Nonlinear seismic behaviour of wall-frame dual systems accounting for soil–structure interaction     

Sandro Carbonari  Francesca Dezi  Graziano Leoni 《地震工程与结构动力学》2012,41(12):1651-1672

The aim of this paper is to study the effects of soil–structure interaction on the seismic response of coupled wall-frame structures on pile foundations designed according to modern seismic provisions. The analysis methodology based on the substructure method is recalled focusing on the modelling of pile group foundations. The nonlinear inertial interaction analysis is performed in the time domain by using a finite element model of the superstructure. Suitable lumped parameter models are implemented to reproduce the frequency-dependent compliance of the soil-foundation systems. The effects of soil–structure interaction are evaluated by considering a realistic case study consisting of a 6-storey 4-bay wall-frame structure founded on piles. Different two-layered soil deposits are investigated by varying the layer thicknesses and properties. Artificial earthquakes are employed to simulate the earthquake input. Comparisons of the results obtained considering compliant base and fixed base models are presented by addressing the effects of soil–structure interaction on displacements, base shears, and ductility demand. The evolution of dissipative mechanisms and the relevant redistribution of shear between the wall and the frame are investigated by considering earthquakes with increasing intensity. Effects on the foundations are also shown by pointing out the importance of both kinematic and inertial interaction. Finally, the response of the structure to some real near-fault records is studied. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Paleomagnetic dating of the most recent silicic eruptive activity at Pantelleria (Strait of Sicily)     

Fabio Speranza  Patrizia Landi  Francesca D’Ajello Caracciolo  Alessandro Pignatelli 《Bulletin of Volcanology》2010,72(7):847-858

We report on the paleomagnetism of ten sites in the products of the most recent silicic eruptive cycle of Pantelleria, Strait of Sicily. Previously radiometrically dated at 5–10 ka, our comparison with proxies for geomagnetic field directions allows us to narrow considerably the time window during which these eruptions occurred. The strongly peralkaline composition causes the magmas to have low viscosities, locally resulting in strong agglutination of proximal fall deposits. This allows successful extraction of paleomagnetic directions from the explosive phases of eruptions. One of our sites was located in the Serra della Fastuca fall deposit, produced by the first explosive event of the eruptive cycle. The other nine sites were located in the most recent explosive (pumice fall and agglutinate from Cuddia del Gallo and Cuddia Randazzo) and effusive (Khaggiar lava) products. The (very similar) paleomagnetic directions gathered from eight internally consistent sites were compared to reference geomagnetic field directions of the last 5–10 ka. Directions from Cuddia del Gallo agglutinate and Khaggiar flows translate into 5.9- to 6.2-ka ages, whereas the Fastuca pumices yield a slightly older age of 6.2–6.8 ka. Hence, the most recent silicic eruptive cycle lasted at most a millennium and as little as a few centuries around 6.0 ka. Paleomagnetically inferred ages are in good agreement with published (and calibrated by us) ¹⁴C dates from paleosols/charcoals sampled below the studied volcanic units, whereas K/Ar data are more scattered and yield ∼30% older ages. Our data show that the time elapsed since the most recent silicic eruptions at Pantelleria is comparable to the quiescence period separating the two latest volcanic cycles.  相似文献   

Seismic fragility curves of as-built single-span masonry arch bridges     

Giovanni Tecchio  Marco Donà  Francesca da Porto 《Bulletin of Earthquake Engineering》2016,14(11):3099-3124

Masonry arch bridges are crucial elements in the railway transportation network throughout Europe. Although significant advances in seismic risk assessment of various bridge types have been made by developing fragility curves of generalized classes of structures, there are no comparable tools for masonry arch structures. In this context, this paper presents the construction of seismic fragility curves of single-span masonry bridges according to the limit analysis method. An iterative procedure is implemented to define the capacity curve of the equivalent single degree of freedom system through non-linear kinematic analysis. The process involves determination of the collapse mechanism, calculation of the limit load multiplier, and definition of the thrust line. The intrinsic variability of the seismic action is incorporated with the use of different sets of elastic spectra compatible with EC 8 Type-1 spectrum for various types of soil, with peak ground acceleration varying over the range 0.05–1.5 g. The fragility curves of the generalized classes of single-span masonry bridges are finally obtained from the effective ranges of the main geometric and material parameters affecting arch bridge capacity.  相似文献   

Spatial and temporal dust source variability in northern China identified using advanced remote sensing analysis   总被引：1，自引：0，他引：1  

A. Taramelli  M. Pasqui  J. Barbour  D. Kirschbaum  L. Bottai  C. Busillo  F. Calastrini  F. Guarnieri  C. Small 《地球表面变化过程与地形》2013,38(8):793-809

The aim of this research is to provide a detailed characterization of spatial patterns and temporal trends in the regional and local dust source areas within the desert of the Alashan Prefecture (Inner Mongolia, China). This problem was approached through multi‐scale remote sensing analysis of vegetation changes. The primary requirements for this regional analysis are high spatial and spectral resolution data, accurate spectral calibration and good temporal resolution with a suitable temporal baseline. Landsat analysis and field validation along with the low spatial resolution classifications from MODIS and AVHRR are combined to provide a reliable characterization of the different potential dust‐producing sources. The representation of intra‐annual and inter‐annual Normalized Difference Vegetation Index (NDVI) trend to assess land cover discrimination for mapping potential dust source using MODIS and AVHRR at larger scale is enhanced by Landsat Spectral Mixing Analysis (SMA). The combined methodology is to determine the extent to which Landsat can distinguish important soils types in order to better understand how soil reflectance behaves at seasonal and inter‐annual timescales. As a final result mapping soil surface properties using SMA is representative of responses of different land and soil cover previously identified by NDVI trend. The results could be used in dust emission models even if they are not reflecting aggregate formation, soil stability or particle coatings showing to be critical for accurately represent dust source over different regional and local emitting areas. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Landslide HotSpot Mapping by means of Persistent Scatterer Interferometry   总被引：1，自引：0，他引：1  

Silvia Bianchini  Francesca Cigna  Gaia Righini  Chiara Proietti  Nicola Casagli 《Environmental Earth Sciences》2012,67(4):1155-1172

Landslide detection and mapping represent fundamental requirements for every hazard and risk evaluation and consequent improvement of the management strategies for such natural hazards. Optical and radar remote sensing can be used to observe landslide-induced ground deformation, ranging from regional to local scales. This work presents a methodology called Landslide HotSpot Mapping; this approach integrates cartographic, thematic and optical data with Persistent Scatterer Interferometry for the identification of extremely slow to very slow moving landslides, and for the evaluation of their state of activity and intensity. This methodology scans wide areas to detect hotspots, which are narrow unstable zones characterized by higher landslide hazard. To these hotspots, priority has to be given when planning field surveys and in situ validation campaigns, so that field work time and effort can be optimized and significantly reduced. The approach is tested in Central Calabria, over a 4,470?km² area located in southern Italy. ENVISAT ascending images acquired between 2003 and 2009 and processed with the Persistent Scatterer Pairs (PSP) technique are used to analyse deformation patterns. Combining conventional photo-interpretation with the analysis of PSP data, 64 new landslides are identified and the spatial (boundaries) and temporal (activity) information of 980 pre-mapped phenomena (23.6% of updated inventory) are updated. 1,012 active (continuous or reactivated) landslides are identified and 4 hotspot areas selected: San Fili, Rende, Lago, Catanzaro. Urgent field checks have to be organized for these hotspots to validate the satellite-based observations and to design appropriate mitigation measures to reduce impacts on the elements at risk.  相似文献   

Collaborative Web‐GIS Design: A Case Study for Road Risk Analysis and Monitoring     

Francesco Pirotti  Alberto Guarnieri  Antonio Vettore 《Transactions in GIS》2011,15(2):213-226

This article presents a methodology for designing a WebGIS framework intended for automatically analyzing spatial data and updating statistics of interest with new information inserted daily by multiple users via a Web portal. A practical example is used on vehicle accident data for assessing risk in specific road segments. Two main blocks integrated together will be described: the collaborative block and the data‐analysis block. The former gives end‐users computer‐aided tools to view, insert, modify and manage data related to accidents and traffic monitoring sensors, whereas the latter is developed to automatically analyze the accident data coming from user's collaboration. Because different agencies can survey accident sites, a collaborative environment is necessary – and a Web‐based solution is ideal – for permitting multi‐user access and data insertion. A centralized approach to process the data in real time is described in all its components. Server‐side Structured Query Language functions optimize performance by using dedicated libraries for spatial processing and re‐structuring the attributes associated with elements which are consequently re‐classified for correct color‐scaling. The end‐product is a system that provides a seamless integration of front‐end tools for user collaboration and back‐end tools to update accident risk statistics in real time and provide them to stakeholders.  相似文献   

Interplanetary fast forward shocks and their geomagnetic effects: CAWSES events     

E. Echer  B.T. Tsurutani  F.L Guarnieri  J.U. Kozyra 《Journal of Atmospheric and Solar》2011,73(11-12):1330-1338

The seven CAWSES interplanetary fast forward shocks and their geomagnetic effects during 2004–2005 have been analyzed. It is found that the arrival time of the shocks at Earth can be estimated within an accuracy of ～5 min. Furthermore, AL decreases are found to occur within 10 min of shock impingement on the magnetopause. It was also determined that there is a direct correlation between the interplanetary magnetic field southward directed (IMF B_s) prior to shock arrival and substorms triggered by the shocks. If the IMF is northward prior to shock arrival, the geomagnetic activity is present but is low. One interpretation of this result is that the preconditioning energy stored in the magnetotail leaks away rapidly. A correlation between substorm peak AL and shock strength (Mach number) has also been noted, which could imply that shock strength is important for the amount of energy released into the magnetosphere/ionosphere.  相似文献   

Engineering ground motion record selection in the ITalian ACcelerometric Archive   总被引：1，自引：1，他引：0  

Iunio Iervolino  Carmine Galasso  Roberto Paolucci  Francesca Pacor 《Bulletin of Earthquake Engineering》2011,9(6):1761-1778

This paper introduces REXELite, an internet version of REXEL, a software for automatic selection of ground motion suites for nonlinear dynamic analysis of structures. REXELite was developed with the aim of integrating an advanced earthquake records’ repository, such as the ITalian ACcelerometric Archive (ITACA), with a tool to define seismic input for engineering seismic analysis according to international standards (with priority to Europe). In fact, REXELite allows to define target design spectra according either to Eurocode 8 or to the Italian building code, and to search ITACA for suitable sets of seven records (comprised of one or two horizontal ground motion components) matching such target spectra: on average, in a user-specified period range, and with the desired tolerance. The records in the set also have, individually and according to some criteria, the most similar spectral shape with respect to that of the code. Selection options include magnitude, source-to-site distance, soil conditions and, if desired, linear scaling of records to reduce further record-to-record variability of the selected suite.  相似文献   

Hydrogen isotope ratios of leaf wax n-alkanes in grasses are insensitive to transpiration     

Francesca A. McInerney  Brent R. Helliker  Katherine H. Freeman 《Geochimica et cosmochimica acta》2011,75(2):541-554

We analyzed hydrogen isotope ratios of high-molecular weight n-alkanes (δD_l) and oxygen isotope ratios of α-cellulose (δ¹⁸O_C) for C₃ and C₄ grasses grown in the field and in controlled-environment growth chambers. The relatively firm understanding of ¹⁸O-enrichment in leaf water and α-cellulose was used to elucidate fractionation patterns of δD_l signatures. In the different relative humidity environments of the growth chambers, we observed clear and predictable effects of leaf-water enrichment on δ¹⁸O_C values. Using a Craig-Gordon model, we demonstrate that leaf water in the growth chamber grasses should have experienced significant D-enriched due to transpiration. Nonetheless, we found no effect of transpirational D-enrichment on the δD_l values. In field samples, we saw clear evidence of enrichment (correlating with relative humidity of the field sites) in both δ¹⁸O_C and δD_l. These seemingly contrasting results could be explained if leaf waxes are synthesized in an environment that is isotopically similar to water entering plant roots due to either temporal or spatial isolation from evaporatively enriched leaf waters. For grasses in the controlled environment, there was no enrichment of source water, whereas enrichment of grass source water via evaporation from soils and/or stems was likely for grass samples grown in the field.Based on these results, evaporation from soils and/or stems appears to affect δD_l, but transpiration from leaves does not. Further evidence for this conclusion is found in modeling expected net evapotranspirational enrichment. A Craig-Gordon model applied to each of the field sites yields leaf water oxygen isotope ratios that can be used to accurately predict the observed δ¹⁸O_C values. In contrast, the calculated leaf water hydrogen isotope ratios are more enriched than what is required to predict observed δD_l values. These calculations lend support to the conclusion that while δ¹⁸O_C reflects both soil evaporation and transpiration, δD_l appears to only record evaporation from soils and/or stems. Therefore, the δD of n-alkanes can likely be used to reconstruct the δD of water entering a leaf, supporting the soil-enrichment model of Smith and Freeman (2006). In both the field and controlled studies, we found significant photosynthetic pathway effects on n-alkane δD suggesting that biochemical pathways or plant phylogeny have a greater effect on leaf wax δD than leaf-water enrichment in grasses.  相似文献   

Two GUIs-based analysis tool for spectroradiometer data pre-processing     

Francesca Garfagnoli  Gianluca Martelloni  Andrea Ciampalini  Luca Innocenti  Sandro Moretti 《Earth Science Informatics》2013,6(4):227-240

A new graphical user interface (GUI) for pre-processing reflectance spectra, built using MATLAB and expressly designed for the ASD FieldSpec® spectroradiometer, was developed to solve problems that generally affect experimental ASD data. The GUI is characterised by an easily readable, graphic visualisation of spectra, from which the absorption band depth (ABD) can be obtained for a selected wavelength. The output format of the ASD data is a binary file with an .asd extension. The binary file, that provides a single spectrum, can be processed using a software functionality, by means of a GUI, that allows to select one or more binary files to produce a spectral library in a unique .txt file. The spectral reflectance is re-calibrated with the “convex-hull” methodology to eliminate the convex shape, which is typical of reflectance spectra. Different examples of the use of the new GUI are provided.  相似文献