Here is how we would typically treat this situation...
For the crane column:
a) Column is assumed to be pinned at both ends (K=1). This requires
longitudinal crane bracing.
b) Lx is whole length of column
c) Ly is maximum brace spacing. (1/3 of height sounds typical)
d) Lt could be = Ly but depends on the detail of the braces, etc. and how
much rotational support it provides.
e) Don't forget to add moment into the column for eccentric loads (crane on
one side of column)
For the main frame column:
a) conservative approach is to not count on the braces providing any extra
stability to the column. I would not count on any weak axis support or
torsional support based upon the typical details used. Strong Axis could be
argued either way but I prefer to not count it since the crane column does
not have significant stiffness in its weak-axis to brace the main frame
a) typically the lateral crane loads are taken into the main frame column
through a "tie" near the top of the runway beam or cap channel. Gantrex has
proprietary ties, but many times we will use ties made from angles, etc.
AISC Design Guide #7 Industrial Buildings has good information regarding
ties... also an article by Jim Fisher was in Modern Steel Construction +-
b) auxilary crane column would be responsible for vertical loads, eccentric
moments, and any strut loads caused by the crane bracing.
A lot of times we would most likely use a 8" deep fab section as the lateral
braces. Typically these would be heavier cranes if aux. crane columns are
req'd so for Class D or E you might need to refer to AISE Tech. Report #13.
Again, the AISC Design guide is a good source.
Hope this helps,
Greg Effland, P.E.
From: Argue and Associates [mailto:bemargue(--nospam--at)sentex.net]
Sent: Tuesday, April 03, 2001 1:39 PM
Subject: Crane Column
I have a situation where a crane column is located directly below the crane
The crane column is tied intermittently to the building column in 3
spaced within the height. The building column has the flanges running
parallel to the
crane runway beam and the crane column flanges running perpendicular to the
The question I have is what is a reasonable effective length of the crane
column in either
direction? For trusses, the compression chord can be supported by the truss
but are assisted because the oppposite chord is normally in tension. In
both "chords" are in compression? If the columns brace each other, then
what would be
a reasonable horizontal force that would be imposed on each of the columns
Brian McDonald P.Eng