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1
Content available Zagrożenia geologiczne w Polsce w 2020 roku
EN
The paper describes geohazard events that took place in 2020on the territory of Poland. The PGI is responsible for geohazard monitoring in four areas of interest :landslides and mass movements within the Landslide Counteracting System (LCS, SOPO in Polish), earthquakes within the Geodynamical Monitoring of Poland and ground motions within the Interferometric Terrain Deformations Monitoring of Poland, and coastal monitoring carried out by the Marine Geology Branch within a framework of the 4D Cartography. In 2020, there were no spectacular geohazard events; however, there were some permanently active phenomena, mostly landslides, which caused significant damages to the infrastructure.
EN
The height of reservoir water is one of the important factors affecting the seismic behaviour of earth dams. A large number of earth dams have been constructed in different countries that are sometimes located in a high-risk geographical zone. The studies on the seismic behaviour of earth dams have been conducted for several decades. However, this study, considering the importance of the subject, it investigates the seismic behaviour of Sumbar rock-fill embankment dam under near- and far-field earthquakes with variation in the water level behind the dam. The ratio of water height of the dam to dam height is considered as an important indicator to investigate the seismic performance of these structures. The analyses were performed using the ABAQUS finite element platform, under 7 near-field and 7 far-field earthquake records. In this research, the changes in dam stresses, displacements, and failure of the dam have been discussed. The results indicated that the effect of near-field earthquakes on the seismic behaviour of earth dams is more significant than far-field earthquakes.
EN
As science keeps evolving over time, new solutions are being put forward for reducing structural damage. One such solution is the use of seismic isolation systems. Seismic isolation systems reduce the response of structures to the force of earthquakes by reducing the input (force) acceleration when the natural period of the structure increases. Therefore, the use of seismic isolation systems is recommended in the analysis of diverse structures. This study was carried out on seismically isolated buildings with 8, 10, and 12 regular steel floors, modeled by a non-linear isolator in two-, or three-second periods. The differences in data and the responses of the buildings were compared with fixedbase buildings with 8, 10, and 12 floors.
PL
Dostęp do mocy obliczeniowej super komputerów oraz możliwość wykorzystania nowoczesnych systemów, np. takich jak Ls-Dyna, pozwala na uzyskanie niezwykle szczegółowych rozwiązań bardzo skomplikowanych problemów inżynierskich.
EN
The article presents some remarks on the dynamic simulations of bridges in the Ls-Dyna system. Some results of two dynamic problems are presented. The first example concerns a viaduct that was hit by a vehicle passing under it. The second one relates to the design of a concrete multi-span bridge subjected to earthquakes of various intensity.
EN
Amplitude and frequency content are two important features of earthquakes that are different for near and far-fault earthquakes and in most of the standards, the effects of near-field earthquakes in loading are not considered. Therefore, study and comparison of these effects on structures is necessary. In this paper, structural operation against near and far fault earthquakes for two near sites and two far sites is investigated. For this purpose and in order to achieve an operation point of a structural model with six staircases with a mean lateral bending frame resistant system seismic hazard information is analyzed with regards to special plan spectrums of 2 different sites using near and far faults. An evaluation of the effects due to near and far fault earthquakes based on the Iran’s standard 2800 ranges on operation point and the comparison of operation effects of near and far fault spectrums with Iran’s standard are results of this research work. After the presentation of results obtained from time history analyses, some suggestions are proposed for design correction based on the regulations in near -field earthquakes.
EN
A number of recent studies suggest that atmospheric changes that precede an earthquake might offer the hope of providing early warning. This study attempts to examine seismo-atmospheric anomalies around the time and the location of some of the major earthquakes in Greece in the period 2001–2015. Daily values of aerosol optical depth (AOD) and total ozone column (TOZ) obtained from satellite observations are used, in the time window between 25 days before and 14 days after each of these events, in a 1° × 1° area centred on the epicentre of each earthquake. For some of these earthquake events, abnormal increases in time series of AOD and TOZ data were detected before and after the occurrence of the earthquake. Nevertheless, in other cases, no clear anomalies were observed around the earthquake date. In addition, examining the statistics of AOD and TOZ daily values, there were many cases of prominent abnormal variations, without, however, being associated with an earthquake event. Therefore, no clear association was found between AOD and TOZ fluctuations and recent earthquakes in Greece.
EN
We investigate the structural properties of a spatio-temporal network of earthquake events that incorporates magnitude information between the connected events. The network creates temporally directed links from an origin event towards a later event if it breaks the record closest distance from the origin among all the events in the catalog so far. Additionally, the links are conditionally classified based on the magnitude difference between connected events: “up” (“down”) connections point from a weaker (stronger) to a stronger (weaker) event. Using earthquake records from the Philippines from 1973 to 2012 and southern California from 1982 to 2012, we observe that the out-degree distributions show slight deviations from the corresponding Poisson distribution of the same mean. The space and time separations of connected earthquakes both show power-law regimes, suggesting spatio-temporal (self)organization. More importantly, the conditional distributions of “up” and “down” connections in space, time, and network structure point to a higher likelihood of a stronger event triggering a nearby weaker event for the first few connections, as in the case of aftershocks. The results are captured by a sandpile-based model where a small but finite probability of preferentially targeting the most susceptible grid site is introduced. Our analysis, coupled with the discrete model analog, provides a quantitative picture of the spatio-temporal and magnitude organization of seismicity beyond just the successive events. The technique may be extended to further characterize similar long-period earthquake records to yield a more complete picture of the underlying processes involved in seismicity.
EN
The present study was focused on determining the effectives of a nonlinear mathematical model in simulating complex mechanical behaviour of a seismic isolation system made of Polymeric Bearings. The proposed mathematical model defines the lateral force as a nonlinear function of the shear displacement and the deformation velocity. The effectiveness of the proposed mathematical model was verified by comparing the seismic response of a 2.30 m high two-storey structure model with the results obtained from the detailed numerical analysis. The results obtained from the numerical investigation using lumped-mass models confirmed that the proposed nonlinear mathematical model can be successfully adopted to simulate the complex mechanical behaviour of the Polymeric Bearings in numerical studies.
PL
W pracy dokonano oceny efektywności modelu matematycznego, opisującego nieliniowe zachowanie prototypu wibroizolacji sejsmicznej w postaci Łożysk Polimerowych. W zaproponowanym modelu matematycznym siła pozioma jest nieliniową funkcją przemieszczenia oraz prędkości. Oceny efektywności modelu matematycznego do opisu nieliniowego zachowania łożysk polimerowych dokonano poprzez porównanie wyników badań eksperymentalnych przeprowadzonych na stole sejsmicznym, w których dwupiętrowy model konstrukcji o całkowitej wysokości 2,30 m poddano różnym obciążeniom dynamicznym, z wynikami analiz numerycznych. Duża zgodność wyników analiz numerycznych z wynikami otrzymanymi z badań eksperymentalnych potwierdziła poprawność zaproponowanego modelu matematycznego do symulacji zachowania Łożysk Polimerowych.
EN
The aftershock records of the magnitude 7.1 earthquake that hit the island of Bohol in central Philippines on 15 October 2013 is investigated in the light of previous results for the Philippines using historical earthquakes. Statistics of interevent distances and interevent times between successive aftershocks recorded for the whole month of October 2013 show marked differences from those of historical earthquakes from two Philippine catalogues of varying periods and completeness levels. In particular, the distributions closely follow only the regimes of the historical distributions that were previously attributed to the strong spatio-temporal correlations. The results therefore suggest that these correlated regimes which emerged naturally from the analyses are strongly dominated by the clustering of aftershock events.
EN
The earthquake inter-event time distribution is studied, using catalogs for different recent aftershock sequences. For aftershock sequences following the Modified Omori’s Formula (MOF) it seems clear that the inter-event distribution is a power law. The parameters of this law are defined and they prove to be higher than the calculated value (2 – 1/p). Based on the analysis of the catalogs, it is determined that the probability densities of the inter-event time distribution collapse into a single master curve when the data is rescaled with instantaneous intensity, R(t; Mth), defined by MOF. The curve is approximated by a gamma distribution. The collapse of the data provides a clear view of aftershock-occurrence self-similarity.
EN
Ground motion prediction equations are essential for several purposes ranging from seismic design and analysis to probabilistic seismic hazard assessment. In seismically active regions without sufficiently strong ground motion data to build empirical models, hybrid models become vital. Georgia does not have sufficiently strong ground motion data to build empirical models. In this study, we have applied the host-totarget method in two regions in Georgia with different source mechanisms. According to the tectonic regime of the target areas, two different regions are chosen as host regions. One of them is in Turkey with the dominant strike-slip source mechanism, while the other is in Iran with the prevalence of reverse-mechanism events. We performed stochastic finite-fault simulations in both host and target areas and employed the hybrid-empirical method as introduced in Campbell (2003). An initial set of hybrid empirical ground motion estimates is obtained for PGA and SA at selected periods for Georgia.
PL
Podczas wstrząsów sejsmicznych o różnym natężeniu, wielokrotnie obserwowano zjawisko zderzania się konstrukcji ze sobą sąsiadujących, co mogło prowadzić nawet do ich całkowitego zniszczenia. Na podstawie obserwacji, badań numeryczny i eksperymentalnych, stwierdzono, że przyczyną kolizji była niedostateczna przerwa pomiędzy konstrukcjami. Ponadto czynnikami, które również mogą doprowadzić do zderzeń są różnice w masach lub sztywnościach budynków, które wpływają na przesunięte w fazie drgania, doprowadzając do kolizji. Celem niniejszej pracy jest przedstawienie wyników badań eksperymentalnych trzech sąsiadujących ze sobą modeli konstrukcji stalowych, o różnych charakterystykach dynamicznych, które na skutek obciążeń sejsmicznych zderzają się ze sobą. Ponadto przeanalizowano wpływ zastosowanych zderzaków styropianowych o grubości 10 mm, umieszczonych w przerwie dylatacyjnej, na odpowiedź poszczególnych konstrukcji. Przeprowadzono wielokrotne pomiary dla różnych wartości dylatacji oraz dwóch wariantów obciążenia modeli, jednak w pracy zostały przedstawione wyniki dla przerwy dylatacyjnej A = 30 mm oraz Wariantu 2 obciążenia wież. Wyniki badań eksperymentalnych wskazują na istotny wpływ zderzeń pomiędzy sąsiadującymi konstrukcjami na ich odpowiedź, prowadząc zarówno do jej zmniejszenia, jak i zwiększenia. Ponadto zastosowanie zderzaków styropianowych, doprowadziło do zmniejszenia przerwy dylatacyjnej, czego efektem była zmiana ekstremalnych wartości przyspieszeń poszczególnych wież.
EN
During moderate to strong ground motions, collisions between neighbouring structures. were repeatedly observed. This phenomenon (called pounding) between insufficiently separated structures may lead to its damages or total collapse. Based on the observations. numerical and experimental analysis, it was found that the mayor reason of collisions was inadequate gap between structures. Furthermore, the differences in mass or stiffness of the buildings may lead to the out-of-phase vibrations, which are identified as main factors of pounding. The aim of this papcr is to show the results of experimental study of collisions of three neighbouring steel structures, with different dynamic characteristics, under seismic excitation. Additionally, the influence of styrofoam bumpers (10 mm thickness) on the structural response was taken under consideration. The tests were provided for changing value of gap distance and for to configuration of the structures. In this paper, only the gap distance of 30 mm and variant 2 of mass configuration was analyzed. The results of the experimental study clearly indicate the influence of earthquake-induced pounding on the structural response, which may lead to its increase. but also its decrease. In addition, the use of styrofoam bumpers lead to reduction of the gap distance, which resulted in change of extreme acceleration values of each tower, as well.
EN
The article presents the likely cause of cracks in the continental and oceanic lithospheric plates, and the probable causes of earthquakes initiating Earth’s speed changes. As the root cause of one of the earthquakes, the author adopts a rotational speed of the globe (reasons: changes of the ocean level, convection currents, or a change in the ice cover) causing the formation of small d’Alambert’s forces with a latitudinal direction, which affect the tectonic plates. The author shows that there is a natural amplifier in the lithosphere, which converts the small d’Alambert’s forces into forces capable of moving tectonic plates on the asthenosphere. The energy to produce the drift of tectonic plates comes from the potential energy of water column in the oceans and some lakes. Thus, the author also explains where the continent-moving forces come from, unlike AlfredWegener who was not able tounravelthis. It should be emphasized that the earthquake in 2011 (Fukushima) occurred during theEarth’s speed change. Current hypotheses should be re-examined and the reason for tectonic plate drift should be re-considered taking into account the hydrostatic pressure – a factor influencing the water column in the oceans and some lakes, and affecting the change in rotation speed of the Earth. The author believes that it is appropriate to carry out work to identify a close relationship between the changes in the Earth’s speed and earthquakes initiated by these changes, which would allow to forecast some earthquakes.
PL
Wobec rozwoju metod opracowania coraz liczniejszych zbiorów obserwacji, np. w postaci „chmur punktów”, dystans interpretacyjny otrzymywanych wyników do rzeczywistości zwiększa się czasem tak znacznie, że zastosowany model trudno odróżnić od metafory. W niniejszej pracy powracamy do korzeni tych metod, pokazując, na konkretnym przykładzie – zaskakującego trzęsienia w pobliżu Waszyngtonu w sierpniu 2011 r., zastosowanie najprostszego modelu „naturalnego”, skracającego dystans interpretacyjny.
EN
Considering the development of processing methods of sets of observations of growing numbers of elements, such as "point cloud", it may be stated that the interpretation distance between obtained results and the reality is so increased that it is difficult to distinguish between the applied model and a metaphor. In this paper the authors return to the roots of those methods and present - using the selected example of the surprising earthquake which happened close to Washington in August 2011 - utilisation of the simplest "natural" model, which shortens interpretation distance.
EN
In the beginning of July 2010, a ground fissure was observed in the field near the village of Mavropigi (Northern Greece) and specifically in its NW side. Later on (early September), a second ground fissure was perceived, close and almost parallel to the first one and very close to the limits of the lignite exploitation mine (by the Public Power Corporation, PPC). It was observed that the village of Mavropigi slides away slowly towards the PPC lignite mine. Geological, seismological, as well as geotechnical survey in the field indicated that the phenomenon is related to the coal mining exploitation in the near vicinity of the village rather than to any seismotectonic activity in the surrounding area.
EN
The earthquake spatial distribution is being studied, using earthquake catalogs from different seismic regions (California, Canada, Central Asia, Greece, and Japan). The quality of the available catalogs, taking into account the completeness of the magnitude, is examined. Based on the analysis of the catalogs, it was determined that the probability densities of the inter-event distance distribution collapse into single distribution when the data is rescaled. The collapse of the data provides a clear illustration of earthquake-occurrence self-similarity in space.
PL
W pracy tej proponuje się bezpośrednie wyznaczenie potencjału grawitacyjnego W=v2/2 przez pomiar czasu t swobodnego spadku ciała z wysokości h. Wyznacza się też natężenie pola grawitacyjnego g. Procedura ta opiera się na prawie fizycznym v=2vm, gdzie vm=h/t, które daje proste zależności: W=2(h/t)2 oraz g=2h/t2. Istnieje więc możliwość skonstruowania prostego potencjometru grawitacyjnego, a nawet gradientometru, jako dwóch sprzężonych potencjometrów. Efektywność tej procedury sprawdziliśmy w prostym eksperymencie symulacyjnym na poziomie precyzji mGal.
EN
In this paper we propose a direct calculation of gravitational potential W=v2/2 by measuring the free fall time t of an object from height h. The intensity of the gravitational field g is also calculated. The procedure is based on the physical law v=2vm, where vm=h/t, which gives W=2(h/t)2 and g=2h/t2. It is therefore possible to construct a simple gravitational potentiometer, and even a gradientometer, as two coupled potentiometers. The effectiveness of this procedure is verified by a simple simulation experiment at the level of precision of mGal.
PL
Przedstawiono wyniki analizy numerycznej zachowania się odłącznika wysokiego napięcia SGF 245 podczas trzęsienia ziemi. W analizie zastosowano model odłącznika zaimplementowany w programie MES. W pierwszym etapie wykonano analizę modalną w celu weryfikacji dokładności modelu numerycznego. Następnie przeprowadzono dokładną nieliniową analizę dynamiczną przy wystąpieniu wymuszenia opisanego składową NS trzęsienia ziemi El Centro z 1940 roku. Wyniki analizy dowodzą, że krytycznym miejscem konstrukcji jest połączenie pomiędzy kolumną a ramą podstawy, w którym to zaobserwowano największe wartości naprężeń.
EN
The aim of the paper is to show the results of the numerical analysis focused on the behaviour of the high voltage disconnector SGF 245 under earthquake excitation. In the study, the FEM model of the analysed structure has been investigated. First, the modal analysis has been conducted so as to verify the accuracy of the numerical model. Then, the detailed nonlinear dynamic analysis has been carried out under the NS component of the El Centro earthquake of 1940. The results of the study show that the connection between the column and the base is the most critical location, in which the highest levels of stress have been observed.
19
Content available remote Czy w Polsce potrzebna jest sejsmiczna norma budowlana?
PL
Weryfikacja ryzyka sejsmicznego terenu Europy, podjęta m.in. w związku z wprowadzaniem od 2010 r. eurokodów w krajach UE, wskazała na istnienie zagrożenia sejsmicznego na terytorium Słowacji, Czech i Polski Południowej. W niniejszym artykule rozważa się, czy wzorem Słowacji lub Czech także na terenie naszego kraju nie należałoby wprowadzić odpowiedniej strefy sejsmicznej Eurokodu 8. Wstępna analiza ryzyka sejsmicznego terytorium Polski wskazuje, że choć powszechne wprowadzenie w Polsce normy sejsmicznej nie wydaje się uzasadnione, to jednak w procesie projektowania budowle specjalne i monumentalne (np. elektrownie atomowe i duże tamy) powinny być poddane sprawdzającym procedurom analiz sejsmicznych poprzedzonych szczegółowymi analizami ryzyka sejsmicznego.
EN
Year 2010 marks the beginning of the process of implementation of Eurocodes in the EU states. This includes also the Eurocode 8 dealing with seismic effects on structures. A wide scale verification of the European seismic risk revealed a minor and moderate seismic risk for Slovakia, Czech Republic and Southern Poland. The paper considers whether also Polish territory should be treated as potential Eurocode 8 seismic zone. An analysis of seismic risk suggests that although the data gathered so far do not suggest any necessity for conventional seismic building code to be applied on Polish territory, the special and monumental structures (e.g. nuclear power plants or big dams) may require more advanced analyses of their seismic risk and respective detailed seismic calculations.
20
Content available remote Badania dynamiczne modeli konstrukcji budowlanych na stole wstrząsowym
PL
Celem niniejszego artykułu jest przedstawienie wyników badań eksperymentalnych przeprowadzonych na stole wstrząsowym, w trakcie których poddawano wymuszeniom sejsmicznym modele dwóch kolidujących ze sobą wież. Wyniki te wskazują, że zderzenia mogą prowadzić do znacznego wzrostu odpowiedzi konstrukcji, ale mogą mieć również pozytywny wpływ i częściowo wytłumić drgania. Ponadto wyniki badań wykazały istotny wpływ rodzaju materiału, z którego wykonane są elementy kolidujące ze sobą na zachowanie się konstrukcji podczas trzęsień ziemi.
EN
The aim of the paper is to show the results of the shaking table experimental study conduced for pounding between two model towers equipped with colliding elements made of different building materials. The results of the study show that pounding may result in substantial increase of the structural response, however it can also play a positive role by reducing vibrations. Moreover, the results show the considerable influence of the type of material used for colliding elements on behaviour of structures during earthquakes.
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