Large amplitude oscillations of suspended bridges under wind-induced loads have been observed due to the non-smooth behavior of the hangers, that behave like unilateral constraints with no resistance to compressive forces. As a consequence, in particular load conditions some hangers may slack and so a part of the bridge deck may experience unacceptable large motion. For long span suspended bridges, such problem has been investigated with different approaches; in particular, some Authors have numerically evaluated the nonlinear oscillations by means of simplified sectional models, while the writers have proposed a continuous approach, that allows to obtain a smooth nonlinear continuous model by means of a regularization technique: as the distance between the hangers is significantly lower than the bridge span, in fact, it can be assumed that the local slackening of hangers produces a smooth variation of the global stiffness of cables and deck, which may be represented by a nonlinear function of their relative displacements. The main advantage is that the dynamical behavior of the continuum model can be evaluated in closed form by means of perturbation methods. This paper generalizes this approach to suspended footbridges and to pedestrian dynamic loads, that is a subject recently dealt with by several Authors. For sample cases of torsional pedestrian-induced loads, the results of the proposed continuous model are discussed in the paper and compared with similar results described in the scientific literature.

The results of an ambient-vibration based investigation conducted on a historical tower in Italy, to update the 3-D finite element model of the building are presented in this work. The main difficulties are related to the extreme in-homogeneity of the building and the presence of an elevator vain that occupies the posterior part of the tower, forcing to locate the accelerometers only on one fac-ade of the building. The assessment procedure include full-scale ambient vibration testing, modal identification from ambient vibration responses using three different identification methods, finite element modeling and dynamic-based identification of the uncertain structural parameters of the model. A very good match between theoretical and experimental modal parameters was reached and the model updating has been performed to identify some structural parameters.

In the present study, a new dissipation device for seismic protection of structures is proposed. This device is designed to dissipate the energy entering a structure during an earthquake through the activation of hysteretic loops of an aluminum plate located in the middle of the device itself. To maximize the amount of dissipated energy, we performed the design of the device requiring that the aluminumplate is stressed in an almost uniformway. In particular, the device is designed to concentrate energy dissipation in the aluminum core, whereas the external steel plates are dimensioned to give an adequate stiffness to the device and to limit instability phenomena. Characterization tests have been performed on two typologies of device designed for different levels of the maximum shear force (20 and 40 kN, respectively). Moreover, to verify the behavior of the aluminum–steel device, we performed characterization tests on the aforementioned devices realized without the aluminum plate. The results show that the steel plates behave elastically in the range of forces expected in the device during an earthquake, confirming that the aluminum plate is the main element for the hysteretic energy dissipation.

The aim of the paper is to present the dynamical identification of the bell tower of the Cathedral of Trani (Bari, Italy). The tower, built in 1200, is about 60 meters high and has a square plan with a side of about 7.50 meters; moreover it is connected to the church through a step supported by a pointed arch. The tower vibrations due to ambient actions have been recorded and analyzed with different modern algorithms in such a way as to estimate the modal parameters of the tower. The identified modal parameters were utilized to evaluate the dynamic interaction between the tower and the church and some mechanical properties of the structural elements.

The aim of the paper is to describe the non-destructive tests performed on the clock tower of the Castle of Trani (Bari, Italy). The tower, built in 1848, was realized in tufa masonry (Stone of Trani); it is about 9 meters high and has a square plan with a side of about 3.9 meters; it is built on the principal enter of the Castle and supported by a barrel vault reinforced with an arch. The non-destructive monitoring was performed by using specific accelerometers placed on the structure at different levels for measuring the acceleration in different points. The particular squat structure of the clock tower suggested the authors to make not only the traditional monitoring, with only environmental actions, but also forced tests by mean of a vibrodine adhoc designed and realized, for determining the building modal parameters. All the phases and the procedures of the experimental monitoring are described and the dynamic identification of the building modal parameters (the frequencies and their corresponding mode shapes) is presented discussing the results in both the operative conditions and the effects of the vibrodine excitation.

The aim of the paper is to present the structural analysis of an important historical building: the San James Theater actually used as the Municipality House in the city of Corfù. The building is made of carves stones and is located in the centre of Corfu, Greece. The study deals with the structural identification of such structure through the analysis of its ambient vibrations recorded by means of very accurate accelerometers. A full dynamic testing was developed using ambient vibrations to identify the main modal parameters and to make a non-destructive characterization of this building The results of these dynamic tests will be used for the model updating of a complex FE simulation of the structure. This analysis may present several problems and uncertainties for this stocky building. Due to the presence of wooden floors, the local modes can be highly excited and, as a consequence, the evaluation of the structural modal parameters presents some difficulties. The paper discusses the experimental tests and compares the results with those obtained from the analysis of a preliminary FE model obtained using a commercial software.

The scope of the paper is to present the analysis of an important historical building the “San James” theater actually used as the Municipality House in the city of Corfù (Greece). The building, that is located in the center of the city, is characterized by an extremely stocky shape, and by the presence of wooden floors. Moreover, the upper part of the building has been realized many years after the end of the works of the main part of the building. The aforementioned considerations do not allow to be sure about the “box” behavior of the building and makes the dynamic analysis and tests of great importance for the exactly comprehension of its structural behavior. With this aim an extensive experimental campaign has been performed: in detail 18 accelerometers with high sensitivity have been installed and the ambient vibrations of building have been recorded. In the present paper the performed experimental tests and the analysis of the experimental data are discussed and compared with a finite element model of the examined building. At this aim an important task of the present research is related to the consideration that all the floors are made by wood and so, the analysis of the experimental data and the dynamical identification could be influenced by the presence of local modes. This problem has been tackled by introducing a ‘single wall analysis’strategy for demonstrating the global behavior of the estimated experimental modes that may be used for updating the building FE model.

The aim of the present paper is to introduce ground penetrating radar (GPR) tests as a support of the structural identification for complex structures as the bell tower of the Cathedral of Trani (Bari, Italy); in particular, the structural identification has been performed by means of the Operational Modal Analysis (OMA) and subsequently the identified modal parameters have been utilized for the updating of a Finite Element model. Nevertheless, considering that the walls of the tower are composed by layers of different thickness and properties, the updating procedure has been implemented matching the results of the GPR tests. The possibility of using the GPR technology for foreseeing the internal composition of the building walls is here discussed and analysed together with the description of all the phases of dynamic identification and tower model updating.

This paper describes a study carried out on the masonry bell tower of “Annunziata” (Corfu, Greece) , which shows a high damaged scenario and, consequently, a high vulnerability to dynamic and seismic forces. It presents the experimental investigations and results useful to define the finite element model of the tower. The monitoring system consists of several elements properly connected: in total twenty-four accelerometers have been positioned, eight for each of the three floors, according to the orthogonal directions x and y. This configuration has been also determined by the many operative problems about the position of the instrumentation due to the limited accessibility of the structure, both for the main access and to reach the top. It is important to emphasize that the data obtained are not connected to external events detected during the acquisitions, so it is possible to identify with a certain confidence the first six frequencies of the tower and their corresponding mode shapes.