1,721,136 research outputs found
Cruz Andreotti, G., ed.. Roman Turdetania: Romanization, Identity and Socio-Cultural Interaction in the South of the Iberian Peninsula between the 4th and 1st centuries BCE [Reseña]
Full text linkCruz Andreotti, G. (ed.), Roman Turdetania: Romanization, Identity and Socio-Cultural Interaction in the South of the Iberian Peninsula between the 4th and 1st centuries BCE. Leiden, Boston, Brill, 2019
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
Seismic vulnerability of deep tunnels: numerical modeling for a fully nonlinear dynamic analysis
No full text
Hazard-dependent soil factors for site-specific elastic acceleration response spectra of Italian and European seismic building codes
No full textSeismic Fragility Functions of Deep Tunnels: A New Cumulative Damage Model Based on Lumped Plasticity and Rotation Capacity
No full textExpansion of mortar joints in direct shear tests of masonry samples: implications on shear strength and experimental characterization of dilatancy
No full textThe expansion of masonry specimens during direct shear tests has been reported in several research studies. This phenomenon, known as dilatancy, is caused by the formation of cracking surfaces in mortar joints. In particular, when the cracking surface is not perfectly flat, the shear displacements tend to increase the volume of the sample. Experimental investigations focused on the characterization of this phenomenon are rather limited for masonry and the effects on shear strength have received little attention, with consequent issues for a correct interpretation of the results. The present article reports the results of an ongoing research on brick masonry aimed to characterize experimentally the dilatancy and to evaluate the role of this phenomenon in the interpretation of the direct shear test. If the expansion of the specimen is significantly restrained, the standard approaches used for the characterization of the mechanical parameters (as per EN 1052-3 and ASTM C1531) tend to overestimate the initial shear strength (fvo) and underestimate friction. Moreover, no indications are generally given to characterize dilatancy with experimental data. This aspect is particularly important for the micro-modelling of masonry because the constitutive models commonly used for mortar joints require this information. One of the objectives of the present article is to propose a simple model for a sound interpretation of the direct shear test of masonry samples taking into account the dilatancy. Several masonry samples composed of calcium silicate units and cement mortar joints have been subjected to triplet tests (EN 1052-3) and laboratory-simulated shove tests. First, a repeatable and objective methodology to measure and characterize the dilatancy is provided. Then, an extension of the standard methodology of the EN 1052-3 and ASTM C1531 that includes the contribution of this phenomenon is proposed. The novel formulation offers the possibility to characterize dilatancy with experimental data and the definition of mechanical parameters that are not biased by the presence of this phenomenon. The model presented in this article has proven to be consistent with the experimental data and it has been validated numerically in another recent research study
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