Fatigue Limit Calculation of Mechanical Couplers

[cgseso]

Currently, I am involved in the design of a bridge. We are utilizing mechanical couplers in lieu of lap splicing. We are just following the code prescribed guide that the tensile strength developed by the mechanical coupler should be at least 1.25 x Yield Strength of the reinforcing bar it joins. At first, but all of a sudden, our client is insisting that we show calculations proving that the mechanical coupler can last up to x million load cycles. As I have read in NCHRP 10-35, there is no analytical method/ calculation available for this. Would like to know if you have previous experience like this and how did you get away with the consultant's request. Or if there is already an analytical method to solve this or more detailed guidelines available.. sharing the said info will highly be appreciated. Thanks!

 

[dhengr]

Cgseso:
If the manufacturer of the coupling hasn’t done this fatigue limit testing, it probably hasn’t been done. And, that’s that. Otherwise, the job ain’t worth it to sell a few couplers They are already designed and built to take 1.25 times the bar strength and that test data is assumed to be available. They have been used for years with very few, if any, failures. And, that’s really all that can be said. With all else going on around them, it is not as simple as a test of the bare bar and coupling. And, that has to be the way you sell them. Was this requirement in the original spec, or is it a change order or extra? If the client wants to pay for the fatigue testing go for it. . Sometimes clients want the moon, but aren’t willing to pay for two bits worth of common sense and engineering logic and experience.