ABSTRACT
As discussed already in previous chapters, typically the loads acting on structures vary with time. They may be increasing slowly on average, such as with the gradual increase over many years in vehicular loads on bridges, or more quickly, such as wind loads generating a dynamic structural response. In all cases, the loads are of uncertain magnitude and the actual magnitude at any point in time will be uncertain. Moreover, the structural strength may vary with time — typically, it will decrease as a result of fatigue, corrosion, or similar deterioration mechanism. How to deal with these types of situations for structural reliability estimation is the topic for this chapter.
