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The Marcus Aurelius Column has been a historical seismometer in Rome since its construction. Most of the seismic events of the past had effects on it. Therefore, the preservation of this monument is of fundamental importance for at least two reasons. First of all, to extend as much as possible its life time, in order to allow enjoying the sight to future generations. Then, the knowledge of these column characteristics will allow to improve the interpretation of historical documents on seismic event in Rome and to continue using it as historical seismometer in the Eternal City. In this paper, the last experimental vibrational analysis carried out on the Column is shown. Twenty-four velocimeter sensors, connected to a single acquisition unit, were used. Both time and frequency domain analysis were performed.

The experimental seismic behaviour of an isolation system, made of high damping rubber bearings, under low energy earthquakes is analysed. The seismically isolated building was instrumented by means of an accelerometer network. It was first characterized dynamically using also fifteen seismometers to record ambient vibrations. Then, all the events of the seismic sequence that struck Central Italy from August 2016 to January 2017 were recorded. These allowed evaluating the effects of earthquakes with different energy on the structure. Due to the long distances from the epicentres of these events, the analysis referred to the behaviour for very low shear strains in the rubber. The resonance frequencies of the base isolated building were much higher than those supposed in the design phase, but the filtering effect was still effective. One of the relative displacement history recorded during the strongest event was applied to the same devices used for the type tests at the construction time. The results obtained in terms of isolator stiffness were consistent with the experimental ones.

The results of an experimental dynamic analysis and structural modelling of the Indiano Cable-Stayed Bridge in Florence, Italy, are presented in this paper. Ambient and traffic-induced vibration tests were first carried out. These allowed extracting the dynamic characteristics of the structure in terms of resonance frequencies, modal shapes and damping. The experimental results were used to set up a finite element model. The geometrical characteristics and the mechanical properties of the materials used in the structural design of the bridge were assumed. The model was then used to evaluate the effects of the static and seismic loads according to the present Italian Technical Code. The results pointed out the good performance of the bridge, even though it had been designed without accounting for the seismic actions.

Curved surface sliders are being used more and more in the seismic isolation of buildings. They are preferred not only because of their lower cost with respect to elastomeric isolators but also of their technical characteristics, such as the fact that the value of the period of vibration is independent of the mass and the automatic coincidence between the gravity mass center of the superstructure and the stiffness center of the isolation system. In this paper, these features are analysed with reference to simple structures, pointing out the possibility of rotations of the superstructure and the loss of contact in some devices. Finally, the importance of the static friction is also emphasized showing the experimental seismic response of an isolation system under a low-energy earthquake. For all these reasons, the use of nonlinear analysis, revised and detailed in this paper, is advisable for the isolation system made of curved surface sliders. © 2018 Fernando Saitta et al.

The seismic vulnerability analysis of a strategic building is presented in this paper. A refined finite-element model was set up on the basis of available experimental results, and updated on the basis of new experimental analyses on materials and structure. As demonstrated by an experimental vibration analysis, the structural behavior is influenced very much by the irregularity of the building and the presence of an adjacent building with no seismic joint. The results indicate a high vulnerability of the building to seismic actions, and the inadequacy of the pile foundation - for which a specific nonlinear analysis was performed - to support horizontal seismic loads. A retrofit intervention, based on the insertion of a seismic isolation system and the realization of a seismic joint with the adjacent building, was proposed, which allows the reduction of horizontal forces in the piles and the torsional movements of the structure. © 2016 American Society of Civil Engineers.

The effects of the traffic-induced vibrations on the external northern wall of the Amphitheatrum Flavium are studied with the two objectives of analyzing the amplitudes of such vibrations and extracting the dynamic characteristics of the structure as part of preservation effort. The results obtained in two experimental campaigns, carried out in 1985 and 2014, respectively, are analyzed also as a starting point for future extensive experimental measurements. Data processing consisted in the time domain and frequency domain analyses, in which Fourier transform, power spectral density and cross spectral density were used to extract resonance frequencies, modal shapes and damping. The not always significant values of phase factors and coherence functions pointed out the presence of complex modes and of the nonlinear behavior, which in conjunction with the complex geometry of the structure and its size make the interpretation of the experimental data quite difficult. © 2017 by Istituto Nazionale di Geofisica e Vulcanologia. All rights reserved.