Structural capacity deterioration is among the main causes of increasing failure probabilities of structural systems, thus maintenance interventions are a crucial task for their rational management. Several probabilistic approaches have been proposed during the last decades for the determination of cost-effective maintenance strategies based on selected performance indicators. However, benefits and drawbacks of each performance indicator with respect to the others should be further analyzed. The objective of this paper is to investigate probabilistic approaches based on the annual reliability index, annual risk, and lifetime distributions for life-cycle maintenance of structural systems. Maintenance schedules are obtained for representative series, parallel, and series-parallel systems considering total restoration of component resistances whenever a prescribed threshold, based on a selected performance indicator, is reached. Effects related to different structural configurations and correlation among failure modes are investigated. The superstructure of an existing bridge is used to illustrate the presented approaches.

Citation: . Life-cycle maintenance of deteriorating structures by multi-objective optimization involving reliability, risk, availability, hazard and cost. Structural Safety, 48, Additional Information:• This is the author's version of a work that was accepted for publication availability and hazard functions) are used in conjunction with total maintenance cost for evaluating Pareto fronts associated with optimal maintenance schedules of deteriorating structures. Essential maintenance actions are considered and optimization is performed by using genetic algorithms. The approach is illustrated on an existing deteriorating bridge superstructure.

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Nonlinear Energy Sinks (NESs) have recently received increasing attention from researchers because of their capability to passively absorb a significant amount of energy over a wide range of frequencies. In most studies, the dynamic response of the main structure coupled with one or more NESs is analysed for impulsive loading. In this paper, the performance of the NES attached to a Single Degree of Freedom (SDOF) system, under random Gaussian white noise base excitations, is investigated through several numerical simulations. In order to determine the optimal configuration for the device, four different objective functions are considered. Sensitivity analyses with respect to the intensity of the random loads, the mass ratio and the main parameters of the primary structure are presented. The authors propose an approximate design approach based on the use of the Statistical Linearization Technique, and an accurate empirical formulation linking the NES optimal parameters to the characteristic of the main structure and the random excitation. Numerical results are validated by Monte Carlo simulations. Finally, a numerical application for a 2-DOFs system equipped with a NES has been presented in order to investigate the applicability of the proposed empirical approach for Multi Degrees of Freedom structures.

Design codes typically define the seismic action in terms of pseudo-acceleration response spectra, encouraging the use of the modal superposition method for the evaluation of the structural response. For linear structural systems, provided that the ground shaking has been appropriately modelled, the full characterization of the response processes of interest can be achieved with the application of the random vibration theory. An analytical model for the power spectral density (PSD) functions consistent with seismic response spectra has been recently proposed. In this paper, taking advantage of this novel PSD model, closed-form approximate expressions of the spectral moments of the structural response are derived and numerically validated for single-and multi-degree of freedom systems. The proposed formulation is applied to the case of base isolated multi-story buildings, aimed at overcoming the difficulties associated with the non-classical nature of their damping. The paper shows how the proposed approach can be used for an accurate and computationally efficient evaluation of the probabilistic distribution of the structural response maxima.

Summary In this paper, several layouts of double‐skin façades (DSFs) used as mass dampers to reduce the vibrations in structures under seismic events are analyzed. First, the mathematical coupled problem is studied considering a non‐classically damped system excited by a set of accelerograms. The design problem aims to determine the optimal values of four parameters, namely, the flexural stiffness and damping of the DSF panel and the stiffnesses of the elements that connect the DSF to the primary structure. Second, four objective functions are investigated. Two of these functions aim to minimise, respectively, the variance of displacements and accelerations of the primary structure for each earthquake record. The remaining two, instead, minimise the average of the displacements and accelerations calculated for all the selected accelerograms. Finally, numerical analyses are performed on a 6‐storey building and four DSF designs are proposed. The particle swarm optimisation is used to estimate the optimal parameters. Comparisons among the DSF layouts are presented in terms of minima of the objective functions and in terms of energy transfer functions, and a simplified design method for the connection elements is discussed.

When a very low damage occurs, the undamaged structural response totally overlaps the damaged one either in time domain or in frequency domain; on the other hand, by considering some characteristics of the analytical signal, such as the phase, it has been possible to develop a damage identification procedure that allows the identification and localization of damage even if the structure experiences multiple damages at the same time. This procedure is also robust with respect to the presence of measuring noise. In order to assess the validity of the proposed damage identification procedure, numerical applications on single degree of freedom and 2 DOF and 4 DOF are presented using data records perturbed by measuring noise too.

The evolution of naval vessels towards high-speed crafts subjected to severe sea conditions has promoted an increasing interest in lightweight high-strength materials. Due to its strength and weight characteristics, aluminum has been proven especially suitable as construction material for hull structures, as well as other vessel parts. However, fatigue in aluminum naval crafts needs to be effectively addressed for the proper life-cycle assessment. Structural health monitoring (SHM) systems constitute effective tools for measuring the structural response and assessing the structural performance under actual operational conditions. In this paper, an approach for using SHM information in the fatigue reliability analysis and service life prediction of aluminum naval vessels is presented. The accumulated fatigue damage and the fatigue reliability are quantified based on SHM data acquired under different operational conditions, specified by the ship speeds, sea states, and heading angles. Additionally, an approach for estimating the reliability-based fatigue life under a given operational profile is presented. Seakeeping trial data of an aluminum high-speed naval vessel are used to illustrate the proposed approach.