User-Defined Load Factors are used to scale up (or down) the applied load according to design specifications. There are two ways to define Load Factors: 1) on a Design Load Case, and 2) on a specific Zone. Each factor type is taken into account. The worst load-scenario resulting from these combinations is what is Analyzed/Sized to.
Limit and Ultimate Load Factors can be defined for each subcase in a Design Load Case in the Design Load Case Form.
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Limit Factor - Applies to the mechanical portion of the load for limit margins of safety.
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Ultimate Factor - Applies to the mechanical portion of the load for ultimate margins of safety.
The Load Factors can be applied on the Zone-level and are then combined with the Design Load Case Factors for that Zone upon analysis. These factors are defined per-Zone in the Zone Settings Form under Loads>FEA Load Factors. Default Factors for an entire Database or Project can also be defined.
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Mechanical Limit - Applies to mechanical loads for limit margins of safety.
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Mechanical Ultimate - Applies to mechanical loads for ultimate margins of safety.
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Thermal Hurt/Help - Applies to thermal loads for both limit and ultimate margins of safety.
Thermal Hurt and Help Factors are applied simultaneously to both the limit and ultimate margins of safety. The worst case is returned and Analyzed/Sized to. Typically, the Thermal Hurt Factor is 1.0 and the Thermal Help Factor is 0.8.
Note
This ensures that the superimposed thermal loads will never increase the margins of safety, but the entire penalty incurred by thermal loads is fully accounted for.
This is more appropriate to use than running ETW and RTD cases independently and using the lowest MS. Because if the ETW case has the lower MS, even if thermal helps and is ignored, the ETW properties are used.