1,358,826 research outputs found
Simulation of fractionally damped mechanical systems by means of a Newmark-diffusive scheme
No full textA Newmark-diffusive scheme is presented for the time-domain solution of dynamic systems containing fractional derivatives. This scheme combines a classical Newmark time-integration method used to solve second-order mechanical systems (obtained for example after finite element discretization), with a diffusive representation based on the transformation of the fractional operator into a diagonal system of linear differential equations, which can be seen as internal memory variables. The focus is given on the algorithm implementation into a finite element framework, the strategies for choosing diffusive parameters, and applications to beam structures with a fractional Zener model
Conversation with Craig Newmark
No full textCraig Newmark is the founder of craigslist, the web-based platform that has fundamentally changed classified advertising. Since its founding in 1995, craigslist has become one of the Internet’s 10 most-visited English language sites.
Born December 6, 1952 in Morristown, NJ, Craig attended Case Western Reserve University, where he earned a B.S. and M.S. in Computer Science in 1975 and 1977 respectively. During his business career, Craig worked with IBM, Charles Schwab, Bank of America, and other firms. Today, he resides in San Francisco\u27s Cole Valley.
In early 2011 Craig launched craigconnects, his initiative to link up everyone on the planet using the Internet to bear witness to good efforts and encourage the same behavior in others.
Part of the IT, Ethics & Law Colloquium Series cosponsored by the High Tech Law Institute; the Center for Science, Technology, & Society; and the Markkula Center for Applied Ethics
Development and Implementation of a Multi-axial Real-time Hybrid Simulation Framework
No full textReal-time hybrid simulation is an efficient and cost-effective experimental testing technique for performance evaluation of structural systems subjected to earthquake loading with rate-of loading behavior. To assess the response of structural components with multi-axial loading, a loading assembly with multiple parallel actuators connected to a rigid moving platform is required to impose realistic boundary conditions on physical components. This loading assembly is expected to exhibit significant dynamic actuator coupling and suffer from systematic errors and potential instabilities. One approach to reduce experimental errors considers a multi-input, multi-output (MIMO) modeling approach to design controllers that could compensate for these undesired effects.
In this study, a framework for three-dimensional, multi-axial real-time hybrid simulation is presented. The methodology consists in designing a real-time system platform to perform dynamic test experiments by controlling the interface boundary conditions on the physical specimen in Cartesian (global) coordinates. First, a kinematic transformation is derived to impose the six-degree-of freedom motion to the loading platform in three-dimensional Cartesian space. Then, a linearized model of the multi-actuator loading assembly is obtained through nonparametric frequency domain system identification techniques. Subsequently, a feedforward-feedback compensator is developed for reference tracking of the multivariate transient signals, which should be sufficiently robust to rule out any disturbances and measurement noises in the experimental closed-loop system. Finally, the numerical substructure, compensators, and kinematic transformations are implemented over an embedded system with a micro-controller unit and digital signal processing capabilities for real-time applications.
The proposed framework is validated using a small-scale version of the Load and Boundary Condition Box (LBCB) from Newmark Civil Engineering Laboratory at University of Illinois, Urbana-Champaign. A one-story, two-bay, moment frame was considered as the reference structure, where the experimental substructure was chosen as a steel column with fixed ends. The hybrid system was subjected to earthquake ground motions chosen according to its importance and destructive characteristics. Comparisons of different compensation strategies are made, and excellent performance is achieved for all situations that incorporates the multivariate controller.Open Restriction set for Item 107537 on 2018-09-20T21:02:00Z with date null by [email protected] by Fernanda Schaefer ([email protected]) on 2018-09-20T21:20:31Z
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Previous issue date: 2018-09Becas Chile Scholarship No. 72140204Fulbright Foreign Student Fellowship IIE Grant No. 15130588Universidad Técnica Federico Santa María Faculty Development Fellowship Grant No. 208-13Nathan M. and Anne M. Newmark Endowed Chair in Civil EngineeringOpe
Development and Implementation of a Multi-axial Real-time Hybrid Simulation Framework
No full textReal-time hybrid simulation is an efficient and cost-effective experimental testing technique for performance evaluation of structural systems subjected to earthquake loading with rate-of loading behavior. To assess the response of structural components with multi-axial loading, a loading assembly with multiple parallel actuators connected to a rigid moving platform is required to impose realistic boundary conditions on physical components. This loading assembly is expected to exhibit significant dynamic actuator coupling and suffer from systematic errors and potential instabilities. One approach to reduce experimental errors considers a multi-input, multi-output (MIMO) modeling approach to design controllers that could compensate for these undesired effects.
In this study, a framework for three-dimensional, multi-axial real-time hybrid simulation is presented. The methodology consists in designing a real-time system platform to perform dynamic test experiments by controlling the interface boundary conditions on the physical specimen in Cartesian (global) coordinates. First, a kinematic transformation is derived to impose the six-degree-of freedom motion to the loading platform in three-dimensional Cartesian space. Then, a linearized model of the multi-actuator loading assembly is obtained through nonparametric frequency domain system identification techniques. Subsequently, a feedforward-feedback compensator is developed for reference tracking of the multivariate transient signals, which should be sufficiently robust to rule out any disturbances and measurement noises in the experimental closed-loop system. Finally, the numerical substructure, compensators, and kinematic transformations are implemented over an embedded system with a micro-controller unit and digital signal processing capabilities for real-time applications.
The proposed framework is validated using a small-scale version of the Load and Boundary Condition Box (LBCB) from Newmark Civil Engineering Laboratory at University of Illinois, Urbana-Champaign. A one-story, two-bay, moment frame was considered as the reference structure, where the experimental substructure was chosen as a steel column with fixed ends. The hybrid system was subjected to earthquake ground motions chosen according to its importance and destructive characteristics. Comparisons of different compensation strategies are made, and excellent performance is achieved for all situations that incorporates the multivariate controller.Becas Chile Scholarship No. 72140204Fulbright Foreign Student Fellowship IIE Grant No. 15130588Universidad Técnica Federico Santa María Faculty Development Fellowship Grant No. 208-13Nathan M. and Anne M. Newmark Endowed Chair in Civil EngineeringOpe
A nonholonomic Newmark method
No full textUsing the nonholonomic exponential map, we obtain a new version of Newmark-type methods for nonholonomic systems (see also Jay and Negrut(2009) for a different extension). We give numerical examples including a test problem where the structure of reversible integrability responsible for good energy behaviour as described in Modin and Verdier (2020) is lost. We observe that the composition of two Newmark methods is able to produce good energy behaviour on this test problem.Fil: Anahory Simoes, Alexandre. IE Universidad; EspañaFil: Ferraro, Sebastián José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Matemática Bahía Blanca. Universidad Nacional del Sur. Departamento de Matemática. Instituto de Matemática Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Matemática; ArgentinaFil: Marrero González, Juan Carlos. Universidad de La Laguna; EspañaFil: Martín de Diego, David. Universidad Nebrija; España. Instituto de Ciencias Matemáticas; Españ
Is Newmark Method Conservative?
No full textNewmark method is a commonly accepted practice in geotechnical earthquake engineering to estimate seismically induced displacement of earth structures. The method currently requires performing a series of analyses using multiple computer programs to 1) identify a potential sliding mass, 2) compute a factor of safety, 3) calculate a yield acceleration, and 4) perform a double integration of that portion of a given horizontal acceleration history that exceeds the yield acceleration. The Newmark method provides satisfactory results for a horizontal sliding surface. However, for an inclined sliding surface the result is unconservative and for a nonplanar one is not clear. To avoid the problems and to facilitate the Newmark method a numerical technique was developed and a computer program was written to carry out the analysis. A single analysis determines a two-dimensional pattern of seismically induced displacement due to given earthquake motions. Results of analyses for three examples are given to demonstrate the comparison between the new method and the Newmark method
Contesting Peter Newmark
No full textWhen l first read Newmark, l was impressed,
educated and, at the same time, somewhat uneasy. l
have since read and reread everything bearing his signature to come my way and last, if he is to be believed
most comprehensive and systematised articulation
of his thoughts on the matter. In the following pages l
shall endeavour to show that, his claims to the contrary
notwithstanding, Newmark does indeed have a single,
coherent theory of translation, that it is a wrong and
didactically dangerous one, and that, despite ali that, he
makes a substantive and most opportune and welcome
contribution to the development of our discipline. l
believe that both Newmark the thinker and translator are
batter than his theory
Wireless Sensor Advances and Applications for Civil Infrastructure Monitoring
No full textStructural Health Monitoring (SHM) using wireless sensor technology (WST) has emerged as a promising solution to challenges associated with the declining state of aging civil infrastructure. Successful implementation of long-term, continuous, and automated SHM using WST is expected to improve public safety, increase structural reliability, enhance inspection quality, and reduce maintenance costs. Moreover, such SHM systems can aid in lifetime monitoring of future construction projects and help to assess emergency facilities and evacuation routes, including bridges and highways, in a timely manner after natural and man-made disasters.
Today, research advances in WST are coming at an unparalleled pace, many leading to a number of full-scale implementations. The June 2010 issue of the Journal of Smart Structures and Systems brings together the most recent Wireless Sensor Advances and Applications for Civil Infrastructure Monitoring. To promote wider distribution of this timely collection of papers, the publishers have generously allowed publication of this special issue in the Newmark Structural Engineering Report Series.is peer reviewedSubmitted by Sung Han Sim ([email protected]) on 2010-06-15T14:33:44Z
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Portrait of Harris Newmark, [s.d.]
No full textPhotographic portrait of Harris Newmark, [s.d.]. Mr. Newmark is shown from his torso to his head and is looking at the camera with his body turned slightly to the right . He is wearing a dark jacket, striped tie, and a white shirt. He is mostly bald, and his remaining hairs, as well as his beard and mustache, are gray. He has a pair of small, round glasses on his face
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