1,721,516 research outputs found
Optimal design of a new seismic passive protection device made in aluminium and steel
No full textIn recent years many techniques for the seismic control of structures have been developed. Among these, the metallic hysteretic devices are able to dissipate a great amount of the energy entering the building during a seismic event, thanks to a stable behavior under cyclic loads that produces a wide hysteretic loop. Steel shear panels are examples of elasto-plastic elements, which dissipate energy under a shear behavior. Generally such dampers are known to possess large energy-dissipation capacity relative to their size; they are cost-effective and are able to protect non-structural elements too. Moreover, the shear panels may be easily installed and substituted in the structure by mean of diagonals on which may be mounted and then connected to the frame. As disadvantage, this kind of energy dissipating devices can dissipate energy only after they sustain inelastic excursions. As a consequence they are ineffective for vibrations that produce interstory drifts smaller than the yielding drift of the device. To overcome this constraint, Rai and Wallace and Foti and Diaferio proposed shear panels made in aluminium alloys. In fact, these alloys are very ductile with a yielding limit lower than ordinary steel. Numerical and experimental researches have been developed on aluminium shear links. Foti and Nobile performed characterization and shaking-table tests on some aluminium shear panels showing instability phenomena and problems of the connections of the devices to the structure.
The aim of the present note is to find out the optimum geometrical configuration of an aluminium-steel shear panel in order to dissipate a large amount of the seismic energy
DYNAMIC RESPONSE OF INFILLED FRAMES
No full textSeveral engineers and researchers have highlighted that in many cases, even for moderate seismic
events, non-structural elements and, in detail, masonry infills have suffered severe damages. This
circumstance required interventions with considerable repair costs and disruption to service use of buildings.
Otherwise, generally, the seismic design of structures omits the influence of such elements in the estimation
of the seismic performance of the structure. The contribution of infills doesn’t influence only the need of
interventions after an earthquake but can also be responsible of a variation of the dynamic response of the
frames, as it can modify the entities of the displacements with respect to the estimated ones. In the cases, for
example, of retrofitting interventions which include the installation of passive devices, the reduction of
displacements may inhibit the activation of such devices and/or may reduce the amount of dissipated energy.
Therefore, the numerical simulation of the infilled frames and the estimation of their modal parameters are the
first step in the design procedure of new structures or of interventions for the improvement of the seismic
performance of existing buildings. The paper deals with this topic, by proposing a simplified model able to take
into account both frame and infills. A numerical analysis is performed to evaluate the influence of the infills
features on the global response of the infilled frames
NUMERICAL PROCEDURE FOR THE ASSESSMENT OF THE MECHANICAL BEHAVOIUR OF BELL TOWERS
No full textDuring the past seismic events, the historical bell towers have been highly damaged due to their
slenderness and geometrical features. The main characteristics of these structures are the high value of the
ratio between the total height and the side length, the existence of significant openings and, usually, of one or
more connections to the main religious building. Several studies have been conducted on such structural
typology because of the great number of such structures in the European territory and of their high seismic
vulnerability. The estimation of the modal parameters plays a key role in the seismic analysis of such structures
which can be obtained by performing dynamic tests and by validating a numerical model based on the
experimental results. The present paper aims to discuss the effect of a different level of complexity of the
experimental setup and, consequently, of the numerical model which is defined to assess the unknown
mechanical parameters. The paper highlights that the estimated modal parameters identified on simplified
setup configurations can be utilised to assess the bell tower mechanical properties with good accuracy
depending on the level of constraint due to the surrounding buildings. The analysis makes use of the case
study of a masonry bell tower located in the South of Italy which is characterised by confining building on three
facades for about a third of its total height
Deep spectroscopic luminosity function of Abell 85 : no evidence for a steep upturn of the faint-end slope
Get PDFIA, AD and ALS acknowledge partial support from the INFN grant InDark and from the grant Progetti di Ateneo TO Call 2012 0011 ‘Marco Polo’ of the University of Torino.We present a new deep determination of the spectroscopic luminosity function (LF) within the virial radius of the nearby and massive Abell 85 (A85) cluster down to the dwarf regime (M* + 6) using Very Large Telescope/Visible Multi-Object Spectrograph (VLT/VIMOS) spectra for ∼2000 galaxies with mr ≤ 21 mag and 〈μe,r〉 ≤ 24 mag arcsec−2. The resulting LF from 438 cluster members is best modelled by a double Schechter function due to the presence of a statistically significant upturn at the faint end. The amplitude of this upturn (αf ~ -1.58+0.19-0.15), however, is much smaller than that of the Sloan Digital Sky Survey (SDSS) composite photometric cluster LF by Popesso et al., αf ∼ −2. The faint-end slope of the LF in A85 is consistent, within the uncertainties, with that of the field. The red galaxy population dominates the LF at low luminosities, and is the main factor responsible for the upturn. The fact that the slopes of the spectroscopic LFs in the field and in a cluster as massive as A85 are similar suggests that the cluster environment does not play a major role in determining the abundance of low-mass galaxies.Peer reviewe
Innovation in traditional materials: greening through ancient technologies in buildings
No full textThe chapter aims to provide awareness on the advantages of proper management of masonry constructions in view of sustainability and environmental impact. Indeed, their conservation and re-use allow to reduce CO2 emissions, waste and raw materials consumption. The focus will be on the assessment of their mechanical properties and structural response for maintenance purposes. These issues are discussed by highlighting applications fields, advantages and limits of the experimental tests with very low or no-impact on structures. Moreover, different possible masonry typologies and the historic and/or monumental value of the examined structures are considered
On the Variability of Conversion Models for Concrete Strength Assessment Based on Pulse Velocity Measurements
No full textThe existence of a wide reinforced concrete (r.c.) building stock, which is reaching the end of its service life, has focused the attention on its vulnerability assessment. The first step of this analysis is the estimation of the concrete compressive strength. In this field, many codes allow to supplement the classical destructive tests with nondestructive ones, because of their versality and of the possibility of reducing the time spent for tests. It is worth noting that the spread of these tests is strictly connected to the accuracy of the conversion models, which correlate the nondestructive measurements to the concrete strength. The present paper deals with this issue by examining the results of the experimental investigations, which made use of destructive and ultrasonic pulse velocity tests, on three r.c. buildings in Bari (Italy). The data are analyzed and rearranged to define several testing conditions, for each one of which a conversion model is calibrated. Moreover, the variability of the parameters of the identified models is discussed with respect to the number of data considered in the calibration process, to the chosen model, and to the accuracy of the assessed strength
Dynamic analysis of a historical fortified tower
No full textThe present paper is centered on the static and dynamic analysis of the fortified tower of San Felice sul Panaro (Italy) citadel. The examined tower, that dated back to the XIV century, is particularly vulnerable to seismic forces, as the recent Emilia Romagna earthquake (2012) has demonstrated, and can be considered representative of a wide class of masonry towers located in the north of Italy. In order to evaluate the structural behavior, detailed numerical models of the tower with different level of complexity have been defined. In particular, the present paper shows the preliminary results of the static and dynamic analysis performed on such models and the influence of some parameters on the tower dynamic behavior
Una tecnica di regolarizzazione per la dinamica non lineare di strutture sospese: validazione agli elementi finiti
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