Andrewstructure
Structural
I am working on adding a column on a crane runway beam at mid-span. Anyone have experience with this so I know what to look out for?
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Adding columns at mid span of crane girder
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Andrewstructure
Structural
Under a top running girder, column bearing on slab on grade.
Short span (25-30 ft), class D crane, 10 ton capacity.
Short span (25-30 ft), class D crane, 10 ton capacity.
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Andrewstructure
Structural
Yes, increased capacity is desired. It is possible that each side gets a column, but at some locations the client wants to keep the bay open and reinforce the runway with web plates.
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Andrewstructure
Structural
"Class D, mill building Spec, AIST Tech Report 13? "
Yep.
Yep.
What you'll wind up with is continuous girders which have been known to have fatigue issues. But this seems like a pretty light crane.
You'll of course have to do all the regular analysis as if the beam were continuous.
Placing the columns on the SOG seems like it might not work.
Also, you'll almost certainly want to put stiffeners in the girder web over the new columns. Stiffeners at supports are usually full depth. Intermediate stiffeners are usually terminated some distance from the tension flange due to fatigue.
You'll of course have to do all the regular analysis as if the beam were continuous.
Placing the columns on the SOG seems like it might not work.
Also, you'll almost certainly want to put stiffeners in the girder web over the new columns. Stiffeners at supports are usually full depth. Intermediate stiffeners are usually terminated some distance from the tension flange due to fatigue.
Column on a SOG doesn't sound good. Check the slab. Verify that it is at least 8" thick (per ACI footing minimum). Check for shear (punching, two way) and for "footing" flexure.
Also - the subgrade under the slab may not be appropriate for the applied loads and you may have some settlement issues under the column.
Agree with the above about continuity over the column and a need to check for fatigue issues there. Also watch out for bracing required at the column/beam connection to avoid rotation and properly take out the lateral forces on the system.
Also - the subgrade under the slab may not be appropriate for the applied loads and you may have some settlement issues under the column.
Agree with the above about continuity over the column and a need to check for fatigue issues there. Also watch out for bracing required at the column/beam connection to avoid rotation and properly take out the lateral forces on the system.
Agree 100% with the last 3 posts.
Settlement or heave of the slab on ground will cause big issues with the crane - this is definately something you should steer them away from - provide proper footings.
One solution to some of the abovementioned issues would be to fix the base of the column to an appropriate footing and design it as a cantilever column.
Settlement or heave of the slab on ground will cause big issues with the crane - this is definately something you should steer them away from - provide proper footings.
One solution to some of the abovementioned issues would be to fix the base of the column to an appropriate footing and design it as a cantilever column.
paddingtongreen
Structural
Another consideration is the degree of fixity to the girder, I would minimize it myself.
I would want to weld, or bolt tight, the column to the girder before grouting the base with non shrink grout or, if that is too much trouble for a couple of columns, dry pack.
I haven't tried this, never had the necessity, but I have wondered about using an upside down king truss on the bottom of a beam that needed reinforcing. I know that some people have used wire rope and a center strut for this.
Michael.
Timing has a lot to do with the outcome of a rain dance.
I would want to weld, or bolt tight, the column to the girder before grouting the base with non shrink grout or, if that is too much trouble for a couple of columns, dry pack.
I haven't tried this, never had the necessity, but I have wondered about using an upside down king truss on the bottom of a beam that needed reinforcing. I know that some people have used wire rope and a center strut for this.
Michael.
Timing has a lot to do with the outcome of a rain dance.
Agree with the fatigue issue. Once used 2-span crane girders for a new facility thinking we were saving both steel and erection costs.
Eight years later started having numerous end span connection failures with bolts, that could see tension when the crane was in the opposite bay, suffering fatigue failures.
Revised all of those connections and now at an additional 10 years in I expect to hear about fatige problems at any time.
Dr. Fisher discusses the pros and cons of simple span vs continuous crane runway girders in AISC's Design Guide No. 7. He recommends against continuous girders whereever fatigue needs to be considered.
gjc
Eight years later started having numerous end span connection failures with bolts, that could see tension when the crane was in the opposite bay, suffering fatigue failures.
Revised all of those connections and now at an additional 10 years in I expect to hear about fatige problems at any time.
Dr. Fisher discusses the pros and cons of simple span vs continuous crane runway girders in AISC's Design Guide No. 7. He recommends against continuous girders whereever fatigue needs to be considered.
gjc
I was going to mention, as mtu1972 has so aptly stated, that by adding mid-span columns the existing connections of the girder to column or girder to bracket may now experience tension or uplift forces that they were not prior to the new columns and most likely were not designed for.
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