Time Effect Factor λ (LRFD Only)

 

Strength ↓ as Load Duration ↑

 

λ tied to specific load combination and 10-minute load duration

ASCE 7 LRFD Load Combination λ
1 1.4(D + F) 0.6
-- 1.2(D + F + T) + 1.6(H) + 0.5(Lr or S or R) 0.6
2 1.2(D + F + T) + 1.6(L + H) + 0.5(Lr or S or R) 0.7 when L is from storage
0.8 when L is from occupancy
1.25 when L is from impact
3 1.2D + 1.6(Lr or S or R) + (L or 0.8W) 0.8
4 1.2D + 1.6W + L + 0.5(Lr or S or R) 1.0
5 1.2D + 1.0E + L + 0.2S 1.0
6 0.9D + 1.6 W + 1.6 H 1.0
7 0.9D + 1.0E + 1.6 H 1.0

consistent reliability for various durations

format conversion factor KF adjusts reference design values to 10-minute duration

λ similar to resistance factor Φ