AISC W-shape designation (e.g. 'W21X50', 'W14X22', 'W30X116'). Must match the designation format in the steel-shapes reference table. Use AISC Steel Construction Manual Table 1-1 for available shapes.

ASTM steel grade for Fy and Fu. Available grades: A36 (Fy=36 ksi), A572-50 (Fy=50 ksi), A992 (Fy=50 ksi, standard for W-shapes), A913-50, A913-65 (Fy=65 ksi). If omitted, defaults to A992.

Simply-supported beam span length in feet. Used for moment, shear, and deflection calculations. Also used as unbraced length Lb if unbraced_length_ft is not specified. Typical: 15-45 ft for floor beams, 30-60 ft for roof beams.

Laterally unbraced length Lb in feet for lateral-torsional buckling check per AISC F2. If omitted, defaults to the full span. Bracing from metal deck, slab, or discrete braces reduces Lb and increases flexural capacity.

Lateral-torsional buckling modification factor per AISC F1. Accounts for moment gradient along the unbraced length. Cb=1.0 is conservative (uniform moment). Typical: 1.14 for uniform load, 1.32 for midspan point load. Must not exceed ~3.0. If omitted, defaults to 1.0 (conservative uniform moment assumption).

Loading configuration on the simply-supported beam. 'uniform' = uniformly distributed load (specify total_load_klf). 'point_center' = single concentrated load at midspan. 'point_third_points' = two equal concentrated loads at third points. If omitted, defaults to uniform.

Total uniformly distributed load in kips per linear foot (factored LRFD load). Includes dead load, live load, and self-weight. Typical: 0.5-3.0 klf for floor beams, 0.1-0.5 klf for roof beams. Only required when load_type is 'uniform'.

Concentrated point load in kips (factored LRFD load). Only required when load_type is 'point_center' or 'point_third_points'.

Fraction of total load that is dead load (0 to 1). Used to estimate live load deflection for the L/360 serviceability check. Typical: 0.3-0.5 for composite floor beams, 0.2-0.4 for roof beams. If omitted, defaults to 0.4.

LRFD resistance factor for flexure per AISC 360-22 Section F1. Standard value is 0.90. Do not change unless using ASD (Omega_b = 1.67) with a custom wrapper. If omitted, defaults to 0.90.

LRFD resistance factor for shear per AISC 360-22 Section G1. Standard value is 1.00 for most rolled W-shapes with h/tw <= 2.24*sqrt(E/Fy). Use 0.90 for other cases. If omitted, defaults to 1.00.