ABSTRACT
ABSTRACT Buildings are major long lasting assets of the society and business enterprises and form a significant part of infrastructure management. They require continual maintenance and in many cases they can become inappropriate for their original purpose due to obsolescence and are demolished. The present contribution explores the obsolescence of buildings and in particular the definitions of obsolescence, the related influencing factors and the associated uncertainties. Thereby definitions of the obsolescence rate based on the physical and useful (service) life are clarified. The experienced useful life of buildings in Finland, Germany and North America is statistically analysed, utilizing available databases, and comparisons with the design (minimum) working life specified in standards are made. The probability of not exceeding the required minimum service life is evaluated and discussed. Whereas many factors affecting the obsolescence rate are beyond the control of civil engineers, particular attention needs to be paid to cases where the service life of the structure is determined by physical aspects related to deterioration. These cases are identified and recommendations to improve structural design are offered. The service life and the related renewal rate is influencing the risk acceptance criteria as given in ISO 2394. Such criteria are derived on the basis of economic optimization and the LQI marginal safety costs principle. A statistical model for the renewal rate is obtained and its influence on the target reliability is investigated for a representative failure limit state. The influence of the obsolescence rate is quantified and critically disputed.
