Nonlinear dynamics

A Model for Collective Free Improvisation

by Clement Canonne

Co-authored with Nicolas B. Garnier
Published in the Proceedings of Mathematics,Computation and Music Conference (2011).

Vibration and symmetry-breaking of boron-nitride nanotubes

by Rajib Chowdhury

Nanotechnology, 2010

The unique features of axial, torsional, transverse and radial breathing vibrations are captured for armchair and... more The unique features of axial, torsional, transverse and radial breathing vibrations are captured for armchair and zigzag singlewalled boron nitride nanotubes (BNNTs) based on molecular mechanics simulations and continuum mechanics theories. Equivalent Young's modulus 1TPa and shear modulus 0.4TPa are obtained independent of the chirality of BNNTs. In particular, a distorted optimized structure is observed for the first time for BNNTs with sufficiently large diameter and length. It is found that the deformed structures result in the behaviours of BNNTs deviating from those of classical columns/beams. Such symmetry breaking could also exert significant impacts on the structural instability (buckling) and the electronic properties of BNNTs that are sensitive to the structural symmetry.

Galactic Nonlinear Dynamic Model

by Cassius de Melo

Inversion of Pattern Anisotropy During CO Oxidation on Pt(110) Correlated with Appearance of Subsurface Oxygen

by Christian Punckt

P. Sadeghi, K. Dunphy, C. Punckt. H. H. Rotermund
J. Phys. Chem. C 116 (2012) 4686

Spatiotemporal patterns occurring during the catalytic oxidation of carbon monoxide on Pt(110) show a strong... more Spatiotemporal patterns occurring during the catalytic oxidation of carbon monoxide on Pt(110) show a strong anisotropy due to differences in the diffusion coefficients along the two major crystallographic axes of the catalyst: Reaction waves propagating parallel to the missing rows of the reconstructed Pt surface are much faster than reaction waves propagating in the perpendicular direction. In this Article, we report on the observation that, as a function of the exposure to reactant gases, the propagation velocities on the Pt surface change drastically, resulting in a complete reversal of the anisotropy. This observation is correlated with the appearance of subsurface oxygen in photoemission electron microscopic images of the reaction patterns.

Element loss analysis of concentrically braced frames considering structural performance criteria

by Farshad Hashemi Rezvani

Published in Steel and Composite Structures, Vol. 12, No. 3 (2012) 231-248.

This research aims to investigate the structural behavior of concentrically braced frames after element loss by... more This research aims to investigate the structural behavior of concentrically braced frames after element loss by performing nonlinear static and dynamic analyses such as Time History Analysis (THA), Pushdown Analysis (PDA), Vertical Incremental Dynamic Analyses (VIDA) and Performance-Based Analysis (PBA). Such analyses are to assess the potential and capacity of this structural system for occurrence of progressive collapse. Besides, by determining the Failure Overload Factors (FOFs) and associated failure modes, it is possible to relate the results of various types of analysis in order to save the analysis time and effort. Analysis results showed that while VIDA and PBA according to FEMA 356 are mostly similar in detecting failure mode and FOFs, the Pushdown Overload Factors (PDOFs) differ from others at most to the rate of 23%. Furthermore, by sensitivity analysis it was observed that among the investigated structures, the eight-story frame had the most FOF. Finally, in this research the trend of FOF and the FOF to critical member capacity ratio for the plane split-X braced frames were introduced as a function of the number of frame stories.

Review on methods and results of linear and nonlinear static and dynamic analyses of progressive collapse in steel structures. (In Persian)

by Farshad Hashemi Rezvani

In: Proceedings of the First National conference on Structure, Earthquake and Geotechnics. Babolsar, Iran 2010.

گسیختگی پیشرونده زمانی اتفاق می افتد که خرابی یک عضو سازه اي منجر به خرابی و گسیختگی اعضاي سازه اي مجاور و یا حتی... more گسیختگی پیشرونده زمانی اتفاق می افتد که خرابی یک عضو سازه اي منجر به خرابی و گسیختگی اعضاي سازه اي مجاور و یا حتی گسیختگی کلی سازه گردد. یعنی سیستم در رسیدن به شرایط تعادل استاتیکی جدید ناتوان باشد. خطرات احتمالی و بارهاي غیر عادي که می تواند موجب گسیختگی پیشرونده شود، شامل برخورد هواپیما، خطاي طراحی یا ساخت، آتش سوزي، انفجار گازها، اضافه بار تصادفی، تصادف وسایل نقلیه، انفجار بمب ها و غیره می باشند. گرچه عدم تناسب بین علت و معلول ویژگی مشترکی است، اما مکانیسم هاي گوناگونی وجود دارد که چنین نتیجه اي را به بار می آورند.  بنابراین تشخیص و شرح انواع مختلف گسیختگی پیشرونده و تلاش براي طبقه بندي بر اساس آن مفید به نظر می رسد. در مقاله حاضر پس از تعریف انواع گسیختگی پیش رونده بر حسب مولفه هاي اساسی هریک طبقه بندي از این گسیختگی ها ارائه گردیده است. سپس روشهاي مختلف تحلیل گسیختگی پیش رونده شامل تحلیل هاي خطی و غیرخطی دینامیکی و استاتیکی به همراه نتایج هرکدام در مورد سازه هاي فولادي باقابهاي خمشی معمولی و ویژه و قابهاي مهاربندي شده ارائه شده است.

Logical operations with localized structures

by Adrian Jacobo

Damage Detection in Nonlinear Systems Using Optimal Feedback Auxiliary Signals and System Augmentations

by Kiran D'Souza

Nonlinear feedback auxiliary signals for system interrogation and damage detection

by Kiran D'Souza

Detection of global and local parameter variations using nonlinear feedback auxiliary signals and system augmentation

by Kiran D'Souza

Multiple augmentations of nonlinear systems and generalized minimum rank perturbations for damage detection

by Kiran D'Souza

Damage detection in nonlinear systems using system augmentation and generalized minimum rank perturbation theory

by Kiran D'Souza

System augmentation and optimal feedback auxiliary signals for interrogating nonlinear systems

by Kiran D'Souza

Damage assessment and retrofit study for the Luxor Memnon Colossi

by Sara Casciati

Casciati S. and Osman A. M. (2005). “Damage assessment and retrofit study for the Luxor Memnon Colossi”. Structural Control & Health Monitoring, 12(2), 139-156. ISSN: 1545-2255.

DATE AND PLACE OF PUBBLICATION: April-June 2005; John Wiley & Sons, Ltd., Chichester PO19 8SQ, W Sussex, England.

ABSTRACT. The structural behaviour of large, monolithic, ancient monuments consisting of heavy stone blocks connected... more ABSTRACT. The structural behaviour of large, monolithic, ancient monuments consisting of heavy stone blocks connected one to the other by the gravity load alone, without the use of mortar, is investigated. The Memnon Colossi, which were built fourteen centuries before Christ at Luxor in Egypt, are the case study for this construction technique. This paper summarizes the results of studies carried out on this structure within the CHIME (Conservation of Historical Monuments in the Mediterranean Area) project, funded by the European Commission.
The modal frequencies of the two statues were identified experimentally from ambient vibration measurements. Analytical models using the finite element method were also elaborated to compare the numerical results with the experimental ones, and to perform dynamic analyses. The results indicated that the distributed cracks characterizing the current state of the structure, play a significant role in the static and dynamic response of the monument. In view of the monuments’ rehabilitation, an innovative technology, based on fastening the cracked blocks by pre-tensioned wires of shape memory alloy, is proposed and numerically simulated.

KEY WORDS: monument; modal identification; damage assessment; retrofit; shape memory alloy

Dynamic FE analysis of South Memnon Colossus including 3D soil-foundation-structure interaction

by Sara Casciati

Casciati S. and Borja R.I. (2004). “Dynamic FE analysis of South Memnon Colossus including 3D soil-foundation-structure interaction”. Computers & Structures, 82(20-21), 1719-1736. ISSN: 0045-7949.

DATE AND PLACE OF PUBLICATION: August 2004; Pergamon–Elsevier Science Ltd, Kidlington, Oxford OX5 1GB, Oxon, England.

ABSTRACT. A full three-dimensional dynamic soil–foundation structure interaction (SFSI) analysis of a famous landmark... more ABSTRACT. A full three-dimensional dynamic soil–foundation structure interaction (SFSI) analysis of a famous landmark in Luxor, Egypt, the South Memnon Colossus, is performed to investigate the response of this historical monument to seismic excitation. The analysis is carried out using the finite element (FE) method in time domain. The statue comprising the upper structure is modeled using 3D brick finite elements constructed from a photogrammetric representation that captures important details of the surface and allows the identification of probable zones of stress concentration. The modeling also takes into account the presence of a surface of discontinuity between the upper part of the statue and its fractured base. FE models of the foundation and the surrounding soil deposit are constructed and coupled with the statue model to analyze the seismic response of the entire system incorporating dynamic SFSI effects. These studies are useful for future conservation efforts of this historical landmark, and more specifically for designing possible retrofit measures for the fractured base to prevent potential collapse of the monument from overturning during an earthquake.

KEYWORDS: Soil–foundation–structure interaction; Multi-body deformable contact; Non-linear dynamic finite element analysis

Structural health monitoring by Lyapunov exponents of non‐linear time series

by Sara Casciati

Casciati F. and Casciati S. (2006). “Structural health monitoring by Lyapunov exponents of nonlinear time series”. Structural Control & Health Monitoring, 13(1), 132-146. ISSN: 1545-2255.

DATE AND PLACE OF PUBLICATION: January-February 2006; John Wiley & Sons, Ltd., Chichester PO19 8SQ, W Sussex, England.

ABSTRACT. In this study, structural health monitoring is pursued by collecting multi-channel measurements and by... more ABSTRACT. In this study, structural health monitoring is pursued by collecting multi-channel measurements and by computing, directly from them, the Lyapunov exponents. The latter quantities are invariants of the dynamic system, so that their different values, associated with different time histories obtained from the same structure, denote damage. First, the problem is framed in the general theory. The structural health monitoring strategy is then formulated, with special care being devoted to its capability of localizing damage. The procedure is finally validated by using the time histories which were collected during the experimental tests on the model of a monumental arch.

KEY WORDS: dynamic system; Kolmogorov entropy; Lyapunov dimension; Lyapunov exponents; observed variables space; structural health monitoring

An Online-Computation Approach to Optimal Finite-Horizon State-Feedback Control of Nonlinear Stochastic Systems

by Marc Deisenroth

Online-Computation Approach to Optimal Control of Noise-Affected Nonlinear Systems with Continuous State and Control Spaces

by Marc Deisenroth

Lawhead - Concepts in Complexity

by Jon Lawhead

Nonlinear aspects of energy dissipation in wood-panel joints

by Sara Casciati

Casciati S. (2007). “Nonlinear aspects of energy dissipation in wood-panel joints”. Earthquake Engineering and Engineering Vibration, 6(3), 259-268. ISSN: 1671-3664.

DATA E LUOGO DI PUBBLICAZIONE: September 2007; Springer, New York, NY 10013, USA.

ABSTRACT: The joints connecting vertical and horizontal elements are the “weak link” in structural systems assembled... more ABSTRACT: The joints connecting vertical and horizontal elements are the “weak link” in structural systems assembled from wood panels. If they are too weak, local failures may occur, resulting in performance that is significantly below expectations. If they are too resistant, the joints may be unable to dissipate energy during vibrations, thus possibly initiating a fast progressive failure. This paper re-processes and re-elaborates the results of shaking table tests previously carried out by the author and other co-workers. The goal is to assess the feasibility of a joint which is able to dissipate energy during vibration, without degrading the connection performance.

KEYWORDS: dynamic excitation - energy dissipation - wood panels joint - monitoring system - shaking table tests