Section Factor

Section factor Am/V for unprotected steel members

The section factor Am/V for unprotected steel members can be determined for two situations in SCIA Engineer. Either the steel member is:

- Exposed to fire on all sides

Am/V = (perimeter) / (cross-section area)

- Exposed to fire on three sides

Am/V = (perimeter - width of the covered flange) / (cross-section area)

Section factor Ap/V for protected steel members

The section factor Ap/V for protected steel members can be determined for four situations in SCIA Engineer. Either the steel member is:

- Exposed to fire on all sides with hollow encasement

Ap/V = (2b + 2h) / (cross-section area)

- Exposed to fire on all sides with contour encasement

Ap/V = (perimeter) / (cross-section area)

- Exposed to fire on three sides with hollow encasement

Ap/V = (2h + b) / (cross-section area)

- Exposed to fire on three sides with contour encasement

Ap/V = (perimeter - width of the covered flange) / (cross-section area)

Supported cross-sections for three sided fire exposure

The following cross-section types are supported for fire exposure on three sides:

• Doubly symmetric I-sections (formcode 1)
• Rectangular Hollow Sections (formcode 2)
• Channel sections (formcode 5)
• Asymmetric I-sections (formcode 101)
• Slimfloor beams (formcode 153)
• Integrated floor beams (formcode 154+155)
• Top hat beams (formcode 156)