Dowel connections securing roof-diaphragms to perimeter walls in historic masonry buildings and in-field testing for capacity assessment     

Alessandra Marini  Ezio Giuriani  Andrea Belleri  Stefania Cominelli 《Bulletin of Earthquake Engineering》2018,16(9):4001-4025

In the seismic retrofit of existing masonry constructions, global interventions are often needed to inhibit the onset of local mechanisms and to engage the whole building box-like structural behaviour. Such interventions are represented by perimeter ties and roof and floor diaphragms. This paper considers the roof diaphragm strengthening solution and investigates the use of stud connections securing the roof thin-folded shell to the perimeter walls. Stud connections serve the dual purpose of collecting and transferring the out-of-plane inertia forces of the masonry walls to the roof diaphragm, as well as transferring the diaphragm reaction forces to the shear walls. Specific detailing of the stud connection and the adoption of an improved lime-mortar overlay on the top of the masonry walls are proposed to improve the connection strength; without such improvements, the connection capacity would be jeopardised by the reduced shear resistance of the masonry wall due to the absence of significant vertical confining action at the roof level. The intervention entirely changes the behaviour of the connection and significantly reduces shear stresses on the masonry wall. The structural behaviour of the connection is analysed and discussed. Emphasis is made on the conceptual design of laboratory and in-field test procedures and testing frames in order to replicate the boundary conditions in real applications. In-situ tests may help during the design of the roof thin-folded shell system and allow for the efficiency assessment of the connections prior to the final intervention, thereby proving the actual feasibility of the retrofit solution.  相似文献   

Quantitative integration of 3D and 4D seismic impedance into reservoir simulation model updating in the Norne Field     

Masoud Maleki  Alessandra Davolio  Denis José Schiozer 《Geophysical Prospecting》2019,67(1):167-187

The ultimate goal of reservoir simulation in reservoir surveillance technology is to estimate long-term production forecasting and to plan development and management of petroleum fields. However, maintaining reliable reservoir models which honour available static and dynamic data, involve inherent risks due to the uncertainties in space and time of the distribution of hydrocarbons inside reservoirs. Recent applications have shown that these uncertainties can be reduced by quantitative integration of seismic data into the reservoir modelling workflows to identify which areas and reservoir attributes of the model should be updated. This work aims using seismic data to reduce ambiguity in calibrating reservoir flow simulation model with an uncertain petro-elastic model, proposing a circular workflow of inverted seismic impedance (3D and 4D) and engineering studies, with emphasis on the interface between static and dynamic models. The main contribution is to develop an updating procedure for adjusting reservoir simulation response before using it in the production forecasting and enhance the interpretive capability of reservoir properties. Accordingly, the workflow evaluates consistency of reservoir simulation model and inverted seismic impedance, assisted by production history data, to close the loop between reservoir engineering and seismic domains. The methodology is evaluated in a complex, faulted, sandstone reservoir, the Norne benchmark field, where a significant reservoir behaviour understanding (about the static and dynamic reservoir properties) is obtained towards the quantitative integration of seismic impedance data. This leads to diagnosis of the reservoir flow simulation reliability and generation of an updated simulation model consistent with observed seismic and well production history data, as well as a calibrated petro-elastic model. Furthermore, as Norne Field is a benchmark case, this study can be considered to enrich the discussions over deterministic or probabilistic history matching studies.  相似文献   

Preface     

Alessandra Celletti  Daniel J. Scheeres 《Celestial Mechanics and Dynamical Astronomy》2017,127(1):1-18

We revisit the relegation algorithm by Deprit et al. (Celest. Mech. Dyn. Astron. 79:157–182, 2001) in the light of the rigorous Nekhoroshev’s like theory. This relatively recent algorithm is nowadays widely used for implementing closed form analytic perturbation theories, as it generalises the classical Birkhoff normalisation algorithm. The algorithm, here briefly explained by means of Lie transformations, has been so far introduced and used in a formal way, i.e. without providing any rigorous convergence or asymptotic estimates. The overall aim of this paper is to find such quantitative estimates and to show how the results about stability over exponentially long times can be recovered in a simple and effective way, at least in the non-resonant case.  相似文献   

Phytoplankton community in the tropical lake of Lagoa Santa (Brazil): Conditions favoring a persistent bloom of Cylindrospermopsis raciborskii   总被引：2，自引：0，他引：2  

Cleber Cunha Figueredo  Alessandra Giani 《Limnologica》2009,(4):264-272

This study presents data on seasonal changes of the phytoplanktonic community of a small tropical lake, Lagoa Santa, in the Brazilian cerrado. Temporal variation in the community structure was small and we observed a permanent dominance of the cyanobacteria Cylindrospermopsis raciborskii. This dominance could be associated to the stability of several environmental conditions. Especially water temperature, always within the optimal growth range for C. raciborskii, and the constant mixed water column may have been important factors driving to the long term dominance of this species in the lake. Remarkable seasonal variation in rainfall, as well as the occasional and non-seasonal variation in nutrient concentrations, were important to explain changes in environmental and biological variables, but were not related to the dominance of C. raciborskii. Pearson's correlation and PCA could just in part explain the stable dominance of this cyanobacterium. Meteorological and chemical factors seem to have no clear control on the variability of the phytoplankton dynamics in Lagoa Santa. The weak relationship between C. raciborskii abundance and environmental variables points to additional intrinsic factors associated to this species that may be important in structuring the phytoplankton assemblage.  相似文献   

Slope dynamics of Lake Albano (Rome,Italy): insights from high resolution bathymetry     

Francesca Bozzano  Paolo Mazzanti  Marco Anzidei  Carlo Esposito  Mario Floris  Gianluca Bianchi Fasani  Alessandra Esposito 《地球表面变化过程与地形》2009,34(11):1469-1486

New detailed data about the morphology of the submerged slopes of Lake Albano (Rome, Italy) have been collected by a sonar multibeam survey financed by the Italian Department of Civil Protection. These data allow for investigation of the subaqueous slope dynamics of the lake, which partially fills a volcanic depression, and the elucidation of the relationships between subaqueous and subaerial slope processes. Subaerial, submerged and combined subaerial/submerged landslide‐related morphologies were detected around the inner slopes of the lake. In the submerged slopes, several gravity‐induced landforms were recognized: landslide scar areas, landslide accumulations, erosional chutes and channels, block fields, isolated blocks, scarps and slope breaks. An attempt to evaluate the state of activity of the submerged slopes was carried out by taking into consideration the relative freshness of some selected landforms. Interpretation of bathymetric data, as well as direct surveys of the subaerial slopes, was used to assess the morphometric features and interpret the type of movement of the landslides. We propose a comprehensive classification based on the landslide's size and type of movement. We recognized rock fall/topples, debris flows, rock slides and slump, complex rock slides/channelled flows and debris slide and slump. The volume of the main landslides ranged between 10¹ and 10³ m³, while a few rock and debris slides have volumes ranging between 10³ and 10⁵ m³. Two large palaeo‐landslides with volumes on the order of 10⁶ m³ were identified in the southern and northern part of the lake, respectively. Velocities of the recognized landslides range from rapid to extremely rapid. Two main landslide hazard scenarios have been depicted from the results of the integrated analysis of both subaerial and submerged gravity‐induced landforms. The most hazardous scenario involves extremely rapid large volume events (>10⁶ m³) that could, if they interacted with water, induce catastrophic tsunamis. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Changes in biomass structure and trophic status of the plankton communities in a highly dynamic ecosystem (Gulf of Venice,Northern Adriatic Sea)     

Alessandra Pugnetti  Anna Maria Bazzoni  Alfred Beran  Fabrizio Bernardi Aubry  Elisa Camatti  Mauro Celussi  Joan Coppola  Erica Crevatin  Paola Del Negro  Alessandro Paoli 《Marine Ecology》2008,29(3):367-374

The changes in the plankton biomass structure in relation to nutrient inputs were studied in the Gulf of Venice (Northern Adriatic Sea), an area characterized by a very marked trophic state variability. The investigation was carried out at two stations, in March, May and July 2005 and 2006, considering the whole water column. The size structure (from picoplankton to mesozooplankton) of both autotrophs and heterotrophs was analysed. Signals of diluted waters and nutrient inputs were more marked in 2005 than in 2006. In 2005, the total plankton biomass was almost double (87 ± 37 μg·C·l^?1) that in 2006 (44 ± 26 μg·C·l^?1). The variations were determined mainly by phytoplankton, with a 70% decrease, and a shift from a community dominated by microphytoplankton (49 ± 12%) in 2005 to one dominated by bacteria (43 ± 11%) in 2006 was observed. The relationship between the heterotrophic (H) and autotrophic (A) biomass indicated a rapid decline of the H/A ratio with increasing phytoplankton biomass. This study, although temporally limited, is consistent with the results reported for other marine environments and it seems to confirm the importance of nutrient inputs in structuring the biomass of plankton community.  相似文献   

Vertically stacked Gilbert-type deltas of Ventimiglia (NW Italy): The Pliocene record of an overfilled Messinian incised valley     

Anna Breda  Donatella Mellere  Francesco Massari  Alessandra Asioli 《Sedimentary Geology》2009,219(1-4):58-76

Overfilled incised valleys develop when the rate of sediment supply outpaces the rate of accommodation. An overfilled incised valley presents simple or compound valley-fill architecture, depending on the depth of the valley incision, compared with the height reached by the following sea-level rise.The Ventimiglia incised valley, exposed on the Ligurian coast, north-western Mediterranean margin, presents a spectacular example of compound incised-valley fill, developed in perennial “overfill” conditions. The valley was subaerially incised during the Messinian Salinity Crisis and rapidly flooded by the sea at the beginning of Pliocene, then filled by eleven coarse-grained Gilbert-type deltas during Early–Middle Pliocene time.The basal Messinian unconformity is locally paved with subaerial scree breccias and bioclastic shallow-marine sandstones, and blanketed by bathyal marls. These deposits record the lowstand, transgressive and early-highstand systems tracts of the first valley-fill sequence. The subsequent progradation of Gilbert-type deltas occurred in four stages, or depositional sequences, separated by transgressive marine-marl intervals. Within each depositional sequence, the deltaic bodies display offlapping architecture, recording falling shoreline trajectory, downward shifts in facies, and overall forced regression. The water depth and accommodation in the inundated coastal valley was gradually decreasing with time. The reduced accommodation allowed the youngest deltas to prograde out to the shelf edge, triggering mass collapses and subsequent filling into the newly created slump scars. Some of the deltas probably acted as “canyon-perched deltas” and supplied sediment to the deep-water slope and floor of the Ligurian Basin.The vertical stacking of Gilbert-type deltas is usually attributed, in tectonically active basins, to fault-related subsidence pulses. In Ventimiglia, the accommodation was created by high-frequency eustatic sea-level rises that, probably accompanied by climate controlled reductions in sediment supply, temporarily outpaced uplift, leading to the development of multiple cycles of infill.  相似文献   

Archaeofacies analysis: Using depositional attributes to identify anthropic processes of deposition in a monumental shell mound of Santa Catarina State,southern Brazil     

Ximena S. Villagran  Paulo C.F. Giannini  Paulo DeBlasis 《Geoarchaeology》2009,24(3):311-335

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Archaeometric Study of Mortars from the Garum Shop at Pompeii,Campania, Italy     

Raffaella De Luca  Domenico Miriello  Alessandra Pecci  Salvador Domínguez‐Bella  Dario Bernal‐Casasola  Daniela Cottica  Andrea Bloise  Gino Mirocle Crisci 《Geoarchaeology》2015,30(4):330-351

This paper presents the results of the compositional study of 29 samples of mortar from the so‐called “Garum Shop” (I, 12, 8) at Pompeii in Southern Italy. The characterization of the samples yielded information on the raw materials used in the mixtures, the production technology of mortars, and the building phases. It was carried out through polarized optical microscopy, X‐ray powder diffraction, X‐ray fluorescence, microanalysis energy‐dispersive X‐ray spectroscopic microanalysis, and image analysis through the JMicroVision software. The resultant data show great compositional homogeneity among the samples, suggesting the presence of a principal construction phase, probably associated with the first phase of the house. Apart from this main construction phase, there are some samples that show differences related either to their different function or to the fact that they come from different construction phases or restoration works. The raw materials used are related to the geology of the area and are fully compatible with the pyroclastic deposits of Vesuvius.  相似文献   

Numerical study on the effects of floodplain vegetation on river planform style     

Alessandra Crosato  May Samir Saleh 《地球表面变化过程与地形》2011,36(6):711-720

The effects of floodplain vegetation on river planform have been investigated for a medium‐sized river using a 2D morphodynamic model with submodels for flow resistance and plant colonization. The flow resistance was divided into a resistance exerted by the soil and a resistance exerted by the plants. In this way it was possible to reproduce both the decrease in bed shear stress, reducing the sediment transport capacity of the flow within the plants, and the increase in hydraulic resistance, reducing the flow velocities. Colonization by plants was obtained by instantaneously assigning vegetation to the areas that became dry at low water stages. This colonization presents a step forward in the modelling of bank accretion. Bank erosion was related to bed degradation at adjacent wet cells. Bank advance and retreat were reproduced as drying and wetting of the computational cells at the channel margins. The model was applied to a hypothetical case with the same characteristics as the Allier River (France). The river was allowed to develop its own geometry starting from a straight, uniform, channel. Different vegetation densities produced different planforms. With bare floodplains, the river always developed a braided planform, even if the discharge was constant and below bankfull. With the highest vegetation density (grass) the flow concentrated in a single channel and formed incipient meanders. Lower vegetation density (pioneer vegetation) led to a transitional planform, with a low degree of braiding and distinguishable incipient meanders. The results comply with flume experiments and field observations reported in the literature.  相似文献