Seismic performance and new design procedure for chevron‐braced frames     

Edoardo M. Marino  Masayoshi Nakashima 《地震工程与结构动力学》2006,35(4):433-452

The paper is concerned with the seismic design of steel‐braced frames in which the braces are configured in a chevron pattern. According to EuroCode 8 (EC8), the behaviour factor q, which allows for the trade‐off between the strength and ductility, is set at 2.5 for chevron‐braced frames, while 6.5 is assigned for most ductile steel moment‐resisting frames. Strength deterioration in post‐buckling regime varies with the brace's slenderness, but EC8 adopts a unique q value irrespective of the brace slenderness. The study focuses on reevaluation of the q value adequate for the seismic design of chevron‐braced frames. The present EC8 method for the calculation of brace strength supplies significantly different elastic stiffnesses and actual strengths for different values of brace slenderness. A new method to estimate the strength of a chevron brace pair is proposed, in which the yield strength (for the brace in tension) and the post‐buckling strength (for the brace in compression) are considered. The new method ensures an identical elastic stiffness and a similar strength regardless of the brace slenderness. The advantage of the proposed method over the conventional EC8 method is demonstrated for the capacity of the proposed method to control the maximum inter‐storey drift. The q values adequate for the chevron‐braced frames are examined in reference to the maximum inter‐storey drifts sustained by most ductile moment‐resisting frames. When the proposed method is employed for strength calculation, the q value of 3.5 is found to be reasonable. It is notable that the proposed method does not require larger cross‐sections for the braces compared to the cross‐sections required for the present EC8 method. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Moment magnitude (Mw) from hydrophone records of low energy volcanic quakes     

Guardato  Sergio  Donnarumma  Gian Paolo  Riccio  Rosario  Del Pezzo  Edoardo  Iannaccone  Giovanni 《Journal of Seismology》2022,26(5):875-882

Earthquake magnitude calibration using hydrophone records has been carried out at Campi Flegrei caldera, an active area close to the highly populated area of Naples city, partly undersea. Definite integrals of the hydrophone records amplitude spectra, between the limits of 1 and 20 Hz, were calculated on a set of small volcano-tectonic earthquakes with moment magnitudes ranging from 1 to 3.3. The coefficients of a linear relationship between the logarithm of these integrals and the magnitude were obtained by linear optimization, thus defining a useful equation to calculate the moment magnitude from the hydrophone record spectra. This method could be easily exported to other volcanic areas, where submerged volcanoes are monitored by networks of hydrophones and seismic sensors on land. The proposed approach allows indeed magnitude measurements of small magnitude earthquakes occurring at sea, thus adding useful information to the seismicity of these volcanoes.

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Array analysis using circular-wave-front geometry:an application to locate the nearby seismo-volcanic source   总被引：4，自引：0，他引：4  

Javier Almendros  Jesús M. Ibáñez  Gerardo Alguacil  & Edoardo Del Pezzo 《Geophysical Journal International》1999,136(1):159-170

The zero-lag cross-correlation technique, used for array analysis in the hypothesis of plane waves, has been modified to allow the wave front to be circular. Synthetic tests have been performed to check the capability of the method, which returns the input test data when the source–array distances are not greater than two or three times the array aperture. For this distance range the method furnishes an estimate of the apparent velocity and the epicentral coordinates of the source. For more distant sources the method becomes equivalent to that based on the planar-wave approximation, which gives an estimate of the backazimuth to the source and the apparent velocity. The method has been applied to seismic data recorded at the active volcano located at Deception Island, Antarctica. 35 volcanic long-period events occurring in a small swarm were selected. Results show that the epicentres are close to the array (between 0.4 and 2 km) and aligned in a SW direction, in agreement with one of the main directions of the fracture system of Deception volcano.  相似文献   

Thorough wetting and drainage of a peat lysimeter in a climate change scenario     

Maurizio Previati  Davide Canone  Edoardo Iurato  Davide Gisolo  Stefano Ferrari  Pietro Teatini  Mario Putti  Stefano Ferraris 《水文研究》2020,34(5):1269-1284

A peat deposit (Zennare basin, Venice coastland, Italy) was monitored in previous field studies to investigate the hydrological response of organic soil to meteorological dynamics. Field tests and modelling predictions highlighted the risk of the complete loss of this peat layer during the next 50 years, due to oxidation enhanced by the increased frequency of warmer periods. Unfortunately, despite the considerable impacts that are expected to affect peat bogs (in this area and worldwide), only a few experimental studies have been carried out to assess the hydrologic response of peat to severe water scarcity. Because of that, an undisturbed 0.7 m³ peat monolith was collected, transferred to the laboratory and instrumented. The total weight (representative of the water content dynamics of the peat monolith as a whole), and two vertical profiles of matric potentials and water content were monitored in controlled water-scarce conditions. After an extended air-drying period, the monolith was used as an undisturbed peat lysimeter and a complete cycle of wetting and drainage was performed. Supplementary measurements of matric potential ψ and water content θ were collected by testing peat subsamples on a suction table apparatus. A set of water retention curves was determined in a range of matric potentials broader (ψ down to −7 m) than the current natural conditions in the field (minimum ψ = −1 m). While water content at saturation showed values similar to those in the original natural conditions (θ ≅ 0.8), a remarkable loss of water holding capacity (even for low potentials) has been highlighted, especially in deep layers that are now permanently below the water table. The retention curves changed shape and values, with a more pronounced hysteresis visible in an increasing distance between wetting and drying data. Hydraulic non-equilibrium between the water content and water potential could be a possible cause and it is worth modelling in future studies. The parameters of the van Genuchten retention curves were obtained for the wetting and the drying phases.  相似文献   

The soil cultural heritage of Italy: Geodatabase, maps, and pedodiversity evaluation   总被引：2，自引：0，他引：2  

Edoardo A.C. Costantini  Giovanni L'Abate 《Quaternary International》2009,209(1-2):142

Soils can possess heritage characteristics and can be classified according to their “cultural value”. “Pedosites”, likewise “geosites”, are important for science and teaching, for tourism and recreation, provide elements in the Environmental Impact Analysis, and enhance the awareness of population towards the value of the land where they live. Pedosite richness and diversity are a resource of a territory that should be evaluated and considered in land planning. The methodology used to evaluate and group pedosites of Italy, and the software developed to collect such information and create a specific geodatabase, are presented in this paper as an example for use in other countries. An Italian geodatabase storing 726 pedosites was created. Soil profiles as cultural heritage were: (i) palaeosols, (ii) soils from archaeological and palaeontological sites, (iii) soils displaying natural or anthropic processes and benchmarks of classifications. Pedosites as soilscapes were: (i) cultural landscapes; (ii) soilscapes determining the amenity of a panorama; (iii) soilscapes in fragile environmental balance; (iv) soilscapes that contribute to the outliving of particular ecosystems. The criteria for the evaluation of pedosites and the suggestions for their protection were indicated as follows: (i) area and (ii) type of scientific interest, (iii) state of conservation, (iv) type and (v) intensity of risk, (vi) level of knowledge, (vii) geological age, (viii) protection and (ix) proposed protection, (x) accessibility, (xi) visibility, (xii) exposure, (xiii) observability. The geodatabase can be used at different scales. Two maps, at national and local levels, exemplify the methodology and show how to use the geodatabase for didactic purposes or the creation of integrated Geoparks. Pedosite indices of diversity highlight the greater pedosite variety in the soil regions of Mediterranean Italy.  相似文献   

Which baseflow metrics should be used in assessing flow regimes of urban streams?          下载免费PDF全文

Perrine Hamel  Edoardo Daly  Tim D. Fletcher 《水文研究》2015,29(20):4367-4378

Determining the impact of urbanisation on baseflow is complex because of the multiplicity of factors that govern subsurface flows. Although many metrics are available to quantify the baseflow regime, the lack of consensus on which metrics need to be used for baseflow characterisation limit their practical application for stormwater management. We performed principal component and correlation analyses on a set of 32 baseflow metrics to identify a subset of non‐redundant metrics for baseflow characterisation. We compared the results for streamflow time series from natural and urban catchments. We found that a subset of five metrics, including at least one metric from each of the four ecologically significant flow characteristic groups (i.e. magnitude, duration, frequency, and timing), explained most of the variability in baseflow regime for both natural and urban catchments. In addition, we analysed the relationship between this set of metrics and some low flow percentiles obtained from flow duration curves. Flow percentiles were only highly correlated to the magnitude and duration metrics, confirming that flow duration curves could be satisfactorily used for baseflow characterisation, but in combination with metrics representing frequency and timing. Metrics based on integration of the flow duration curve, however, cannot simply substitute the consideration of a suite of metrics. We discuss the practicality of our results with a regional regression study; the analyses show how the metrics can be used to quantify the alterations to baseflow caused by urbanisation, and to determine baseflow restoration objectives for urbanised catchments based on pre‐development baseflow regime. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Forward logistic regression for earth-flow landslide susceptibility assessment in the Platani river basin (southern Sicily,Italy)   总被引：2，自引：0，他引：2  

Dario Costanzo  José Chacón  Christian Conoscenti  Clemente Irigaray  Edoardo Rotigliano 《Landslides》2014,11(4):639-653

Forward logistic regression has allowed us to derive an earth-flow susceptibility model for the Tumarrano river basin, which was defined by modeling the statistical relationships between an archive of 760 events and a set of 20 predictors. For each landslide in the inventory, a landslide identification point (LIP) was automatically produced as corresponding to the highest point along the boundary of the landslide polygons, and unstable conditions were assigned to cells at a distance up to 8 m. An equal number of stable cells (out of landslides) was then randomly extracted and appended to the LIPs to prepare the dataset for logistic regression. A model building strategy was applied to enlarge the area included in training the model and to verify the sensitivity of the regressed models with respect to the locations of the selected stable cells. A suite of 16 models was prepared by randomly extracting different unoverlapping stable cell subsets that have been appended to the unstable ones. Models were finally submitted to forward logistic regression and validated. The results showed satisfying and stable error rates (0.236 on average, with a standard deviation of 0.007) and areas under the receiver operating characteristic (ROC) curve (AUCs) (0.839 for training and 0.817 for test datasets) as well as factor selections (ranks and coefficients). As regards the predictors, steepness and large-profile and local-plan topographic curvatures were systematically selected. Clayey outcropping lithology, midslope drainage, local and midslope ridges, and canyon landforms were also very frequently (from eight to 15 times) included in the models by the forward selection procedures. The model-building strategy allowed us to produce a performing earth-flow susceptibility model, whose model fitting, prediction skill, and robustness were estimated on the basis of validation procedures, demonstrating the independence of the regressed model on the specific selection of the stable cells.  相似文献   

Hybrid stochastic-mechanical modeling of precipitation thresholds of shallow landslide initiation     

Rundeddu  Edoardo  Lizárraga  José J.  Buscarnera  Giuseppe 《Natural Hazards》2022,110(2):1083-1095

Natural Hazards - International and domestic tourism is a growing industry in Costa Rica, with the most attractive places located along the coast. Despite their beauty, Costa Rican beaches can pose...  相似文献   

Landform classification: a high-performing mapping unit partitioning tool for landslide susceptibility assessment—a test in the Imera River basin (northern Sicily,Italy)     

Martinello  Chiara  Cappadonia  Chiara  Conoscenti  Christian  Rotigliano  Edoardo 《Landslides》2022,19(3):539-553

In landslide susceptibility studies, the type of mapping unit adopted affects the obtained models and maps in terms of accuracy, robustness, spatial resolution and geomorphological adequacy. To evaluate the optimal selection of these units, a test has been carried out in an important catchment of northern Sicily (the Imera River basin), where the spatial relationships between a set of predictors and an inventory of 1608 rotational/translational landslides were analysed using the multivariate adaptive regression splines (MARS) method. In particular, landslide susceptibility models were prepared and compared by adopting four different types of mapping units: the largely adopted grid cells (PX), the typical contributing area–controlled slope units (5000_SLU), the recently optimized parameter-free multiscale slope units (PF_SLU) and a new type (LCL_SLU) of slope unit obtained by crossing classic hydrological partitioning with landform classification. At the same time, once a pixel-based model was prepared, four different SLU modelling strategies were applied to each of the obtained slope unit layers, including two different types of pixel score zoning, a pixel score re-modelling and a factor-based SLU re-modelling. According to the achieved results, LCL_SLUs produced the highest performance and reliability, offering an optimal compromise between the high-performing but scattered and the smoothed but lower-performing prediction images that were obtained from pixel-based and hydrologic SLU–based modelling, respectively. Additionally, among the four adopted SLU modelling strategies, the new proposed procedure, which uses the zoned pixel–based score deciles as the LCL_SLU predictors for a new regression, resulted in the best outstanding performance (ROC_AUC?=?0.95).

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Towards a dedicated impact portal to bridge the gap between the impact and climate communities : Lessons from use cases     

Céline Déandreis  Christian Pagé  Pascale Braconnot  Lars Bärring  Edoardo Bucchignani  Wim Som de Cerff  Ronald Hutjes  Sylvie Joussaume  Constantin Mares  Serge Planton  Maarten Plieger 《Climatic change》2014,125(3-4):333-347

Future climate evolution is of primary importance for the societal, economical, political orientations and decision-making. It explains the increasing use of climate projections as input for quantitative impact studies, assessing vulnerability and defining adaptation strategies in different sectors. Here we analyse 17 national and representative use cases so as to identify the diversity of the demand for climate information depending on user profiles as well as the best practices, methods and tools that are needed to answer the different requests. A particular emphasis is put on the workflow that allows to translate climate data into suitable impact data, the way to deal with the different sources of uncertainty and to provide a suited product to users. We identified three complementary tools to close the gap between climate scientists and user needs: an efficient interface between users and providers; an optimized methodology to handle user requests and a portal to facilitate access to data and elaborated products. We detail in the paper how these three tools can limit the intervention of experts, educate users, and lead to the production of useful information. This work provides the basis on which the ENES (European Network for Earth System Modelling) Portal Interface for the Climate Impact Communities is built.  相似文献