Load case combinations for fire resistance calculations

With regard to the fire resistance calculations there are certain limitations and assumptions concerning load case combinations.

Fire resistance – detailing provisions

For Type of calculation = "Input by user" and "Automatic" all types of load cases/combinations/ classes can be used.

For Type of calculation = "from temp. curves" an accidental combination must be created:

• EN-ULS Accidental – Psi1,

• EN-ULS Accidental – Psi2.

Simplified method

This type of calculation is supported only for accidental combinations:

• EN-ULS Accidental – Psi1,

• EN-ULS Accidental – Psi2.

Remarks

• For detailing provisions (Type of calculation = "from temp. curves") and for simplified calculation (check response and check capacity) only accidental combinations (EN-ULS Accidental – Psi1 and EN-ULS Accidental – Psi2 can be used,

• Temperature curves can be defined only in a load case with action type = "accidental".

• A load case with action type = "accidental" in an accidental combinations is in all linear combinations that will be generated from these accidental combinations.

• Only one load case with action type = "accidental" can be in one accidental combination.

• If an accidental combination without load case with action type = "accidental" appears in checks of fire resistance, the Document will contain an error message.

Advanced calculation

• Only nonlinear combinations are supported.

• There is a combo box Fire type in the dialog for the definition of a nonlinear combination:

• • prefire,

  • during fire,

  • post fire.

• For this calculation new types of nonlinear combinations have to be generated

• • Prefire,

  • During fire ,

  • Post fire.

• These nonlinear combinations are available only if functionalities Fire resistance (of concrete) and Physical non-linearity for reinforced concrete are turned on in the Project data dialogue.

• If type of combination = "prefire" and a nonlinear combination contains a load case of type "Temperature distribution curves", then such a load case is ignored in the calculation.

• If type of combination = "post fire" and a nonlinear combination contains a load case of type "Temperature distribution curves" , then such a load case is ignored in the calculation.

• If type of combination = "during fire" and a nonlinear combination does not contain a load case of type "Temperature distribution curves", then a warning is issued that: "The nonlinear combination does not contain load case of type "Temperature distribution curves"".

• If type of combination = "during fire" and a nonlinear combination contains more than one load case of type "Temperature distribution curves" , then a warning is issued that: "The nonlinear combination contains several load cases of type "Temperature distribution curves"".