Section 5
5-195
5.31.2.4 Japanese Seismic Load
Purpose
The purpose of this command is to define and generate static
equivalent seismic loads as per Japanese specifications using a
static equivalent approach similar to those outlined by UBC.
Depending on this definition, equivalent lateral loads will be
generated in horizontal direction(s).
See Sections
1.17.2, 5.32.12 and
xamples manual
roblem no. 14
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 :
Seismic zone coefficient and parameter values are supplied by the
user through the DEFINE AIJ LOAD command.
Program calculates the natural period of building T utilizing the
following equation
T = h ( 0.02 + 0.01 α)
where,
h = height of building
α = ratio of steel part
Design spectral coefficient ( Rt ) is calculated utilizing T and Tc
as follows
R
t
= 1.0 when T < T
c
= 1 - 0.2 ( T/T
c
- 1)
2
when T
c
≤ T ≤ 2T
c
= 1.6 T
c
/ T when 2T
c
≤ T
