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Study of Existing Sensors for the Diagnosis of Common Damages in Jacket Offshore Platforms

Khozein, Hossein | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42864 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Golafshani, Ali Akbar
  7. Abstract:
  8. Offshore platforms are the most important and enormous wealth of each country that these structures are in situation thatthelikelihoodof damageinhigh. With considering this pointthatplatformsaresubjected to oscillatinglateralloads, so the occurrenceand growth offatigue crack sinthe misvery common. These cracks are always seen in jacket connections, cause these connections are bearing large forces and have massive welding and the presence ofresidualstresses. The fatigue crack caused negligible change in stiffness of connections and in consequence insignificant change in stiffness of structure; So for this reason, they are difficult to detect in global methods. Fiber optic sensors and piezoelectric transducer are of the most widely used sensors in civil engineering structures and in components of aerospace engineering. Fiber optic sensors are the most accurate and the cheapest sensors for measuring strain and other structural properties. Piezoelectric transducers in wave propagation methods have sensors role and actuator too. One of the important structural health monitoring methods are wave propagation methods that they have capability of detection such small damage that couldn’t detected in global method because of their negligible effect on properties of structure. Wave propagation methods are different in terms of kind of structure, wave and damage that would be detected. importance of these methods lie in the fact that the fatigue cracks caused a brittle and catastrophic failure in structure. In this contribution members and connections of jacket structure with damage has been simulated in finite element package and damages has been detected by propagating of lamb wave in model. Lamb wave is one of the most widely used and the most sensitive wave for detecting of cracks and damages in metal shells. Since the ratio of thickness to diameter of jacket members is low, they can be considering as shell structure.
  9. Keywords:
  10. Lamb Wave ; Piezoelectric Transducers ; Fatigue Crack ; Finite Element Simulation ; Structural Health Monitoring ; Wave Propagation ; Jacket Connections

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