Corrective eccentricities for assessment by the nonlinear static method of 3D structures subjected to bidirectional ground motions     

Melina Bosco  Aurelio Ghersi  Edoardo M. Marino 《地震工程与结构动力学》2012,41(13):1751-1773

Nonlinear static methods are reliable in the evaluation of the seismic response of planar structural schemes, but they are not very effective in the assessment of three-dimensional building structures. The authors of this paper have recently proposed a nonlinear static approach for asymmetric structures, which is an improvement on that stipulated by seismic codes. This method is based on the observation that the distribution of the maximum dynamic displacements of the deck can be enveloped by two pushover analyses performed by applying the lateral force with two eccentricities with respect to the center of mass of the deck. These eccentricities, named “corrective eccentricities”, are defined so that the two corresponding pushover analyses provide displacements that are equal to those evaluated by nonlinear dynamic analysis at the two sides of the deck. In this paper, the corrective eccentricities are determined for a wide set of single-story systems. The equations for their analytical evaluation are determined and their reliability is demonstrated. Finally, the analysis of a multi-story structure is conducted to show how the method can be applied to real buildings. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

GIS analysis to assess landslide susceptibility in a fluvial basin of NW Sicily (Italy)   总被引：10，自引：1，他引：9  

Christian Conoscenti  Cipriano Di Maggio  Edoardo Rotigliano   《Geomorphology》2008,94(3-4):325

Landslide hazard assessment, effected by means of geostatistical methods, is based on the analysis of the relationships between landslides and the spatial distributions of some instability factors. Frequently such analyses are based on landslide inventories in which each record represents the entire unstable area and is managed as a single instability landform. In this research, landslide susceptibility is evaluated through the study of a variety of instability landforms: landslides, scarps and areas uphill from crown. The instability factors selected were: bedrock lithology, steepness, topographic wetness index and stream power index. The instability landform densities computed for all the factors, which were arranged in Unique Condition Unit, allowed us to derive a total of three prediction images for each landslide typology. The role of the instability factors and the effects generated by the use of different landforms were analyzed by means of: a) bivariate analysis of the relationships between factors and landslide density; b) predictive power validations of the prediction images, based on a random partition strategy.The test area was the Iato River Basin (North-Western Sicily), whose slopes are moderately involved in flow and rotational slide landslides (219 and 28, respectively). The area is mainly made up of the following complexes: Numidian Flysch clays (19%, 1%), Terravecchia sandy clays (5%, 1%), Terravecchia clayey sands (3%, 0.3%) and San Cipirello marly clays (9%, 0%). The steepness parameter shows the highest landslide density in the [11–19°] class for both the typologies (8%, 1%), even if the density distributions for rotational slides are right-asymmetric and right-shifted. We obtained significant differences in shape when we used different instability landforms. Unlike scarps and areas uphill from crowns, landslide areas produce left-asymmetric and left-shifted density distributions for both the typologies. As far as the topographic wetness index is concerned, much more pronounced differences were detected among the instability landforms of rotational slides. In contrast, the flow landslides produce normal-like density distributions. The latter and the rotational slide landslide areas produce the highest density values in the class [5.5–6.7], despite an abrupt decreasing trend starting from the first class [3.2–4.4], which is generated by the density values of the rotational slide scarps and areas uphill from crowns. The stream power index at the foot of the slopes, which was automatically derived using a GIS-procedure, shows a positive correlation with the landslide densities marked by the maximum classes: [4.8–6.0] for flows, and [6.0–7.2] for rotational slides. The validation procedure results confirmed that the choice of instability landform influences the results of the susceptibility analysis. Furthermore, the validation procedure indicates that: a) the predictive models are generally satisfactory; b) scarps and zones uphill from crown areas are the most diagnostically unstable landforms, for flow and rotational slide landslides respectively.  相似文献   

On the displacement of marked pebbles on two coarse-clastic beaches during short fair-weather periods (Marina di Pisa and Portonovo, Italy)   总被引：1，自引：1，他引：0  

Duccio Bertoni  Edoardo Grottoli  Paolo Ciavola  Giovanni Sarti  Giuliano Benelli  Alessandro Pozzebon 《Geo-Marine Letters》2013,33(6):463-476

The aim of the investigation was to define the mechanisms of sediment transport in the swash zone of microtidal coarse-clastic beaches in the very short term by evaluating the displacement rates of marked pebbles under low-energy wave conditions. Tests were performed at two sites (Marina di Pisa, Ligurian Sea, and Portonovo, central Adriatic Sea) to check the consistency of the data over a range of different grain sizes. Two recovery campaigns were carried out at both sites, one 6 h and the other 24 h after the injection. During the experiments wave action was at a minimum (wave heights never exceeded 0.3 m). The results show that 20% of pebbles ranging in diameter from 30–90 mm moved significantly (more than 0.5 m) already 6 h after the injection, with some tracers being lost (3%). After 24 h, 40% of the pebbles were significantly displaced and 10% were lost. The preferential downslope movement of tracers, which suggests that coarse sediment movement under low-energy conditions is mainly controlled by gravity processes enhanced by steep beachface slopes, represents the novelty of the results reported here. It would appear that swash processes on low-energy beaches cause a significant rate of pebble displacement through the destabilization induced by wave uprush and backwash. Despite the microtidal range, the position of the mean water level plays a major role in changing the beach level at which swash processes can actually trigger pebble movement. The results of this study show that considerable, and mostly seaward-directed, coarse sediment transport takes place even during short fair-weather periods.  相似文献   

On the evaluation of seismic response of structures by nonlinear static methods   总被引：1，自引：0，他引：1  

Melina Bosco  Aurelio Ghersi  Edoardo M. Marino 《地震工程与结构动力学》2009,38(13):1465-1482

In the most recent seismic codes, the assessment of the seismic response of structures may be carried out by comparing the displacement capacity, provided by nonlinear static analysis, with the displacement demand. In many cases the code approach is based on the N2 method proposed by Fajfar, which evaluates the displacement demand by defining, as an intermediate step, a single degree‐of‐freedom (SDOF) system equivalent to the examined structure. Other codes suggest simpler approaches, which do not require equivalent SDOF systems, but they give slightly different estimation of the seismic displacement demand. The paper points out the differences between the methods and suggests an operative approach that provides the same accuracy as the N2 method without requiring the evaluation of an equivalent SDOF system. A wide parametric investigation allows an accurate comparison of the different methods and demonstrates the effectiveness of the proposed operative approach. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Weakening of gneiss surfaces colonized by endolithic lichens in the temperate climate area of northwest Italy          下载免费PDF全文

Sergio E. Favero‐Longo  Edoardo Accattino  Enrica Matteucci  Alessandro Borghi  Rosanna Piervittori 《地球表面变化过程与地形》2015,40(15):2000-2012

A role of lithobionts in geomorphological processes is increasingly argued, but the spatio‐temporal scale of their impact is largely unexplored in many ecosystems. This study first characterizes in the temperate zone (northwest Italy) the relationships between lithobiontic communities including endolithic lichens and the hardness of their siliceous rock substrate (Villarfocchiardo Gneiss). The communities are characterized, on humid and xeric quarry surfaces exposed for decades and natural outcrops exposed for centuries, in terms of lichen and microbial constituents, using a combined morphological and molecular approach, and with regard to their development on and within the gneiss. A lichen species belonging to Acarosporaceae (Polysporina‐Sarcogyne‐Acarospora group, needing taxonomic revision) chasmoendolithically colonizes both the humid and xeric quarry surfaces, on which epilithic cyanobacterial biofilms and epilithic pioneer lichens respectively occur. Light and electron microscopic observations show the development of the endolithic thalli within rock microcracks and the hyphal penetration along crystal boundaries down to depths of 1 to 3 mm, more pronounced within the humid surfaces. Such colonization patterns are likely related to biogeophysical deterioration, while no chemical alteration characterizes minerals contacted by the endolithic lichen. By contrast, on natural outcrops, where the endolithic colonization is negligible, a reddish rind below epilithic lichens indicates chemical weathering processes. Schmidt Hammer measurements highlight that the endolithic lichens deeply affect the hardness of the gneiss (down to ?60% with respect to fresh controls and surfaces only colonized by cyanobacteria), exerting a significantly higher weakening effect with respect to the associated epilithic lithobionts. The phenomenon is more remarkable on humid than on xeric quarry surfaces and natural outcrops, where epilithic lichens are likely involved in long‐term hardening processes supporting surface stabilization. Endolithic lichens are thus active biogeomorphological agents at the upper millimetric layer of siliceous rocks in temperate areas, exerting their weakening action during the early decade‐scaled stages of surface exposure. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Seismic retrofitting of braced frame buildings by RC rocking walls and viscous dampers          下载免费PDF全文

Francesca Barbagallo  Melina Bosco  Edoardo M. Marino  Pier Paolo Rossi 《地震工程与结构动力学》2018,47(13):2682-2707

A design procedure for seismic retrofitting of concentrically and eccentrically braced frame buildings is proposed and validated in this paper. Rocking walls are added to the existing system to ensure an almost uniform distribution of the interstorey displacement in elevation. To achieve direct and efficient control over the seismic performance, the design procedure is founded on the displacement‐based approach and makes use of overdamped elastic response spectra. The top displacement capacity of the building is evaluated based on a rigid lateral deformed configuration of the structure and on the ductility capacity of the dissipative members of the braced frames. The equivalent viscous damping ratio of the braced structure with rocking walls is calculated based on semi‐empirical relationships specifically calibrated in this paper for concentrically and eccentrically braced frames. If the equivalent viscous damping ratio of the structure is lower than the required equivalent viscous damping ratio, viscous dampers are added and arranged between the rocking walls and adjacent reaction columns. The design internal forces of the rocking walls are evaluated considering the contributions of more than one mode of vibration. The proposed design procedure is applied to a large set of archetype braced frame buildings and its effectiveness verified by nonlinear dynamic analysis.  相似文献   

Three magnitude 7 earthquakes on a single fault in central Italy in 1400 years,evidenced by new palaeoseismic results          下载免费PDF全文

Paolo Galli  Biagio Giaccio  Paolo Messina  Edoardo Peronace 《地学学报》2016,28(2):146-154

New palaeoseismic trenching across the main splay of the Fucino fault system provides evidence for a High Middle Age surface‐faulting episode conceivably associated with a disruptive earthquake, similar to the one that occurred in 1915 (Mw 7.0). The existence of this event, which has already been suggested by some previous studies, implies a shortening of the recurrence interval for Mw 7.0 earthquakes with respect to current knowledge. If we assume that the palaeoseismic Holocene record is complete, this shortening is focused in the historical period, when the Fucino structure sourced three strong earthquakes in only 1.4 ka. A similar clustering of energy release in the recent past is consistent with both palaeoseismological studies on other faults affecting the Apennine divide, and the high GPS strain rates observed in the same chain sectors.  相似文献   

Read all about it!? Public accountability,fragmented global climate governance and the media     

Sylvia I. Karlsson-Vinkhuyzen  Lars Friberg  Edoardo Saccenti 《Climate Policy》2013,13(8):982-997

The way that the media reports and comments on key events in the fragmented global climate governance landscape is one important route to strengthening public accountability of such governance. Editorials and other opinion pieces provide key contributions to the public sphere, but have been almost entirely neglected in media research on climate change. Another understudied aspect in such research is the reporting on the fragmentation of global climate governance across numerous forums. This article provides an exploratory approach to address these two research gaps. It presents a quantitative analysis of how often leading newspapers in seven countries (Finland, India, Laos, Norway, South Africa, UK and USA) wrote about 18 meetings in six different global climate governance forums between 2004–2009 and whether they provided commentaries about them. The study shows that media coverage (articles and opinion pieces) is limited or absent for many meetings that are not attended by heads of state, are the launch of a new process or do not have the convening power of the United Nations Framework Convention on Climate Change. The pattern of coverage differs significantly among individual newspapers and there is no clear distinction between developed and developing country newspapers. The article concludes that overall news coverage, and editorial commentary in particular, of global climate meetings in the selected newspapers is too low and too patchy to significantly support domestic publics to hold their own (and indirectly other) governments accountable with regard to fragmented global climate governance.

Policy relevance

This study is instructive for the media and civil society, who should both act as accountholders of governments with regard to how they act in global climate governance and its implementation. Reporting and commentaries need to reflect the overarching process, not only sporadic coverage of high-level meetings, but also critical analysis of what is achieved. They should also take a broader scope in terms of the kinds of meetings and processes in global governance that they cover. Civil society should encourage the media to increase coverage along these lines, e.g. by adequate monitoring of government actions (or lack thereof) and share this with the media.  相似文献   

Assessment of meteorological climate models as inputs for coastal studies     

Debora Bellafiore  Edoardo Bucchignani  Silvio Gualdi  Sandro Carniel  Vladimir Djurdjević  Georg Umgiesser 《Ocean Dynamics》2012,62(4):555-568

Modeling studies of future changes in coastal hydrodynamics, in terms of storm surges and wave climate, need appropriate wind and atmospheric forcings, a necessary requirement for the realistic reproduction of the statistics and the resolution of small scale features. This work compares meteorological results from different climate models in the Mediterranean area, with a focus on the Adriatic Sea, in order to assess their capability to reproduce coastal meteorological features and their possibility to be used as forcings for hydrodynamic simulations. Five meteorological datasets are considered. They are obtained from two regional climate models, implemented with different spatial resolutions and setups and are downscaled from two different global climate models. Wind and atmospheric pressure fields are compared with measurements at four stations along the Italian Adriatic coast. The analysis is carried out both on simulations of the control period 1960–1990 and on the A1B Intergovernmental Panel for Climate Change scenario projections (2070–2100), highlighting the ability of each model in reproducing the statistical coastal meteorological behavior and possible changes. The importance of simulated global- and regional-scale meteorological processes, in terms of correct spatial resolution of the phenomena, is also discussed. Within the Adriatic Sea, the meteorological climate is influenced by the local orography that controls the strengthening of north-eastern katabatic winds like Bora. Results show indeed that the increase in spatial resolution provides a more realistic wind forcing for the hydrodynamic simulations. Moreover, the chosen setup and the global climate models that drive the regional downscalings appear to play an important role in reproducing correct atmospheric pressure fields. The comparison between scenario and control simulations shows a small increase in the mean atmospheric pressure values, while a decrease in mean wind speed and in extreme wind events is observed, particularly for the datasets with higher spatial resolution. Finally, results suggest that an ensemble of downscaled climate models is likely to provide the most suitable climatic forcings (wind and atmospheric pressure fields) for coastal hydrodynamic modeling.  相似文献   

Shallow velocity model of the Northern Flank of Stromboli Volcano, deduced by high frequency surface wave dispersion     

Simona Petrosino  Mario La Rocca  Edoardo del Pezzo 《Journal of Seismology》1999,3(1):83-94

The wavefield produced by the Stromboli volcano explosion quakes shows a significant amount of surface waves. Rayleigh waves recorded by a linear array have been investigated to infer the shear-wave velocity model of the Stromboli northern flank. The group velocity dispersion curve was obtained using the multiple filter technique, while the phase velocity dispersion curve was calculated both by phase-matched filtering and performing a p– stack on the observed waveforms. Through the inversion of these curves we were able to recover the shear-wave structure to a depth of about 190 m.  相似文献