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STAAD Commands and Input Instructions
Section 5
5-162
direction spring goes slack, the X and Z springs at the same joint
are made inactive as well.
The procedure for analysis of Tension-only or Compression-only
springs requires iterations for every load case and therefore may be
quite involved.
Since this command does not specify whether the spring is in the
positive or negative direction from the joint, it is assumed in
STAAD to be in the negative direction. For negative displacement
the spring is in compression and for positive the spring is in
tension.
If a CHANGE command is used (because of a change in list of
tension springs, supports, etc.), then the SET NL command must
be used to convey to STAAD that multiple analyses and multiple
structural conditions are involved.
Example
SPRING TENSION
12 17 19 TO 37 65
SPRING COMPRESSION
5 13 46 TO 53 87 KFY
Notes
1) A spring declared as TENSION only or COMPRESSION only
will carry axial forces only. It will not carry moments.
2)
The SPRING TENSION / COMPRESSION commands should
not be specified if the INACTIVE MEMBER command is
specified.
3)
Do not use Load Combination to combine these cases.
Tension/Compression cases are non-linear and should not be
linearly combined as in Load Combination. Use a primary
load case with the Repeat Load command.
4)
The following is the general sequence of commands in the
input file if the SPRING TENSION or COMPRESSION