Benefits of non-linear structural analysis for optimising the seismic assessment and retrofitting of a CEA laboratory

Within the scope of extending the service life of a CEA nuclear facility, a seismic assessment using non-linear transient analysis was carried out between 2017 and 2019. The facility in question was built in the early sixties and was not designed to resist earthquake loads. In the early 2000s, its utilities and engineered structures were refurbished to meet the design requirements of a plausible historically maximum earthquake (PHME). About ten years later, it was decided to continue the activities in this facility beyond the duration that was initially defined following the refurbishment work completed in the early 2000s. Therefore further seismic assessments were initiated to identify any other engineered structures reinforcement required to resist an earthquake combining the effects of both a safe shutdown earthquake and a paleo-earthquake. A test campaign was carried out to collect the data needed to develop a more refined model of the behaviour of some reinforcement work completed in the 2000s to meet the PHME requirements. These new seismic assessments used non-linear transient dynamic analysis to consider the behaviour of reinforced concrete, incorporating the results of the test campaign, the possible uplift of the columns' footings, and the in-plane and out-of-plan behaviour of the masonry panels. This article describes the context of the facility subject to these seismic studies, followed by the objectives, methodology and design assumptions. It then details the modelling with respect to the characterisation test results, the implementation of these results, and the local calculations performed to both precisely define the strengthening's works needed and to demonstrate structural stability and resistance. Lastly, the programme of strengthening's works' defined on the basis of these studies is presented.