Bending Moment Resistance for FIre Reduced Sections

From CLT Handbook 8, 4.1.4.1, the bending moment calculation for for fire-reduced sections is modified as follows:

Final charred layer

The depth used in the calculation of effective section modulus S_eff does not include the final partially charred layer on the exposed side if is transverse to the axis of loading.

Calculation of S_eff

The calculation of S_eff considers the change in the location of the neutral axis as follows, from CLT Handbook, chapter 8, section 4.1.4.1, equation 13:

S_eff = (EI)_eff / E ( h_f – ỹ)

where:

• h_f is the fire-reduced effective panel section depth
• ỹ is the location of the neutral axis of the fire-reduced section, as described in Effective Stiffness for Fire-reduced Sections
• EI_eff is also modified for fire design as described in Effective Stiffness for Fire-reduced Sections