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symbolic vs pro

SYSREL Sample "Crash": Program Handling

The Logical Model is simply the intersection of the 3 failure domains;
also displayed is the context sensitive help

The failure functions in the State Function window together with the Stochastic Model

For better readability the failure functions for the Symbolic Processor are repeated here

FLIM(1){Conditional failure event of column}=
     1 - kappa*Mass*Stiffnes*
         (Speed0^2-2.*Decelera*Dist/SIN(Phi*PI/180)) / (Fc*Fc)

FLIM(2){Condition of braking before hit}=
                     2.*Decelera*Dist/SIN(Phi*PI/180)-Speed0^2

FLIM(3)(auxiliary limit for event probabilities)=
                   Uaux - ICPHI(t*n*lamda*b/SIN(Phi*PI/180))

Note the special formulation for the first failure function which numerically is much more convenient than the direct formulation. It avoids not only negative roots but is also well scaled in that the second term is a number around unity.

In the third failure function ICPHI = (the inverse of the standard normal integral) is one of the many built-in functions of the Symbolic Processor.

This example is numerically a somewhat tricky one. It requires a large number of function calls and a careful setting of algorithmic constants. The second event, of course, never should become active.