Numerical prediction of tunnel performance during centrifuge dynamic tests   总被引：2，自引：1，他引：1  

Angelo Amorosi  Daniela Boldini  Gaetano Falcone 《Acta Geotechnica》2014,9(4):581-596

In this paper, a comparison between numerical analyses and centrifuge test results relative to the seismic performance of a circular tunnel is provided. The considered experimental data refer to two centrifuge tests performed at Cambridge University, aimed at investigating the transverse dynamic behaviour of a relatively shallow tunnel located in a sand deposit. For the same geometry, different soil relative densities characterise the two tests. The four seismic actions considered, of the pseudo-harmonic type, are characterised by increasing intensity. The 2D numerical analyses were performed adopting an advanced soil constitutive model implemented in a commercial finite element code. The comparison between numerical simulations and measurements is presented in terms of acceleration histories and Fourier spectra as well as of profiles of maximum acceleration along free-field and near-tunnel verticals. In addition, loading histories of normal stress and bending moments acting in the tunnel lining were considered. In general, very good agreement was found with reference to the ground response analyses, while a less satisfactory comparison between observed and predicted results was obtained for the transient and permanent loadings acting in the lining, as discussed in the final part of the paper.  相似文献   

Atmospheric Background Measurement in the 300–400 nm Band with a Balloon Borne Experiment During a Nocturnal Flight     

Giovanni La Rosa  Gaetano Agnetta  Benedetto Biondo  Osvaldo Catalano  Filippo Celi  Renato Di Raffaele  Salvatore Giarrusso  Angelo Mangano  Francesco Russo  John Linsley  Angelo Lo Bue 《Astrophysics and Space Science》2001,276(1):219-226

  相似文献   

L’Istituto vulcanologicom l’ Osservatorio etneo e l’attività scientifica del personale     

Gaetano Ponte 《Bulletin of Volcanology》1937,2(1):201-204

  相似文献   

Damage‐dependent vulnerability curves for existing buildings     

Maria Polese  Marco Di Ludovico  Andrea Prota  Gaetano Manfredi 《地震工程与结构动力学》2013,42(6):853-870

Seismic behavior of damaged buildings may be expressed as a function of their REsidual Capacity (REC), which is a measure of seismic capacity, reduced by damage. REC can be interpreted as the median value of collapse vulnerability curves. Its variation owing to damage is a useful indication of increased building vulnerability. REC reduction, indicating the lowering of seismic safety after an earthquake (performance loss, PL), represents an effective index for assessing the need of seismic repair/strengthening after earthquakes. The study investigates the applicability of a pushover‐based method in the analysis of damaged structures for the case of existing under‐designed RC buildings. The paper presents a systematization of the procedure in an assessment framework that applies the capacity spectrum method based on inelastic demand spectra; furthermore, the vulnerability variation of a real building is investigated with a detailed case study. The behavior of damaged buildings is simulated with pushover analysis through suitable modification of plastic hinges (in terms of stiffness, strength and residual drift) for damaged elements. The modification of plastic hinges has been calibrated in tests on nonconforming columns. The case study analysis evidenced that, for minor or moderate damages, the original structural displacement capacity was only slightly influenced, but the ductility capacity was significantly reduced (up to 40%) because of the increased structure deformability. This implied performance loss in the range 10%–20%. For severe damages the PL ranged between 41% and 56%. Local mechanism types exhibit PL nearly double with respect to global mechanism types. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Magnetic Field Line Transport in Anisotropic Magnetic Turbulence: Anomalous, Quasilinear, and Percolative Regimes Versus the Kubo Number     

Gaetano Zimbardo  Pierluigi Veltri  Pierre Pommois 《Astrophysics and Space Science》2001,277(1-2):101-102

The transport of plasma and of energetic particles because of magnetic turbulence is relevant to many space plasmas, ranging from the planetary magnetospheres to the solar corona and to the heliosphere. Various transport regimes for magnetic field lines can be obtained depending on the Kubo number. Here we show, by means of a numerical simulation, that the Kubo number also determines the level of chaos of the field lines. Weak chaos, closed magnetic surfaces, and anomalous transport regimes are obtained for R≪ 1; widespread chaos, destroyed magnetic surfaces, and quasilinear scaling of the diffusion coefficient for R ≳ 0.3; and global stochasticity as well as percolation scaling of the diffusion coefficient for R≫ 1. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Cumulative demand of the earthquake ground motions in the near source     

Gaetano Manfredi  Maria Polese  Edoardo Cosenza 《地震工程与结构动力学》2003,32(12):1853-1865

In this paper the effects of near‐fault earthquakes are investigated through the study of parameters related to both input energy and plastic cycles demand. Based on the results of two different regression analyses performed with 128 near‐fault and 122 far‐field registrations, respectively, the Cosenza and Manfredi adimensional Id index was found to be the best seismological parameter correlated to the number n and amplitude m of plastic cycles in the vicinity of the source as well as far from it. Analytical formulations for n,m and for the equivalent number of plastic cycles neq are proposed for near‐fault and far‐field regions. The study of Id and neq shows the tendency of such parameters to increase as the distance increases. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Performance evaluation of a shallow foundation built on structured clays under seismic loading     

Gaetano Elia  Mohamed Rouainia 《Bulletin of Earthquake Engineering》2014,12(4):1537-1561

Due to the increased need of storage, larger and higher structures are being built all over the world, thus requiring a more careful evaluation of the mechanical performance of their foundation deposits both in terms of bearing capacity and compressibility behaviour. The design of such structures and their serviceability and stability is largely governed by the effects of the dynamic loading conditions principally because of their significantly elevated risk in seismic prone zones. In this paper, numerical analyses using an advanced constitutive model, able to account for the initial soil structure and its progressive degradation, have been performed to investigate the seismic response of a silo foundation built on structured clays. The proposed analyses involve the use of a fully-coupled finite element approach. For the dynamic simulations, three different input motions have been selected form earthquake databases according to the seismic hazard study of the specific site. The results of the silo dynamic response are illustrated in terms of signal amplification, permanent excess pore water pressures, accumulated displacements and structure induced degradation during and after the seismic loading. The dynamic behaviour of the footing indicates that extreme earthquake events can induce large destructuration in natural clays, leading to ground settlements up to twice the observed ones under static loads, which need to be properly accounted for in the design. This suggests that there are significant advantages in using advanced models which recognise the existence of initial soil structure and its subsequent damage due to the applied dynamic loads.  相似文献   

Seismic fragility of plasterboard partitions via in‐plane quasi‐static tests          下载免费PDF全文

Crescenzo Petrone  Gennaro Magliulo  Pauline Lopez  Gaetano Manfredi 《地震工程与结构动力学》2015,44(14):2589-2606

The seismic damage of internal partitions may cause significant earthquake loss; this phenomenon is caused by (a) their tendency to exhibit damage for low demand levels and (b) the consequent loss of inventory and breakdown that their collapse can cause. Quasi‐static tests are performed on six 5‐m‐high plasterboard internal partitions, which represent typical partitions in industrial and commercial buildings in the European area. A steel test setup is designed to transfer the load, which is provided by the actuator, to the partition. The testing protocol provided by Federal Emergency Management Agency (FEMA) 461 is adopted for the quasi‐static tests. The typical failure mode of the specimens is the buckling of a steel stud, which involves the boards that are attached to the buckled stud. The buckling failure usually concentrates across the plasterboard horizontal joints. A frictional behavior is exhibited for low demand levels, whereas a pinched behavior is shown for moderate‐to‐high demand levels. The interstory drift ratios required to reach a given damage limit state are evaluated using a predefined damage scheme. Based on the experimental data, the fragility curves for three different damage states (DS1, DS2, and DS3) are estimated. The fragility curve yields median interstory drift ratio values of 0.28%, 0.81%, and 2.05% and logarithmic standard deviations of 0.39, 0.42, and 0.46 for DS1, DS2, and DS3, respectively. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Preliminary ranking of alternative scalar and vector intensity measures of ground shaking   总被引：3，自引：3，他引：0  

Hossein Ebrahimian  Fatemeh Jalayer  Andrea Lucchini  Fabrizio Mollaioli  Gaetano Manfredi 《Bulletin of Earthquake Engineering》2015,13(10):2805-2840

  相似文献   

Model updating and seismic loss assessment for a portfolio of bridges     

Andrea Miano  Fatemeh Jalayer  Raffaele De Risi  Andrea Prota  Gaetano Manfredi 《Bulletin of Earthquake Engineering》2016,14(3):699-719

The majority of bridge infrastructures in Italy were built in the 1960s and ‘70s without any specific seismic provision being made. As a consequence, it is expected that these bridges would be highly vulnerable if subjected to a significant seismic event. Given this background, it is natural that the rapid and accurate assessment of economic losses incurred to the bridge infrastructure as a result of such an event could play a crucial role in emergency management in the immediate aftermath of an earthquake. Focusing on the infrastructure system of highway bridges in the Campania region in Italy, this paper demonstrates how both state-of-the-art methodologies in portfolio loss assessment and the available data can be used to assess the probability distribution of the repair costs incurred due to the 1980 Irpinia earthquake. Formulating a probabilistic loss assessment for a portfolio of bridges as a standard Monte Carlo simulation problem helps to resolve the spatial risk integral efficiently. One of the specific features of this case study is the use of statistical methods for updating models of: (a) ground motion predictions, (b) vulnerability/fragility and (c) exposure/costs, based on the available data. It has been observed that alternative hypotheses concerning the ground motion correlation structure can significantly affect the distribution of direct economic losses. Furthermore, updating the ground motion prediction based on available recordings may significantly reduce the dispersion in the estimate of the direct economic losses.  相似文献