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Use of fragility curves to assess the seismic vulnerability in the risk analysis of mountain tunnels
No full textThe high uncertainties involved in the design and construction of mountain tunnels have driven the development
of risk analysis procedures to control the risk level within an acceptable range. Since underground constructions
have proven to perform better than above-ground structures during the past earthquakes, the assessment of the
seismic risk of this kind of infrastructures is generally disregarded. Yet, post-earthquake investigations have
shown that tunnels are exposed to seismic risk because they are vulnerable to ground shaking. For this reason, a
comprehensive risk analysis should also include the seismic risk assessment. Fragility curves, which express the
conditional probability to manifest a certain level of seismic damage given a certain seismic intensity measure
(e.g. Peak Ground Acceleration), represent a suitable tool that can be implemented in the risk analysis of
mountain tunnels for a rapid seismic risk assessment. The currently available fragility curves for rock tunnels are
based on expert-opinion or empirical approach, without a properly consideration of the system variability (e.g.
tunnel type and rock characteristics, depth of the construction). This article proposes a comprehensive numerical
methodology to construct fragility curves for mountain tunnels subjected to transversal seismic loading. The
proposed numerical technique, which is based on fully-nonlinear dynamic analyses accounting for the nonlinearity
of both ground and tunnel support, allows to consider the features of the tunnel (e.g. type of support,
geometry, type of rock mass and depth of construction) as well the variability of the seismic input motion in a
more systematic way. Different sets of fragility curves for tunnels bored in fractured rock have been defined in
this article. Finally, two simplified case studies have been presented aiming to illustrate the potential uses of the
fragility curves within the risk analysis of mountain tunnels. In the first case study the fragility curves are used to
evaluate the probability of seismic damage of several tunnels to assess the functionality of the road network in
the post-seismic phases. In the second case study, the fragility curves are used to optimize the selection of the
tunnel support with regard to the seismic action. In particular, fragility curves are used to evaluate the level of
seismic risk associated to the selection of two different types of final lining
Deformation of landfill from measurements of shear wave velocity and damping - Discussion
Full text linkThe author presents a method for using in-situ seismic test results to estimate the short-term deformations of geomaterials. The effort to introduce rational algorithms for the evaluation of settlements of shallow foundations on the basis of measured physical quantities is noteworthy, considering that current geotechnical design, especially on small-scale projects, is often based on empirical correlations between
settlements and penetration test results that rarely reflect the actual site conditions. In this context the development of simple procedures based on the results of relatively inexpensive in-situ tests including seismic tests is of paramount importance.
Nevertheless it is important to account properly for the physics of wave propagation when inferring material parameters from seismic test results. In this respect, the writers would like to make some observations related to the methods used to evaluate the shear wave velocity and material
damping ratio of the solid waste from surface wave measurements. This discussion is focused on and restricted to the aspects of the paper related to the use of surface wave methods to estimate the waste properties
Probabilistic assessment of the earthquake-induced soil liquefaction hazard at national scale: macrozonation of the Italian territory
No full textSeismic soil liquefaction is one of the most relevant phenomena of ground failure that may induce disastrous consequences on structures, infrastructures and the environment. This article presents the first probabilistic zonation for liquefaction hazard at national scale, carried
out with reference to Italy. Macrozonation is the geospatial identification of areas in a national territory that, in case of an earthquake, may be affected by phenomena associated to soil liquefaction by using a probabilistic approach. Zonation of a large territory for earthquake-induced liquefaction hazard seems to be, at least at a first glance, an unachievable goal, since liquefaction occurs at a very local scale. In this study, the strategy for macrozoning consists in combining and processing geospatial predictors, which represent both ground susceptibility to liquefaction and expected seismic loading. A database was built for the Italian territory including the explanatory variables adopted as proxies for soil density, degree of saturation and ground motion intensity. This database represents the starting point for the application of a geospatial methodology based on logistic regression for assessing the liquefaction hazard in Italy. The outcomes are macrozonation charts computed for three return periods (i.e. 475, 975 and 2475 years) with a spatial resolution on the order of 500 m. The mapping was validated by superimposing historical liquefaction and then compared with the coarser charts recently delivered for Europe. Despite their intrinsic limitations, national scale maps of liquefaction hazard may support decision-makers, civil protection agencies, insurance and re-insurance companies to fund zonation projects at regional or even at urban/suburban scale
Hazard-dependent soil factors for site-specific elastic acceleration response spectra of Italian and European seismic building codes
No full text
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
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