On the structural integrity assessment of elastic–plastic redundant cracked structures

Abstract

The methods currently used for the assessment of the structural integrity of cracked structures do not consider, for the evaluation of the stresses acting on the flawed sections, the singularity introduced by the presence of the cracks. The effect of this presence is more pronounced in structures constituted of ductile materials, that behave in the elastic–plastic regime, because they are able to sustain a significant crack propagation before fracture. The formulation provided by the so-called “simplified procedures for the evaluation of cracked structures” allows the designer to consider the existence of cracks in the integrity assessments. The work herein presented, which is the follow-up of a previous one that defines the methodology to be applied taking into account the crack presence [Gorrochategui I. Comportamiento en Rotura de Tuberías de Alta Tenacidad con Sustentación Hiperestática en Régimen Elastoplástico, Tesis Doctoral, Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos, Universidad de Cantabria, Diciembre 1993, Gorrochategui I, Gutiérrez-Solana F. A method for the assessment of hypersyatic cracked structures in the elastic–plastic regime, Engng Fract Mech 1998;61:519–35, Gorrochategui I, Gutiérrez-Solana F, González JJ, Varona JM. An extension of the application of elastic–plastic assessment to cracked pipework systems. Nucl Engng Des 1998;182:141–7], illustrates the way to perform this type of evaluation through the resolution of a realistic example. After a review of the currently existing “simplified procedures”, the Engineering Treatment Model (ETM) [Schwalbe K-H, Zerbst U, Kim Y-J, Brocks W, Cornec A, Heerens J, et al. The ETM Method for Assessing the Significance of Crack-Like Defects in Engineering Structures, Comprising the Versions ETM 97/1 and ETM 97/2. GKSS- Forschungszentrum Geesthacht GmbH, 1998] has been selected for this application and its selection is justified. The results of these calculations show the benefits obtained in the estimation of the maximum load bearing capacity of cracked structures if the existence of the flaws is considered.