1,721,037 research outputs found
A simplified approach for the integrated design of viscoelastically damped structural systems
No full textIn this work, a simplified approach for the integrated design of the structural and the viscoelastic bracing-damper systems is presented. With reference to the viscous or viscoelastic dampers, the optimal integrated design is based on the possibility of achieving the seismic protection through the integration of the elastic lateral stiffness resources and the viscoelastic properties of a dissipative bracing-damper system. The optimal design is defined by determining the combination of the variables which minimizes a total cost function. Then a validation of the integrated procedure is performed by verifying that the dynamic response of an optimal single-degree-of-freedom integrated system achieves in average the expected performance displacement by considering a set of seven unscaled acceleration records compatible in average with the elastic spectrum relative to the life safety state, provided by the new Italian seismic code. Finally the extension of this procedure to a proportionally damped multidegrees- of-freedom integrated system, having a regular stiffness distribution in elevation, is developed on the basis of specific hypotheses by evaluating the different energy rates and the average displacement of the time history responses to the seven unscaled acceleration records and highlighting the effectiveness of the proposed integrated design methodology
SEISMIC RELIABILITY OF BASE-ISOLATED STRUCTURAL SYSTEMS THROUGH FPS
No full textThe paper deals with the seismic reliability of structural systems equipped with friction pendulum isolators (FPS). The behavior of these systems is analyzed by employing a two-degree-of-freedom model accounting for the superstructure flexibility, whereas the FPS isolator behaviour is described by adopting a widespread model which considers the variation of the friction coefficient with the velocity. The uncertainty in the seismic inputs is taken into account by employing a set of synthetic records, obtained through Monte Carlo simulations within the power spectral density method, with different characteristics depending on the soil dynamic parameters, and scaled to increasing intensity levels. The friction coefficient at large velocity is considered as random variable modeled through a uniform probability density function. Incremental dynamic analyses are developed in order to evaluate the probabilities exceeding different limit states related to both superstructure and isolation level defining the seismic fragility curves through an extensive parametric study carried out for different structural system properties. Finally, considering the seismic hazard curves related to L'Aquila site (Italy), the seismic reliability of the superstructure systems is evaluated as well as seismic reliability-based design (SRBD) abacuses are derived with the aim to design the radius in plan of the friction pendulum isolators in function of the structural system properties and the selected reliability level
Seismic reliability of base-isolated structures with friction pendulum bearings
No full textThe friction pendulum system (FPS) is becoming a widely used technique for seismic protection and retrofit
of buildings, bridges and industrial structures due to its remarkable features such as the stability of
physical properties and durability respect to the elastomeric bearings. Experimental data also showed
that the coefficient of friction depends on several effects (i.e., sliding velocity, apparent pressure, air temperature,
cycling effect) so that it can be assumed as a random variable. The aim of the study consists in
evaluating the seismic reliability of a base-isolated structure with FP isolators considering both isolator
properties (i.e., coefficient of friction) and earthquake main characteristics as random variables. Assuming
appropriate density probability functions for each random variable and adopting the Latin Hypercube
Sampling (LHS) method for random sampling, the input data set has been defined. Several 3D non-linear
dynamic analyses have been performed considering both the vertical and horizontal components of each
seismic excitation in order to evaluate the system response. In particular, monovariate and multivariate
(joint) probability density and cumulative distribution functions have been computed and, considering
the limit state thresholds and domains (performance objectives) defined respectively on mono/bi-directional
displacements, assumed as earthquake damage parameter (EDP) according to performance-based
seismic design, the exceeding probabilities (structural performances) have been evaluated. Estimating
the reliability of the superstructure, substructure and isolation level led to define and propose reliability-
based abacus and equations useful to design the FP system
Robustness of 3D Base-Isolated R.C. Systems with FPS
Full text linkThis study evaluates the seismic robustness of 3D r.c. structures isolated with single-concave friction pendulum system (FPS) devices by computing the seismic reliability of different models related to different malfunction cases of the seismic isolators. Considering the elastic response pseudoacceleration as the relevant random variable, the input data have been defined by means of the Latin Hypercube Sampling technique in order to develop 3D inelastic time-history analyses. In this way, bivariate structural performance curves at each level of the r.c. structural systems as well as seismic reliabilitybased design abacuses for the FP devices have been computed and compared in order to evaluate the robustness of the r.c. system considering different failure cases of the FP bearings. Moreover, the seismic robustness is examined by considering both a configuration equipped with beams connecting the substructure columns and a configuration without these connecting beams in order to demonstrate their effectiveness and provide useful design recommendations for base-isolated structural systems equipped with FPS
Life-cycle cost and seismic reliability analysis of 3D systems equipped with FPS for different isolation degrees
No full textThe aim of the study consists in evaluating the life-cycle costs of a r.c. 3D system isolated by singleconcave
FPS bearings with different isolated periods in order to evaluate the potential benefits provided
by increasing values of the isolation degree. In particular, assuming the elastic response pseudoacceleration
related to each isolated period and the coefficient of friction as random variables relevant
to the problem characterized by appropriate probability density functions, the Latin Hypercube
Sampling method has been adopted as random sampling technique in order to define the input data
and perform 3D non-linear dynamic analyses. Thus, bivariate structural performance curves for each
story of the superstructure and for the substructure as well as seismic reliability-based design (SRBD)
abacuses for the isolation level have been defined for the different values of the isolation degree.
Finally, the life-cycle cost analysis of the isolated system with different curvature radius of the FP bearings
has been accomplished taking into account both the initial costs and the expected loss costs, due to
future earthquakes, of the overall system during its design life (50 years) in order to evaluate the influence
of the isolation degree on both the seismic performance and the total costs.The aim of the study consists in evaluating the life-cycle costs of a r.c. 3D system isolated by singleconcave
FPS bearings with different isolated periods in order to evaluate the potential benefits provided
by increasing values of the isolation degree. In particular, assuming the elastic response pseudoacceleration
related to each isolated period and the coefficient of friction as random variables relevant
to the problem characterized by appropriate probability density functions, the Latin Hypercube
Sampling method has been adopted as random sampling technique in order to define the input data
and perform 3D non-linear dynamic analyses. Thus, bivariate structural performance curves for each
story of the superstructure and for the substructure as well as seismic reliability-based design (SRBD)
abacuses for the isolation level have been defined for the different values of the isolation degree.
Finally, the life-cycle cost analysis of the isolated system with different curvature radius of the FP bearings
has been accomplished taking into account both the initial costs and the expected loss costs, due to
future earthquakes, of the overall system during its design life (50 years) in order to evaluate the influence
of the isolation degree on both the seismic performance and the total costs
SEISMIC RELIABILITY ANALYSIS OF 3D NON-LINEAR BASE-ISOLATED STRUCTURES WITH FPS
No full textThe aim of the study consists in evaluating the seismic reliability and life-cycle costs of a reinforced concrete 3D system isolated by FPS bearings with different isolated periods in order to evaluate the potential benefits provided by increasing values of the isolation degree. Assuming the elastic response pseudo-acceleration related to each isolated period and the coefficient of friction as random variables relevant to the problem characterized by appropriate probability density functions, the Latin Hypercube Sampling method has been adopted as random sampling technique in order to define the input data. Several 3D non-linear dynamic analyses have been performed considering both the vertical and horizontal components of each seismic excitation in order to evaluate the system performance. Thus, bivariate structural performance curves for each story of the superstructure and for the substructure as well as seismic reliability-based design (SRBD) curves for the isolation level have been defined for the different values of the isolation degree. Finally, the life-cycle cost analysis of the isolated system with different curvature radius of the FP bearings has been accomplished taking into account both the initial costs and the expected loss costs, due to future earthquakes, of the overall system during its design life (50 years) in order to evaluate the influence of the isolation degree on both the seismic performance and the total costs
Effects of the axial force eccentricity on the time-variant structural reliability of aging r.c. cross-sections subjected to chloride-induced corrosion
No full textReinforced concrete structures are generally affected by degradation phenomena, which may include changes in strength and stiffness beyond the baseline conditions which are assumed in structural design. Some of these aging effects may cause component or system strengths to degrade over time, particularly when the concrete is exposed to an aggressive environment which may increase the risk of structural failure. For r.c. structures, due to the uncertainties in material and geometrical properties, in the magnitude and distribution of the loads, in the physical parameters which define the deterioration process, the structural safety should realistically be considered time-variant. In this context, this paper implements a computational probabilistic approach to predict the time-evolution of the mechanical and geometrical properties of a r.c. structural element (i.e., bridge pier) subjected to corrosion-induced deterioration as a consequence of the diffusive attack of chlorides in order to evaluate its service life. Adopting appropriate degradation models of the material properties, concrete and reinforcing steel, as well as assuming appropriate probability density functions related to mechanical and deterioration parameters, the proposed sectional approach is based on Monte Carlo simulations in order to evaluate time-variant axial force-bending moment resistance domains, with the aim to estimate the time-variant reliability index β for different axial force eccentricity values. Finally, an application of the proposed methodology to estimate the expected lifetime of a deteriorating r.c. bridge pier is described and discussed
Palazzo (B.), O. P., L'Arap-Djami ou église Saint-Paul à Galata
No full textPalazzo (B.), O. P., L'Arap-Djami ou église Saint-Paul à Galata. In: Revue des études byzantines, tome 6, 1948. p. 142
Varoni E, Tschon M, Palazzo B, Nitti P, Martini L, Rimondini L. Agarose gel as biomaterial or scaffold for implantation surgery: characterization, histological and histomorphometric study on soft tissue response.
No full textDental biomaterials and natural products represent two of the main growing
research fields, revealing plant-derived compounds may play a role not only as
nutraceuticals in affecting oral health, but also in improving physico-chemical properties of
biomaterials used in dentistry. Therefore, our aim was to collect all available data concerning
the utilization of plant polysaccharides, proteins and extracts rich in bioactive phytochemicals
in enhancing performance of dental biomaterials. Although compelling evidences are
suggestive of a great potential of plant products in promoting material-tissue/cell interface,
to date, only few authors have investigated their use in development of innovative dental
biomaterials. A small number of studies have reported plant extract-based titanium implant
coatings and periodontal regenerative materials. To the best of our knowledge, this review
is the first to deal with this topic, highlighting a general lack of research findings in an
interesting field which still needs to be investigate
Palazzo (B.), O. P., L'Arap-Djami ou église Saint-Paul à Galata
No full textPalazzo (B.), O. P., L'Arap-Djami ou église Saint-Paul à Galata. In: Revue des études byzantines, tome 6, 1948. p. 142
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