Calculate Allowable Bending Stress for Wood
Fb - Reference design value for bending
Cd - Load duration factor
Cm - Wet service factor
Ct - Temperature factor
Ci - Incising factor
CL - Beam stability factor
Cf - Size factor
Cfu - Flat use factor
Cr - Repetitive member factor
TEF - Time effect factor
Fb'(ASD) - allowable bending stress
Fb'(LRFD) - allowable bending stress