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Observed behavior of buildings seismically isolated with CSSs under a low energy earthquake
No full textThe observed behavior of four buildings, seismically isolated by means of curved surface sliders (CSS), under a moderate seismic event is analyzed in the framework of their structural health monitoring. The results showed that the CSS isolation systems were not activated for most of the buildings, even though the acceleration peaks in the superstructures were significant. The reason for this behavior is related to an inaccurate evaluation of the friction coefficients under the vertical loads acting on the devices in seismic conditions. Actually, vertical loads influence the friction and so the onset of motion. The importance of a continuous monitoring of the actual seismic behavior is also evident to analyze the structural health status of the devices and to plan maintenance interventions when needed
Onset of Motion of Curved Surface Sliders Used in Seismic-Isolation Systems
No full textCurved surface sliders are generally preferred for the seismic isolation of buildings because of their technical features, such as the fact that the value of the vibration period is theoretically independent of the mass. Given the experimental evidence that indicates that the isolated system did not work under low seismic actions, in this paper, the influence of the static friction on the global behavior of some structures is studied in detail. By adopting a suitable model of friction, the onset of motion is analyzed with reference to simple isolation systems in which the influence of the friction values and its variability among the isolation devices are analyzed. The results pointed out that the behavior of curved surface sliders is not independent of the vertical load and highlights the importance of a suitable choice of the design friction, which must be different for devices with different vertical loads
Structural assessment of the pedestrian bridge accessing Civita di Bagnoregio, Italy
Full text linkThe paper presents the results of the vibration tests carried out on the pedestrian bridge accessing Civita di Bagnoregio, Italy. The structure was in bad health condition. The external beams were damaged due to deterioration exacerbated by the combined actions of rain and wind. The circular piers were also damaged with several cracks where the concrete cover was spliced and the reinforcement bars were exposed. The analysis presented in the paper focuses on the highest five piers, which seemed to show an irregular behavior during a preliminary experimental campaign. The results of the experimental campaign presented in this paper showed that the structural behavior of the bridge was qualitatively similar to the expected one. The reduced stiffness, due to the observed widespread damage state, amplified the vibrations uniformly along the structure. The Italian Guidelines for the risk and safety assessment of bridges and viaducts, issued in 2020, have been applied and tested in this study and the results are presented in the paper
Observed Seismic Behaviour of Base Isolation Systems in Italy
No full textThe observed behaviour of seismically isolated structures in different countries allowed testifying the suitability of this technique to protect structures against strong earthquakes. In Italy, up to now, base isolated buildings have been subjected only to low energy earthquakes. This paper describes and compares the observed behaviours under a low energy earthquake of three buildings with different isolation systems. In the first one, seismically isolated by means of HDRBs, the structure showed resonance frequencies higher than the design ones but the decoupling was always guaranteed also thanks to the high stiffness of the superstructure. In the second one, seismically isolated with CSSs, the onset of motion was governed by the friction, which was much higher than the design one. Finally, in a building seismically isolated with HDRBs and SDs, the onset of motion was governed by the SDs and the successive motion by the HDRBs
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Influence of Friction in the Seismic Behaviour of HDRB+SD Isolation Systems
No full textThe response of an isolation system made of HDRBs and SDs under low energy earthquakes, classified on the basis of the energy at the basement, is analyzed. The study pointed out that for very low values of the energy, measured by means of the Arias intensity, the isolation system was not put in action, and the superstucture behaved like a fixed base one. The behaviour has been correlated to the ratio between the inertial force resultant and the maximum friction forces of the slider devices. For higher values of the energy, instead, the isolation system was activated and a value of the Arias intensity was individualized, which separates the two behaviours. The variability of the first resonance frequencies with the input energy has been particularly analyzed, as well as the structural response in terms of maximum accelerations, maximum displacements and relative horizontal displacements in the building
Designing Base Isolated Buildings According to the Italian Technical Code: A Benchmark for Comparison
No full textSeismic isolation is one of the most effective protection techniques used against seismic events all over the world. It can be easily used in different types of structures, especially for new constructions. While the basic concepts are almost similar in all countries, some specific rules and standards are different in each country. In this paper, the design of a base isolated building according to the Italian code is presented for comparison with other codes. The building is a seven-storey reinforced concrete condominium. Two isolation systems, composed of high damping rubber bearings and sliding devices, were designed according to the Italian Technical Code. For the seismic input, the Italian site with the maximum horizontal acceleration was chosen, with soil type C. The results can be easily compared with those obtained using other technical codes
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