What is the difference between a Live or Dead Load?
A Live Load is typically a moving load. This can be vehicles on a bridge or occupants and vehicles in a building. Dead loads are (relatively permanent loads).
These are simple ways to differentiate the type of load, but why do we care?
The basic answer is, "Because the Code cares."
Why does the Code differentiate between a Live Load and a Dead Load?
There are two reasons why loads are sorted into groups:
- Different Load Combinations are described
- Different Load Factors are applied
The load combinations are standard groupings of loads that can occur simultaneously. The load factors take into account how accurately a load can be calculated.
In most Codes that use them, Live Loads have a higher load factor than Dead Loads. This is because it is easier to calculate the Dead Loads than it is to calculate the Live Loads. Especially with vehicles, you have little control over the weight of the actual vehicle.
Live Loads have more variability.
This is the only reason why there is a difference between what gets placed in the two groups. The live loads have a higher factor of safety.
What other factors apply?
Another thing to consider is that a moving load has the ability to create an additional Impact Load. If this is the case in this situation, then a separate Impact Load should be included.
What is the end result?
In the end, it may not matter which category gets assigned to the load. The main criteria will be how confident you are in the loading that will be imposed on the structure from the moving platform. If the load isn't likely to change, then you could consider it as a Dead (Permanent) Load. If it is likely to change, then be more conservative in calculating the load or apply a higher factor to it.
All codes will allow you to be more conservative if you choose to be.