huangyhg

lateral bracing for crane bays
in an industrial building, i have three building columns with brackets attached to each flange to support crane beams for lightly loaded 5-ton cranes running parallel each side of the column. the longitudinal loads are small, about 2 kips, but regardless, i need to provide bracing between the columns to resist the longitudinal crane forces.
i would typically run x-bracing from column web to web. unfortunately, there is a 12" cmu infill wall between the building columns and separating the parallel running cranes. i want to avoid imparting any lateral load to the masonry.
if the crane beams sat on their own columns instead of brackets, i could run x-bracing in the plane of the crane runway beam, but for such a lightly loaded crane this is inefficient (and prohibitive since the building is unfortunately already in construction)
my only solution thus far is to run a horizontal portal beam between the building columns at the elevation of the crane runway beam and design it to also carry the masonry above.
does anyone have any other ideas of how to include bracing for this condition?
hello enigma2,
it would be preferable to tie the 12" masonry wall securely to the crane columns. in that way, the wall provides all the longitudinal bracing you need and cross bracing may be omitted. use bond beams in the wall at, say 8'-0" centers. provide holes in the column webs so that the bond beams can be tied together through the columns.
lateral crane forces should be primarily carried by the crane columns. if you are worried about lateral forces on the wall, use enough reinforcement to control excessive cracking.
best regards,
ba
since you do not want to use the cmu as a shear wall, can you create a portal frame using whatever
using the cmu wall as a shear wall isn't really an option, because it is a non-load bearing wall with a slip connection at the head, so it doesn't connect to the roof diaphragm.
my new thought is to beef up the building columns enough to have capacity for bending and torsion imparted from crane forces and skip additional bracing altogether...
i like your first idea of using portal bracing. this may require reinforcing the columns in that direction, as they may not have enough capacity in their weak direction.
you say this bracing is to resist the crane longitudinal force, but what resists the lateral building loading? as these are building columns with brackets rather than separate crane columns, wouldn't the same bracing which works for the building work for the crane?
put a girt on top of the wall and design it as a shearwall. what is the problem with that? why is the wall so thick what is the height of wall? what is the spacing between columns?
beefing up the building columns to sustain all of the crane loads sounds to me like an extremely inefficient solution to the problem, but without some idea of the geometry, it is difficult to provide a valid alternative. i think that you really must provide a little more detail.

best regards,
ba
enigma2,
another option is to provide cross bracing on each flange of the column, one each side of the wall. two braced bays may be enough, one near each end of the crane beam.

best regards,
ba
the building columns are w14's and the spacing between columns is either 27-30 feet. the story height is also 27 feet.
the cmu wall is 12" thick and the architect and owner agreed to move it so it is centered with respect to the columns. i was pleasantly surprised to see the columns columns along this gridline are already oversized, because they needed a 10" flange, so there's additional capacity to account for the added torsion due to longitudinal crane forces. so, i'm off the hook in this plane.
so i'm left with one more row of crane columns where the inside face of the 12" cmu wall aligns with the column centerline.
i don't have building columns here, and the contractor has limited what i can do with respect to the foundation, so i'm introducing what boils down to some wind columns that bolt to the underside of the roof framing above.
i've thought about bracing at the flanges as baretired suggests, but only one flange is available.

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