On reliability assessment of existing structures

This contribution discusses the reliability assessment of existing structures emphasizing on developments within or initiated by the JCSS. After a bibliographical review, the principles of reliability updating, i.e. Bayesian updating of random variables and updating of event probabilities are summarized. Developments in standards and established verification formats—partial factor or load and resistance factor, reliability-based, and risk-informed—are briefly presented and discussed. The impact of JCSS work in recent standards such as ISO 13822, the draft Eurocode prEN1990-2, and the fib Model Code 2020 as well as in national standards is highlighted. Criteria for defining target reliabilities for existing structures including human safety and optimization are critically reviewed. Obstacles for a wider implementation of reliability-based and risk-informed methods in practice are identified and conclusions for future developments are drawn. Finally, Annex A illustrates updating procedures for resistance variables and Annex B presents a case study.