Gamma modeling of continuous deterioration and cumulative damage in life-cycle analysis of earthquake-resistant structures

Stochastic modeling of structural deterioration at the scale of the life - cycle is the subje ct of the study . The categories of degradation phenomena considered are those two typical of structures, that is , co n- tinuous degradation of mechanical characteristics (i.e., aging ) a nd cumulative damage due to point overloads ( i.e., earthquakes ) . The wearing structural parameter is the seismic capacity expressed in terms of kinematic ductility to conventional collapse. The gamma distribution is considered to model damages produced by earthquakes and a c lose d - form approximation for structural reliabilit y assessment is obtained. Moreover, a gamma stochastic process is considered for continuous deterioration. F inally, the possible transformation of the repeated - shock effect due to earthquakes in an equivalent aging ( i.e., forward virtual age ) , leading to a close - form for the superposition of the two processes, is discussed. An e xample , referring to a simple bilinear elastic - perfectly - plastic system , illustrate s potential applicability and limitations of the approach within the performance - based earthquake e ngineering framework.