2. Example

In this example, the analysis time is 10 s, and a step load is applied during the first second. The structure is fixed by means of an ebc (essential boundary condition) while the load is applied by means of a nbc (natural boundary condition), e.g. a pressure load. The Rayleigh damping coefficients have been calculated from a free-vibration analysis.

(duration=10.)
case 1
  analysis                   dynamic_linear
  stage                      2 sfactor (duration)
end

stage 2
  ebc            1
  nbc            1 sfunction 't<1?1:0'
  step_size      (0.001*duration)
  rayleigh_alpha +6.4e-02
  rayleigh_beta  +9.0e-06
end

adir
  case 1
end

The analysis time of 10 s is realized by having two case; case 1 references stage 2 (multiple stages are possible) of duration 10. The step load is realized with the expression 't<1?1:0', which means that for t (the analysis time, going from 0 to 10) smaller than 1, the load is applied.