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Articles 61 - 79 of 79
Full-Text Articles in Engineering
Control Of Large-Scale Structures With Large Uncertainties, Simon Laflamme
Control Of Large-Scale Structures With Large Uncertainties, Simon Laflamme
Simon Laflamme
Performance-based design is a design approach that satisfies motion constraints as its primary goal, and then verifies for strength. The approach is traditionally executed by appropriately sizing stiffnesses, but recently, passive energy dissipation systems have gained popularity. Semi-active and active energy dissipation systems have been shown to outperform purely passive systems, but they are not yet widely accepted in the construction and structural engineering fields. Several factors are impeding the application of semi-active and active damping systems, such as large modeling uncertainties that are inherent to large-scale structures, limited state measurements, lack of mechanically reliable control devices, large power requirements, …
Wavelet Network For Semi-Active Control, Simon Laflamme, J.J.E. Slotine, J.J. Connor
Wavelet Network For Semi-Active Control, Simon Laflamme, J.J.E. Slotine, J.J. Connor
Simon Laflamme
This paper proposes a wavelet neurocontroller capable of self-adaptation and self-organization for uncertain systems controlled with semi-active devices, ideal candidates for control of large-scale civil structures. A condition on the sliding surface for cantilever-like structures is defined. The issue of applicability of the control solution to largescale civil structures is made the central theme throughout the text, as this topic has not been extensively discussed in the literature. Stability and convergence of the proposed neurocontroller is assessed through various numerical simulations for harmonic, earthquake, and wind excitations. The simulations consist of semi-active dampers installed as a replacement to the current …
Strongly Enhanced Sensitivity In Elastic Capacitive Strain Sensors, Matthias Kollosche, Hristiyan Stoyanov, Simon Laflamme, Guggi Kofod
Strongly Enhanced Sensitivity In Elastic Capacitive Strain Sensors, Matthias Kollosche, Hristiyan Stoyanov, Simon Laflamme, Guggi Kofod
Simon Laflamme
Strain sensors based on dielectric elastomer capacitors function by the direct coupling of mechanical deformations with the capacitance. The coupling can be improved by enhancing the relative permittivity of the dielectric elastomer. Here, this is carried out through the grafting of conducting polymer (poly-aniline) to the elastomer backbone, leading to molecular composites. An enhancement in capacitance response of 46 times is observed. This could help to extend the possible range of miniaturization towards even smaller device features.
Motivating Technical Writing Through Study Of The Environment, J. Linsdell, Thalia Anagnos
Motivating Technical Writing Through Study Of The Environment, J. Linsdell, Thalia Anagnos
Thalia Anagnos
Today’s engineers must be more than just technically competent. To be successful in our increasingly global economy in which teamwork and interdisciplinary interaction are the norm, engineers must have excellent communication skills. In recognition of industry needs, the San José State University College of Engineering redesigned its technical communication course to ensure that students graduate with writing and speaking skills that will transfer readily to their career needs and the global arena. The course aims to motivate students through exploring topics that are meaningful to them and using communication formats that they will see in the workplace. Combing technical communication …
The Homotopy Perturbation Method For Free Vibration Analysis Of Beam On Elastic Foundation, Baki Ozturk, Safa Bozkurt Coskun
The Homotopy Perturbation Method For Free Vibration Analysis Of Beam On Elastic Foundation, Baki Ozturk, Safa Bozkurt Coskun
Safa Bozkurt Coskun
In this study, the homotopy perturbation method (HPM) is applied to free vibration analysis of beam on elastic foundation. This numerical method is applied on three different axially loaded cases, namely: 1) one end fixed, the other end simply supported; 2) both ends fixed and 3) both ends simply supported cases. Analytical solutions and frequency factors are evaluated for different ratios of axial load N acting on the beam to Euler buckling load, Nr. The application of HPM for the particular problem in this study gives results which are in excellent agreement with both analytical solutions and the variational iteration …
Nonlinear Finite Element Analysis Of Prestressed Concrete, Akram Shaker Mahmood, Mohamed N. Mahmood
Nonlinear Finite Element Analysis Of Prestressed Concrete, Akram Shaker Mahmood, Mohamed N. Mahmood
Akram Shaker Mahmood
In the present study a nonlinear finite element analysis is carried out on twenty prestressed concrete cantilever beams having different lengths vary from 1.0m to 3.0m with 0.5m increments and subjected to a concentrated torque at the free end using ANSYS V10 finite element package. This study emphasizes on the effect of beam length to depth ratio on the strength, behavior of prestressed concrete beams and effectiveness of prestressing strands in the pre and post cracking stages of loading. This work is part of a PhD research program at the University of Mosul to investigate the non-linear three dimensional behavior …
01june2010_Building Collapse_Begunbari, Md. Nurul Alam
01june2010_Building Collapse_Begunbari, Md. Nurul Alam
Md. Nurul Alam
No abstract provided.
Nonlinear Finite Elements Modeling Of Hybrid Reinforced Concrete Beams, Akram Shaker Mahmood
Nonlinear Finite Elements Modeling Of Hybrid Reinforced Concrete Beams, Akram Shaker Mahmood
Akram Shaker Mahmood
This paper presents results from a nonlinear finite element analysis of a hybrid reinforced concrete rectangular section beams. The concept of hybrid R.C. concrete structures was applied in many designers for using in constructions of bridge superstructure. Although using the steel reinforcements are often modeled as a linear-elastic material until failure, the linear finite element analysis could not predict the behavior of the R.C. concrete beams model up to its failure. The materials, loadings, section properties with boundary conditions are taken from reference [Ref.3]. Results from material tests and loading tests of beams model indicated that the nonlinearity of concrete …
Damage Detection In Wind Turbine Blades Using Time-Frequency Analysis Of Vibration Signals, Breiffni Fitzgerald
Damage Detection In Wind Turbine Blades Using Time-Frequency Analysis Of Vibration Signals, Breiffni Fitzgerald
Breiffni Fitzgerald
The dynamic behaviour of modern multi-Megawatt wind turbines has become an important design consideration. One of the major aspects related to the reliability of operation of the turbines concerns the safe and adequate performance of the blades. The aim of this paper is to develop a time-frequency based algorithm to detect damage in wind turbine blades from blade vibration signals. It is important that damage to blades is detected before they fail or cause the turbine to fail. A wind turbine model was developed for this paper. The parameters considered were the rotational speed of the blades and the stiffness …
Large-Scale Capacitance Sensor For Health Monitoring Of Civil Structures, Simon Laflamme, Matthias Kollosche, Jerome J. Connor, Guggi Kofod
Large-Scale Capacitance Sensor For Health Monitoring Of Civil Structures, Simon Laflamme, Matthias Kollosche, Jerome J. Connor, Guggi Kofod
Simon Laflamme
In this paper, a new type of sensing technique for damage localization on large civil structures is proposed. Specifically, changes in strain are detected using a capacitance sensor built with a soft-stretchable dielectric polymer with attached stretchable metal film electrodes. This sensor is sensitive to a change in strain that causes a change in its capacitance. Fixed to a structure, small changes in the strain can be monitored directly by measuring the change in the capacitance of the unit. This technology allows for simple yet highly accurate measurements of cracks occurring due to deformation, aging, or other structural failures. The …
Intelligent Controller For Smart Base Isolation Of Masonry Structures, Simon Laflamme, T.Y. Yu, Jerome J. Connor
Intelligent Controller For Smart Base Isolation Of Masonry Structures, Simon Laflamme, T.Y. Yu, Jerome J. Connor
Simon Laflamme
In this paper, an intelligent controller to control a smart base-isolated masonry structure is proposed. The smart base isolation consists of rubber bearings and a magnetorheological damper. This semi-active scheme takes advantage of the low power requirement of magnetorheological devices to achieve structural control. The controller is capable of mapping the behaviour of the controlled structure sequentially, using a self-organizing neural network which has time-varying learning rates. This neurocontroller is augmented by a sliding mode controller to account for the uncertainty on the semi-active damping forces. Wavelets are used as functions in the single hidden layer for their capability of …
Application Of Self-Tuning Gaussian Networks For Control Of Civil Structures Equipped With Magnetorheological Dampers, Simon Laflamme, Jerome J. Connor
Application Of Self-Tuning Gaussian Networks For Control Of Civil Structures Equipped With Magnetorheological Dampers, Simon Laflamme, Jerome J. Connor
Simon Laflamme
This paper proposes an adaptive neural network composed of Gaussian radial functions for mapping the behavior of civil structures controlled with magnetorheological dampers. The online adaptation takes into account the limited force output of the semi-active dampers using a sliding mode controller, as their reaction forces are state dependent. The structural response and the actual forces from the dampers are used to adapt the Gaussian network by tuning the radial function widths, centers, and weights. In order to accelerate convergence of the Gaussian radial function network during extraordinary external excitations, the learning rates are also adaptive. The proposed controller is …
Reliability Assessment Of Railway Prestressed Concrete Sleepers, Sakdirat Kaewunruen, Alexander Remennikov
Reliability Assessment Of Railway Prestressed Concrete Sleepers, Sakdirat Kaewunruen, Alexander Remennikov
Alex Remennikov
This paper carries out the assessment of reliability indices of railway prestressed concrete sleepers designed in accordance with Australian Standard: AS1085.19. The current design approach of the prestressed concrete sleeper relies on the permissible stresses over crosssectional area. Loading condition acting on railway sleepers is considered from axle burden and dynamic amplification factor. On the basis of Australian design of railway prestressed concrete sleepers, only service limit states are considered; however, the design challenge is to provide adequate resistance of certain cross sections to both positive and negative bending moments. In this paper, the service limit states functions are formulated …
Impact Damage Classification Of Railway Prestressed Concrete Sleepers, Sakdirat Kaewunruen, Alexander Remennikov
Impact Damage Classification Of Railway Prestressed Concrete Sleepers, Sakdirat Kaewunruen, Alexander Remennikov
Alex Remennikov
Commonly, railway tracks suffer with the extreme loading conditions, which are attributed to the train operations with either wheel or rail abnormalities such as flat wheels, dipped rails, etc. These loads are of very high magnitude but short duration, as well as they are of low-possibility occurrence during the design life of the prestressed concrete sleepers. In spite of the most common use of the prestressed concrete sleepers in railway tracks, their impact responses and behaviours are not deeply appreciated nor taken into the design consideration. Up until recently, a new limit states design approach, whereas the dynamic effects are …
Nonlinear Finite Element Analysis Of Polymer Members, Akram Shaker Mahmood, Arz Y. Rzayeg
Nonlinear Finite Element Analysis Of Polymer Members, Akram Shaker Mahmood, Arz Y. Rzayeg
Akram Shaker Mahmood
An investigation study is made for verify the behavior of polymer members (Epoxsy & Polyester). The results of nonlinear analysis are illustrated with experimental work results. The ANSYS model accounts for nonlinear material phenomenon, such as, Tension Softening Material (TSM) and Enhanced Multilinear Isotropic Softening (EMIS) models. The polymer specimens are modeled using PLANE82 element – eight node plane element -, which is capable of simulating the failure behavior of polymer material members. The intention of this paper is thereby to discuss the proposed softening models to validate the complete Stress-Strain and Load-Deflection response of prismatic specimens subjected to uniaxial …
An Assessment Of The Use Of Structural Deformation As A Method Of Determining Area Of Fire Origin, Andrew Tinsley, David Icove
An Assessment Of The Use Of Structural Deformation As A Method Of Determining Area Of Fire Origin, Andrew Tinsley, David Icove
Andrew T Tinsley
Current methodologies of origin investigation have yet to include the structural deformations seen in steel buildings as a viable indicator of the area of origin of a given fire. As many steel structures are of relatively large size, it is often difficult to determine the area of origin using the typical dig and sift methods advocated in NFPA 921, especially if the extent of the fire was large and there were no witnesses as to the origin of the fire. As has been investigated for years, the performance of steel is highly affected by the application of heat. The science …
Repetitive Impact Response Of A Beam Structure Subjected To Harmonic Base Excitation, Elizabeth K. Ervin, Jonathan A. Wickert
Repetitive Impact Response Of A Beam Structure Subjected To Harmonic Base Excitation, Elizabeth K. Ervin, Jonathan A. Wickert
Jonathan A. Wickert
This paper investigates the forced response dynamics of a clamped–clamped beam to which a rigid body is attached, and in the presence of periodic or non-periodic impacts between the body and a comparatively compliant base structure. The assembly is subjected to base excitation at specified frequency and acceleration, and the potentially complex responses that occur are examined analytically. The two sets of natural frequencies and vibration modes of the beam-rigid body structure (in its in-contact state, and in its not-in-contact state), are used to treat the forced response problem through a series of algebraic mappings among those states. A modal …
Online Learning Algorithm For Structural Control Using Magnetorheological Actuators, Simon Laflamme
Online Learning Algorithm For Structural Control Using Magnetorheological Actuators, Simon Laflamme
Simon Laflamme
Magnetorheological actuators are promising devices for mitigating vibrations because they only require a fraction of energy for a similar performance to active control. Conversely, these semi-active devices have limited maximum forces and are hard to model due to the rheological properties of their fluid. When considering structural control, classical theories necessitate full knowledge of the structural dynamic states and properties most of which can only be estimated when considering large-scale control, which may be difficult or inaccurate for complicated geometries due to the non-linear behaviour of structures. Additionally, most of these theories do not take into account the response delay …
Design And Characteristics Of A Split Hopkinson Pressure Bar Apparatus, Radek Glaser, Jesse Haines, Christopher Knight
Design And Characteristics Of A Split Hopkinson Pressure Bar Apparatus, Radek Glaser, Jesse Haines, Christopher Knight
Radek Glaser
A Split Hopkinson Pressure Bar Apparatus, also known as Kolsky Bar that is capable of conducting compressive strain rate testing in the approximate ranges from 50 to 10^4 in/in per second was designed as a part of a Senior Design Project. Generally, this device is similar to that first used by Kolsky in 1949. The design of this device is presented here in two stages: 1. Research, design and manufacturing of the Stress Generating System 2. Experimental Part – Testing of the apparatus to obtain necessary data. The present phase of the design was focused mostly on the stress generating …