Concentrically braced steel frames under seismic actions: Non-linear behaviour and design coefficients     

Federico Perotti  G. Paolo Scarlassara 《地震工程与结构动力学》1991,20(5):409-427

The paper deals with the non-linear dynamic analysis of concentrically braced pinned frames under earthquake conditions. A model is first presented for the behaviour of bars subjected to cyclic axial force, which takes into account the overall and local buckling phenomena, section shape, residual stresses, material behaviour and damage accumulation due to low-cycle fatigue and fracture. Dynamic analyses of bracing systems are then described: these have been performed, on the basis of the axially loaded bar model, within the framework of a simplified procedure for the determination of optimal design factors. The results obtained are first reported for the case of one-storey systems; an example of the behaviour of a four-storey system is given finally.  相似文献   

Clinopyroxene chemistry of the high-Potassium suite from the Alban Hills,Italy     

Prof. M. Federico  Dr. A. Gianfagna  Dr. C. Aurisicchio 《Mineralogy and Petrology》1988,39(1):1-19

Summary Chemical data on clinopyroxene phenocrysts in twenty-four lava samples from the Alban Hills (Roman comagmatic region) show coexistence, within the same rock, of two core-rim evolution trends: diopside-salite and salite-diopside, respectively. The Alban volcanics can be divided in two groups depending on which type of core predominates.Geochemical mixing tests, conducted with elements showing a different degree of incompatibility, such as Ce, Sr, Th, La, Ta, and Hf, show no evidence of a mixing process which might be responsible for coexistence of both diopside and salite clinopyroxenes within the same lava.Taking into account the results of known experiments on the influence of water on clinopyroxene composition in potassium rich lavas, the reverse zoning trend observed and the consequent predominance of salite cores in some lavas are ascribed to the effect of volatiles, and particularly to water. Changes of water pressure may also be responsible for phenocryst corrosion and salitic clinopyroxene replacement by olivine, phlogopite and titaniferous magnetite.The prominent role of water in the Alban Hills magma evolution is also supported by the high fluorine content found in the Alban products, which enhances water solubility in the magmas, by the frequent occurrence of mica in the rock groundmass and, finally, by the explosive character of Alban volcanism.

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Zusammenfassung Die Ergebnisse chemischer Analysen von Klinopyroxen in vierundzwanzig Lavaproben aus den Albaner Bergen (Römische Komagmatische Region) zeigen die Koexistenz von zwei Kern-Rand-Entwicklungstendenzen: Diopsid-Salit und Salit-Diopsid. Die Vulkanite können auf Grund der Zusammensetzung der Kerne in zwei Gruppen unterteilt werden.Mit Elementen verschiedener Inkompatibilität, wie Ce, Sr, Th, La, Ta und Hf, ausgeführte Mischversuche geben keinen Hinweis dafür, daß ein Mischungsprozeß für die Koexistenz von Diopsid und Salit in derselben Lava verantwortlich sei.In Anbetracht der Ergebnisse von Experimenten über den Einfluß von H₂O auf die Klinopyroxen-Zusammensetzung in K-reichen Laven, werden die beobachtete Zonierung und die daraus folgende Dominanz von Salit-Kernen in bestimmten Lavatypen der Wirkung von volatilen Bestandteilen, besonders Wasser, zugeschrieben. änderungen des H₂O-Drucks können für Phenokristall-Korrosion und Verdrängung der salitischen Klinopyroxene durch Olivin, Phlogopit und Titanomagnetit verantwortlich sein.Die entscheidende Rolle des Wassers in der Entwicklung des Magmas stimmt mit dem hohen Fluor-Gehalt der Produkte, der die H₂O-Löslichkeit in Magmen erhöht, mit der Häufigkeit des Glimmers in der Grundmasse der Gesteine und mit der explosiven Natur des Vulkanismus im Untersuchungsgebiet überein.

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Zur Chemie der Klinopyroxene in den Kali-reichen Gesteinen der Albaner Berge

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Tschermak fractionation in calc-alkaline magmas: the Eocene Sabzevar volcanism (NE Iran)     

Federico Lucci  Federico Rossetti  John Charles White  Hadi Shafaii Moghadam  Alireza Shirzadi  Mohsen Nasrabady 《Arabian Journal of Geosciences》2016,9(10):573

Calc-alkaline arc magmatism at convergent plate margins is volumetrically dominated by metaluminous andesites. Many studies highlighted the importance of differentiation via fractionation processes of arc magmas, but only in the last decades, it has been demonstrated that not all rock-forming minerals may affect the evolution of calc-alkaline suites. In particular, a major role exerted by Al-rich hornblende amphibole as fractionating mineral phase has been documented in many volcanic arc settings. The aim of this work is to understand the role of the Tschermak molecule (CaAlAlSiO₆) hosted in the hornblende and plagioclase fractionation assemblage in driving magma differentiation in calc-alkaline magmatic suites. We explore this issue by applying replenishment–fractional crystallization (RFC) and rare earth element–Rayleigh fractional crystallization (REE-FC) modeling to the Sabzevar Eocene (ca. 45–47 Ma) calc-alkaline volcanism of NE Central Iran, where hornblende-controlled fractionation has been demonstrated. Major element mass balance modeling indicates RFC dominated by a fractionating assemblage made of Hbl_52.0–52.5 + Pl_44.1–44.2 + Ttn_3.3–3.9 (phases are expressed on total crystallized assemblage). REE-FC modeling shows, instead, a lower degree of fractionation with respect to RFC models that is interpreted as due to hornblende and plagioclase resorption by the residual melt. Calculations demonstrate that fractionation of the Tschermak molecule can readily produce dacite and rhyolite magmas starting from a calc-alkaline andesite source (FC = ca. 30 %). In particular, the Tschermak molecule controls both the heavy rare earth elements (HREE) and light rare earth element (LREE) budgets in calc-alkaline differentiation trends.  相似文献   

Lithological control on thrust-related deformation in the Sassa-Guardistallo Basin (Northern Apennines hinterland, Italy)     

Andrea Cerrina Feroni  Marco Bonini†  Patrizia Martinelli  Giovanna Moratti†  Federico Sani‡  Domenico Montanari†‡  Chiara Del Ventisette†‡ 《Basin Research》2006,18(3):301-321

The Sassa‐Guardistallo Basin (SGB) is located close to the Tyrrhenian Sea and represents one of the most internal Neogene–Quaternary hinterland basins of the Northern Apennines fold‐and‐thrust belt. Its sedimentary succession consists of ca. 400‐m‐thick Late Tortonian–Messinian continental – largely conglomeratic – units overstepping a mainly shaly substratum (Palombini Shales) and overlain by Late Messinian evaporites and marine to continental Pliocene–Pleistocene sediments. This stratigraphic succession can be approximated to a composite rheological multilayer that dictated the style of basin deformation. Detailed geological mapping and structural analysis revealed that basin deposits were affected by compressional deformations that can be found both at map and outcrop scales. Decametric splay thrusts emanating from the substratum–conglomerate interface locally double the continental succession and are bounded by a roof thrust along the Late Messinian evaporite décollement, defining a deformation pattern consistent with a duplex‐like structure. The time–space structural evolution of the basin inferred from the fieldwork was addressed and tested by analogue modelling that approximated the rheological stratification of the study area to a layered brittle–ductile system. The model results support the hypothesis that the evolution of the thrust system affecting the SGB started as an early floor imbricate fan thrust system that successively evolved to a duplex structure as the link thrusts propagated into the upper décollement layer that resulted from the deposition of the Late Messinian evaporites. Models display many structural features that may be compared with the natural prototype, and highlight the importance of syntectonic sedimentation in the development and evolution of tectonic structures. The results of this study retain relevant implications for the Neogene evolution of the Tyrrhenian Basin–Northern Apennines system. This study also supports that combining between field structural analyses and analogue modelling can give useful hints into the evolutionary history of tectonically complex areas.  相似文献   

The geodynamical evolution of the Northern Apennines chain (Central Italy): an exploring numerical model     

Cristina Pauselli  Costanzo Federico 《Physics of the Earth and Planetary Interiors》2004,141(4):327-341

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Identifying Wrinkle Ridges from Mars MGS and Viking Mission Data: Using GRASS GIS in Planetary Geology     

Alessandro Frigeri  Costanzo Federico  Cristina Pauselli  Giorgio Minelli 《Transactions in GIS》2004,8(2):255-262

During the past few decades, numerous missions to Mars have sent information about the red planet. The missions have shown that Mars has ice on its poles and that ice could be present all over the planet subsurface. The presence of ice on the subsurface could drive particular geological structures called ‘wrinkle ridges’. In this work, Viking image data and the latest Mars Global Suveyor (MGS) data have been imported and stored in a common geospatial database using GRASS GIS as a tool for planetary geology. This study has focused on a subregion of Solis Planum where wrinkle ridges have been localised and both Viking images and MGS altimetry and imagery data are available. Raster data at different resolutions and with different projection parameters have been imported into GRASS GIS and projected in a common reference system. Raw, unprojected data have been processed and rectified using the GRASS image modules. Imagery data have been used to detect planimetric features, whereas basic morphometrical analysis has been performed from the gridded elevation data coming from MGS Mars Orbiter Laser Altimeter.  相似文献   

Procedure of reduction of travel-time curves ofP andS waves at the focal surface     

A. Bottari  B. Federico  M. Pietrafesa  A. Teramo 《Pure and Applied Geophysics》1993,140(4):641-653

A method for the calculation of seismic waves velocities at focal depth is here proposed. A stratified earth model with spherical symmetry and the analytical relationship between the epicentral distance and the travel times of seismic waves are used.This method, applied to the southern Tyrrhenian region and to the Japanese islands, allows to reduce the observed travel times to the focal depth independently of a particular velocity model.  相似文献   

Semi-automated regional classification of the style of activity of slow rock-slope deformations using PS InSAR and SqueeSAR velocity data     

Crippa  Chiara  Valbuzzi  Elena  Frattini  Paolo  Crosta  Giovanni B.  Spreafico  Margherita C.  Agliardi  Federico 《Landslides》2021,18(7):2445-2463

Large slow rock-slope deformations, including deep-seated gravitational slope deformations and large landslides, are widespread in alpine environments. They develop over thousands of years by progressive failure, resulting in slow movements that impact infrastructures and can eventually evolve into catastrophic rockslides. A robust characterization of their style of activity is thus required in a risk management perspective. We combine an original inventory of slow rock-slope deformations with different PS-InSAR and SqueeSAR datasets to develop a novel, semi-automated approach to characterize and classify 208 slow rock-slope deformations in Lombardia (Italian Central Alps) based on their displacement rate, kinematics, heterogeneity and morphometric expression. Through a peak analysis of displacement rate distributions, we characterize the segmentation of mapped landslides and highlight the occurrence of nested sectors with differential activity and displacement rates. Combining 2D decomposition of InSAR velocity vectors and machine learning classification, we develop an automatic approach to characterize the kinematics of each landslide. Then, we sequentially combine principal component and K-medoids cluster analyses to identify groups of slow rock-slope deformations with consistent styles of activity. Our methodology is readily applicable to different landslide datasets and provides an objective and cost-effective support to land planning and the prioritization of local-scale studies aimed at granting safety and infrastructure integrity.

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Nano‐Powdered Calcium Carbonate Reference Materials: Significant Progress for Microanalysis?     

Klaus Peter Jochum  Dieter Garbe‐Schnberg  Marina Veter  Brigitte Stoll  Ulrike Weis  Michael Weber  Federico Lugli  Anna Jentzen  Ralf Schiebel  Jasper A. Wassenburg  Dorrit E. Jacob  Gerald H. Haug 《Geostandards and Geoanalytical Research》2019,43(4):595-609

Homogeneity, mass fractions of about forty trace elements and Sr isotope composition of Ca carbonate reference materials (RMs) between original and nano‐powdered pellets are compared. Our results using nanosecond and femtosecond LA‐(MC)‐ICP‐MS show that the nano‐pellets of the RMs MACS‐3NP, JCp‐1NP and JCt‐1NP are about a factor of 2–3 more homogeneous than the original samples MACS‐3, JCp‐1 and JCt‐1, and are therefore much more suitable for microanalytical purposes. With the exception of Si, the mass fractions of the synthetic RM MACS‐3 agree with its fine‐grained analogue MACS‐3NP. Very small, but significant, differences between original and nano‐pellets are observed in the RMs JCp‐1 and JCt‐1 for some trace elements with very low contents, indicating the need for re‐certification. Strontium mass fractions in the analysed RMs are high (1500–7000 mg kg^?1), and their isotope compositions determined by LA‐MC‐ICP‐MS in the original and the nano‐pellets agree within uncertainty limits.  相似文献   

The ground-based InSAR monitoring system at Stromboli volcano: linking changes in displacement rate and intensity of persistent volcanic activity   总被引：1，自引：1，他引：0  

Federico Di Traglia  Emanuele Intrieri  Teresa Nolesini  Federica Bardi  Chiara Del Ventisette  Federica Ferrigno  Sara Frangioni  William Frodella  Giovanni Gigli  Alessia Lotti  Carlo Tacconi Stefanelli  Luca Tanteri  Davide Leva  Nicola Casagli 《Bulletin of Volcanology》2014,76(2):1-18

Stromboli volcano (Aeolian Archipelago, Southern Italy) experienced an increase in its volcanic activity from late December 2012 to March 2013, when it produced several lava overflows, major Strombolian explosions, crater-wall collapses pyroclastic density currents and intense spatter activity. An analysis of the displacement of the NE portion of the summit crater terrace and the unstable NW flank of the volcano (Sciara del Fuoco depression) has been performed with a ground-based interferometric synthetic aperture radar (GBInSAR) by dividing the monitored part of the volcano into five sectors, three in the summit vents region and two in the Sciara del Fuoco. Changes in the displacement rate were observed in sectors 2 and 3. Field and thermal surveys revealed the presence of an alignment of fumaroles confirming the existence of an area of structural discontinuity between sectors 2 and 3. High displacement rates in sector 2 are interpreted to indicate the increase in the magmastatic pressure within the shallow plumbing systems, related to the rise of the magma level within the conduits, while increased displacement rates in sector 3 are connected to the lateral expansion of the shallow plumbing system. The increases and decreases in the displacement rate registered by the GBInSAR system in the upper part of the volcano have been used as a proxy for changes in the pressure conditions in the shallow plumbing system of Stromboli volcano and hence to forecast the occurrence of phases of higher-intensity volcanic activity.  相似文献