Applies To
	Product(s):	STAAD.Pro
	Version(s):	All
	Environment:	N/A
	Area:	Modeling Solutions
	Subarea:	Supports
	Original Author:	Global Technical Support

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Multi Linear Spring Support

To assign the multilinear attribute to the support which is basically a plot of displacement vs corresponding spring stiffness at that displacement. One should start with the most negative displacement and the corresponding stiffness and then go to the most positive value of displacement and its corresponding stiffness value.

The non-linear behavior of the soil (such as when its behavior in tension differs from its behavior in compression) can be modeled using multi-linear supports. Please note here that these supports presents a non-linear condition so, they will initiate an iterative analysis to be separated by the CHANGE command and PERFORM ANALYSIS command. The SET NL command must be provided to specify the total number of primary load cases and convergence check cycle.

General Format:

Support
100 Pinned
200 400 FIXED BUT KFY 40.
MultiLinear Springs
200 400 Spring -1 40 -5 50 …

Multilinear springs should not be used in the following conditions:
 
Modal dynamics
Buckling analysis
Imperfection analysis
PDELTA analysis
NONLINEAR analysis
Advanced cable analysis
Direct analysis
Models with tension/compression members and/or supports
Models with inclined supports