Pounding Effects on Bridge s during Extreme Earthquakes
Author: Tzu-Ying Lee 1, Kai-Tien Chen 1, Chun-Chuan Su 1 1Department of Civil Engineering, National Central University, No.300, Jhongda Road, Jhongli, Taiwan | Size: 486 KB | Format:PDF | Quality:Unspecified | Publisher: Proceedings of the 8th International Conference on Structural Dynamics, EURODYN 2011 Leuven, Belgium, 4-6 July 2011 G. De Roeck, G. Degrande, G. Lombaert, G. M¨uller (eds.) | Year: 2011 | pages: 06 | ISBN: 978-90-760-1931-4
In the past extreme earthquakes, a number of bridges suffered damage with unseating of superstructures.
Whenever unseating failure occurs, local cracking or crushing due to pounding between superstructures can be observed in the
sites. Therefore, this paper is aimed to study pounding effect on isolated bridges in ultimate situation through numerical analysis.
The Vector Form Intrinsic Finite Element (VFIFE) is superior in managing the engineering problems with material nonlinearity,
discontinuity, large deformation, large displacement and arbitrary rigid body motions of deformable bodies. The VFIFE is thus
selected to be the analysis method in this study. Since the VFIFE is in its infant stage of development, there are still a number of
elements to be developed. Three types of impact models are developed for VFIFE to simulate the pounding effect. The
developed impact elements are verified to be accurate by a model comprising two SDOF systems. Two adjacent single-span
isolated bridges are then analyzed to study the pounding effect under extreme earthquakes. The results show insignificant
difference of the pounding effect by any impact model with or without energy dissipation. It is interesting to observe that the
column ductility demand remains identical regardless of the strength of unseating prevention device. The larger the mass ratio of
the two adjacent decks, the larger the intensity of the ground motion the column reaches its ultimate ductility.
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POUNDING OF ADJACENT RC BUILDINGS DURING SEISMIC LOADS
Author: Mizam DOĞAN1, Ayten GÜNAYDIN2 | Size: 1.7 MB | Format:PDF | Quality:Unspecified | Publisher: Journal of Engineering and Architecture Faculty of Eskişehir Osmangazi University, Vol: XXII, No:1, 2009 | Year: 2009 | pages: 17
Turkey is in high seismic risk zone. On a possible earthquake, adjacent buildings which are not separated from each other properly are under pounding risk. Although gap size requirements are given in Turkish Earthquake Code (TEC), in Turkey, adjacent buildings are still been constructing with insufficient gap sizes. In this paper; results of pounding and effects of pounding to structural elements of buildings are studied. Stress analyses are made on frame models for different impact points and analysis results are discussed. It is concluded that pounding forces are not completely absorbable because of their high values but their effects on structure can be reduced by placing elastic materials between adjacent buildings or by reinforcing structural systems with cast-in-place reinforced concrete (RC) walls
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Pounding between base-isolated and fixed-base RC buildings during earthquakes
Author: Deepak Raj Pant, Anil C. Wijeyewickrema Department of Civil and Environmental Engineering, Tokyo Institute of Technology, Japan | Size: 438 KB | Format:PDF | Quality:Unspecified | Publisher: Proceedings of the 8th International Conference on Structural Dynamics, EURODYN 2011 Leuven, Belgium, 4-6 July 2011 G. De Roeck, G. Degrande, G. Lombaert, G. M¨uller (eds.) | Year: 2011 | pages: 07 | ISBN: 978-90-760-1931-4
Pounding of base-isolated buildings during earthquakes could have detrimental effects on the performance of such buildings. Most previous studies on seismic pounding of base-isolated buildings have been carried out using simplified lumped mass numerical models. However, these simplified models cannot incorporate the nonlinear properties of realistic building materials such as reinforced concrete (RC). Therefore, the response of a base-isolated RC building during pounding with an adjacent structure is not well understood. Owing to the increasing use of base-isolation technology for seismic protection of mid-rise RC buildings around the world, it is important to study seismic pounding response of such buildings. This paperinvestigates the seismic pounding of a typical 4-story base-isolated RC building with 4-story and 8-story fixed-base RC buildings. Three-dimensional numerical models with due consideration of material and geometric nonlinearities are developed. Performance of the base-isolated building is evaluated in terms of story drift, story shear and overall damage index. It is foundthat the pounding of the base-isolated building with the 4-story fixed-base building is more critical than the pounding with the 8- story fixed-base building. The findings of the study are expected to assist design and evaluation of typical mid-rise baseisolated RC buildings.
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Lightweight, high-strength materials are used to construct flexible, long-span floors. These floors sometimes result in annoying levels of vibration even under ordinary loading
situations. These vibrations do not possess any threat to the structural integrity of the floor, but they may render the floor unusable by the human occupants of the building in extreme cases.
The wide variety of scales and prediction techniques is an indication of the complex nature of floor vibrations. The increasing incidence of building vibration due to human
rhythmic activities led to a specific design criterion for rhythmic excitations (Allen et al. 1985,Bachmann and Ammann, 1987,Faisca, 2003,Murray et al., 2003, Silva et al.,
2008). Floor vibrations often leads to structural failure as demonstrated by the Hyatt Regency Hotel Walkway in Kansas city, US, (McGrath and Foote, 1981) and London Millennium Footbridge (BBC news, 2000 and Sample, 2002).This is the motivation for the development of a design methodology on the structural system subjected to dynamic loads due to human activities. But, it is very difficult to interpret the magnitude of the motion, the environment surrounding sensor and the human sensor in accounting the floor vibrations
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Development of a numerical model for the prediction of ground-borne noise and vibration in buildings
Author: Péter F IALA M.Sc.E.E | Size: 5.2 MB | Format:PDF | Quality:Unspecified | Year: 2008 | pages: 128
Significant vibration in buildings near surface or underground railway tracks or roads is attributed to moving vehicles. Traffic induced vibrations in dense urban environments can cause structural damage in buildings and annoyance to the inhabitants of surrounding buildings in the form of vibrations or re-radiated noise.The vibrations within a building have several effect on the building’s structure. The vibrations can vary in a large range from imperceptible to levels causing structural damage. The limit above which the vibrations damage the structure is not clear. Some authors claim
that traffic induced ground-borne vibrations can not damage the structures and at worst disturb the occupants. Others [Cro65], however, state that the damaging effect of low frequency vibrations is cumulative and causes the uneven soil settlement under buildings over a long
time period.
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Now nearing its 30th year of publication, WELDING: PRINCIPLES & APPLICATIONS (WP&A), 7th Edition is the authoritative introduction to the subject of welding. It's designed for students in a wide range of academic and workforce training programs who want to pursue careers as skilled welders and welding supervisors.
The text also supports the needs of learners who need to achieve a basic level of proficiency in welding in their chosen skilled trade. While covering the procedural and safety information all students need, WELDING: PRINCIPLES & APPLICATIONS also explains underlying theories. The combination of hands-on information with clear explanations of theory is a hallmark of this book. The depth of coverage allows it to be used as the core text in a multi-course welding curriculum, generally starting with shielded metal arc welding, and then covering other basic processes and more advanced techniques.
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Experimental studies of the ultimate behavior of seismically-isolated structures
Author: Clark, Peter W.; Aiken, Ian D.; Kelly, James M. | Size: 4 MB | Format:PDF | Quality:Unspecified | Publisher: NISEE e-Library | Year: 1997 | pages: 322
A large-scale earthquake simulator study of a seismically isolated, three-story reinforced concrete building was performed in conjunction with a series of component tests of reduced-scale high-damping rubber isolators. The goal of the study was to experimentally verify the behavior of structures founded on elastomeric isolators under severe ground motions and to provide data for future correlative computer analyses and building code development. The reinforced concrete frame structure was constructed at 0.4 scale to represent one of two identical buildings on the campus of Tohoku University in Sendai, Japan. The Sendai buildings were built as a research environment for the performance of seismically isolated structures during actual earthquakes. The research program described in this report was intended to augment the field results by subjecting a large-scale isolated model to beyond-design-level earthquake ground motions on an earthquake simulator. A parallel investigation of the large-displacement behavior of individual high-damping rubber isolators was undertaken to quantify their fundamental mechanical properties as well as their ultimate capacities and failure mechanisms. The test results indicate that properly designed and manufactured bearings exhibit both a gradual stiffening and an increase in energy dissipation under shear loading due to strain crystallization in the rubber compound. The particular bearings studied displayed stable response with substantial energy dissipation over a wide range of shear deformations although they were subject to softening and subsequent rapid stiffness recovery after cycling to large strains. The seismically isolated reinforced concrete building model was subjected to simulated earthquakes of a range of intensities. The properties of the reduced-scale isolators were selected to match those of the first high-damping rubber bearings installed in the full-size building in the 1980s. The stiffness of the system is, therefore, greater than designs following current practice in the United States because it reflects the conservatism associated with implementing a new technology. This larger stiffness reduced the effectiveness of the isolation system under moderate shaking, which is undesirable from a design standpoint; but under the most severe ground motions, the bearings stiffened and acted as a fail-safe mechanism. The larger shear forces transmitted to the structure led to distributed yielding in the frame, but it was demonstrated that the isolators were not the weak link.
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Dear students, the purpose of this textbook is to give you an insight into the area of measuring vibrations and the use of measuring vibrations in vibration diagnostics. Vibration diagnostics is one of the non-destructive methods used for condition monitoring of machines in operation. All the machines while operating vibrate more or less, and with most of them the vibrations are unwanted and the effort is to minimize them. Only with some types of machines, vibrations are directly a working principle of the machine and are caused deliberately (e.g. vibrating screeners). Though, this group of machines is not of interest to vibration diagnostics. Diagnostic work can be thought of by analogy with activities of a practising physician who during preventive inspection detects and evaluates one's medical condition. Basically, three situations can occur: You will learn that 1) you are healthy and you can live as before, 2) you have high blood pressure and you should start taking the medication for its reduction and/or change your lifestyle, or 3) your condition requires hospitalization and a more detailed examination and/or a surgery. Machines are at exactly the same situation. Based on a diagnostician’s assessment they can either continue in operation, or a tiny intervention is necessary, or they need to be shut down and repaired thoroughly. Purpose of all this is, in case of both humans and machines, to save the cost of repair or to prevent a disaster and its associated costs. As the name vibration diagnostics suggests, machine condition is diagnosed on the base of an analysis of vibration. Successful application of vibration diagnosis requires in practice staff with considerable degree of knowledge and experience. Routine work in data collection may be carried out by trained personnel without academic qualifications, but data processing and assessment of the state of a machine is a task for an engineer who has knowledge in various areas (design of machines, dynamics, mathematics, signal processing, etc.) and who is able to use this knowledge in context. A graduate in Applied Mechanics specialization is an ideal candidate for becoming a skilled vibration diagnostician after several years of practice. This text is almost your first encounter with the experimental mechanics. We believe that we will convince you that it is a beautiful and promising area which should become an integral part of your engineering practice and mastering of which will contribute to your becoming a full member of the team of experts addressing complex technical problems
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