1,721,044 research outputs found
Shear panel for seismic protection of structure
No full textThe paper describes a new dissipation device that can be used to preserve the structural integrity of civil engineering structures under seismic loads. The proposed device is made in aluminum and dissipates energy through the hysteretic behavior and the local plasticization. It is a very simple device with a low cost of production. The proposed dissipator has been tested using a monotonic type of experiment in order to define its main characteristics, then its dynamic characteristic behavior has been obtained through some tests on a 3D shaking table. The frame has been subjected to a series of accelerograms allowing to determine the dynamic behavior of the shear panels under severe work conditions, and to assess the efficiency of the device
Identification of the Modal Properties of a Building of the Greek Heritage
No full textIn this paper, the experimental modal identification analysis of the public building “San
Giacomo” in Corfu (Greece) is illustrated. It represents the unique example of a structure built
utilising carves stones inside the city of Corfu. The building has a rectangular plan shape with
dimensions 24.75 x 14 m, and height 9 m; all the floors are made by wood. The monitoring system
consists of several elements properly connected: the units of acquisitions or piezoelectric
accelerometers (in total 18 installed on the different walls) with a sensitivity of 1000 mV/g; the data
acquisition system or DAQs positioned at each monitored level; the laptop with an acquisition
software; the cables that connect all elements to each other.
The paper describes the phases of the investigations, the technical details of the performed in-situ
tests, the first identified frequencies of the building by means of the classical methods of
Operational Modal Analysis (OMA) and the comments about the acquired data
ANALYTICAL DEVELOPMENTS AND SHAKING TABLE TESTS ON DYNAMIC BEHAVIOR OF SQUAT SILOS CONTAINING GRAIN-LIKE MATERIAL
No full textFor the seismic design of flat-bottom grain silos containing grain-like material, the Eurocode 8
suggests that the horizontal actions on the walls of the silo are evaluated under the hypotheses
of (1) stiff behavior of the silo and its contents and (2) the effective mass which pushes on the
walls corresponds to the whole content of the silo except the base cone with an inclination
equal to the internal friction angle of the grain. This design approach seems to be overconservative
for squat silos. In a previous research work, the authors developed an analytical
study, which allows for substantial reductions in the seismic actions for silos characterized
by squat geometrical configuration. The analyses are developed by means of plain dynamic
equilibrium considerations and by simulating the earthquake ground motion with constant
vertical and horizontal accelerations and lead to the subdivision of the ensiled material into
three different portions. The findings indicate that, in the case of squat silos the portion of grain
mass that interacts with the silo walls turns out to be lower than the total mass of the grain in
the silo. Shaking table tests are currently under development at the lab facilities of the Bristol
University, under uniaxial constant, sinusoidal and earthquake input
Groin vaults-scaled by 3d printers: Seismic behavior with shaking table tests
No full textThis paper presents some preliminary results from a shaking table experimental campaign on a scaled model of a groin pointed vault, executed at the Earthquake and Large Structures (EQUALS) Laboratory at the University of Bristol, (UK) under the auspices of a H2020 SERA project (SEBESMOVA3D)
Optimum Design of a New Hysteretic DissipaterDesign Optimization of Active and Passive Structural Control Systems
No full textIn this chapter, a new seismic protection device is proposed. It is designed to dissipate the energy entering a structure subject to seismic action through the activation of hysteresis loops of the material that composes it. These devices are characterized by a high capacity to absorb the seismic energy and the ability to concentrate the damage on it and, consequently, to keep the structure and the structural parts undamaged. Moreover, after a seismic event they can be easily replaced. In particular, this chapter proposes a new shear device that shows the plasticity of some areas of the device at low load levels. In order to maximize the amount of dissipated energy, the design of the device was performed by requiring that the material be stressed in an almost uniform way. In particular, the device is designed to concentrate energy dissipation for plasticity in the aluminum core while the steel parts are responsible to make stiffer the device, limiting out-of-plane instability phenomena. The geometric configuration that maximizes the energy dissipation has been determined using a structural optimization routine of finite element software
Ambient vibration testing and operational modal analysis of a historic tower
No full textAn accurate knowledge of the dynamical parameters of structures is definitely useful for seismic assessment and for the design of risk mitigation interventions. In this paper, the opportunities provided by dynamic identification techniques for the non-destructive evaluation of heritage structures are discussed with focus on the bell tower of Announziata (Corfù, Greece), a masonry tower, which shows a high damaged scenario and, consequently, a high vulnerability to dynamic and seismic forces. The paper presents the experimental investigations and operational modal analysis results, useful for defining 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 and oriented according to the orthogonal directions x and y. This configuration has been also conditioned by many operative problems about the position of the instrumentation due to the limited accessibility of the structure, not only to the main access but also 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
Dynamic behavior of new aluminum-steel energy dissipating devices
Full text linkIn 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. In order to maximize the amount of dissipated energy, the design of the device has been performed requiring that the aluminum plate is stressed in an almost uniform way. In particular, the device is designed to concentrate energy dissipation in the aluminum core, while the external steel plates are dimensioned in order 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 kN and 40 kN, respectively). Moreover, in order to verify the behavior of the aluminum-steel device, characterization tests have been performed 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
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
PRELIMINARY RESULTS OF A SHAKING TABLE TESTS ON A 3-STOREY BUILDING REALIZED WITH CAST IN PLACE SANDWICH SQUAT CONCRETE WALLS
No full textStructural systems composed of cast in place sandwich squat concrete walls, which make use
of a lightweight material (for example polystyrene) as a support for the concrete, are widely
used for construction in non seismic areas or in areas of low seismicity, and appreciated for their
limited constructions costs, limited installation times, great constructions flexibility and high
energy and acoustic efficiency. If these cast-in-place squat concrete walls are assembled with
appropriate connections, a cellular/box behavior of the structural system is obtained which
leads to high strength resources (which allows not to use the post-elastic behavior and the ductility
resources) and high torsional stiffness. In recent years, from an exhaustive experimental
campaign it has been possible to obtain the structural performances of single panels composed
of cast-in-place sandwich squat concrete walls. A series of shaking table tests have been carried
out at the EUCENTRE in Pavia. The structural specimen which has been tested is a full-scale 3-
storey structural system composed of cast-in-place squat sandwich concrete walls characterized
by 5.50 × 4.10 meters in plan and 8.25meters in height. Shaking table tests have been developed
to validate the theoretically and partially-experimentally anticipated (through cyclic tests under
horizontal loads) good seismic behavior of cellular structures composed of cast in place squat
sandwich concrete walls
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