Fixing of Crane Runway Girder to Concrete Corbel

[sybie99]

Good Day All,

I am designing multiple concrete structures which will house large lifting cranes, up to 20tonne lifting capacity.

I have searched far and wide but cannot find an example of a typical connection between the steel beam and the concrete corbel. I intend to bolt the bottom flange of the beam to the corbel (cast in bolts). Is it necessary to fix the top flange of the crane runway girder to the concrete column? If this is needed it may be problematic as we cannot cast bolts to the side of the column, so will have to post fix which is problematic as when drilling we could hit the rebar.

Has anyone done such a detail, how did you approach it.

Thanks!

 

[JAE]

Most of the crane beam systems that you see in various publications show a steel beam sitting on a craneway column next to a building column (dual column system with the columns laced together).

For your case with a concrete column and a corbel under the beam, I think the detail would be very similar at the beam area.

Yes, the beam top flanges need to be tied back to the column to take out the lateral forces from the crane. But the tie-backs must also allow rotation of the crane way beam ends.

See AISC's Industrial Building Design Guide 7: AISC Design Guide 7 link

 

[ToadJones]

I have worked on some runways like this (never designed a new)

Watch where you bolt the bottom flange of the runway girder to the corbel. Usually the corbel is rather wide compared to a typical steel column. If this is the case and say 12" of the girder bears on the corbel and you bolt the girder say 2" from the end, you'll get prying on the anchors as the girder end rotates. I have seen very loose bolts like this on cranes as small as 5 ton with short spans. You'll need to minimize the effects of the girder end rotation on the anchors. One way is to install a steel bearing pad on the corbel such that the bearing area of the bottom flange of the girder on the corbel is minimized.

You will obviously need to have girder tie-backs on the top flange. If you cannot drill the column, try to come up with something that will encompass the column (wrap around it) to attach the tie backs to. Seems drastic, but from my experience, post installed anchors don't fair well under cyclic loading.

 

[rowingengineer]

Yes top flange must be connected. don't understand why you cannot get a anchor into the column at this point, just needs to be nailed to the form work before it is used as part of the walls.

I would suggest a channel seat or rail clips on castin anchors cast for your connection, these things need to be very straight and cast in anchors bolted to the flange are never located properly.


How could you do anything so vicious? It was easy my dear, don't forget I spent two years as a building contractor. - Priscilla Presley & Ricardo Montalban

 

[PlugginAway]

You can use a hot-rolled steel slotted anchor channel cast in the concrete (precast or c.i.p.)in both the top surface of the corbel, transverse to the length of the steel beam. Also, cast a piece in the column surface that faces the top flange at the elevation of the top of flange. For the bottom, use HS T-Bolts that lock into the anchor channel on either side of the bottom flange and come up through holes in the steel flange for bolt down. The channel provides transverse adjustment for the steel beam. Also, you don't have to worry about bolts being cast in the corbel at exactly the right location and the shipping damage that may occur if they aren't protected properly. The same applies for the upper channel. I would embed it in the side that faces the steel beam, centered and parallel with the top flange. Parallel orientation will give you adjustability along the length of the beam to hit your bolt-up location. You could embed the slotted channel vertical to accommodate shimming of the beam if needed, usually more of an issue with c.i.p. columns. Design a steel brace that uses a top flange thru-bolt to grab the brace at the beam end and an end plate at the other end of the brace. This allows a HS T-bolt, locked into the anchor channel, to bolt the other end of the brace to the column. Proper design will provide the rotational restraint you need. If top edge of beam is close enough to face of column (depends on crane manufacturer)you may be able to just use an angle bolted to the face of the column and the underneath top of steel beam flange. These type of precast or c.i.p. concrete columns are usually at least 12"x12" for the loads you're carrying. The slotted anchor channels should not be longer than 8" and centered in the column and corbel to give the minimum 2" edge clearance required for embed pullout development strength. The slotted anchor channels for this application are specialty anchors so they generally do not come under the ACI 318 Appendix D requirements but will generally require full calculation package backup. Do not use cold rolled slotted anchor channel for this application due to the high loads and the potential for localized corrosion. Use yhe hot-rolled slotted anchor channel. Wish you the best with it.

 

[hokie66]

Agree with ToadJones about not bearing on the whole length of the corbel. Use bearing pads to keep the load away from the edges and prevent prying.

The top flange brace is essential, but as others have said, it needs to be flexible parallel to the beam. Instead of casting in bolts, I would cast in ferrules. Post installed anchors are not the way to go.

 

[sybie99]

Thanks for all the very useful replies,

I have one further question. Or should I say two. The crane rail girder is 6 x 5.2m spans. Now would you rather have continuous beams or 6 x simply supported beams? I would think that the longest beam that can be safely transported to this site is about 16m. If it is continuous and I use channels as suggested in some of the replies to fix the beam to the corbel, the bottom flange may move laterally nder compression, causing buckling. Is it not therefore better to have simply supported sections?

Secondly, seeing that the rail is a total of 31.2m long, thermal expansion and contraction could be an issue. How would you deal with this issue. Also with regards to the rail that fixes to the top flange of the girder and which I assume must be continuous?

 

[spats]

Continuous crane beams are generally not a good idea. There is little cost savings, and the constant stress reversals cause fatigue problems. Also, a continuous beam greatly complicates the process if they ever have to replace or reinforce the runway beams. If you insist on doing it, don't go more than two span.

And as indicated above, fatique is a major issue when designing crane beams and their connections, and cannot be overlooked.