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Top 20 Most Read Articles
October 2008
The 20 articles with the most full-text downloads during the month, in descending order.
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STEEL SHEAR WALLS, BEHAVIOR, MODELING AND DESIGN AIP Conf. Proc. 1020, pp. 5-18; doi:http://dx.doi.org/10.1063/1.2963889 (14 pages) Online Publication Date: 8 July 2008
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In recent years steel shear walls have become one of the more efficient lateral load resisting systems in tall buildings. The basic steel shear wall system consists of a steel plate welded to boundary steel columns and boundary steel beams. In some cases the boundary columns have been concrete‐filled steel tubes. Seismic behavior of steel shear wall systems during actual earthquakes and based on laboratory cyclic tests indicates that the systems are quite ductile and can be designed in an economical way to have sufficient stiffness, strength, ductility and energy dissipation capacity to resist seismic effects of strong earthquakes. This paper, after summarizing the past research, presents the results of two tests of an innovative steel shear wall system where the boundary elements are concrete‐filled tubes. Then, a review of currently available analytical models of steel shear walls is provided with a discussion of capabilities and limitations of each model. We have observed that the tension only “strip model”, forming the basis of the current AISC seismic design provisions for steel shear walls, is not capable of predicting the behavior of steel shear walls with length‐to‐thickness ratio less than about 600 which is the range most common in buildings. The main reasons for such shortcomings of the AISC seismic design provisions for steel shear walls is that it ignores the compression field in the shear walls, which can be significant in typical shear walls. The AISC method also is not capable of incorporating stresses in the shear wall due to overturning moments. A more rational seismic design procedure for design of shear walls proposed in 2000 by the author is summarized in the paper. The design method, based on procedures used for design of steel plate girders, takes into account both tension and compression stress fields and is applicable to all values of length‐to‐thickness ratios of steel shear walls. The method is also capable of including the effect of overturning moments and any normal forces that might act on the steel shear wall. |
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Detection of atoms consisting of π+ and π− mesons at PS CERN AIP Conf. Proc. 619, pp. 745-748; doi:http://dx.doi.org/10.1063/1.1482531 (4 pages) Online Publication Date: 7 June 2002
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The DIRAC experiment aims to measure the lifetime of π+π− atoms in the ground state with 10% precision, using the 24 GeV/c proton beam of the CERN Proton Synchrotron. As the value of the above lifetime of order 10−15s is dictated by a strong interaction at low energy, the precise measurement of this quantity enables to determine a combination of S‐wave pion scattering lengths to 5%. Pion scattering lengths have been calculated in the framework of chiral perturbation theory with high precision. Thus the accurate measurement of these values would submit the understanding of chiral symmetry breaking of QCD to a crucial test. Some preliminary results from the analysis of a 2000 data sample are presented. © 2002 American Institute of Physics |
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New Upgrade Project for the Photon Factory Storage Ring AIP Conf. Proc. 705, pp. 161-166; doi:http://dx.doi.org/10.1063/1.1757759 (6 pages) Online Publication Date: 21 June 2004
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A new project for upgrading the 2.5‐GeV Photon Factory (PF) storage ring is now being undertaken to create six new short‐straight sections and to lengthen the existing eight straight sections. The short‐straight sections will provide an opportunity to install short‐period narrow‐gap undulators, while the extensions of existing straight sections will be taken advantage of updating current insertion devices to the latest models in future. To this end, the lattice configuration around the straight sections is modified by replacing old quadrupole magnets with new shorter ones and placing them closer to the near‐by bending magnets. Necessary replacement of the vacuum ducts and the beamline front ends will be carried out together. This project will be completed by the end of September, 2005, after six months of shutdown. © 2004 American Institute of Physics |
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The Impact of Dam‐Reservoir‐Foundation Interaction on Nonlinear Response of Concrete Gravity Dams AIP Conf. Proc. 1020, pp. 585-594; doi:http://dx.doi.org/10.1063/1.2963887 (10 pages) Online Publication Date: 8 July 2008
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To study the impact of dam‐reservoir‐foundation interaction on nonlinear response of concrete gravity dams, a two‐dimensional finite element model of a concrete gravity dam including the dam body, a part of its foundation and a part of the reservoir was made. In addition, the proper boundary conditions were used in both reservoir and foundation in order to absorb the energy of outgoing waves at the far end boundaries. Using the finite element method and smeared crack approach, some different seismic nonlinear analyses were done and finally, we came to a conclusion that the consideration of dam‐reservoir‐foundation interaction in nonlinear analysis of concrete dams is of great importance, because from the performance point of view, this interaction significantly improves the nonlinear response of concrete dams. |
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AIP Conf. Proc. 1020, pp. 100-108; doi:http://dx.doi.org/10.1063/1.2963716 (9 pages) Online Publication Date: 8 July 2008
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The seismic protection of historical and monumental buildings, namely dating back from the ancient age up to the 20th Century, is being looked at with greater and greater interest, above all in the Euro‐Mediterranean area, its cultural heritage being strongly susceptible to undergo severe damage or even collapse due to earthquake. The cultural importance of historical and monumental constructions limits, in many cases, the possibility to upgrade them from the seismic point of view, due to the fear of using intervention techniques which could have detrimental effects on their cultural value. Consequently, a great interest is growing in the development of sustainable methodologies for the use of Reversible Mixed Technologies (RMTs) in the seismic protection of the existing constructions. RMTs, in fact, are conceived for exploiting the peculiarities of innovative materials and special devices, and they allow ease of removal when necessary. This paper deals with the experimental and numerical studies, framed within the EC PROHITECH research project, on the application of RMTs to the historical and monumental constructions mainly belonging to the cultural heritage of the Euro‐Mediterranean area. The experimental tests and the numerical analyses are carried out at five different levels, namely full scale models, large scale models, sub‐systems, devices, materials and elements. |
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X‐ray System for Early Diagnosis of Breast Cancer AIP Conf. Proc. 902, pp. 37-40; doi:http://dx.doi.org/10.1063/1.2723617 (4 pages) Online Publication Date: 9 April 2007
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Increasing rate of breast cancer in Japan is enormous in these years. Nevertheless only 2–3 % of female may receive mammography. In order to improve this number for early detection of breast cancer we have started development of a refraction‐based visualization of breast cancer. This system comprises two types of imaging: one is for a regular annual or biyearly check of the breast cancer. This is a 2‐D mode x‐ray dark‐field imaging where a Laue transmission type of angle analyzer with thickness of 2.124 mm is used for the FOV of 90 mm × 90 mm that can provide the spatial resolution better than 50 microns; the other a 3‐D reconstruction for further detailed check to specify type and location of breast cancer. © 2007 American Institute of Physics |
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Computer Simulation of Material Flow in Warm‐forming Bimetallic Components AIP Conf. Proc. 908, pp. 1029-1034; doi:http://dx.doi.org/10.1063/1.2740946 (6 pages) Online Publication Date: 25 May 2007
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Bimetallic components take advantage of two different metals or alloys so that their applicable performance, weight and cost can be optimized. However, since each material has its own flow properties and mechanical behaviour, heterogeneous material flows will occur during the bimetal forming process. Those controls of process parameters are relatively more complicated than forming single metals. Most previous studies in bimetal forming have focused mainly on cold forming, and less relevant information about the warm forming has been provided. Indeed, changes of temperature and heat transfer between two materials are the significant factors which can highly influence the success of the process. Therefore, this paper presents a study of the material flow in warm‐forming bimetallic components using finite‐element (FE) simulation in order to determine the suitable process parameters for attaining the complete die filling. A watch‐case‐like component made of stainless steel (AISI‐316L) and aluminium alloy (AL‐6063) was used as the example. The warm‐forming processes were simulated with the punch speeds V of 40, 80, and 120 mm/s and the initial temperatures of the stainless steel TiSS of 625, 675, 725, 775, 825, 875, 925, 975, and 1025 °C. The results showed that the AL‐6063 flowed faster than the AISI‐316L and so the incomplete die filling was only found in the AISI‐316L region. A higher TiSS was recommended to avoid incomplete die filling. The reduction of V is also suggested because this can save the forming energy and prevent the damage of tooling. Eventually, with the experimental verification, the results from the simulation were in agreement with those of the experiments. On the basis of the results of this study, engineers can gain a better understanding of the material flow in warm‐forming bimetallic components, and be able to determine more efficiently the punch speed and initial material temperature for the process. © 2007 American Institute of Physics |
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CP violation in a six-quark model AIP Conf. Proc. 424, pp. 15-25; doi:http://dx.doi.org/10.1063/1.55099 (11 pages) Online Publication Date: 27 March 2008
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Author’s personal recollections of the early 70’s when the six-quark model was proposed to explain CP violation are presented. A brief summary of the mechanism of CP violation in the model and an analysis of the neutral K-meson system are also given. © 1998 American Institute of Physics. |
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AIP Conf. Proc. 1044, pp. 331-339; doi:http://dx.doi.org/10.1063/1.2993731 (9 pages) Online Publication Date: 22 September 2008
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Concentrating Solar Power (CSP) has the potential to contribute significantly to the generation of electricity by renewable energy resources in the U.S.. Thermal storage can extend the duty cycle of CSP beyond daytime hours to early evening where the value of electricity is often the highest. The potential solar resource for the southwest U.S. is identified, along with the need to add power lines to bring the power to consumers. CSP plants in the U.S. and abroad are described. The CSP cost of electricity at the busbar is discussed. With current incentives, CSP is approaching competiveness with conventional gas‐fired systems during peak‐demand hours when the price of electricity is the highest. It is projected that a mature CSP industry of over 4 GWe will be able to reduce the energy cost by about 50%, and that U.S. capacity could be 120 GW by 2050. |
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The Status and Future of Wind Energy Technology AIP Conf. Proc. 1044, pp. 340-359; doi:http://dx.doi.org/10.1063/1.2993732 (20 pages) Online Publication Date: 22 September 2008
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AIP Conf. Proc. 1020, pp. 569-576; doi:http://dx.doi.org/10.1063/1.2963885 (8 pages) Online Publication Date: 8 July 2008
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The deep investigation of soil‐foundation interaction behaviour during earthquakes represent one of the key‐point for a right seismic design of structures, which can really behave well during earthquake, avoiding dangerous boundary conditions, such as weak foundations supporting the superstructures. The paper presents the results of the FEM modeling of a shaking table test involving a concrete shallow foundation resting on a Leighton Buzzard sand deposit. The numerical simulation is performed using a cap‐hardening elasto‐plastic constitutive model for the soil and specific soil‐foundation contacts to allow slipping and up‐lifting phenomena. Thanks to the comparison between experimental and numerical results, the power and the limits of the proposed numerical model are focused. Some aspects of the dynamic soil‐foundation interaction are also pointed out. |
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Liquefaction Potential Assessment Of Silty And Silty‐Sand Deposits: A Case Study AIP Conf. Proc. 1020, pp. 434-441; doi:http://dx.doi.org/10.1063/1.2963867 (8 pages) Online Publication Date: 8 July 2008
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The paper shows a case study concerning the liquefaction potential assessment of deposits which mainly consist of non plastic silts and sands (FC>35%,Ip<10%, CF negligible). The site under study has been characterized by means of in situ tests (CPTU, SPT and DPSH), boreholes and laboratory tests on undisturbed and remolded samples. More specifically, classification tests, cyclic undrained stress‐controlled triaxial tests and resonant column tests have been performed. Liquefaction susceptibility has been evaluated by means of several procedures prescribed by codes or available in technical literature. The evaluation of liquefaction potential has been carried out by means of three different procedure based on in situ and laboratory tests. |
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Realistic Ground Motion Scenarios: Methodological Approach AIP Conf. Proc. 1020, pp. 378-385; doi:http://dx.doi.org/10.1063/1.2963860 (8 pages) Online Publication Date: 8 July 2008
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The definition of realistic seismic input can be obtained from the computation of a wide set of time histories, corresponding to possible seismotectonic scenarios. The propagation of the waves in the bedrock from the source to the local laterally varying structure is computed with the modal summation technique, while in the laterally heterogeneous structure the finite difference method is used. The definition of shear wave velocities within the soil cover is obtained from the non‐linear inversion of the dispersion curve of group velocities of Rayleigh waves, artificially or naturally generated. Information about the possible focal mechanisms of the sources can be obtained from historical seismicity, based on earthquake catalogues and inversion of isoseismal maps. In addition, morphostructural zonation and pattern recognition of seismogenic nodes is useful to identify areas prone to strong earthquakes, based on the combined analysis of topographic, tectonic, geological maps and satellite photos. We show that the quantitative knowledge of regional geological structures and the computation of realistic ground motion can be a powerful tool for a preventive definition of the seismic hazard in Italy. Then, the formulation of reliable building codes, based on the evaluation of the main potential earthquakes, will have a great impact on the effective reduction of the seismic vulnerability of Italian urban areas, validating or improving the national building code. |
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Analysis Of The Interface Behavior Under Cyclic Loading AIP Conf. Proc. 1020, pp. 658-665; doi:http://dx.doi.org/10.1063/1.2963898 (8 pages) Online Publication Date: 8 July 2008
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This paper analyses the frictional behavior between soil and structures under cyclic loading conditions. In particular, the attention is focused on the stress degradation occurring in sand‐metal interface tests and on the relevant parameters playing a role in such kind of tests. Also, the paper reports the analysis of the experimental data from the constitutive point of view with a two‐surface elastoplastic model. |
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Evaluation of Pseudo‐Static Coefficients According to Performance‐Based Criteria AIP Conf. Proc. 1020, pp. 501-508; doi:http://dx.doi.org/10.1063/1.2963876 (8 pages) Online Publication Date: 8 July 2008
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A rational procedure is presented for the selection of the equivalent seismic coefficient to be introduced in the pseudo‐static analysis of geotechnical systems which, at failure, behave as a 1‐degree of freedom system. It is shown that although pseudo‐static and displacement analyses may be regarded as alternative methods of analysis, the seismic coefficient may be related to earthquake‐induced permanent displacements and, then, to the expected level of damage. Following the proposed procedure a pseudo‐static analysis in accordance with performance based design can be carried out. |
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Design Of Bridges For Non Synchronous Seismic Motion AIP Conf. Proc. 1020, pp. 666-672; doi:http://dx.doi.org/10.1063/1.2963899 (7 pages) Online Publication Date: 8 July 2008
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this paper aims to develop and validate structural design criteria which account for the effects of earthquakes spatial variability. In past works [1, 2] the two simplest forms of this problem were dealt with: differential displacements between two points belonging to the soil or to two single degree of freedom structures. Seismic action was defined according to EC8 [3]; the structures were assumed linear elastic sdof oscillators. Despite this problem may seem trivial, existing codes models appeared improvable on this aspect. For the differential displacements of two points on the ground, these results are now validated and generalized using the newly developed response spectra contained in the new seismic Italian code [4]; the resulting code formulation is presented. Next, the problem of statistically defining the differential displacement among any number of points on the ground (which is needed for continuos deck bridges) is approached, and some preliminary results shown. It is also shown that the current codes (e.g. EC8) rules may be improved on this aspect |
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Assessment of the Structural Conditions of the San Clemente a Vomano Abbey AIP Conf. Proc. 1020, pp. 76-83; doi:http://dx.doi.org/10.1063/1.2963912 (8 pages) Online Publication Date: 8 July 2008
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The simultaneous use of a Finite Element (FE) accurate modeling, dynamical tests, model updating and nonlinear analysis are used to describe the integrated approach used by the authors to assess the structural conditions and the seismic vulnerability of an historical masonry structure: the Abbey Church of San Clemente al Vomano, situated in the Notaresco territory (TE, Italy) commissioned by Ermengarda, daughter of the Emperor Ludovico II, and built at the end of IX century together with a monastery to host a monastic community. Dynamical tests “in operational conditions” and modal identification have been used to perform the FE model validation. Both a simple and direct method as the kinematic analysis applied on meaningful sub‐structures and a nonlinear 3D dynamic analysis conducted by using the FE model have been used to forecast the seismic performance of the Church. |
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AIP Conf. Proc. 1020, pp. 642-649; doi:http://dx.doi.org/10.1063/1.2963896 (8 pages) Online Publication Date: 8 July 2008
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Near‐fault ground motions have notable characteristics such as velocity time histories containing large‐amplitude and long‐period pulses caused by forward directivity effects and acceleration time histories with high frequency content. These specifications of near‐fault earthquake records make structural responses to be different from those expected in far‐fault earthquakes. In this paper, using moving average filtering, a set of near‐fault earthquake records containing forward directivity pulses are decomposed into two parts having different frequency content: a Pulse‐Type Record (PTR) that possesses long period pulses, and a relatively high‐frequency Background Record (BGR). Studying the structural response to near‐fault records reveals that elastic response spectra for fixed‐base systems, in contrast to their response to ordinary earthquakes, show two distinct local peaks related to BGR and PTR parts. Also, the effect of Soil‐Structure Interaction (SSI) on response of structures subjected to this type of excitations is investigated. Generally, the SSI effect on the response of structures is studied through introducing a replacement single‐degree‐of‐freedom system with longer period and usually higher damping. Since this period elongation for the PTR‐dominated period range is greater than that of the BGR‐dominated one, the spectral peaks become closer in the case of soil‐structure systems in comparison to the corresponding fixed‐base systems. |
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Evaluation of liquefaction potential for building code AIP Conf. Proc. 1020, pp. 370-377; doi:http://dx.doi.org/10.1063/1.2963859 (8 pages) Online Publication Date: 8 July 2008
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The standard approach for the evaluation of the liquefaction susceptibility is based on the estimation of a safety factor between the cyclic shear resistance to liquefaction and the earthquake induced shear stress. Recently, an updated procedure based on shear‐wave velocities (Vs) has been proposed which could be more easily applied. These methods have been applied at La Plaja beach of Catania, that experienced liquefaction because of the 1693 earthquake. The detailed geotechnical and Vs information and the realistic ground motion computed for the 1693 event let us compare the two approaches. The successful application of the Vs procedure, slightly modified to fit historical and safety factor information, even if additional field performances are needed, encourages the development of a guide for liquefaction potential analysis, based on well defined Vs profiles to be included in the italian seismic code. |
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Site Response Analysis of the Monte Po Hill in the City of Catania AIP Conf. Proc. 1020, pp. 240-251; doi:http://dx.doi.org/10.1063/1.2963841 (12 pages) Online Publication Date: 8 July 2008
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The Monte Po Hill is located in the North‐eastern part of the city of Catania; this area is prone to high seismic risk due to the presence of several constructions, including a school, in the vicinity of a toe of a slope, characterized by precarious stability conditions. For site characterization of the soil, deep site investigations have been undertaken. Borings and dynamic in situ tests have been performed. Among them Down‐Hole (D‐H) and Seismic Dilatometer Marchetti Tests (SDMT) have been carried out, with the aim to evaluate the soil profile of shear waves velocity (Vs). The Seismic Dilatometer Marchetti Tests were performed up to a depth of 15 meters. The results show a very detailed and stable shear waves profile. The shear waves profiles obtained by SDMT compare well with other in situ tests. Synthetic seismograms have been drawn for the site long a set of receivers placed at different depths, starting from the surface up to almost 40 m. After evaluating the synthetic accelerograms at the bedrock, the ground response analysis at the surface, in terms of time history and response spectra, has been obtained by a 1‐D non‐linear model. In particular the study has regarded the evaluation of site effects in correspondence of the site, to which corresponds a different value of the Seismic Geotechnical Hazard. In the beginning of 2007 a seismic station has been also located into the school building, with the aim of recording seismic events. Seismograms obtained by the seismic station have been also used to evaluate the ground response analysis at the surface. In the beginning of 2007 a seismic station has been also located into the school building, with the aim of recording seismic events. Seismograms obtained by the seismic station have been also used to evaluate the ground response analysis at the surface. Finally the 1‐D computer code EERA was also used to model the equivalent‐linear earthquake site response analyses of layered soil deposits of the hill. The detail with which the hill has been studied has allowed the construction of a detailed 2‐D model of its structure. It has been explored the differences between the computed ground motion for different Vs profiles using QUAD4M 2‐D code. It has been also possible to compare the results from different 1‐D models reflecting current approaches to the determination of site response. |
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