uEvaluation of structural integrity with partial safety factor methodv

 

We are making study of applying the partial safety factor (PSF) method that enables the rational and quantitative evaluation based on probability of failure to structural integrity evaluation. It is the purpose of our research to determine simply and rationally whether the detected defects in plants in service are acceptable or unacceptable by using partial safety factor method.

While the traditional method insure the safety of structures by multiplying the strength term by the sole safety factor, partial safety factor method multiplies both strength and load terms by multiple safety factors.

Partial safety factors are not determined uniquely for an objective reliability and depend on the variance of parameters. For this reason, we have to use appropriate factors for their variances. We focus on a crack like flaw, which is one of the most dangerous defects in plants, and analyze sensitivity of the variances of the stress, yield stress and fracture toughness to partial safety factors. Fig.1 shows the definition of the limit state function based on R-6 method, which is widely used for the assessment of crack like flaws. Fig.2 shows the calculation result. When evaluating the clack like flaw in the plastic collapse dominant region, different partial safety factors in accordance with the variance of the yield stress must be used.

 

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u       Y. MogamiCS. SakaiCT. SasakiChEvaluation of Structural Integrity with Partial Safety Factor MethodhCJSME M&M2008Ci2008j

 

 

 

Fig1. Definition of limit state function based on R-6 method

 

 

 

(a)@PSF for the stress and the crack length@(b) PSF for the fracture toughness and the yield stress

 

Fig2 Partial safety factors calculated for each variance of the yield stress