Cam-based passive variable friction device for structural control

2019 ◽  
Vol 188 ◽  
pp. 430-439 ◽  
Author(s):  
Austin Downey ◽  
Connor Theisen ◽  
Heather Murphy ◽  
Nicholas Anastasi ◽  
Simon Laflamme
Keyword(s):  
Structural Control ◽  
Variable Friction

Passive Variable Friction Damper for Increased Structural Resilience to Multi-Hazard Excitations

2018 ◽  
Author(s):  
Austin Downey ◽  
MohammadKazem Sadoughi ◽  
Liang Cao ◽  
Simon Laflamme ◽  
Chao Hu
Keyword(s):  
Structural Control ◽  
Seismic Event ◽  
Active Damping ◽  
Friction Damper ◽  
Strength Based ◽  
Story Drift ◽  
Variable Friction ◽  
Wind Events ◽  
Better Than ◽  
Damping Systems

Structural control systems, including passive, semi-active and active damping systems, are used to increase structural resilience to multi-hazard excitations. While semi-active and active damping systems have been investigated for the mitigation of multi-hazard excitations, their requirement for real-time controllers and power availability limit their usefulness. This work proposes the use of a newly developed passive variable friction device for the mitigation of multi-hazard events. This passive variable friction device, when installed in a structure, is capable of mitigating different hazards from wind and ground motions. In wind events, the device ensures serviceability, while during earthquake events, the device reduces the building’s inter-story drift to maintain strength-based motion requirements. Results show that the passive variable friction device performs better than a traditional friction damper during a seismic event while not compromising any performance during wind events.

Variable friction device for structural control based on duo-servo vehicle brake: Modeling and experimental validation

2015 ◽  
Vol 348 ◽  
pp. 41-56 ◽  
Author(s):  
Liang Cao ◽  
Austin Downey ◽  
Simon Laflamme ◽  
Douglas Taylor ◽  
James Ricles
Keyword(s):  
Structural Control ◽  
Experimental Validation ◽  
Variable Friction

Biomimetic materials: An introduction

1992 ◽  
Vol 50 (2) ◽  
pp. 1020-1021 ◽  
Author(s):  
M. Sarikaya ◽  
J. T. Staley ◽  
I. A. Aksay
Keyword(s):  
Self Assembly ◽  
Structural Control ◽  
Hierarchical Structures ◽  
Ceramic Composites ◽  
Advanced Materials ◽  
Length Scale ◽  
Spider Webs ◽  
Biomimetic Materials ◽  
Synthetic Materials ◽  
All Ceramic

Biomimetics is an area of research in which the analysis of structures and functions of natural materials provide a source of inspiration for design and processing concepts for novel synthetic materials. Through biomimetics, it may be possible to establish structural control on a continuous length scale, resulting in superior structures able to withstand the requirements placed upon advanced materials. It is well recognized that biological systems efficiently produce complex and hierarchical structures on the molecular, micrometer, and macro scales with unique properties, and with greater structural control than is possible with synthetic materials. The dynamism of these systems allows the collection and transport of constituents; the nucleation, configuration, and growth of new structures by self-assembly; and the repair and replacement of old and damaged components. These materials include all-organic components such as spider webs and insect cuticles (Fig. 1); inorganic-organic composites, such as seashells (Fig. 2) and bones; all-ceramic composites, such as sea urchin teeth, spines, and other skeletal units (Fig. 3); and inorganic ultrafine magnetic and semiconducting particles produced by bacteria and algae, respectively (Fig. 4).

Structural Control of Porous Nano-Space in Dye-Sensitized TiO2Solar Cells*

1998 ◽  
Vol 1 (1) ◽  
pp. 33-40
Author(s):  
Shozo Yanagida ◽  
Shingo Kambe ◽  
Wataru Kubo ◽  
Kei Murakoshi ◽  
Yuji Wada ◽  
...  
Keyword(s):  
Structural Control ◽  
Dye Sensitized

Parametric Study of Damping Characteristics of Magneto-Rheological Damper: Mathematical and Experimental Approach

2020 ◽  
Vol 15 (3) ◽  
pp. 37-48
Author(s):  
Zubair Rashid Wani ◽  
Manzoor Ahmad Tantray
Keyword(s):  
Structural Control ◽  
Research Work ◽  
Testing Machine ◽  
Input Voltage ◽  
Damping Coefficient ◽  
Control Technique ◽  
Damping Force ◽  
Active Devices ◽  
Active Structural Control ◽  
Magneto Rheological

The present research work is a part of a project was a semi-active structural control technique using magneto-rheological damper has to be performed. Magneto-rheological dampers are an innovative class of semi-active devices that mesh well with the demands and constraints of seismic applications; this includes having very low power requirements and adaptability. A small stroke magneto-rheological damper was mathematically simulated and experimentally tested. The damper was subjected to periodic excitations of different amplitudes and frequencies at varying voltage. The damper was mathematically modeled using parametric Modified Bouc-Wen model of magneto-rheological damper in MATLAB/SIMULINK and the parameters of the model were set as per the prototype available. The variation of mechanical properties of magneto-rheological damper like damping coefficient and damping force with a change in amplitude, frequency and voltage were experimentally verified on INSTRON 8800 testing machine. It was observed that damping force produced by the damper depended on the frequency as well, in addition to the input voltage and amplitude of the excitation. While the damping coefficient (c) is independent of the frequency of excitation it varies with the amplitude of excitation and input voltage. The variation of the damping coefficient with amplitude and input voltage is linear and quadratic respectively. More ever the mathematical model simulated in MATLAB was in agreement with the experimental results obtained.

Folding-Controlled Assembly of Ortho-Phenylene-Based Macrocycles

2020 ◽  
Author(s):  
Viraj kirinda ◽  
Scott Hartley
Keyword(s):  
Self Assembly ◽  
Structural Control ◽  
Structural Changes ◽  
Condensation Product ◽  
Gel Permeation Chromatography ◽  
Emergent Behavior ◽  
Order Structure ◽  
High Level ◽  
Alkoxy Groups ◽  
Energy Surfaces

The self-assembly of foldamers into macrocycles is a simple approach to non-biological higher-order structure. Previous work on the co-assembly of ortho-phenylene foldamers with rod-shaped linkers has shown that folding and self-assembly affect each other; that is, the combination leads to new emergent behavior, such as access to otherwise unfavorable folding states. To this point this relationship has been passive. Here, we demonstrate control of self-assembly by manipulating the foldamers’ conformational energy surfaces. A series of o-phenylene decamers and octamers have been assembled into macrocycles using imine condensation. Product distributions were analyzed by gel-permeation chromatography and molecular geometries extracted from a combination of NMR spectroscopy and computational chemistry. The assembly of o-phenylene decamers functionalized with alkoxy groups or hydrogens gives both [2+2] and [3+3] macrocycles. The mixture results from a subtle balance of entropic and enthalpic effects in these systems: the smaller [2+2] macrocycles are entropically favored but require the oligomer to misfold, whereas a perfectly folded decamer fits well within the larger [3+3] macrocycle that is entropically disfavored. Changing the substituents to fluoro groups, however, shifts assembly quantitatively to the [3+3] macrocycle products, even though the structural changes are well-removed from the functional groups directly participating in bond formation. The electron-withdrawing groups favor folding in these systems by strengthening arene–arene stacking interactions, increasing the enthalpic penalty to misfolding. The architectural changes are substantial even though the chemical perturbation is small: analogous o-phenylene octamers do not fit within macrocycles when perfectly folded, and quantitatively misfold to give small macrocycles regardless of substitution. Taken together, these results represent both a high level of structural control in structurally complex foldamer systems and the demonstration of large-amplitude structural changes as a consequence of a small structural effects.

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