Effects of column axial force – bending moment interaction on inelastic seismic response of steel frames     

Marina Como  Mario De Stefano  Roberto Ramasco 《地震工程与结构动力学》2003,32(12):1833-1852

It is well known that axial force – bending moment interaction (N–M interaction) affects to a large extent the cyclic inelastic behaviour of structural elements, especially columns in framed structures, with reduction in bending capacity and loss of available ductility. A few studies have also shown that significant inelastic axial shortening affects the response of column elements subjected to medium–high levels of axial loads and cyclic bending. This paper is primarily aimed at evaluating the effects of column N–M interaction on the inelastic seismic response of steel frames. By considering the contemporaneous action of vertical loads, due to gravity, and of horizontal seismic excitation, it is shown that the progressive axial shortening of adjacent columns may differ substantially, thus inducing significant relative settlements at the ends of the connecting beams and, then, remarkable amplifications in beam plastic rotations. An evaluation of additional beam plastic rotations induced by column N–M interaction is carried out for real structures by investigating the inelastic response of steel frames designed according to European standards under horizontal and vertical earthquake excitations. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Morphologic changes in the Paraná River channel (Argentina) in the light of the climate variability during the 20th century     

Mario L. Amsler  Carlos G. Ramonell  Horacio A. Toniolo   《Geomorphology》2005,70(3-4):257

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Potassium-argon dating of igneous activity in the central Chilean Andes — latitude 33°S     

Robert E. Drake  Garniss Curtis  Mario Vergara   《Journal of Volcanology and Geothermal Research》1976,1(3):285-295

Potassium-argon dating of volcanic and plutonic rocks in the Andean region of central Chile has revealed previously unrecognized episodes of igneous activity during Cretaceous and Cenozoic time. These results indicate the need to re-evaluate the classic stratigraphic subdivisions that have evolved on lithologic rather than time-stratigraphic criteria.Four radiometric age groups have been identified in the coast range volcanic belt:

1. (1) Las Chilcas Formation — Early Cretaceous continental volcanic strata (120-110 m.y.).

2. (2) Lo Valle Formation — Late Cretaceous continental volcanic strata (78-65 m.y.).

3. (3) Late Oligocene extrusive volcanics (31-28 m.y.).

4. (4) Early Miocene intrusive volcanics (20.6–19.5 m.y.).

Two radiometric age groups have also been identified in the adjacent Andean Cordillera:

1. (1) Farellones Formation — continental volcanic strata (18.5–17.3 m.y.).

2. (2) Early Pliocene extrusive volcanics (5-4 m.y.).

An older group of continental volcanic strata in the Andes represented by the Abanico Formation remains undated but is intruded by plutons dated at 19.5 and 24 m.y.Available chronologic evidence indicates that volcanic activity moved eastward from the coast range volcanic belt to the Andean Cordillera between 20 and 18 m.y. ago and remained there to the present time.  相似文献   

Seven landslide dams of old seismic origin in southeastern Sicily (Italy)   总被引：3，自引：0，他引：3  

Pier Giorgio Nicoletti  Mario Parise   《Geomorphology》2002,46(3-4)

This paper focuses on origin, morphology and evolution of seven landslide dams in southeastern Sicily. These landforms are part of a set of 146 landslides recently recognised in this area, which was hitherto considered to have little or no slope instability. Southeastern Sicily consists of a plateau (the Hyblaean Mountains) incised by canyons and surrounded by lower lands. It is underlain mostly by subhorizontal, moderately to well-lithified carbonate rocks. Relief is low.Several lines of evidence justify the assumption of a seismic trigger for the landslides in this area: (1) the geo-climatic environment is not favourable to landsliding, (2) low-angle basal shear surfaces are very frequent, (3) landslide distribution is consistent with the known magnitude–distance relationships for earthquake-induced landslides, (4) historical documents testify to earthquake-triggered slope instability and (5) a specific landslide can be exactly dated.The phenomena illustrated here include six rock slides (one with a debris-flow component) and one rock fall. Slip surfaces are mostly non-circular. Landslide volume ranges from about 50×10³ to 34×10⁶ m³.With reference to the Costa and Schuster [Geol. Soc. Am. Bull. 100 (1988) 1054] classification of landslide dams, five cases belong to type II (spanning the entire valley), and two to type IV (failures from both valley sides, with frontal or side contact between failed masses). With reference to Crozier and Pillans [Catena 18 (1991) 471] classification of landslide lakes, all cases show a main valley lake while tributary valley, back and supra lakes are sporadically present. One damming is attributable to the 1693 earthquake with certainty; another damming, to the same earthquake with high probability. Three dams were reincised, one breached or reincised, one is slightly reincised and two more or less intact; correspondingly, five silting up deposits were reincised, one is being reincised at present and two are still under formation.  相似文献   

Cyclostratigraphy and high-frequency carbon isotope fluctuations in Upper Cretaceous shallow-water carbonates, southern Italy   总被引：2，自引：0，他引：2  

Francesco P. Buonocunto  Mario Sprovieri†  Adriana Bellanca†  Bruno D'Argenio‡  Vittoria Ferreri‡  Rodolfo Neri†  Gaetano Ferruzza† 《Sedimentology》2002,49(6):1321-1337

Abstract A detailed carbon isotope study has been carried out on a Santonian (Upper Cretaceous) carbonate platform succession that crops out at Monte Sant'Erasmo (southern Italy). Previous centimetre‐scale studies on this succession have shown that high‐frequency eustatic changes, resulting from the Earth's orbital fluctuations, controlled the hierarchical organization of the depositional and early diagenetic features in elementary cycles, bundles (groups of three to five elementary cycles) and superbundles (groups of three or four bundles). The elementary cycles, which correspond to single beds, suggest a control caused by Earth's precession; the bundles and superbundles record the short (≈ 100 kyr) and long (≈ 400 kyr) eccentricity periodicity respectively. The δ¹³C signal of the Monte Sant'Erasmo succession is cyclic in nature and may be considered to be a reliable proxy for the sedimentary evolution (and related sea‐level history) of the analysed sequence. The carbon isotope cyclicity is recorded at bundle and superbundle level, but it is not evident at the scale of the elementary cycles, at least with the sampling interval used in this study. Spectral analysis of the δ¹³C record shows two main peaks corresponding to the short‐ and long‐eccentricity periodicity, whereas the precession signal is not evident in the power spectrum. In addition, lithofacies analysis shows that, in each bundle (and superbundle), higher C isotope values occur in sediments characterized by marine cements, whereas lower values are normally found in more restricted deposits overprinted by early meteoric diagenesis. Early diagenesis, driven by periodic sea‐level fluctuations, developed in either shallow‐subtidal (marine diagenesis) or subaerial‐exposed (meteoric overprint) sedimentary environments and directly influenced the carbon isotope signature. As a consequence, the δ¹³C record at Monte Sant'Erasmo reflects high‐frequency climatic oscillations controlling both environmental and early diagenetic changes. The long‐term isotopic record is similar to that of contemporaneous pelagic sections in England and elsewhere in Italy. It is concluded that the δ¹³C signature of shallow‐water carbonates, such as those of Monte Sant'Erasmo, offers great potential for correlation with coeval sections, including those of the pelagic realm.  相似文献   

Macroinfaunal assemblages associated with mussel and clam beds in an estuary of Southern Chile     

Pedro Quijón  Mario Pino 《Estuaries and Coasts》1996,19(1):62-74

Samples were collected from September 1990 to February 1992, at three subtidal sites of the middle reaches of the Queule River estuary, southern Chile, to analyze the spatial and temporal variability of the macroinfauna inhabiting substrata with different abundances of bivalves. In addition, water and sediment samples were obtained to study the relationships between the temporal variability in macroinfaunal abundances, physical factors and chlorophylla content. Temperature, salinity, and chlorophylla showed a rather strong seasonal variability but slight between-site differences. Sediment characteristics and bivalve abundances, by contrast, exhibited little temporal variability but large differences between sites. The macroinfauna was primarily represented by polychaetesPrionospio (Minuspio) patagonica being dominant in the three areas. Most dominant species showed similar trends of temporal variability, with maximum abundances recorded during spring and fall. The appearance of recruits was restricted to the summer with little difference among sites. Multiple regression analyses showed that the temporal variability of macroinfaunal adults and recruits, was primarily associated with variability in salinity and water temperature, respectively. Spatial variability of these organisms was also explained by variations in these factors, together with those of sediment texture and organic matter content. No evidence of interactions (significant relationships) was found between the abundances of bivalves and those of the macroinfauna, nor among macroinfaunal organisms.  相似文献   

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   

The contribution of geoscience to the EC survey on European historic cities     

Mario Panizza  Sandra Piacente 《Engineering Geology》1990,29(4):399-401

The EC Executive Commission has established a permanent survey for historic cities in Europe. The survey will evaluate the economic and social yield of architectural and archeological restoration and preservation projects, establish basic criteria for decisions regarding the preservation of buildings or their reconstruction and conversion, their being closed for research purposes or rendering them accessible to the public, and indicate the type of use most suited to the characteristics of the landmark.

One aspect of fundamental importance, to which primary consideration should be given in order to correctly evaluate the restoration project and future use, concerns the relationship between the architectural structure and its environment. Three sectors of this aspect are indicated, along with examples, with particular emphasis on geological implications.

(1) Environmental hazards: earth (erosion, earthquakes, volcanoes, subsidence etc.); water (floods, seastorms, pollution etc.); air (hurricanes, whirlwinds, pollution etc.); biological factors (deteriorated areas, infestation etc.).

(2) Causes and effects: the study of the environmental factors that have led to the construction and the typology of the architectural landmark; forecasts of the consequences for the environment of the various types of conversion of the historical landmark.

(3) Environment education: informative and educational programs for an integral knowledge of the environment in which the historical city is situated and to promote an environmental consciousness.  相似文献   

Confronto fra i regimi pluviometrici di Genova e Savona     

Mario Bossolasco  Ida Gennaro 《Pure and Applied Geophysics》1948,11(1):127-131

Riassunto L'esame dei giorni di ciascun anno dal 1886 al 1900 nei quali si sono avute precipitazioni apprezzabili tanto a Genova quanto a Savona (località distanti fra loro 35 km) viene istituito utilizzando l'indice di similitudineS recentemene introdotto daM. Bouët. La discussione dei risultati dimostra fra l'altro come le località marittime a ridosso di catene montuose siano più adatte a mettere in luce le variazioni nel tempo delle caratteristiche climatiche.

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Zusammenfassung Ausgehend von der Anzahl der gleichzeitigen Niederschlagstagen in Genua und Savona (Abstand 35 km) wurde der AehnlichkeitsindexS nachBouët für jedes Jahr der Periode 1886–1900 berechnet. Die Diskussion der Ergebnisse zeigt u.a., dass die maritimen Orte, die am Fusse einer Bergkette liegen, gewöhnlich besser als die kontinentalen geeignet sind die zeitlichen Veränderungen der klimatischen Verhältnisse darzustellen.

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Sull'idrologia del Foehn     

Carlo Bernasconi  Mario Bossolasco 《Pure and Applied Geophysics》1951,19(3-4):179-185

Riassunto Per alcuni casi diFöhn delle Alpi Italiane, interessanti il Piemonte e la Lombardia, sono state esaminate le variazioni dei deflussi nei giorni in cui soffiava tale vento nonchè in quelli adiacenti, trovando che di regola, quando non intervengono precipitazioni od altri fattori, ilFöhn provoca una diminuzione netta delle portate, che può raggiungere e superare il 10% e che si esplica con relativa prontezza. Si spiega tale riduzione con la forte evaporazione causata dalFöhn.

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Summary Researches have been undertaken on the influence of the Föhn in the italian Alps, regarding the runoff-variations. The Föhn causes as a rule a decrease of the runoff, which, in absence of precipitation, can reach or exceed 10%. It can be explained by the strong evaporation during the Föhn.

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Zusammenfassung Anhand einiger Föhnfälle in den italienischen Alpen wurde der Einfluss des Föhns auf die Aenderungen der Abflussmenge untersucht. Wenn empfindliche Niederschläge oder andere Faktoren nicht vorkommen, verursacht in der Regel der Föhn eine Abnahme der Abflussmenge, die 10% erreichen oder sogar überschreiten kann. Die Erklärung ist in der starken Verdunstung während des Föhns zu suchen.

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