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Continuous crane girders questions

Continuous crane girders questions

Continuous crane girders questions

(OP)
I'm working on the superstructure for a new hydroelectric powerplant and we are putting in a 100 ton crane for which I am designing the runway. The superstructure is a steel stepped column moment frame with about 18 feet of space between bays. It's been about 30 years since anyone in the office has had to design a crane this large, and after reading all the literature out there (Design Guide 7, Tips for avoiding crane runway problems, AIST TR 13 etc) it seems the industry in general tends to be going towards simply supported girders. My understanding is that this is primarily being done because of fatigue concerns.

I don't foresee fatigue being an issue as the crane will rarely be in use, being utilized to haul the 90 ton runner out of the concrete substructure for maintenance only. Many other plants in our inventory that were built in the 1960s and have all utilized continuous girders with a large rocker that allows plenty of rotation. See the details (far left of the pdf) and photo below. I'm being pushed by senior engineers to go with what has worked in the past and if fatigue is the primary concern I tend to think they are right but I am open to suggestions. Also I realize that tying back the girder from the middle to the column is no longer recommended because of cracking in the girder web so I will be changing that part of the detail.

Thanks

RE: Continuous crane girders questions

IMHO, it would foolish to use a 45 to 50 year old design for this application. Much has been learn about potential problems with heavily loaded structural steel since then. Use the modern recommendations (Design Guide 7) to take advantage of the increase in knowledge.

Since you are looking for something more substantial than opinions... here is a possible one:
You and your colleagues are right that the 100 ton crane will not see to much use. However, I expect that the 100 ton crane will also have a lower capacity auxiliary hook - perhaps about 20 ton capacity. Over time, the auxiliary hook (and of course the crane runway) will get a lot more use than would be expected.

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