Life-cycle robustness : quantification and challenges Wendner, Roman; Tamparopoulos, Alexios E.; Bergmeister, Konrad
Life-cycle robustness is achieved when a structural member or a system is designed to maintain its intended function and required safety level within its desired life-cycle. The different character of effects that each element of the system needs to undergo (damage, ageing, extreme events, changes in usage) in conjunction with the diversity in the intrinsic material properties, form a demanding problem. Further complexity emerges when one realizes that time is not simply a variable, but a factor permeating model choices and uncertainty representation approaches. Different effects in the load side, and properties in the resistance side develop differently in time. Depending on the scale of the problem, the spatial randomness of materials such as concrete may be relevant for the accurate quantification of failure probabilities, and may require careful modelling, even at a mesoscale. For a long-term analysis, where the influence of uncertainties may dominate over predictability, robust design concepts and analyses methods that are relatively insensitive to small variations in variable inputs related to secondary effects and processes can prove decisive. On the computational side, challenges are associated with the computational cost of simulations and nonlinear analyses required to determine time-variable reliability profiles, considering all likely scenarios. Furthermore, statistical characteristics of the inputs, in particular their tail behaviour and their statistical dependence, needs to be properly captured and reproduced while maintaining sufficiently small sample size, and thus acceptable computational cost. Within this contribution, a framework for the quantification of life-cycle robustness is presented in the context of fasteners subjected to sustained load and extreme events. The emerging challenges are presented and briefly discussed.
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