In this article, an experimentally validated model is proposed in order to take into account main sources of performance degradation that could be experienced by friction-based devices during a seismic event. Particular attention is dedicated to the degradation of friction characteristics due to repetition of cycles and consequent temperature rise. This effect can be responsible for overestimate of the dissipation capacity of the device. The proposed model of frictional behavior is suitable for immediate implementation in generalized structural analysis codes and provides an important design tool for realistic assessment of the seismic response of structures equipped with friction-based isolators.

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SUMMARY This paper deals with a procedure for the identification of the damage in bridge structures equipped with isolators and/or energy dissipating devices. The procedure is based on the availability of accelerometric records from any simple sensor network installed on existing bridges. The proposed algorithm provides an assessment of the performance degradation of conventional structural components as well as installed isolators and energy dissipators, obtained from changes in modal characteristic of the structural response. A new index localization and severity index is introduced to be used for ordinary structural elements and anti‐seismic devices. For the validation of the procedure, the algorithm has been applied to a continuous beam as well as to a bridge structure equipped with Friction Pendulum devices. The proposed procedure shows a high level of accuracy in the damage localization and severity assessment also in a complex scenario of damage. The severity index is also interpreted in terms of physical quantities (e.g. friction coefficient) representative of the specific device performance. For this reason the procedure appears feasible for implementation on real structures with the advantage of providing direct indicators of the early stages of degradation of performance parameters. This information can be used to design inspection and maintenance plans. Copyright © 2011 John Wiley & Sons, Ltd.

The papers deals with the use of dissipative braces as retrofit solutions for existing moment resisting frame buildings. Braces are widely used in order to enhance performances of existing buildings under seismic loads, by adding stiffness and strength against inertial forces induced by earthquake ground motions. The braces can be equipped with supplemental dissipators in order to increase the overall energy dissipation capacity of the system and reduce stresses in the existing structures. In the present work, general design criteria for dampers and supporting braces are given and a simple design procedure based on the actual mechanical interaction between dampers and braces has been carried out. A number of design procedures have been proposed for dissipative bracing systems in frame structures. The procedures are often based on simplifying assumptions, due to the complexity of mechanical behavior of systems equipped with dissipative braces. Those assumptions make the procedures easier to use, but at the same time, less reliable in predicting the behavior of complex structures. In the present work, results are obtained without using two of the most common simplifying assumptions that neglect interaction between frame and braces: the use of the floor stiffness in order to characterize the frame behavior, and the use of equivalent systems with a single degree of freedom. The proposed design procedure has been tested on a moment resisting frame building and appears feasible for implementation on real structures.

Abstract:In a hybrid electric vehicle (HEV), the hybrid system, which is equipped with an engine and a motor, is a key component. However, given the multimode characteristics of HEV, the original extreme load of the engine or motor is not independent and the random variables cannot be directly fitted by the extreme value theory (EVT). Thus, this paper proposes a mode-decomposing application method (MDAM) using EVT. Based on the method, three typical distributions, including the Fréchet distribution, the Gumbel distribution, and the Weibull distribution, were combined as a unified expression, and it was adopted to fit the extreme loads within different modes of HEV. By comparing the fitting results, especially the shapes of the curves, the distributions of the load under different modes vary from each other, so the feasibility and necessity of MDAM in HEV are proved, and a new thought for fitting the extreme load in HEV is provided, which will contribute to improve the fitting accuracy.