Explain the ASME code equation for shaft design under combined loading.

The ASME code considers combined bending and torsion with shock factors. The equivalent torque Te = sqrt((Km x M)^2 + (Kt x T)^2), where M is bending moment, T is torque, Km is bending shock factor (1.5-2.0), and Kt is torsion shock factor (1.0-1.5). Shaft diameter d = (16Te / (pi x tau_allowable))^(1/3). For fluctuating loads, fatigue factors are applied. This ensures shaft withstands combined stresses with adequate safety margin.