Bridge Crane Side Thrust
Bridge Crane Side Thrust
(OP)
I am designing some new bridge crane runways for a client. When determining the side thrust load to the columns, is that load split between each side (50%) or applied 100% to each column.
For example: Side Thrust load= 60k. Is that 30k to each side or 60k to each side.
For example: Side Thrust load= 60k. Is that 30k to each side or 60k to each side.






RE: Bridge Crane Side Thrust
RE: Bridge Crane Side Thrust
RE: Bridge Crane Side Thrust
RE: Bridge Crane Side Thrust
RE: Bridge Crane Side Thrust
Additionally, the rails are crowned.
Tapered wheels on crowned rail tend to center the trucks on a train, or the bridge on a crane. When it's done right, the flanges hardly ever touch the rail.
Mike Halloran
Pembroke Pines, FL, USA
RE: Bridge Crane Side Thrust
As above, I design for 100% each side.
RE: Bridge Crane Side Thrust
Just enough to get a CAD drawing all screwed up if you don't snap to the center of the arc.
Ask your rail supplier for a drawing, or zoom in on a section in your CAD file.
Mike Halloran
Pembroke Pines, FL, USA
RE: Bridge Crane Side Thrust
The rail I'm dealing with;
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It's also common to use 50 x 25mm Flat bar as 'rail' here for light cranes.
RE: Bridge Crane Side Thrust
RE: Bridge Crane Side Thrust
It's also amazingly heavy.
Mike Halloran
Pembroke Pines, FL, USA
RE: Bridge Crane Side Thrust
RE: Bridge Crane Side Thrust
Though you may assign 100% of the side thrust load to act at one end of the bridge (as I would) this does not necessarily mean that 100% of that load goes to one crane column.
Straight from AISE Tech. Report No. 13:
"...The recommended total side thrust shall be distributed with due regard for the lateral stiffness of the structures supporting the rails...."
If in a building with roof trusses and bottom chord bracing (or any other build for that matter) the side thrust loading will be distributed to several columns to either side of a given column, even if the crane is directly in line with one column.
This is why it is important to design bottom chord bracing in such structures properly.
RE: Bridge Crane Side Thrust
So at best, the sideways loads would be concentrated at one column or between two columns on both sides, but at the full sideways load each time. The crane is not going to "pull" equally on one rail while it pushes equally on the other rail during these acceleration times - friction neglected.
RE: Bridge Crane Side Thrust
I do not suggest, Stillerz, that one arbitrarily assumes that the lateral load is distributed. Much depends on the integrity and design of the rail-to-bridge girder connection, and the location and treatment of rail splices in relation ot eh column locaitons. A signifidcant portion of the lateral load applied to the rop of the crane rail can be imparted directly to the nearest column--at least initially, until deflection/movement in connections and bracing is terminated, both within the runway girder-to-crane/building column connection and within the buidling bracing system itself. While these loads are not usually severe or of significant magnitude, given the proper circumstances, they can be problematic.
Finally, the sidethrust load imparted by an overhead crane trolley is dependent on trolley speed, trolley and load weight, decelration/acceleration rates, and type and properties of the trolley endtruck bumpers. the lod values will reflect both normal operating conditions and "crash" values, obtained by trolley strking the endstops at full speed, with full load, closely coupled (raised). More information can be found in the Crane Manufacturers Association of America (CMAA) Specificaton No. 70.
RE: Bridge Crane Side Thrust
Do not distribute lateral thrust without looking/understand entire structure system. Often times the building columns are simply stub out from the runway columns, it is more like pinned/hinged support at just below the runway level. Furthermore, these building columns could be another 20'-30' above the runway so the highest point of the crane can clear the bottom chord with M.J. or Y.M. standing on the trolley do the dumps.
Just some noise to draw attentions.
RE: Bridge Crane Side Thrust
One could assume that the crane is lined-up directly with the column and impart the full load into that column. It would just be slightly conservative and would also be ignoring the relative stiffness of the bracing system as one function of the bottom chord bracing is to distribute the lateral loading to adjacent columns. With a proper 3-d model, this would be achieved nearly by default.
It could be the case that the overwhelming majority of the load is imparted to one column, that does not make any "arbitrary" assumption. It is not as if I suggested that you only impart 50% of the load to the column, I was merely suggesting that you follow the suggestions of a widely used and highly regarded design guide in order to achieve an efficient design. If you are doing a simple hand calculation, then you might be stuck using the full side thrust load at the column.
I work for a man who was a committee member for AISE Tech. Report 13 up thru the 1997 publication. I am not trying to name drop, just stating that I have had lengthy discussions on this very topic.
Part of the reason for load factors and allowable stresses is that we recognize that an veritable armageddon of combinations of loads is not likely to happen and should it happen, we still have not overstressed our members.