Reliability-based Assessment of Existing Structures Using Partial Factors and the Influence of Fractile Estimation

摘要

In contrast to the design of new structures, the assessment of existing structures often relies on the subjective judgment of the investigating engineer.However, in previous contributions the author has shown that an objective verification format for existing structures is feasible and two methods namely the Design Value Method and the Adjusted Partial Factor Method for existing structures were developed, enabling a rather simple and straightforward, but objective and coherent safety evaluation of existing concrete structures by practitioners.The proposed framework is compatible with the current Eurocodes for the design of new structures, but additionally enables to incorporate alternative values for the target reliability level, alternative values for the reference period and also updated information based on e.g.on-site inspection data and data from testing, as these all considerably influence the partial factors in the structural reliability assessment of existing structures.Further, in case of concrete structures the estimation of the characteristic strength values from limited data is a difficult, but important task.There are currently different assessment methods available in literature, i.e.the classical coverage method, a Bayesian procedure with vague prior distributions and the method described in the European standard EN 13791.In this contribution the developed Adjusted Partial Factor method will be briefly described and the influence of the different fractile estimation methods on the safety level of concrete structures is investigated using Monte Carlo simulations and structural reliability methods of Level Ⅱ.