General

fb (Bending Stress) for typical beam

• fb = M/S

• NDS 3.3

Applied moment for simply supported beam with uniformly distributed load

• M = wl²/8

• Handbook 4.1.7

Sx (Section modulus) for typical beam

• S = bd²/6

• NDS 3.3

fv (shear stress) for typical beam

• fv = VQ/Ib

• NDS 3.4.2

ASD Design

• Uses adjustment factors to decrease nominal strength to design strength

• Used for wood and masonry design

LRFD Design

• Uses strength reduction factors to decrease nominal strength to design strength AND uses load combinations to increase service loads to ultimate loads

• Used for concrete, steel and bridge design

Nominal strength

• Calculated strength of a material before being reduced/factored

• Letter with subscript n

Design strength

• Reduced/factored strength of a material using strength reduction factors

• Phi next to letter with subscript n

Strength Reduction and Adjustment Factors

Factors provided in each codebook to decrease calculated material capacities for factors of safety, used for both ASD and LRFD design

Service Load

• The nominal or unfactored calculated applied load on a member

Ultimate Load

• The increased/factored applied load on a member

• Letter with subscript u

Load combinations

A series of load factors found in each codebook that are dependent on loading conditions