A time‐domain seismic SSI analysis method for inelastic bridge structures through the use of a frequency‐dependent lumped parameter model          下载免费PDF全文

Nikolaos Lesgidis  Oh‐Sung Kwon  Anastasios Sextos 《地震工程与结构动力学》2015,44(13):2137-2156

It is highlighted in the past that the soil–structure interaction phenomenon can produce a significant alteration on the response of a bridge structure. A variety of approaches has been developed in the past, which is capable of tackling the soil–structure interaction problem from different perspectives. The popular approach of a discretized truncated finite element model of the soil domain is not always a numerically viable solution, especially for computationally demanding simulations such as the probabilistic fragility analysis of a bridge structure or the real time hybrid simulation. This paper aims to develop a complete modeling procedure that is capable of coping with the soil–structure interaction problem of inelastic bridge structures through the use of a frequency dependent lumped parameter assembly. The proposed procedure encounters accuracy and global stability issues observed on past methods while maintaining the broad applicability of the method by any commercial FEM software. A case study of an overpass bridge structure under earthquake excitations is illustrated in order to verify the proposed method. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

A frequency‐dependent and intensity‐dependent macroelement for reduced order seismic analysis of soil‐structure interacting systems          下载免费PDF全文

Nikolaos Lesgidis  Anastasios Sextos  Oh‐Sung Kwon 《地震工程与结构动力学》2018,47(11):2172-2194

The computational demand of the soil‐structure interaction analysis for the design and assessment of structures, as well as for the evaluation of their life‐cycle cost and risk exposure, has led the civil engineering community to the development of a variety of methods toward the model order reduction of the coupled soil‐structure dynamic system in earthquake regions. Different approaches have been proposed in the past as computationally efficient alternatives to the conventional finite element model simulation of the complete soil‐structure domain, such as the nonlinear lumped spring, the macroelement method, and the substructure partition method. Yet no approach was capable of capturing simultaneously the frequency‐dependent dynamic properties along with the nonlinear behavior of the condensed segment of the overall soil‐structure system under strong earthquake ground motion, thus generating an imbalance between the modeling refinement achieved for the soil and the structure. To this end, a dual frequency‐dependent and intensity‐dependent expansion of the lumped parameter modeling method is proposed in the current paper, materialized through a multiobjective algorithm, capable of closely approximating the behavior of the nonlinear dynamic system of the condensed segment. This is essentially the extension of an established methodology, also developed by the authors, in the inelastic domain. The efficiency of the proposed methodology is validated for the case of a bridge foundation system, wherein the seismic response is comparatively assessed for both the proposed method and the detailed finite element model. The above expansion is deemed a computationally efficient and reliable method for simultaneously considering the frequency and amplitude dependence of soil‐foundation systems in the framework of nonlinear seismic analysis of soil‐structure interaction systems.  相似文献   

An algorithm developed in Matlab for the automatic selection of cut-off frequencies,in the correction of strong motion data     

Georgios Sakkas  Nikolaos Sakellariou 《Acta Geophysica》2018,66(4):425-448

Strong motion recordings are the key in many earthquake engineering applications and are also fundamental for seismic design. The present study focuses on the automated correction of accelerograms, analog and digital. The main feature of the proposed algorithm is the automatic selection for the cut-off frequencies based on a minimum spectral value in a predefined frequency bandwidth, instead of the typical signal-to-noise approach. The algorithm follows the basic steps of the correction procedure (instrument correction, baseline correction and appropriate filtering). Besides the corrected time histories, Peak Ground Acceleration, Peak Ground Velocity, Peak Ground Displacement values and the corrected Fourier Spectra are also calculated as well as the response spectra. The algorithm is written in Matlab environment, is fast enough and can be used for batch processing or in real-time applications. In addition, the possibility to also perform a signal-to-noise ratio is added as well as to perform causal or acausal filtering. The algorithm has been tested in six significant earthquakes (Kozani-Grevena 1995, Aigio 1995, Athens 1999, Lefkada 2003 and Kefalonia 2014) of the Greek territory with analog and digital accelerograms.  相似文献   

Mainshock-consistent ground motion record selection for aftershock sequences     

Athanasios N. Papadopoulos  Mohsen Kohrangi  Paolo Bazzurro 《地震工程与结构动力学》2020,49(8):754-771

In recent years, the additional risk posed to the built environment due to aftershock sequences and triggered events has been brought to attention, and several efforts have been directed towards developing fragility functions for structures in damaged conditions. Despite this rise of interest, a rather fundamental component for such tasks, namely that of aftershock ground motion record selection, has remained under-scrutinized. Herein, we propose a pragmatic procedure that can be applied for the selection of mainshock-aftershock ground motion pairs using consistent causal parameters and accounting for the correlation between their spectral accelerations. In addition, a structural analysis strategy that can be employed for the analytical derivation of damage-dependent fragility functions is outlined and presented through a case study. A more conventional back-to-back IDA analysis is also carried out in order to compare the derived damage-dependent fragility functions with the ones obtained with the proposed procedure. The results indicate that record selection remains a crucial factor even when assessing the structural vulnerability of damaged buildings, and should thus be treated cautiously.  相似文献   

Setting,sulfur isotope variations,and metamorphism of Jurassic massive Zn‐Pb‐Ag sulfide mineralization associated with arc‐type volcanism (Skra,Vardar zone, Νorthern Greece)     

Nikolaos Skarpelis 《Resource Geology》2020,70(4):311-335

Massive Zn‐Pb‐Ag sulfide mineralization appears conformable with felsic volcanism, developed in an Upper Jurassic volcanic arc to the Southwest (SW) of the Serbo‐Macedonian continent in Northern Greece. The host volcanic sequence of the mineralization comprises mylonitized rhyolitic to rhyodacitic lavas, pyroclastics, quartz‐feldspar porphyries, and cherty tuffs. A “white mica—quartz—pyrite” mineral assemblage characterizes the volcanic rocks in the footwall and hanging‐wall of massive sulfide ore layers, formed as a result of greenschist‐grade regional metamorphism on “clay‐quartz‐pyrite” hydrothermal alteration haloes. Massive ore lenses are usually underlain by deformed Cu‐pyrite and quartz‐pyrite stockworks. Most of the sulfide ore bodies have proximal‐type features. Ductile deformation and regional metamorphism have transformed many of the stockwork structures. The mineralization is characterized by high Zn, Pb, and Ag contents, while Cu and critical metals are low. Primary depositional textures, for example, layering, clastic pyrite, colloform, and atoll textures were identified. The overall textural features of the mineralization indicate it has undergone mechanical deformation. The most prominent features of the effects of metamorphism, folding and shearing, are modification of the ore body morphology toward flattened and boudinage structures and transformation of the ore textures toward the dominance of planar fabrics. Sulfur isotope analyses of sulfides along with textural observations are consistent with a dual source of sulfide sulfur. Sulfur isotope values for sphalerite, non‐colloform pyrite, galena, and chalcopyrite fall in a limited range from ?1.6 to +4.8‰ (mean δ³⁴S + 2‰), indicating a hydrothermal source derived from the reduction of coeval seawater sulfate in the convective system. Pyrites with colloform and atoll textures are characterized by a ³⁴S depletion, indicating a bacterial reduction of coeval seawater sulfate. The morphology of ore beds, the mineralogy, sulfide textures, and ore chemistry along with the petrology and tectonic setting of the host rocks can be attributed to typical of a bimodal‐felsic metallogenesis. Although similar in many respects to classic Kuroko‐type volcanogenic massive sulfide mineralization, it has some atypical features, like the absence of barite ore, which is possibly a result of significant temporal depletion in sulfate due to bacterial reduction, a conclusion supported by the widespread occurrence of colloidal and atoll textures of pyrite.  相似文献   

Evening and Morning Transition of Katabatic Flows   总被引：1，自引：1，他引：0  

K. H. Papadopoulos  C. G. Helmis 《Boundary-Layer Meteorology》1999,92(2):195-227

An experimental investigation of the evening and morning transition phases of katabatic slope flows has been conducted to identify the mechanisms for their development and destruction over an isolated slope. The momentum and energy equations of the flow have been used to describe these mechanisms for the particular topographic features of the studied slope, and to outline the differences from the dynamics of well-developed simple slope flows. In the lowest portion of the slope, frontal characteristics have been identified in early evening periods when the local pre-existing near-surface thermal structure does not impose a katabatic acceleration. The frontal shape is determined by the near-surface thermal stability and ambient wind. The flow initiation is distinctly different when it is linked to the local surface cooling, in which case it develops gradually and produces a slight local warming.The erosion of the katabatic layer at mid-slope precedes that at the foot and is closely linked to dilution of the local surface inversion. The flow erosion at the foot is often delayed, as the warming of air proceeds uniformly at all heights near the ground, so maintaining the inversion due to warming produced by mixing and advective processes linked to the upslope flow development. The latter initiates first at mid-slope and then at the foot, where for a non-negligible time period it flows over the persistent katabatic flow. The prerequisite for the development of this structure is the maintenance of a shallow inversion in the first 2–3 m above the ground surface.The morning dilution of the katabatic flow is apparently different from common experience over simple slopes and may be attributed to the steep upper portion of the slope in association with its easterly orientation, which results in strong non-uniformity of the solar heating along the slope.  相似文献   

Obituary: Professor Anders Rapp     

Jan . Mattsson  Nikolaos Solakius 《Geografiska Annaler: Series A, Physical Geography》1999,81(3):359-359

  相似文献   

Newtonian and post-newtonian tidal theory: Variable G and earthquakes     

D. D. Dionysiou  E. N. Sarris  P. G. Tsikouras  G. A. Papadopoulos 《Earth, Moon, and Planets》1993,60(2):127-140

A mathematical analysis of the Newtonian and parametrized Post-Newtonian tidal stresses is applied to tidal triggering mechanism for earthquakes. We investigate a possible correlation.The procedure used for calculating the solid earth tidal stress is described by the Newtonian theory and the parametrized Post-Newtonian metric. We calculate tidal stress histories for earthquakes between 1908 and 1991 in Greek area. Although no significant tidal correlation was found for the entire data set, which contained earthquakes of magnitudeM 6.0, a fairly striking correlation was observed for an earthquake-tide correlation by computing tidal functions at the time and place of the earthquake events. A successful correlation as used in this paper means that: earthquake events occur during a certain part of the tidal cycle.Also, we have studied a variation of the gravitational constant according to the variation of the velocity of the Earth and the uniform velocity of the Solar System with respect to a preferred Universal rest frame.This work has been supported by the Greek General Secretariat of Research and Technology under Grant No. 89e160.  相似文献   

Fractal approach of the temporal earthquake distribution in the Hellenic arc-trench system     

Gerassimos A. Papadopoulos  Vassilis Dedousis 《Pure and Applied Geophysics》1992,139(2):269-276

The time clustering of earthquakes occurring in the Hellenic arc-trench system is quantitatively analyzed by means of the fractal dimension,D, of their time distribution in the time intervals of 1950–1985 (M _s >-4.5) and 1964–1985 (M _s 4.0). The results obtained imply that scale-invariant clustering holds over very large scale lengths of time,T, with 2²–2⁸T (in min) 2²⁰–2²², depending on the seismotectonic segment considered. In all segments a common feature is the relation between theD ₁,D ₂ andD ₃-values found for shallow, intermediate-depth and all-depth shocks, respectively:D ₃>D₁>D₂. TheD-values found for shallow shocks range between 0.137 and 0.191 with the exception of the Ionian Islands and Cretan segments where anomalously high values (D=0.221–0.251) have been determined. We discuss possible seismotectonic interpretations of the results.  相似文献   

Retroward extrusion of high‐pressure rocks: An example from the Hellenides (Pelion Blueschist Nappe,NW Aegean)          下载免费PDF全文

Nikolaos Gerogiannis  Paraskevas Xypolias 《地学学报》2017,29(6):372-381

Current tectonic models interpret the Hellenides as a unidirectional, SW‐vergent orogenic belt. New (micro‐)structural and amphibole chemistry analyses show, instead, that the exhumation of the Pelion Blueschist Nappe (PBN) of the Internal Hellenides was achieved by retroward (ENE)‐directed ductile extrusion, which opposes the principal (proward) orogenic vergence. Retroward extrusion occurred between two sub‐parallel, major ductile shear zones (Basal thrust and Upper detachment) with opposite shear senses, which operated simultaneously under blueschist‐ to greenschist‐facies conditions during the late Eocene–Oligocene. Because the PBN is tectonically sandwiched between Pelagonian basement rocks, we suggest that the PBN protolith was accumulated during the Late Cretaceous in an incipient backarc basin developed above the NE‐dipping subduction of the Pindos Ocean beneath the Pelagonian microcontinent. Subsequent Apulian–Pelagonian collision triggered basin inversion and the proward‐dipping intracontinental subduction that caused the early/middle Eocene blueschist‐facies metamorphism followed by the retroward extrusion of the PBN.  相似文献