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STAAD Commands and Input Instructions
Section 5
5-218
Program calculates the natural period of building T utilizing clause
4.2.4 of RPA 99.
Design spectral coefficient (D) is calculated utilizing T as,
sec 3.0 T when,(3/T) . /3)(T . 2.5
sec 3.0 T T when,/T)(T . 2.5
T T 0 when,η 2.5D
5/32/3
2
2
2/3
2
2
>η=
≤<η=
≤
≤
=
where
η
= factor of damping adjustment ………….. Eq. 4.3
T
2
= specific period ………………………….Table 4.7
Total lateral seismic load, V is distributed by the program among
different levels.
There are 2 stages of command specification for generating lateral
loads. This is the first stage and is activated through the DEFINE
RPA LOAD command.
General Format
DEFINE RPA LOAD
A f1 rpa-spec
SELFWEIGHT
JOINT WEIGHT
Joint-list
WEIGHT w
(See section 5.31.2.2 for complete weight input definition)