210.92||1125 / 5493|
Struts under the floor are designed and selected to match the load carrying capacity of the floor panels. If you upgrade the floor panels you will need to look at the struts as well.
So now I understand the floor, what about the DMX-4? How can I calculate the loadings that I might experience in my data center? The fist stage is to find the technical specifications of the equipment, particularly the dimensions and weight as well as the area and number of the rollers, wheels or stands that the equipment is to be resting on. The specification for the EMC DMX-4 is here.
- There are two types of cabinet in a DMX-4, a System Bay (737.5 Kg) and a Storage Bay (1098.6 Kg).
- The area occupied by each is System Bay (0.61m x 1.045m = 0.64 m2) and Storage Bay (0.763m x 1.064m = 0.81m2).
- The static load is therefore System Bay (737.5 / 0.64 = 1158 Kg/m2) and Storage Bay (1098.6 / 0.81 = 1353.2 Kg/m2).
This shows that we really need tiles at the top end of the Static Load bearing range, Concrete, type 5 or Heavy Duty to be safe and allow for further load concentration with EMC’s next range.
What should I do if the floor is not sufficiently strong to support the loading of my equipment?
Typically the approaches are as follows:
- Rolling or Dynamic load – lay out spreader plates on the plenum floor along the route from loading bay to final location.
- Concentrated load – lay a spreader plate under the wheels or stands that the equipment is resting on so as to spread the load over a larger area of the floor. The spreader plate needs to be very stiff so as to avoid transferring the concentrated load straight through to the underlying floor – typically mild steel sheet is used. A similar approach can be used for Static load.
- Static load – increase the number and concentration of struts supporting the plenum floor and ensure that the highest load tiles (Heavy Duty) are used.
Note: If you choose to add spreader plates, take their load into consideration when doing the loading calculations.
One final point, the underlying slab needs to be strong enough to support the gross load of the entire floor, including the struts, tiles, equipment and M&E plant. If in doubt instruct a Structural Engineer or consult the initial design documents for your building.