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STAAD Commands and Input Instructions
Section 5
5-182
5.31.2.1 UBC 1997 Load Definition
Purpose
This feature enables one to generate horizontal seismic loads per
the UBC 97 specifications using a static equivalent approach.
Depending on this definition, equivalent lateral loads will be
generated in horizontal direction(s).
Description
The seismic load generator can be used to generate lateral loads in
the X & Z directions for Y up or X & Y for Z up. Y up or Z up is
the vertical axis and the direction of gravity loads (See the SET Z
UP command). All vertical coordinates of the floors above the
base must be positive and the vertical axis must be perpendicular
to the floors.
Methodology
See Sections
1.17.2, 5.32.12
and
E
xample
s
manual
p
roblem no. 14
The design base shear is computed in accordance with Section
1630.2.1 of the UBC 1997 code. The primary equation, namely,
30-4, as shown below, is checked.
W
TR
IC
V
v
=
…………………. Eqn 30-4 of UBC 1997
In addition, the following equations are checked :
Equation 30-5 – The total design base shear shall not exceed
W
R
IC
V
a
5.2
=
Equation 30-6 - The total design base shear shall not be less than
IWCV
a
11.0
=