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Section 5
5-225
Floor Weight is used if the pressure is on a region bounded by
beams, but the entity which constitutes the region, such as a slab,
is not defined as part of the structural model. It is used in the same
sort of situation in which one uses FLOOR LOADS (see section
5.32.4 of STAAD Technical Reference Manual for details of the
Floor Load inpuut).
The weights have to be input in the order shown.
Generation of NRC Load
The load so defined as above is applied on the structure in the
NRC loadcases. These loadcases have to be the first loadcases in
the input file. Built-in algorithms will automatically distribute the
base shear among appropriate levels and the roof per the relevant
code specifications.
The following general format should be used to generate loads in a
particular direction.
LOAD i
NRC LOAD {Dir}(f1)
Where Dir = The direction in which the NRC load is generated—
X,Y or Z.
i = load case number
f1 = factor to be used to multiply the NRC Load (default = 1.0).
May be negative.
Notes
1) By providing either PX or PZ or both, you may override the
period calculated by STAAD using Rayleigh method. If you do
not define PX or PZ, the period for Method 2(b) above will be
calculated by the program using Rayleigh method and the
stipulations of sentence 7(c) of section 4.1.9.1
2) Some of the items in the output for the NRC analysis are
explained below.
T
a
= Time period calculated per sentence 7(a) or 7(b) of
section 4.1.9.1