Luca Martinelli

Extending the Benchmark Cable-Stayed Bridge for Transverse Response under Seismic Loading

AbstractAn updated version of the ASCE benchmark on controlled cable-stayed bridges has been recently developed in the ANSYS framework. It includes new aspects in the relative transversal motion of the main girder with respect to the towers in the simulation of the stay cable dynamics with respect to the coupled motion of the main girder in the soil-structure interaction and the numerical formulation by assuming full geometric nonlinearities. Analyses are carried out in a multiple support framework in a time domain by using the earthquake records as collected from the benchmark original statement. The original benchmark configuration considered earthquake restrainers in the transverse direction. The proposed updated bridge model first reproduces this kinematic arrangement, and a new configuration with transversal releases is subsequently implemented. The control strategies consist of passive and decentralized semiactive systems working in the horizontal plane and are also those studied in a previous inves...

Earthquake-Resilience-Based Control Solutions for the Extended Benchmark Cable-Stayed Bridge

Structural control solutions can offer a decisive contribution to reducing the consequences of strong events in earthquake-affected areas, enhancing structural resilience. Furthermore, the inherent feature of some control systems, which can adapt themselves to different loading levels, can be exploited when structural conditions change due to local failures. This occurs by changing the working parameters of the control system in real time or, even if very short, over the period between two seismic events. This work deals with resilience of seismic control solutions for cable-stayed bridges through a case study represented by a standard bridge control benchmark from the literature. A strategy for recovering the optimal configuration of the controlled bridge after a damaging event is presented. Emphasis is given to the time interval between the damage occurrence and the restoration, which represent the essential aspect of the resilient behavior. Finally, the formulation of a robustness index and general procedures that suggest how to quantify resilience for the control system of cable-stayed bridges in the context of multiple hazards are explored.

Finite element modeling of cable galloping vibrations. Part II: Application to an iced cable in 1:2 multiple internal resonance

The aim of this paper is to validate the finite element formulations proposed in a companion paper for the study of the nonlinear dynamic behavior of cable structures. A well-known suspended cable in multiple 1:2 “internal resonance” conditions is herein considered. A uniform ice deposit, along the length of the cable, makes it prone to galloping vibrations under a steady wind flow. Different modeling strategies, relying on different assumptions regarding both the mechanical model as well as the aerodynamic response, are investigated and compared with results coming from analytical, semi-analytical and numerical models from the literature. The role of torsional and flexural stiffness terms, and of the initial undeformed configuration, is critically assessed. The results obtained show the significant effect coming from the adoption of a beam finite element formulation that includes the effect of torsional rotation in the evaluation of the aerodynamic loads.

ON THE MODELING OF SELF-DAMPING IN STRANDED CABLES

A new formulation is presented to model the hysteretic bending behaviour of metallic strands. The interaction between the wires of the strand is modeled through a frictional contact model based on the Amontons-Coulomb law and accounts for the effects of the tangential compliance mechanism. The new model is presented with reference to a single-layered mono-metallic strand and is applied to the study of the energy dissipation in cyclic bending.

Assessing the Performance of a High Damping Rubber Bearing in Beyond-design Conditions

In the recent past, passive isolation systems have been largely employed as a valuable earthquake-resistant strategy in the design of civil engineering structures, particularly with reference to the large class of ordinary buildings. Although their introduction for the seismic protection of strategic buildings is currently still limited, base isolation systems are likely to become a widespread solution in the design of structures and facilities for which superior performances are needed against design actions and functionality after a seismic event is of utmost importance. The present paper is focused on evaluation of the performance of a filled high damping rubber bearing in limit state conditions. Suitable finite element models have been developed by employing the mesh overlapping technique. Some initial results are shown and compared with the outcomes of an experimental campaign. doi: 10.12783/SHM2015/135

Wind Driven Damage Localization in a High-rise Building

The size of high-rise buildings makes appealing adoption of ambient vibration as the excitation used in damage identification algorithms. The randomness of the source, however, makes quite challenging to evaluate the accuracy of the structural health assessment. The Interpolation Damage Detection Method (IDDM), based on the detection of reductions of smoothness in the structure’s Operational Deformed Shapes (ODSs), has recently been applied to structures subjected to a known excitation. The focus of this paper is the extension of IDDM to the case of a structure subjected to an unknown excitation which, herein, is induced by wind. The algorithm is applied to a calibrated finite element model of a high-rise wall-frame building, lately designed to be built in Italy. The structural response of the undamaged and of the damaged structure to wind loading is computed with the numerical model, simulating damage through a reduction of the elastic modulus of the material of selected structural elements. doi: 10.12783/SHM2015/63

IL CONTROLLO STRUTTURALE DELLE VIBRAZIONI NELL'INGEGNERIA CIVILE

Structural control is becoming more and more important for civil structures, particularly for mitigating vibrations due to natural phenomena as well as due to human action. This note examines in its first part structural control strategies (active, semi-active, passive) applicable to civil structures, pointing out the differences with other fields of engineering, recalling the principles on which are based, the peculiarities and advantages. Particularly, semi-active strategies have been proved advantageous. For this reason, in its second part, the note presents a review of the principal families of devices with relation to their applicability in the field of control of civil structures and to their suitability of being used inside semi-active control schemes.