Fatigue

Owned by Becca Alford (Unlicensed)
Jun 22, 2020
2 min read

LRFD

Fatigue check is not required in LRFD under Article 5.5.3.1.

 

Standard Specification

The fatigue stress limits on reinforcement due to the repeated application of live loads are necessitated by the high reinforcement stresses resulting from Load Factor Design and the high allowable stresses for Grade 60 reinforcement in Service Load Design.  These limits have a substantial effect for culverts under low fill heights.  AASHTO Article 8.16.8.3 is followed.

 The range between a maximum and minimum stress in straight reinforcement caused by live load plus impact at service load shall not exceed:

At a section where stress is not reversed:

At a section where stress is reversed:

In many cases, with low fill heights, the area of the flexural reinforcement is increased to satisfy the fatigue serviceability requirement.

 

CHBDC

Per 7.8.10, box culverts with depths of cover less than 0.6m (23.62”) shall be checked for fatigue requirements (8.5.3.1).  Per 8.5.3.1 the stress range in straight bars shall not exceed 125 MPa.  The program applies this stress range to all bars.