TpaRAF
Structural
- Oct 22, 2002
- 59
I am designing a 3-span continuous, reinforced concrete flat slab bridge using LRFD methods. The fatigue loads do not seem to be influencing the design! What is your experience on this?
In my past experience with LFD / AWS slab design methods, the flexural reinforcing, then the fatigue reinf and finally the minimum reinf determined the locations where the reinforcing steel could be terminated.
In this LRFD design, the minimum reinforcing requirements [AASHTO §5.10.8.2] exceed that required for fatigue! This just doesn't "feel" right, but I can't spot where I have gone astray.
I determined the fatigue envelope two ways -- using the difference between the LRFD + and - fatigue truck load cases, and using the differene between the + and - LL service envelopes. While the service range provided larger forces, it did not exceed that required for minimum reinforcing. The required fatigue steel is about 60% of the required minimum steel (= 0.35in^2/ft).
Has this been your experience with LRFD concrete design?
Thanks for your help! RAF
In my past experience with LFD / AWS slab design methods, the flexural reinforcing, then the fatigue reinf and finally the minimum reinf determined the locations where the reinforcing steel could be terminated.
In this LRFD design, the minimum reinforcing requirements [AASHTO §5.10.8.2] exceed that required for fatigue! This just doesn't "feel" right, but I can't spot where I have gone astray.
I determined the fatigue envelope two ways -- using the difference between the LRFD + and - fatigue truck load cases, and using the differene between the + and - LL service envelopes. While the service range provided larger forces, it did not exceed that required for minimum reinforcing. The required fatigue steel is about 60% of the required minimum steel (= 0.35in^2/ft).
Has this been your experience with LRFD concrete design?
Thanks for your help! RAF
