Which cap plate is preferred for a crane column to runway?

[dlclarkii]

A cap plate with four bolts on the outside of the column OR a cap plate with (4) bolts on the inside of the column?

In other words, a cap plate wider than the column with two bolts on each side of the outside of the column OR a cap plate same width as the column with the four bolts on this inside of the column?

Are there any references stating which is correct? I've always detailed cap plates with the bolts on the outside of the column but was recently asked to detail the cap plate with the bolts on the inside.

And speaking of cranes, web stiffeners. If you have a two span runway (40' OAL) with an intermediate column (at 20'). Is the web stiffener requirements to be checked on the overall length of the runway beam (40') or only the length between columns (20')? Assuming the runway beams are not braced at the top flange. The columns are actually braced instead. I'm not sure if the web is unbraced for 20' or 40'?

Thanks,

 

[jimstructures]

Is the connection you are dealing with a pinned connection or a fixed connection?

If pinned then bolts on the inside. If fixed then at least bolts on the outside of the column flange. Clearly there must be enough bolts to make the connection work, in other words you can't overload any of the bolts.

Continuous crane beams, i.e. two span or more may increase fatigue issues. Aren't the web stiffeners used to support the point loads from the crane wheels or the point loads at the crane beam supports? How heavy is the crane you are designing for?

Finally, I have never seen a crane beam that was not tied back to the column/braced at the column. Again How heavy is this crane load and how many wheels do the end-trucks have on them?

Sorry one more question. A sketch showing the crane layout and loads would be very helpful in answering any of your questions.

Jim

 

[hokie66]

I disagree with some of what jimstructures has said. In general, all runway beam to column connections are considered pinned. If it is quite a light duty crane where fatigue is not a consideration, you can put the bolts inside. If it is a heavier duty crane, bolts inside and subject to prying would likely eventually cause problems. The bolts are best placed outside the column flanges so that the flanges flex as the beam rotates, and the bolts are not placed in tension.

I agree with him about two span runway beams, and have never designed other than single span runways.

 

[dlclarkii]

Thanks for the input. As I figured bolts on the inside of the column is more of a prying issue than anything. Connection is pinned. If it's fixed then I typically do 8 bolts; four on the outside and four on the inside.

The capacities are low; 10T and under. Typ is 5T or 3T. Class C. I agree two-spans aren't ideal but sometimes it's necessary when building columns are 40' to 50' centers and you have to drop a column in the middle to break up the runway beam span otherwise it becomes a very large beam at 40' (W16x67 vs W21x132). The web is fine for wheel loads, typically two wheel end trucks. It's web stiffeners at the supports, especially on these long span runway beams. Not sure if the web stiffener requirements should be checked for the overall length (40') or the length between columns (20'). A lot of times end users don't like crane runways braced to the building columns so a diagonal tubes is used a kicker brace against the column to the slab.

 

[dlclarkii]

I don't know how to edit my post; but I'm checking web stiffener requirements based on beam rxn's and not wheel loads. Not sure what the unbraced length is for a two-span beam if the top flange is not braced at all. Do the center column act as a brace? I'm guessing no and looking for an answer. Thanks

 

[jayrod12]

You would need to design and detail it like a cantilever column which is tough to do at the base but not impossible. Otherwise you would need to brace the top of the column.

Although for the reaction calculation in the vertical direction I don't see how that is affected by unbraced length.

 

[jimstructures]

hokie66: I wasn't trying to recommend either solution. I was trying to draw the OP into telling us what they are doing. It sounds like he has a freestanding craneway system that he doesn't want to tie to the existing building columns. I feel he has not described his problem in enough detail to make a suggestion. Maybe he might need to think about truss bracing the top flange of the crane beam if he cant brace it to the supporting column which he seems to be saying he doesn't want to do. I would also like to know if he/she has a cap channel on the top flange. although again 3 to 5 Tons is very light.

Jim

 

[FLCraneBuilder]

1. Agreed that bolts can be interior or exterior to col flange - if interior keep them close to flange to avoid Prying
2. 100% Disagree on avoiding continuous beams - we've done literally 1000's of them. This has never been a problem - but I note that we keep vertical deflections low... Often L/800 or better. Similarly, we keep lateral deflections Low - L/600 or better. the l/600 & 400 published by AISC & AIST can at times yield beams that Move around a bit to much for owners "perception"... plus deflection yields more fatigue at connections... which is where crane runway failures almost always occur. Note: we do go to NON-continuous beams for class E & above cranes - but have had great success for even fairly heavy Class D cranes.
3. Example of the reducing deflection for free.. Go to W24 x 131 in place of the 21x132 you mentioned... much better vertical - very similar lateral. Plus the W21 family you mentioned has a premium price at the mills
3. Web stiffs at col are rarely need on the Light systems you mentioned. As the thread noted, It is calced using the axial col load
4. If I understand what you were saying about what I call knee braces (diagonal kickers from col to underside of RY beam) - its a bad design - don't do it ... better to have diagonal strut down to foundation. We've been successful with 1 every 125 to 150' of ry length. (depending on loads and foundation capability of course)Customers at times don't like these - but then they don't like there systems swaying either.
5. When using the W16 x 67 column to break up a long runway bay span, insure the anchors & foundations are capable of withstanding the lateral loads (which by the way are lower when using the shorter bay span)