Analytical fragility assessment using unscaled ground motion records   总被引：1，自引：0，他引：1       下载免费PDF全文

Fatemeh Jalayer  Hossein Ebrahimian  Andrea Miano  Gaetano Manfredi  Halil Sezen 《地震工程与结构动力学》2017,46(15):2639-2663

It is desirable that nonlinear dynamic analyses for structural fragility assessment are performed using unscaled ground motions. The widespread use of a simple dynamic analysis procedure known as Cloud Analysis, which uses unscaled records and linear regression, has been impeded by its alleged inaccuracies. This paper investigates fragility assessment based on Cloud Analysis by adopting, as the performance variable, a scalar demand to capacity ratio that is equal to unity at the onset of limit state. It is shown that the Cloud Analysis, performed based on a careful choice of records, leads to reasonable and efficient fragility estimates. There are 2 main rules to keep in mind for record selection: to make sure that a good portion of the records leads to a demand to capacity ratio greater than unity and that the dispersion in records' seismic intensity is considerable. An inevitable consequence of implementing these rules is that one often needs to deal with the so‐called collapse cases. To formally consider the collapse cases, a 5‐parameter fragility model is proposed that mixes the simple regression in the logarithmic scale with logistic regression. The joint distribution of fragility parameters can be obtained by adopting a Markov Chain Monte Carlo simulation scheme leading directly to the fragility and its confidence intervals. The resulting fragility curves compare reasonably with those obtained from the Incremental Dynamic Analysis and Multiple Stripe Analysis with (variable) conditional spectrum–compatible suites of records at different intensity levels for 3 older reinforced concrete frames with shear‐, shear‐flexure‐, and flexure‐dominant behavior.  相似文献   

Paleolakes, paleofloods, and depressions in Aurorae and Ophir Plana, Mars: Connectivity of surface and subsurface hydrological systems     

Goro Komatsu  Gaetano Di Achille  Ciprian Popa  Stefano Di Lorenzo  Jose Alexis Palmero Rodriguez 《Icarus》2009,201(2):474-491

The plains of Aurorae and Ophir in the equatorial region of Mars display geomorphic evidence indicative of extensive but generally short-lived paleohydrological processes. Elaver Vallis in Aurorae Planum south of Ganges Chasma is an outflow channel system >180 km long, and here inferred to have formed by cataclysmic spillover flooding from a paleolake(s) contained in the Morella crater basin. Ganges Cavus is an enormous 5-km-deep depression of probable collapse origin located in the Morella basin. The fluid responsible for the infilling of the Morella basin likely emerged at least partially through Ganges Cavus or its incipient depression, and it may have been supplied also from small-scale springs in the basin. Similar paleohydrological processes are inferred also in Ophir Planum. It is reasonable to assume that water, sometimes sediment-laden and/or mixed with gases, was the responsible fluid for these phenomena although some of the observed features could be explained by non-aqueous processes such as volcanism. Water emergence may have occurred as consequences of ground ice melting or breaching of cryosphere to release water from the underlying hydrosphere. Dike intrusion is considered to be an important cause of formation for the cavi and smaller depressions in Aurorae and Ophir Plana, explaining also melting of ground ice or breaching of cryosphere. Alternatively, the depressions and crater basins may have been filled by regional groundwater table rising during the period(s) when cryosphere was absent or considerably thin. The large quantities of water necessary for explaining the paleohydrological processes in Aurorae and Ophir Plana could have been derived through crustal migration from the crust of higher plains in western Ophir Planum where water existed in confined aquifers or was produced by melting of ground ice due to magmatic heating or climatic shift, or from a paleolake in Candor Chasma further west.  相似文献   

A decision support system for post-earthquake reliability assessment of structures subjected to aftershocks: an application to L��Aquila earthquake, 2009     

Fatemeh Jalayer  Domenico Asprone  Andrea Prota  Gaetano Manfredi 《Bulletin of Earthquake Engineering》2011,9(4):997-1014

The post-earthquake assessment of existing structures can be further complicated by the progressive damage induced by the occurrence of a sequence of aftershocks. This work presents a simple methodology for the calculation of the probability of exceeding a certain limit state in a given interval of time. The time-decaying mean daily rate of occurrence of significant aftershock events is modeled by employing a site-specific aftershock model for the L??Aquila 2009 aftershock sequence (central Italy). The number of aftershock events occurring in a given interval of time elapsed after the main event is modeled using a non-homogenous Poisson model. An equivalent single-degree of freedom structure with cyclic stiffness degradation is used in order to evaluate the progressive damage caused by a sequence of aftershock events. Given the time history of the main-shock and the residual damage caused by it, the probability of exceeding a set of discrete limit states in a given interval of time is calculated. Of particular importance is the time-variant probability of exceeding the limit state in a 24-h (a day) interval of time which can be used as a proxy for the life-safety considerations regarding the re-occupancy of the structure and to complement the results of visual inspections for prioritizing the emergency operations. The method presented herein can also be used in an adaptive manner, progressively conditioned on the time-histories of aftershock events following the main-shock and on the corresponding residual damage caused by them.  相似文献   

Preliminary analysis of a soft‐storey mechanism after the 2009 L'Aquila earthquake     

Gerardo M. Verderame  Flavia De Luca  Paolo Ricci  Gaetano Manfredi 《地震工程与结构动力学》2011,40(8):925-944

Observation of damage caused by the recent Abruzzo earthquake on April 6th 2009 showed how local interaction between infills and RC structures can lead to soft‐storey mechanisms and brittle collapses. Results of the present case study are based on observed damage caused by the earthquake in the zone of Pettino. Analytical model based on simulated design procedure was built up and time history analyses were employed to verify the causes of the structural collapse, as highlighted by observed damage. This failure mechanism was investigated taking into consideration all components of the ground motion. Nonlinear behavior of brick masonry infills was taken into account and two parametric hypotheses for infill mechanical properties were considered, given the uncertainties that typically characterize these nonstructural elements. Nonlinear modeling of infills was made by a three‐strut macro‐model aimed at considering both local and global interaction between RC frame and infills. Seismic input was characterized by the real signal registered during the mainshock near the case‐study structure. Different shear capacity models were considered in the assessment. Analytical results seem to confirm with good approximation the likely collapse scenario that damage observation highlighted; the lack of proper detailing in the columns made the local interaction between infills and RC columns and the strong vertical component of the ground motion to be the main causes of the brittle failure. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

The use of damage functionals in earthquake engineering: A comparison between different methods     

Edoardo Cosenza  Gaetano Manfredi  Roberto Ramasco 《地震工程与结构动力学》1993,22(10):855-868

The behaviour of the EPP-SDOF model under seismic actions is analysed herein by different ‘damage functionals’ to define collapse under cyclic loading. In particular, the damage functionals based on the concept of maximum ductility and dissipated plastic energy are first compared. Afterwards the methods of Banon and Veneziano, Park and Ang and the linear cumulative law of plastic fatigue are reviewed and extensively analysed. Comparisons in the case of simple cyclic histories and in terms of acceleration collapse spectra are carried out with reference to significant earthquake records. In particular, it is shown in which cases the damage functionals of Banon and Veneziano, Park and Ang and the linear cumulative law of plastic fatigue, completely defined by the value of a single parameter, degenerate in the limit methods of ductility or dissipated energy and in which cases they provide similar results.  相似文献   

Phylogeographic study on the chub mackerel (Scomber japonicus) in the Northwestern Pacific indicates the late Pleistocene population isolation          下载免费PDF全文

Shuai Yan  Gaetano Catanese  Christopher L. Brown  Ming Wang  Chaopin Yang  Tingbao Yang 《Marine Ecology》2015,36(3):753-765

In the present study, the population genetic structure and historical demography of the chub mackerel, Scomber japonicus, in the Northwestern Pacific were examined based on the full‐length sequences of the mitochondrial control region and cytochrome b gene. A total of 320 individuals was sampled from 11 localities along the coast of China and Japan from August 2011 to May 2013. Two main clades representing Chinese and Japanese populations, respectively, were detected, suggesting population isolation of S. japonicus during the late Pleistocene era. The Chinese clade was further divided into two small clades and the distribution of haplotypes were not related to sampling locality, which may be a signature of secondary contact following past division. Analyses of molecular variance and pairwise F_ST revealed significant genetic differentiation between the Chinese and Japanese populations, but a lack of genetic structure for the populations along the coast of China. Both neutrality tests and mismatch distribution analysis suggested that the populations along the coast of China experienced population expansion during the late Pleistocene. Historical events, biological characteristics and other extrinsic forces such as ocean currents may all be associated with the current phylogeographic pattern of S. japonicus in the Northwestern Pacific.  相似文献   

L’Etna dall’Agosto 1923 a tutto il 1925     

Gaetano Ponte 《Bulletin of Volcanology》1926,2(2):219-222

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Numerical Simulation of phytoplankton productivity in partially mixed estuaries     

David H. Peterson  John F. Festa 《Estuarine, Coastal and Shelf Science》1984,19(5):563-589

A two-dimensional steady-state model of light-driven phytoplankton productivity and biomass in partially mixed estuaries has been developed. Effects of variations in river flow, suspended sediment concentration, phytoplankton sinking, self-shading and growth rates on distributions of phytoplankton biomass and productivity are investigated.Numerical simulation experiments show that biomass and productivity are particularly sensitive to variations in suspended sediment concentrations typical of natural river sources and to variations in loss rates assumed to be realistic but poorly known for real systems. Changes in the loss rate term within the range of empirical error (such as from dark bottle incubation experiments) cause phytoplankton biomass to change by a factor of two. In estuaries with adequate light penetration in the water column, it could be an advantage for phytoplankton to sink. Species that sink increase their concentration and form a phytoplankton maximum in a way similar to the formation of the estuarine turbidity maximum. When attenuation is severe, however, sinking species have more difficulty in maintaining their population.  相似文献   

The stability of UO2OH+ and UO2[HPO4]22− complexes at 25°C (reply to a comment by V. S. Tripathi)     

Donald Langmuir  Gaetano Dongarra 《Geochimica et cosmochimica acta》1982,46(10):2005

Tripathi argues that we could not determine the stability constant (β₂) of UO₂[HPO₄]₂^2? in our solutions because they were supersaturated with respect to solid uranyl triphosphate. This is irrelevant because no phosphate solids were present in solution during our experiments. He further argues that the conditions of our experiments were not ideal for us to determine the potentially most accurate value of β₂. This is also irrelevant. The point is that our published value of log β₂ = 18.3 ± 0.2 is given with an uncertainty which clearly acknowledges the inaccuracy of its determination based on our experimental and computational approach.  相似文献   

Solar and stellar activity: The theoretical approach     

Gaetano Belvedere 《Solar physics》1985,100(1-2):363-383

The unified sight of solar and stellar activity has revealed a worthwhile concept under several aspects, gaming in the last decade the increasing favour of observers and theorists, and the term solar-stellar connection has recently been introduced to point out the complementarity of solar and stellar observations in the background of the basic role played by the magnetic field.The great development of stellar activity observations suggests a much wider scenario than it were possible to imagine even a few years ago and stimulates theoretical work, most of which is in the framework of the - dynamo theory.Although dynamo theory seems to be plausible and successful in capturing the fundamental mechanism of solar and stellar activity, several uncertainties and intrinsic limits do still exist and are discussed together with alternative or complementary suggestions.Further, it is stressed the relevance of nonlinear problems in dynamo theory — as magnetoconvection, growth and stability of flux tubes against magnetic buoyancy, hydromagnetic global dynamos — to improve our understanding of both small and large scale interaction of rotation, turbulent convection and magnetic field, and of the transition from linear to nonlinear regime. Finally, recent dynamo models of stellar activity are critically reviewed, as to the dependence of activity indexes and cycles on rotation rate and spectral type.Open problems to be solved by future work are outlined, pointing out the role of ever increasing stellar data in widening out our comprehension of the dynamo operation modes, which seem to depend on stellar structure, rotation and age.  相似文献