Failure Modes Available Only for Action Elements

There are two failure modes types that are available only for Action elements.

• Demand>Capacity. For this failure mode, you specify a Demand on the system (e.g., a load) and a Capacity of the system (e.g., a strength). If the demand exceeds the capacity when the action is triggered, failure occurs:
  
  
  Typically, at least one of these two inputs would be defined using a Stochastic element An element that can be used to quantitatively represent the uncertainty in a model input., which should be triggered for resampling whenever the Action element is triggered.

Note: The Capacity and Demand must be entered as dimensionless values. However, theoretically, they will typically have dimensions An output attribute for an element that defines the dimensionality (in terms of Length, Time and other fundamental dimensions) of the output.. To represent these in your models, they should be entered with units, and then cast to dimensionless values (e.g., MassLimit|kg|).

• Unreliable. For this failure mode, you specify the element's Reliability. This is a value between 0 and 1 that defines the (random) probability that it will successfully perform its action when it is triggered:
  
  

Note: The Unreliable failure mode does not actually cause the Action element to fail. Rather, it allows the user to specify the probability that an Action element's Action will be carried out successfully when it is triggered.