In this paper, the classical linear tuned mass damper (TMD) is coupled with an inerter, a two-terminal device resisting the relative\ud acceleration of its terminals, in various tuned mass-damper-inerter (TMDI) topologies to suppress excessive wind-induced oscillations in\ud tall buildings causing occupant discomfort. A parametric numerical study is undertaken involving a top-floor-TMD-equipped planar frame\ud accurately capturing the in-plane dynamic behavior of a 74-story benchmark building exposed to a quasi-stationary spatially correlated windforce\ud field accounting for vortex shedding effects in the across-wind direction. It is found that the TMDI reduces peak top-floor acceleration\ud more effectively than the TMD by considering smaller attached-mass values, and TMDI topologies in which the inerter spans more stories in\ud linking the attached mass to the host structure. Moreover, the inclusion of the inerter dramatically reduces the TMD stroke, and it has been\ud verified that the magnitude of the developing inerter forces can be readily accommodated by the host structure. Pertinent illustrative examples\ud are included showcasing that the TMDI meets code-prescribed serviceability design requirements for new tall buildings using significantly\ud smaller attached mass compared with the TMD, and that inerter devices can be used to upgrade the performance of existing TMD-equipped\ud tall buildings without changing the attached mass

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The tuned mass-damper-inerter (TMDI) couples the classical tuned mass-damper (TMD), with an inerter device developing a resisting force proportional to the relative acceleration of its ends by the "inertance" constant. Previous works demonstrated that the inclusion of the TMDI leads to more efficient broadband vibration control for a range of different structures under different actions. This paper proposes a novel optimal TMDI design formulation to address occupants' comfort in wind-excited slender tall buildings susceptible to vortex shedding (VS) effects and to explore optimal TMDI's potential for transforming part of the windinduced kinetic energy to usable electricity in tall buildings. Attention is focused on investigating benefits of TMDIs with different inertial properties (i.e., secondary mass/weight and inertance) configured in different topologies defined by the number of floors spanned by the inerter device to connect the secondary mass to the building structure. Optimally designed TMDIs for a wide range of inertial properties and three different topologies are obtained through numerical solution of the underlying optimization problem for a benchmark 305.9m tall building with more than 6 height-to-width ratio subjected to experimentally calibrated spatiallycorrelated across-wind force field accounting for VS effects. Performance-based design (PBD) graphs on the TMDI inertial (mass-inertance) plane are furnished demonstrating that any fixed structural performance level in terms of occupants' comfort (i.e., peak top floor acceleration) can be achieved through lightweight TMDIs if compared with classical TMDs as long as sufficient inertance is provided. Further, TMDI robustness to host structure properties and to reference wind velocity is shown to increase by increasing inertance or by spanning more floors in connecting the secondary mass with the host structure by the inerter. Lastly, it is found that increased available energy for harvesting in wind excited tall buildings is achieved by incorporating electromagnetic motors in TMDIs with varying damping property, while concurrent reduced floor acceleration and increased available energy for harvesting is accomplished by TMDI topologies with inerters spanning more floors.

In this paper, the concept of an ideal grounded linear inerter, endowing supplemental inertia to passive linear tuned mass-dampers (TMDs) through its inertance property without increasing the TMD mass, is considered to reduce lateral displacement demands in base isolated structural systems (BISs). Optimal tuned mass-damper-inerter (TMDI) design parameters are numerically determined to maximize energy dissipation by the TMDI under stationary white noise support excitation. Performance of these optimally designed TMDI-equipped BISs is assessed for stationary white and colored noise excitations as well as for four recorded earthquake acceleration ground motions (GMs) with different non-stationary frequency content. It is found that for fixed mass ratio the inclusion of the grounded inerter reduces significantly secondary mass displacement and stroke for all considered excitations while it improves appreciably BIS displacement demands except for the particular case of a near-fault accelerogram characterized by early arrival of a high-energy low-frequency pulse as captured in its wavelet spectrogram. More importantly, it leads further to reductions to BIS acceleration demands with the exception of colored noise excitation for which an insignificant increase is noted. The positive effects of the inerter saturate with increasing inertance and BIS damping ratio demonstrating that small inertance values are more effective in vibration suppression of BISs with low inherent damping. Overall, it is recommended to combine low damping isolation layers with large inertance and low secondary mass TMDIs.

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A probabilistic procedure for the performance-based design of tall buildings subject to wind actions is illustrated. The central objective of the procedure is the assessment of the adequacy of the structure through the probabilistic description of a set of decision variables (DVs). Each DV is a measurable attribute that represents a specific structural performance (no collapse, occupant safety, accessibility, full functionality, admissible displacements or accelerations, etc.). The structural risk is conventionally measured by the probability of exceeding a relevant value of the corresponding DV; the probability is evaluated by taking into account the Aeolian hazard at the site, the calculated structural response and damage and the correlation between the attained damage and the relevant DV. The procedure is applied to an example case: the assessment of the comfort requirement for a 74-storey building. Probabilistic calculations are carried out in frequency domain, but the parameters of the wind velocity field are calibrated on the basis of the time histories of the forces that have been obtained by experimental tests on a 1: 500 scale rigid model of the building. The occupant comfort is related to motion perception and measured by the probability of not exceeding threshold values of the across-wind acceleration at the top of the building

SummaryThis paper presents a procedure for seismic design of reinforced concrete structures, in which performance objectives are formulated in terms of maximum accepted mean annual frequency (MAF) of exceedance, for multiple limit states. The procedure is explicitly probabilistic and uses Cornell's like closed-form equations for the MAFs. A gradient-based constrained optimization technique is used for obtaining values of structural design variables (members' section size and reinforcement) satisfying multiple objectives in terms of risk levels. The method is practically feasible even for real-sized structures thanks to the adoption of adaptive equivalent linear models where element-by-element stiffness reduction is performed (2 linear analyses per intensity level). General geometric and capacity design constraints are duly accounted for. The procedure is applied to a 15-storey plane frame building, and validation is conducted against results in terms of drift profiles and MAF of exceedance, obtained by multiple-stripe analysis with records selected to match conditional spectra. Results show that the method is suitable for performance-based seismic design of RC structures with explicit targets in terms of desired risk levels. 1 It has been extensively recognized 2 that, due to the large uncertainty affecting input motion and to a variable extent also structural properties, as well as response and capacity modelling, 3-5 performance should be evaluated probabilistically in PBSD to be really able to claim that "target performance is achieved," eg, with an acceptable value of the mean annual frequency (MAF) of exceedance. Research efforts directed at providing fully probabilistic, rigorous PBSD approaches, eg, Vamvatsikos and Papadimitriou 6,7 and Lagaros and Papadrakakis, 7 are so far characterized by a complexity that makes them unsuitable for practical design problems, or use nonlinear equivalent SDOF system as a proxy (with the obvious limitations), rather than a full MDOF. 8 On the other hand, practice-oriented implementations of PBSD do not model uncertainty explicitly, neither they express the results in probability terms, eg, Kappos and Stefanidou. 9 At an even lower level, design codes prescribe deterministic seismic design with "characteristic" values of capacity parameters, assuming that uncertainties on capacity and on response at a given seismic intensity are covered by "design factors," including partial load and resistance factors, 10 the desired risk level being implicitly attained in the design process by the combination of these factors. The more robust element of probability entering in the design is in the seismic action, which is defined through uniform hazard response spectra