A two degree-of-fredom primary/secondary damped oscillator¶
We consider a two degree-of-fredom primary-secondary damped oscillator. This system is composed of a two-stage oscillator characterized by a mass, a stiffness and a damping ratio for each of the two oscillators. This system is submitted to a white-noise excitation. The limit-state function is highly nonlinear, mainly due to the interactions between the two stages of the system, and presents one failure zone.
The limit state function is defined as follows:
The natural frequency of the first oscillator is equal to:
The natural frequency of the secondary oscillator is equal to:
The average natural frequency of the system is equal to:
The average damping ratio of the system is equal to:
The mass ratio is equal to:
The tuning parameter of the system is equal to:
Eight uncertainties are considered in the system:
on the masses of the primary and secondary systems ( and ),
on the spring stiffeness of the primary and secondary oscillators ( and ),
on the damping ratios of the primary and secondary systems ( and ),
on the loading capacity of the secondary spring (),
on the intensity of the white noise excitation ().
We consider the following distribution fResponse of Two-Degree-of-Freedom Systems to White-Noise Base Excitation:
The failure probability is:
The value of is:
References¶
Der Kiureghian, A. and De Stefano, M. (1991). Efficient Algorithm for Second-Order Reliability Analysis, Journal of engineering mechanics, 117(12), 2904-2923
Dubourg, V., Sudret, B., Deheeger, F. (2013). Metamodel-based importance sampling for structural reliability analysis. Probabilistic Engineering Mechanics, 33, pp. 47–57
API documentation¶
- class Oscillator
Data class for the oscillator example.
Examples
>>> from openturns.usecases import oscillator >>> # Load the oscillator >>> osc = oscillator.Oscillator()
- Attributes:
- dimint
dim = 8, dimension of the problem
- model
SymbolicFunction
The limit state function
- muMpfloat
muMp = 1.5, mean of the mass of the primary system
- sigmaOverMuMpfloat
sigmaOverMuMp = 0.1, coefficient of variation of the mass of the primary system
- distributionMp
LogNormal
distribution of the mass of the primary system distributionMp = ot.LogNormalMuSigmaOverMu(muMp, sigmaOverMuMp).getDistribution()
- muMsfloat
muMs = 0.01, mean of the mass of the primary system
- sigmaOverMuMsfloat
sigmaOverMuMs = 0.1, coefficient of variation of the mass of the primary system
- distributionMs
LogNormal
distribution of the mass of the secondary system distributionMs = ot.LogNormalMuSigmaOverMu(muMs, sigmaOverMuMs).getDistribution()
- muKpfloat
muKp = 1, mean of the spring stiffness of the primary system
- sigmaOverMuKpfloat
sigmaOverMuKp = 0.2, coefficient of variation of the spring stiffness of the primary system
- distributionKp
LogNormal
distribution of the spring stiffness of the primary system distributionKp = ot.LogNormalMuSigmaOverMu(muKp, sigmaOverMuKp).getDistribution()
- muKsfloat
muKs = 0.01, mean of the spring stiffness of the secondary system
- sigmaOverMuKsfloat
sigmaOverMuKs = 0.2, coefficient of variation of the spring stiffness of the secondary system
- distributionKs
LogNormal
distribution of the spring stiffness of the secondary system distributionKs = ot.LogNormalMuSigmaOverMu(muKs, sigmaOverMuKs).getDistribution()
- muZetapfloat
muZetap = 0.05, mean of the damping ratio of the primary system
- sigmaOverMuZetapfloat
sigmaOverMuZetap = 0.4, coefficient of variation of the damping ratio of the primary system
- distributionZetap
LogNormal
distribution of the damping ratio of the primary system distributionZetap = ot.LogNormalMuSigmaOverMu(muZetap, sigmaOverMuZetap).getDistribution()
- muZetasfloat
muZetas = 0.02, mean of the damping ratio of the secondary system
- sigmaOverMuZetasfloat
sigmaOverMuZetas = 0.5, coefficient of variation of the damping ratio of the secondary system
- distributionZetas
LogNormal
distribution of the damping ratio of the secondary system distributionZetas = ot.LogNormalMuSigmaOverMu(muZetas, sigmaOverMuZetas).getDistribution()
- muFsfloat
muFs = 27.5, mean of the loading capacity of the secondary spring
- sigmaOverFsfloat
sigmaOverFs = 0.1, coefficient of variation of the loading capacity of the secondary spring
- distributionFs
LogNormal
distribution of the loading capacity of the secondary spring distributionFs = ot.LogNormalMuSigmaOverMu(muFs, sigmaOverFs).getDistribution()
- muS0float
muS0 = 100, mean of the intensity of the white noise
- sigmaOverS0float
sigmaOverS0 = 0.1, coefficient of variation of the intensity of the white noise
- distributionS0
LogNormal
distribution of the intensity of the white noise distributionS0 = ot.LogNormalMuSigmaOverMu(muS0, sigmaOverS0).getDistribution()
- distribution
JointDistribution
The joint distribution of the input parameters
Examples based on this use case¶
Using the FORM - SORM algorithms on a nonlinear function