STAAD Commands and Input Instructions
Section 5
5-192
5.31.2.3 Colombian Seismic Load
Purpose
The purpose of this command is to define and generate static
equivalent seismic loads as per Colombian 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).
Description
See Sections
1.17.2, 5.32.12 and
xamples manual
roblem no. 14
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 COLOMBIAN LOAD command.
Program calculates the natural period of building T utilizing clause
1628.2.2 of UBC 1994.
Design spectral coefficient (Sa) is calculated utilizing T as,
Sa = Aa I (1.0 + 5.0 T) when, 0 ≤ T ≤ 0.3 sec
= 2.5 Aa I when, 0.3 < T ≤ 0.48 S in sec
= 1.2 Aa S I / T when, 0.48 S < T ≤ 2.4 S in sec
= Aa I / 2 when, 2.4 S < T
where,
Aa = Seismic Risk factor (user input)
S = Soil Site Coefficient (user input)
I = Coefficient of Importance (user input)
