PSI - Issue 1

Fernando Teixeira et al. / Procedia Structural Integrity 1 (2016) 181–188 Author name / Structural Integrity Procedia 00 (2016) 000 – 000

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These concepts were developed by Freudenthal in the 50s The formulations and functions involved were difficult to solve, so reliability analysis of the practical applications were only possible with the pioneering work of Cornell and Lind in the late '60s and early '70s. From the 70s different projects were developed by various researchers with respect to structural reliability applied in the design phase as well as evaluation of existing structures and the development of methods for optimizing these analyzes. In terms related to evaluating the structural reliability of existing structures, Diamantidis (1987) examines, in a general way on the implementation of probabilistic methods in the assessment of the structural reliability of existing structures with the application of the FORM method ("First Order Reliability Method" ) in offshore structures. Vanhazebrouck (2008) proposed a method based on the concepts of structural reliability and application of the FORM method ("First Order Reliability Method"), to evaluate the residual strength of pipeline defects caused by corrosion. Amaral (2011) also carried a review of corroded metal ducts, observing the evolution over time of the security index for various operating conditions. Câmara (2011) used the concepts of structural reliability to support the process of defining inspections on ships structures subject to fatigue and corrosion. Carvajalino (2013) evaluated the probability of failure of natural gas pipelines and oil for different events that occur in the life of a structure. Soares (2013) determined the reliability of a rectangular steel plate subjected to compressive stress with non uniform corrosive wear on its surface and its evolution over the time. In terms of structural reliability as a support tool to the decision-making process, Gomes (2013) proposes an optimization of risks in random processes of corrosion and fatigue through strategies for inspection and maintenance. In several works, there are initiatives for the assessment of existing structures by means of structural reliability concepts. These concepts are used to support the decision making process regarding inspections and maintenance policies. However, an objective and systematic approach to the use of the parameters generated by the analysis of structural reliability for application in operations for the maintenance engineering still requires further development. Thus, the intention of this work is to contribute to the decision making process, for possible interventions in an asset or structure, through a methodology for assessing the safety level and probability of failure through structural reliability. A concept to this methodology will be developed. This concept will be given the name of PCBM (Probabilistic Condition Based Maintenance) as an extension of the existing concept of CBM (Condition Based Maintenance) where the own safety index and the probability of failure becomes the monitoring variable. By monitoring the evolution of safety parameters and probability of failure over time, the ideal time for a intervention can be established, as well as changes in the operational aspects to the asset back to an acceptable level of safety. Nomenclature f P Probability of failure ( ) G U Failure function  Reliability index N Number of cycles R  Ultimate stress

max  Maximum stress min  Minimum stress ( ) f U Probability density function CPM Cycles per minute COV Coefficient of variation