The vertical impact load is 25% of an individual unit
load. Vertical impact loads equivalent to the unit load
factored by 1.25 should be used in the design of individual
beams and connectors.
11.3 METHODS OF STRUCTURAL ANALYSIS
11.3.1 Upright Frames
The RMI Speci®cation (Ref. 11.1) states that computations
for safe loads, stresses, de¯ections, and the like shall be
made in accordance with conventional methods of struc-
tural design as speci®ed in the latest edition of the AISI
Speci®cation for cold-formed steel components and struc-
tural systems and the latest edition of the AISC Speci®ca-
tion for hot-rolled steel components and systems except as
modi®ed or supplemented by the RMI Speci®cation. Where
adequate methods of design calculations are not available,
designs shall be based on test results.
In the ®rst-order method of analysis, the structure is
analyzed in its undeformed con®guration. The ®rst-order
bending moments are ampli®ed within the beam-column
interaction equations (see Section 8.2), using the buckling
load of the frame based on the appropriate effective
lengths. In the case of down-aisle stability, a value of
K
x
L
x
=L of 1.7 is suggested if a rational buckling analysis
is not performed. However, it is recommended that the
value of effective length be determined accurately, account-
ing for the joint ¯exibility and the restraint provided at the
column bases. Detailed equations are included in the
Commentary to the RMI Speci®cation in Section 6.3.1.1
(racks not braced against side sway) for the determination
of the G
A
and G
B
factors when calculating the effective
lengths using the AISI Speci®cation. Example 11.6 demon-
strates these calculations.
The in¯uence of the joint ¯exibility is best determined
experimentally using the portal test described in Section
Chapter 11
358