AISC Appendix 3 Fatigue Design
AISC Appendix 3 Fatigue Design
(OP)
In equation A-3-1, is there a "typical" or rule of thumb regarding the value of N, the number of stress range fluctuations, for an industrial crane runway and its connections?
I have no idea how many lifts/day the Owner may make with his 5 ton crane. I searched the threads and the Internet for some guidance and should have started here first. I'm looking for a range of use for a "light" industrial operation.
I have no idea how many lifts/day the Owner may make with his 5 ton crane. I searched the threads and the Internet for some guidance and should have started here first. I'm looking for a range of use for a "light" industrial operation.






RE: AISC Appendix 3 Fatigue Design
RE: AISC Appendix 3 Fatigue Design
RE: AISC Appendix 3 Fatigue Design
First, am I correct in assuming that one cycle is a lift (up & down)?
Secondly, let's say the crane makes 2 lifts/hr in a 10 hour day, 365 days/yr over a 30 year life span for the crane and runway. That equates to 219,000 cycles over the useful life for the value of N. Is that reasonable? For (6) lifts/hr under the same conditions gives a value for N of 657,000 cycles. When plugged into AISC Eq. A-3-1 give 39 and 57 respectively, which is greater than Fth = 7 from Table A3-1. Therefore, fatigue can be ignored – right?
Are these values of N reasonable in light of standard practice?
RE: AISC Appendix 3 Fatigue Design
39 and 57 are greater than Fth, therefore you MUST consider fatigue. You have it backwards.
I don't know if your N values are reasonable or not. Perhaps someone else can chime in on what values are typically used.
RE: AISC Appendix 3 Fatigue Design
RE: AISC Appendix 3 Fatigue Design
http://www
may be helpful - have to buy it.
Also - from an AISC conference proceedings in 2000:
National Steel Construction Conference Proceedings, 2000, Las Vegas. "New Fatigue Provisions for the Design of Crane Runway Girders," Fisher, J.M. and Van de Pas, J.P.
This is available from the AISC website (free to members and non-members can purchase)
RE: AISC Appendix 3 Fatigue Design
You don't have to count every lift, because not all lifts are at full rated load/full stress range. Also, with a standard work year being 2080 hours, at 8 hours per day, works out to be the equivalent of 260 work days per year. you don't have to use 365 days, unless that is the actual case.
AISC fatigue provisions have changed since the 9th Edition. The attached reference is the latest info I have.
RE: AISC Appendix 3 Fatigue Design
RE: AISC Appendix 3 Fatigue Design
Spats: Thanks! I used the 365 days because that is what is in the AISC Eq. A-3-1, however I like your formulation better, it seems more realistic.
Thanks to all who replied.
RE: AISC Appendix 3 Fatigue Design