Tool 19 · AASHTO MBE Art. 6A.4 (LRFR)

Load Rating Factor

Design-load rating at Strength I: RF = (φ_cφ_sφ·R_n − 1.25·DC − 1.50·DW) / (γ_LL·g·LL_HL-93+IM), with γ_LL = 1.75 (inventory) and 1.35 (operating), and the MBE floor φ_cφ_s ≥ 0.85. Feed per-lane demand from the HL-93 tool and g from the DF tool — the links carry the numbers.

Capacity & factors

M_n (nominal)kN·m

V_n (nominal)kN

φ flexure—

φ shear—

φ_c condition—

φ_s system—

Demand · per girder DC/DW, per lane LL

M_DCkN·m

V_DCkN

M_DWkN·m

V_DWkN

M_LL+IM per lanekN·m

V_LL+IM per lanekN

g momentlanes/girder

g shearlanes/girder

DC, DW are per-girder effects at the section being rated. LL+IM is the per-lane HL-93 envelope value; g converts it to per-girder.

Rating factors · Strength I

RF ≥ 1.0 at inventory means the member carries HL-93 with full design-level reliability indefinitely; RF ≥ 1.0 at operating only means the load can pass but service life is consumed faster. Legal and permit ratings, distribution for the rated case, and section-loss surveys are outside this preliminary check. Indicative values only — not a substitute for a rating engineer's evaluation.