Formulation of workshop conclusions: Session No. I use of finite element analysis in safety assessments; Session No. 2 concrete containment structures under accident loads; Session No. 3 concrete structures under extreme environmental load; Conclusions and Recommendations

This document gives the conclusions (summary and key observations) of each three sessions of the workshop related to the finite element analysis of degraded concrete structures. Conclusions of the first session (the use of finite element analysis in safety assessments) were the following: Finite Element Methods are widely used to meet regulatory requirements for assurance of structural safety; the computer programs selected, the assumptions made, the model refinements, and the accuracy of numerical results are the responsibility of the structural analyst; in general, regulatory bodies provide very little formal guidance for the use of Finite Element Methods; the burden of ensuring adequacy resides with the licensee; regulatory review is on a case-by-case basis; the level of review varies from cursory assessment of the analysis documentation to independent confirmatory analysis, depending on the perceived level of uncertainty in the accuracy of the results and the safety significance of the analysis conclusions. Conclusions of the second session (concrete containment structures under accident loads) were the following: a number of non-linear FE modeling techniques have been presented which can be used to predict the response of concrete containment structures under accident loads; some scatter and uncertainty in the results have been identified which should be improved; with few exceptions, analysis of initially degraded concrete containments has not been adequately investigated; there is very limited experimental data on degraded concrete structures to permit confirmation / benchmarking of the non-linear FE analytical methods. Conclusions of the third session (concrete structures under extreme environmental load) were the following: the modeling of unique non-linearities of concrete structures and the application / improvement of non-linear FE analysis to degraded RC structures were the main themes of this session; the use of discrete crack models was emphasized in two papers to properly account for the degraded condition of concrete structures; the test results for the shear transfer in cracked RC panels are very useful to develop / refine such crack models for degraded structures; the application of non-linear FE analysis to degraded concrete structures is considered to be a relatively new research subject; several new ideas were presented in the papers in this area, including the modeling of bond-slippage relationships, use of discrete crack models, and modeling of degradation conditions in terms of non-linear hysteresis rules; overall, the papers reflected some recent advances in the state-of-the-art of the nonlinear FE analysis on degraded concrete structures