Development of Structural Monitoring and Inspection on Baysian Reliability Analysis

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In the present investigation, the applicability of structural monitoring and inspection on Baysian reliability analysis are discussed. The main results are summarized as follows ;(1) Life of structures which are subject to fatigue failures involves high degree of uncertainty and risk. In order to design such systems it is necessary to take into account several stochastic elements. As the structure ages, the relationship among initial cost, inspections, maintenance and reliability level becomes important, and it has to be studied in order to achieve a good design from the costeffectiveness point of view. This paper analyzes this relationship and proposes a method to take the best decision among a set of alternatives structural regarding structural dimensions using a new class of Baysian loss functions that are based on the concepts of under and over design.(2) Two type of fatigue monitoring methods are experimentally examined for metal structures ; fatigue crack detection and fatigue life prediction.As the detection method, five kinds of crack sensors, i.e., conductive film-sensor, conductive-paint sensor, plastic optical-fiber sensor, glass optical-fiber sensor and carbon-fiber sensor are made on an experimental basis. The sensors are bonded on the surface of a welded joint model and a compact specimen by adhesives or painting, and performances of each sensor are examined through the fatigue tests.As the prediction method, a fatigue coupon indicator of adhesive-type is developed. The main body of the coupon is a center cracked thin plate with 60mm-long, 10mm-width and 0.25mm-thickness, madefrom mild steel. The middle part in length of the plate is coated by Teflon film and the whole is sandwiched in between two thin epoxy resin plates. The coupon is bonded on a smooth specimen by adhesives, and the performance is investigated by pulsating tension and fully reversed fatigue tests.(3) We try to investigate on possibility of strain measurement by optical fiber.