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Seismic Regions (seismic + regions)
Selected AbstractsEffect of cumulative seismic damage and corrosion on the life-cycle cost of reinforced concrete bridgesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2009R. Kumar Abstract Bridge design should take into account not only safety and functionality, but also the cost effectiveness of investments throughout a bridge life-cycle. This paper presents a probabilistic approach to compute the life-cycle cost (LCC) of corroding reinforced concrete (RC) bridges in earthquake-prone regions. The approach is developed by combining cumulative seismic damage and damage associated with corrosion due to environmental conditions. Cumulative seismic damage is obtained from a low-cycle fatigue analysis. Chloride-induced corrosion of steel reinforcement is computed based on Fick's second law of diffusion. The proposed methodology accounts for the uncertainties in the ground motion parameters, the distance from the source, the seismic demand on the bridge, and the corrosion initiation time. The statistics of the accumulated damage and the cost of repairs throughout the bridge life-cycle are obtained by Monte-Carlo simulation. As an illustration of the proposed approach, the effects of design parameters on the LCC of an example RC bridge are studied. The results are valuable in better estimating the condition of existing bridges and, therefore, can help to schedule inspection and maintenance programs. In addition, by taking into consideration the two deterioration processes over a bridge life-cycle, it is possible to estimate the optimal design parameters by minimizing, for example, the expected cost throughout the life of the structure. A comparison between the effects of the two deterioration processes shows that, in seismic regions, the cumulative seismic damage affects the reliability of bridges over time more than the corrosion even for corrosive environments. Copyright © 2008 John Wiley & Sons, Ltd. [source] An attenuation model for distant earthquakesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2004Adrian Chandler Abstract Large magnitude earthquakes generated at source,site distances exceeding 100km are typified by low-frequency (long-period) seismic waves. Such induced ground shaking can be disproportionately destructive due to its high displacement, and possibly high velocity, shaking characteristics. Distant earthquakes represent a potentially significant safety hazard in certain low and moderate seismic regions where seismic activity is governed by major distant sources as opposed to nearby (regional) background sources. Examples are parts of the Indian sub-continent, Eastern China and Indo-China. The majority of ground motion attenuation relationships currently available for applications in active seismic regions may not be suitable for handling long-distance attenuation, since the significance of distant earthquakes is mainly confined to certain low to moderate seismicity regions. Thus, the effects of distant earthquakes are often not accurately represented by conventional empirical models which were typically developed from curve-fitting earthquake strong-motion data from active seismic regions. Numerous well-known existing attenuation relationships are evaluated in this paper, to highlight their limitations in long-distance applications. In contrast, basic seismological parameters such as the Quality factor (Q -factor) could provide a far more accurate representation for the distant attenuation behaviour of a region, but such information is seldom used by engineers in any direct manner. The aim of this paper is to develop a set of relationships that provide a convenient link between the seismological Q -factor (amongst other factors) and response spectrum attenuation. The use of Q as an input parameter to the proposed model enables valuable local seismological information to be incorporated directly into response spectrum predictions. The application of this new modelling approach is demonstrated by examples based on the Chi-Chi earthquake (Taiwan and South China), Gujarat earthquake (Northwest India), Nisqually earthquake (region surrounding Seattle) and Sumatran-fault earthquake (recorded in Singapore). Field recordings have been obtained from these events for comparison with the proposed model. The accuracy of the stochastic simulations and the regression analysis have been confirmed by comparisons between the model calculations and the actual field observations. It is emphasized that obtaining representative estimates for Q for input into the model is equally important.Thus, this paper forms part of the long-term objective of the authors to develop more effective communications across the engineering and seismological disciplines. Copyright © 2003 John Wiley & Sons, Ltd. [source] Strike-slip earthquakes in the oceanic lithosphere: observations of exceptionally high apparent stressGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2002George L. Choy Summary The radiated energies, ES, and seismic moments, M0, for 942 globally distributed earthquakes that occurred between 1987 to 1998 are examined to find the earthquakes with the highest apparent stresses (,a=,ES/M0, where , is the modulus of rigidity). The globally averaged ,a for shallow earthquakes in all tectonic environments and seismic regions is 0.3 MPa. However, the subset of 49 earthquakes with the highest apparent stresses (,a greater than about 5.0 MPa) is dominated almost exclusively by strike-slip earthquakes that occur in oceanic environments. These earthquakes are all located in the depth range 7,29 km in the upper mantle of the young oceanic lithosphere. Many of these events occur near plate-boundary triple junctions where there appear to be high rates of intraplate deformation. Indeed, the small rapidly deforming Gorda Plate accounts for 10 of the 49 high- ,a events. The depth distribution of ,a, which shows peak values somewhat greater than 25 MPa in the depth range 20,25 km, suggests that upper bounds on this parameter are a result of the strength of the oceanic lithosphere. A recently proposed envelope for apparent stress, derived by taking 6 per cent of the strength inferred from laboratory experiments for young (less than 30 Ma) deforming oceanic lithosphere, agrees well with the upper-bound envelope of apparent stresses over the depth range 5,30 km. The corresponding depth-dependent shear strength for young oceanic lithosphere attains a peak value of about 575 MPa at a depth of 21 km and then diminishes rapidly as the depth increases. In addition to their high apparent stresses, which suggest that the strength of the young oceanic lithosphere is highest in the depth range 10,30 km, our set of high- ,a earthquakes show other features that constrain the nature of the forces that cause interplate motion. First, our set of events is divided roughly equally between intraplate and transform faulting with similar depth distributions of ,a for the two types. Secondly, many of the intraplate events have focal mechanisms with the T -axes that are normal to the nearest ridge crest or subduction zone and P -axes that are normal to the proximate transform fault. These observations suggest that forces associated with the reorganization of plate boundaries play an important role in causing high- ,a earthquakes inside oceanic plates. Extant transform boundaries may be misaligned with current plate motion. To accommodate current plate motion, the pre-existing plate boundaries would have to be subjected to large horizontal transform push forces. A notable example of this is the triple junction near which the second large aftershock of the 1992 April Cape Mendocino, California, sequence occurred. Alternatively, subduction zone resistance may be enhanced by the collision of a buoyant lithosphere, a process that also markedly increases the horizontal stress. A notable example of this is the Aleutian Trench near which large events occurred in the Gulf of Alaska in late 1987 and the 1998 March Balleny Sea M= 8.2 earthquake within the Antarctic Plate. [source] Das Magnitude 8.8 Maule (Chile)-Erdbeben vom 27.BAUTECHNIK, Issue 8 2010Februar 2010, Ingenieuranalyse der Erdbebenschäden Das Maule (Chile)-Erdbeben vom 27. Februar 2010 gehört zu den stärksten, weltweit jemals registrierten Erdbeben. Die Bruchzone erstreckt sich über eine Länge von 500 km und eine Breite von 100 km, so dass acht Millionen Einwohner Chiles von dem Erdbeben mehr oder weniger direkt von den Schütterwirkungen betroffen waren. Bilder von spektakulären Schadensfällen aus der ca. 330 km entfernten Hauptstadt prägten die internationale Berichterstattung. Das seismische Ereignis löste einen Tsunami aus, der verheerende Schäden an der Küste Chiles verursachte und auch an den Küsten Hawaiis noch deutlich wahrgenommen werden konnte. Die seismischen Bodenbewegungen wurden bis ins Nachbarland Argentinien verspürt. Die Stärke des Bebens und ereignisspezifische Besonderheiten waren Motivation, im Rahmen einer Erkundungsmission der Ingenieurgruppe der Deutschen TaskForce Erdbeben im betroffenen Gebiet die Bauwerksschäden aufzunehmen und ihre regionale Verteilung zu dokumentieren. In fünf temporär, mit Starkbeben-Sensoren instrumentierten Gebäuden konnten mehrere Nachbeben aufgezeichnet werden, deren Beschleunigungsamplituden für allgemeine Hochbauten in deutschen Erdbebengebieten von Interesse bzw. maßgeblich wären. Die vorliegenden Messdaten ermöglichen die Interpretation der realen Gebäudereaktion und können in Folgeuntersuchungen zur Kalibrierung analytischer Modelle herangezogen werden. Der Beitrag vermittelt einen Eindruck von den erdbebenbedingten Schäden und soll das Verhalten der typischen Bauweisen unter diesen extremen Einwirkungen aufzeigen, das vor Ort festgestellte geringe Schadensausmaß durch die Umsetzung von Baunormen und darin verankerten Bemessungskonzepten erklären und letztlich die Übertragbarkeit dieser Beobachtungen auf andere Erdbebenregionen hinterfragen. In einem Folgebeitrag [1] werden die Schäden aus dem Tsunami einer Ingenieuranalyse unterzogen und die wesentlichen Wirkungsmechanismen bzw. einfachen baulichen Schutzmaßnahmen herausgearbeitet. The Magnitude 8.8 Maule (Chile) Earthquake of February 27, 2010 , Engineering analysis of earthquake damage. The Maule (Chile) February 27, 2010 Earthquake is regarded as one of the strongest earthquakes ever recorded world-wide. The rupture zone reached a length of about 500 km and a width of about 100 km; almost 8 million inhabitants were directly affected by the consequences of the earthquake. Photos from spectacular failure cases in the Capital (330 km away) were documented across the world and dominated the international reporting. The seismic event triggered a tsunami which caused serious damage alongside the coastal border; the waves were observed in the far-distant Hawaii Islands, too. The seismic ground motions were felt in the neighboring country Argentina, as well. The strength of the earthquake and the event-specific characteristics motivated the "Engineering Group of the German Task Force for earthquake" to analyze the building damage and to document their regional distribution. Five multi-storey RC structures were temporarily equipped with Strong-Motion sensors. Several aftershocks could be recorded; the peak acceleration amplitudes were in a level which was of interest for buildings in highest zone of German earthquake regions. In a first attempt, the measurements are used to interpret the response of real buildings in both horizontal directions; in ongoing studies data are used for the calibration of analytical models. The paper provides an overview of the earthquake induced damages in several building types and its variation within different structural systems. Reasons of low to moderate observed damage will be discussed in close relation to the code development and the preferred design concepts. The application of observed effects and derived lessons to other seismic regions is critically reviewed. In a subsequent paper [1] the damage caused by the tsunami is investigated in more detail. The engineering analysis will include the currently used models for the impact description and will elaborate simple, but quite efficient measures of protection. [source] Bauten in deutschen Erdbebengebieten , zur Einführung der DIN 4149: 2005BAUTECHNIK, Issue 8 2005Jochen Schwarz Dr.-Ing. Die Einführung der DIN 4149: 2005 bildet eine wichtige Voraussetzung, um im Kontext der Harmonisierung europäischer Baubestimmungen ein erdbebensicheres und wirtschaftliches Bauen in den Erdbebengebieten Deutschlands zu ermöglichen. Verschiedene Phasen der Erarbeitung werden in einer chronologischen Form beleuchtet und mit einem Ausblick auf die weitere Normenentwicklung abgeschlossen. Es werden interdisziplinäre Forschungsarbeiten gewürdigt, die wesentlich dazu beigetragen haben, das Regelwerk der seismischen Lastannahmen für Bauwerke neu zu konzipieren. Insbesondere durch die Festlegung geologie- und untergrundbezogener Bemessungsspektren wird eine differenzierte Beschreibung seismischer Einwirkungen und auf die regionalen Besonderheiten deutscher Erdbebengebiete ausgerichtete Bauwerksbemessung gewährleistet. Der erreichte Grad der Harmonisierung europäischer Erdbebenbaunormen wird anhand aktueller Zonenkarten sowie der Festlegungen zu Bemessungsbeschleunigungen entlang der nationalen Grenzen beispielhaft nachvollzogen. Da die neue Gefährdungszonenkarte eine veränderte regionale Verteilung der Erdbebenzonen bedingt, wird auf die Notwendigkeit einer Bewertung der Erdbebentauglichkeit der vorherrschenden Bauweisen und die Identifikation der im Katastrophenfall bedeutenden Anlagen und Einrichtungen hingewiesen. Buildings in German seismic regions , to the introduction of the revised German Seismic Code DIN 4149: 2005. The introduction of the revised Seismic Code DIN 4149: 2005 can be regarded as an important step towards earthquake resistant and economic building design in German earthquake regions. Different stages of its elaboration are described chronologically, concluding in an outlook on the ongoing development in European code standardization. Interdisciplinary research projects, which influenced the redrafting of the general rules and the implementation of new approaches, substantially, are recognized for their contributions. In particular, the concept of geology- and subsoil-dependent response spectra enables a refined description of seismic action and building design while reflecting the existing site conditions realistically. The attained state of harmonisation of national regulations is discussed exemplary by comparing peak ground and derived design accelerations alongside the borders with neighbouring countries like Belgium, France and Switzerland. With respect to the new zoning map and the modifications of affected areas, the need of practical implementation is directed towards two tasks: evaluation of the existing building stock and the predominant building types and identification of those structures and facilities which are of high importance in cases of catastrophic events. [source] Überprüfung und Bewertung der seismischen Bemessungsgrößen nach DIN 19700 am Beispiel der Thüringer TalsperrenBAUTECHNIK, Issue 12 2004Jochen Schwarz Dr.-Ing. Durch die DIN 19700 werden Talsperren u. ä. Wasserbauwerke hinsichtlich ihrer Bedeutung, ihres Stauvolumens und Höhe (bzw. Stauhöhe) in unterschiedliche Klassen eingeteilt, verbunden mit unterschiedlichen Anforderungen an die Auslegung und Nachweisführung. Da die Talsperren in seismisch unterschiedlich aktiven Erdbebengebieten liegen, sind die Nachweisanforderungen in Abhängigkeit von der Gefährdung (Erdbebenzonen mit bestimmten Intensitätsintervallen) zu staffeln. Es wird untersucht, welche Anforderungen aus der Einführung DIN 19700 abzuleiten sind und wie auf Ebene der Bundesländer die praktische Umsetzung erfolgen kann. In diesem Zusammenhang wird die Thüringer Technische Anleitung Stauanlagen gesondert gewürdigt, die gegenüber der DIN veränderte Festlegungen beinhaltet. Im folgenden werden Grundzüge einer vereinheitlichten Vorgehensweise für den Freistaat Thüringen entwickelt und die notwendigen Bearbeitungsphasen erläutert. Sie sind so gestaltet, daß Synergieeffekte erreicht werden können und eine Übertragbarkeit auf die anderen Bundesländer gewährleistet ist. Examination and evaluation of seismic design criteria according to DIN 4149 by the example of the Thuringia dams. According to the new DIN 19700 dams and other water retaining structures are classified with respect to their storage capacity and height leading to differentiated demands on design and safety verification. Since the dams are located in quite different seismic regions, these demands have to reflect the level of seismic hazard (in terms of zones expressing different intensity intervals). The paper investigates the requirements connected with the introduction of DIN 19700 and the problems arising when implementing the code in a nation-wide scale acknowledging the federal system in Germany. In this context and due to some normative elements, deviating from DIN 19700, the Thuringian Technical Guide is considered more in detail. Basic contours of a unified strategy for the state of Thuringia and the required steps of action are presented. The procedure allows for effects of synergy by maintaining the transformability of the guidelines to other German States. [source] | ||||||||||