Dynamic models of subduction: geophysical and geological evidence in the Tyrrhenian Sea   总被引：1，自引：0，他引：1  

Carlo Giunchi  Roberto Sabadini  Enzo Boschi  Paolo Gasperini 《Geophysical Journal International》1996,126(2):555-578

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Inelastic response and design criteria of plan-wise asymmetric systems     

Mario De Stefano  Giuseppe Faella  Roberto Ramasco 《地震工程与结构动力学》1993,22(3):245-259

The study of the torsional response of buildings in the inelastic range of behaviour is of great interest since the ability of structures to resist strong earthquakes mainly relies on their ductility and capacity for energy dissipation. Furthermore, an examination of the performance of structures during past earthquakes demonstrates that plan-asymmetric buildings suffered greater damage due to torsional response. The paper deals with this subject by analysing a model which idealizes a one-storey building with resisting elements oriented along two perpendicular directions. In addition to the parameters of the elastic behaviour, the inelastic system response depends on full yield capacity and plan-wise strength distribution. The influence of the criterion adopted for the design of resisting elements on local ductility demand and damage has been evaluated by parametric analysis. In particular, a comparison has been carried out between systems with equal design levels for all elements and systems with design levels dependent on the element location. For a given elastic behaviour and total capacity, the strength distributions in plan have been defined which minimize ductility demand and structural damage. Finally, based on these findings, responses from models designed according to several seismic codes have been compared.  相似文献   

Damped resonant appendages to increase inherent damping in buildings     

Roberto Villaverde  Leslie A. Koyama 《地震工程与结构动力学》1993,22(6):491-507

It is demonstrated that the addition of a tuned mass-spring-dashpot system with a relatively small mass and a high damping ratio can be an effective way to increase the inherent damping characteristics of buildings and reduce, thus, their response to earthquake excitations. The demonstration is based on a theoretical formulation and on numerical and experimental studies that confirm this formulation. In the theoretical formulation, it is shown first that, if certain conditions are satisfied, the damping ratios in two of the modes of the system that is formed by a building and an appendage in resonance are approximately equal to the average of the corresponding damping ratios of the building and the appendage. Based on this finding, it is then shown that an attached appendage with a high damping ratio and tuned to the fundamental frequency of a building may increase the damping ratio in the fundamental mode of the building to a value close to half the damping ratio of the appendage. In the numerical study, the response of a ten-storey shear building is analysed under two different earthquake ground motions with and without the proposed resonant appendages. Appendages with damping ratios of 20 and 30 per cent are considered. In this study, it is found that under one of the ground motions the maximum displacement of the building's roof is reduced 30 per cent with the appendage with 20 per cent damping and 39 per cent with the one with 30 per cent damping. Similarly, with these two appendages the building's base shear is reduced 31 and 41 per cent, respectively. In the experimental study, a wooden three-storey structural model is tested in a shaking table with and without an appendage designed and constructed to have a damping ratio of 53-5 per cent. The test is conducted under random and sinusoidal base excitations. In the shaking table test under random excitation, the attached appendage reduces the response of the model 38-6 per cent, while in that under sinusoidal vibration 45-2 per cent.  相似文献   

The use of damage functionals in earthquake engineering: A comparison between different methods     

Edoardo Cosenza  Gaetano Manfredi  Roberto Ramasco 《地震工程与结构动力学》1993,22(10):855-868

The behaviour of the EPP-SDOF model under seismic actions is analysed herein by different ‘damage functionals’ to define collapse under cyclic loading. In particular, the damage functionals based on the concept of maximum ductility and dissipated plastic energy are first compared. Afterwards the methods of Banon and Veneziano, Park and Ang and the linear cumulative law of plastic fatigue are reviewed and extensively analysed. Comparisons in the case of simple cyclic histories and in terms of acceleration collapse spectra are carried out with reference to significant earthquake records. In particular, it is shown in which cases the damage functionals of Banon and Veneziano, Park and Ang and the linear cumulative law of plastic fatigue, completely defined by the value of a single parameter, degenerate in the limit methods of ductility or dissipated energy and in which cases they provide similar results.  相似文献   

Rosenblueth's modal combination rule for systems with non-classical damping     

Roberto Villaverde 《地震工程与结构动力学》1988,16(3):315-328

A simple rule is derived to combine, within the framework of a complex mode superposition, the maximum modal responses of systems such as soil-structure and structure-equipment systems, for which closely spaced natural frequencies are likely, and for which, because of the large difference in the damping values of their various components, the assumption of an orthogonal damping matrix may lead to significant errors. The rule constitutes the generalization of Rosenblueth's rule for systems with closely spaced natural frequencies and classical modes, and is expressed in terms of their complex mode shapes and natural frequencies. Its derivation is based on the theory of a complex modal analysis for systems with non-classical modes of vibration and on Rosenblueth's original derivation. As in this original derivation, earthquake ground motions are modelled as a stationary white noise process, but the formulae obtained under this assumption are modified later on to account for the transient nature of actual earthquakes. A numerical example is presented to illustrate the application of the rule, and a comparative study with numerical integration solutions is performed to assess its accuracy. In this comparative study, it predicts the numerical integration solutions with an average error of 0.3 per cent.  相似文献   

Chironomid-inferred temperature changes of the last century in anoxic Seebergsee,Switzerland: assessment of two calibration methods     

Isabelle Larocque-Tobler  Roberto Quinlan  Monique M. Stewart  Martin Grosjean 《Quaternary Science Reviews》2011,30(13-14):1770-1779

Chironomids (non-biting midges) can provide accurate climate reconstructions from the Late Glacial to the present. Until now, anoxic lakes have been avoided for temperature reconstructions since chironomid assemblages are sensitive to changes in oxygen concentrations in the hypolimnion. However, anoxic lakes may have varved sediments, providing the possibility for near-annual climate reconstructions. Here, we tested the applicability of two calibration methods to reconstruct mean July air temperatures from chironomid assemblages preserved in the sediments of the anoxic Seebergsee located in the northern Swiss Alps: a calibration-in-space approach and a calibration-in-time approach. The calibration-in-space approach (i.e. chironomid assemblages from surficial lake sediments (0–1 cm) calibrated against meteorological data) provided accurate inferences (i.e. similar temperature changes as measured at the closest meteorological station, and at regional stations) in the Seebergsee stratigraphy until anoxia increased in the lake. With the increase of anoxia, the chironomid-inferred temperatures were generally colder than measured temperatures. A calibration-in-time approach (i.e. calibration of chironomid assemblages in a time series against instrumental data from the closest meteorological station) provided accurate reconstructions (i.e. similar to the regional records) for the past 100 years, including the time period of inferred anoxia. However, its applicability should be further tested on longer temporal scales.  相似文献   

Applications of Bayesian model selection to cosmological parameters     

Roberto Trotta 《Monthly notices of the Royal Astronomical Society》2007,378(1):72-82

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The Millennium Galaxy Catalogue: the B-band attenuation of bulge and disc light and the implied cosmic dust and stellar mass densities     

Simon P. Driver  Cristina C. Popescu  Richard J. Tuffs  Jochen Liske  Alister W. Graham  Paul D. Allen  Roberto De Propris 《Monthly notices of the Royal Astronomical Society》2007,379(3):1022-1036

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Petrology, structure and tectonic significance of the Tuclame banded schists in the Sierras Pampeanas of Córdoba and its relationship with the metamorphic basement of northwestern Argentina     

Roberto D. Martino  Alina B. Guereschi  Jorge A. Sfragulla   《Journal of South American Earth Sciences》2009,27(4):280-298

In the northwest of the Sierras Pampeanas of Córdoba (Central Argentina), in the Tuclame area, rocks called ‘banded schists’ are recognized. They are known since 120 years ago and are one of the most important lithologies of the metamorphic complex in this region. The compositional banding is the most conspicuous structural mesoscopic feature, composed of quartz-rich and mica-rich layers. It is a tectonic banding produced by pressure solution during a compressive event. P–T conditions of 557 ± 25 °C and 3.9 ± 1 kb were obtained for the main metamorphic event. A detailed field checking allowed recognition of the banded schists as decimetric or centimetric xenoliths isolated within the regional migmatites and the anatectic granitoids and as kilometric-scale belts within Sierras de Córdoba and San Luis. The authors have also identified banded schists in the Sierras de Aconquija, Ambato, Ancasti and Guasayán. Other workers recognized them in the Puna, Cumbres Calchaquíes, Sierras de Quilmes and Fiambalá, among the most well known outcrops. The banded schists have systematic petrological features and a distinctive mesoscopic structure that allow their identification and correlation with the other outcrops, which are arranged as a huge belt 2000 km long and 150 km wide, between 64°00′–66°30′W and 25°00′–41°34′S. In this work, all these rocks are proposed to be integrated into the Puncoviscana Basin, since field evidence indicated that the banded schists transitionally pass by transposition to phyllitic rocks typical of this metamorphosed basin, which would cover a region of about 300,000 km². At present, there is no accurate geochronology available for the metamorphic and deformation events proposed in this work for the Tuclame banded schists. However, considering the regional geological evidence, the great spread of the petrostructural process forming these rocks, the transition between the Puncoviscana Formation and the banded schists, and the earlier idea that the Puncoviscana Formation is the shallowest equivalent of deeper structural levels in the Sierras Pampeanas, we favor for the moment the hypothesis that the banded schists could be part of the oldest evolution of the Pampean orogeny (early Pampean stage) and could represent different structural levels of the same orogen, probably a late Precambrian–early Palaeozoic orogen. The events of migmatization and emplacement of anatectic granitoids could represent a late Pampean stage of early Palaeozoic age. Thus, the Pampean orogeny could have lasted around 30–40 Ma (570–530 Ma).  相似文献   

1.94–1.93 Ga charnockitic magmatism from the central part of the Guyana Shield, Roraima, Brazil: Single-zircon evaporation data and tectonic implications     

Lêda Maria Fraga  Moacir Jose Buenano Macambira  Roberto Dall&#x;Agnol  Joo Batista Sena Costa 《Journal of South American Earth Sciences》2009,27(4):247-257

Age and origin of the charnockitic rocks of the central part of the Guyana Shield have been a matter of discussion. These rocks have been interpreted either as Transamazonian granulites metamorphosed around 2.02 Ga or as 1.56 Ga old igneous charnockites. Recently, most of the Roraima charnockitic rocks have been recognized as igneous rocks and included into the Serra da Prata Suite (SPS). Five Pb–Pb single-zircon evaporation ages were obtained for samples representative of different facies of the SPS and these constrained the age of the charnockitic magmatism between 1943 ± 5 Ma and 1933 ± 2 Ma. This charnockitic magmatism may be related to a post-collisional setting after the evolution of the Cauarane-Coeroeni Belt (～2.00 Ga), or may represent a post-collisional (or intracontinental?) magmatism related to orogenic activities along the plate margins around 1.95–1.94 Ga.  相似文献