Modeling of Seismic Isolation Bearings Including Shear Deformation and Stability Effects

1989 ◽  
Vol 42 (11S) ◽  
pp. S113-S120 ◽  
Author(s):  
Chan Ghee Koh ◽  
James M. Kelly
Keyword(s):  
Seismic Isolation ◽  
Dynamic Stiffness ◽  
Viscoelastic Model ◽  
Compressive Load ◽  
Buckling Load ◽  
Simplified Model ◽  
Damping Factor ◽  
Symmetric Model ◽  
Shear Rigidity ◽  
The Stability

Elastomeric bearings designed for aseismic base isolation typically have a low shear rigidity in order to achieve a low isolation frequency and are thus modeled by a flexural-shear column on the basis of Haringx’s theory. The buckling load of a flexural-shear column is considerably reduced by the shear effect. It is therefore essential to account for the stability effect due to a compressive load on the dynamic performance of these bearings. In this paper, an exact viscoelastic model consistent with Haringx’s theory is first reviewed. A simplified symmetric model consisting of springs and rigid plates is then discussed. Experimental results for four different sets of natural rubber bearings are presented. It is shown that both models can describe with good accuracy the stability effects on the dynamic stiffness, damping factor and height reduction of bearings. In spite of its simplicity, the simplified model is found to agree very well with the exact model. Lastly, using the simplified model, the applicability of the Southwell plot to predict the buckling load of elastomeric isolation bearings is examined.

scholarly journals Buckling of sheared and compressed microfibrils

2010 ◽  
Vol 7 (52) ◽  
pp. 1581-1589 ◽  
Author(s):  
Nichole Nadermann ◽  
Ajeet Kumar ◽  
Sachin Goyal ◽  
Chung-Yuen Hui
Keyword(s):  
Friction Force ◽  
Compressive Load ◽  
Compressive Force ◽  
Static Friction ◽  
Buckling Load ◽  
Shear Displacement ◽  
The Other ◽  
Euler Buckling ◽  
The Stability

In this paper, we study the stability of an initially straight elastic fibril clamped at one end, while the other end is subjected to a constant normal compressive force and a prescribed shear displacement. We found the buckling load of a sheared fibril to be always less than the Euler buckling load. Furthermore, if the end of the fibril loses adhesion, then the buckling load can be considerably less. Our result suggests that the static friction of microfibre arrays can decrease with increasing normal compressive load and, in some cases, friction force can actually become negative.

Simplified Modeling Research of Reinforced Concrete Based on the Dynamic Stiffness Equivalence

2012 ◽  
Vol 446-449 ◽  
pp. 458-462
Author(s):  
Jie Hu ◽  
Jia Quan Feng ◽  
Xi Nong Zhang
Keyword(s):  
Reinforced Concrete ◽  
Reference Model ◽  
Dynamic Stiffness ◽  
Optimization Method ◽  
Simplified Model ◽  
Response Analysis ◽  
Reinforced Concrete Structure ◽  
Optimization Function ◽  
Nature Frequency ◽  
Simplified Modeling

This paper proposed a simplified modeling method of reinforced concrete based on the equivalence of dynamic stiffness, the parameters of simplified model were modified to make the error of nature frequency between reference model and simplified model as small as possible, and an appropriate optimization function was designed. The essentiality of the proposed method is parameter optimization, with the advantages such as fewer elements and calculation assumption. The numerical simulation result indicated that this optimization method is suitable for the dynamic response analysis of complicated reinforced concrete structure.

Stability and resonance conditions of second-order fractional systems

2016 ◽  
Vol 24 (4) ◽  
pp. 659-672 ◽  
Author(s):  
Elena Ivanova ◽  
Xavier Moreau ◽  
Rachid Malti
Keyword(s):  
Second Order ◽  
Damping Factor ◽  
Fractional Differentiation ◽  
Resonance Amplitude ◽  
Fractional Systems ◽  
Integral Number ◽  
At Resonance ◽  
Fractional System ◽  
The Stability ◽  
Normalized Gain

The interest of studying fractional systems of second order in electrical and mechanical engineering is first illustrated in this paper. Then, the stability and resonance conditions are established for such systems in terms of a pseudo-damping factor and a fractional differentiation order. It is shown that a second-order fractional system might have a resonance amplitude either greater or less than one. Moreover, three abaci are given allowing the pseudo-damping factor and the differentiation order to be determined for, respectively, a desired normalized gain at resonance, a desired phase at resonance, and a desired normalized resonant frequency. Furthermore, it is shown numerically that the system root locus presents a discontinuity when the fractional differentiation order is an integral number.

Vibration Modeling of Machine Tool Spindles: A Calibrated Dynamic Stiffness Matrix Method

2013 ◽  
Vol 651 ◽  
pp. 710-716 ◽  
Author(s):  
Omar Gaber ◽  
Seyed M. Hashemi
Keyword(s):  
Stiffness Matrix ◽  
Natural Frequencies ◽  
Dynamic Stiffness ◽  
Dynamic Stiffness Matrix ◽  
Spring Element ◽  
Linear Spring ◽  
Beam Bending ◽  
The Stability ◽  
Spinning Speed ◽  
Vibration Modeling

The effects of spindles vibrational behavior on the stability lobes and the Chatter behavior of machine tools have been established. The service life has been observed to reducethe system natural frequencies. An analytical model of a multi-segment spinning spindle, based on the Dynamic Stiffness Matrix (DSM) formulation, exact within the limits of the Euler-Bernoulli beam bending theory, is developed. The system exhibits coupled Bending-Bending (B-B) vibration and its natural frequencies are found to decrease with increasing spinning speed. The bearings were included in the model usingboth rigid, simply supported, frictionless pins and flexible linear spring elements. The linear spring element stiffness is then calibrated so that the fundamental frequency of the system matches the nominal value.

The Energy Solutions for the Stability of Tower Crane

2012 ◽  
Vol 170-173 ◽  
pp. 3159-3165
Author(s):  
Ming Xin Huang ◽  
Jian Ping Xu ◽  
Jian Guo Wu
Keyword(s):  
Energy Method ◽  
Buckling Load ◽  
Tower Crane ◽  
The Stability ◽  
Design And Construction

The energy method is used to solve the buckling load of tower crane. It can conclude the effect law on the stability of different section parameters of tower crane and thus provides some references for the design and construction of tower crane.

scholarly journals Dynamic magneto-viscoelastic model for magnetorheological nanocomposites with imperfect interface

2019 ◽  
Vol 28 (8) ◽  
pp. 1248-1260 ◽  
Author(s):  
Xiangrong Chen ◽  
Rui Li ◽  
LZ Sun
Keyword(s):  
Carbon Nanotubes ◽  
Dynamic Stiffness ◽  
Viscoelastic Model ◽  
Imperfect Interface ◽  
Model Framework ◽  
Mechanical Coupling ◽  
Interfacial Conditions ◽  
Micro Particles ◽  
The Matrix ◽  
Multi Walled Carbon Nanotubes

A dynamic magneto-viscoelastic interface model is proposed to study the effective magneto-mechanical responses of magnetorheological nanocomposites filled with carbon nanotubes. It is incorporated with the fundamental micromechanics principles, microstructural magnetic and mechanical coupling, and computational homogenization procedures. The field-dependent effective dynamic stiffness and damping of randomly dispersed, chain-structured nanocomposites are investigated with the consideration of imperfect interfacial conditions among nanofillers, micro-particles and the matrix. Comparisons are performed between the model prediction and experimental data for a specific type of Fe particle-reinforced elastomer nanocomposites filled with multi-walled carbon nanotubes to demonstrate the capability of the proposed model framework.

Research on dynamic stiffness of the damping element in bellows-type fluid viscous damper by a simplified model

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiaolei Jiao ◽  
Jinxiu Zhang ◽  
Hongchao Zhao ◽  
Yong Yan
Keyword(s):  
Frequency Domain ◽  
Analytical Model ◽  
High Frequency ◽  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Simplified Model ◽  
Viscous Damper ◽  
Content Type ◽  
Fluid Viscous Damper ◽  
Frequency Domains

Purpose Bellows-type fluid viscous damper can be used to isolate micro vibration in high-precision satellites. The conventional model cannot describe hydraulic stiffness in the medium- and high-frequency domain of this damper. A simplified analytical model needs to be established to analyze hydraulic stiffness of the damping element in this damper. Design/methodology/approach In this paper, a bellows-type fluid viscous damper is researched, and a simplified model of the damping element in this damper is proposed. Based on this model, the hydraulic stiffness and damping of this damper in the medium- and high-frequency domains are studied, and a comparison is made between the analytical model and a finite element model to verify the analytical model. Findings The results show that when silicone oil has low viscosity, a model that considers the influence of the initial segment of the damping orifice is more reasonable. In the low-frequency domain, hydraulic stiffness increases quickly with frequency and remains stable when the frequency increases to a certain value; the stable stiffness can reach 106 N/m, which is much higher than the main stiffness. Excessive dynamic stiffness in the high-frequency domain will cause poor vibration isolation performance. Adding compensation bellows to the end of the original isolator may be an effective solution. Practical implications A model of the isolator containing the compensation bellows can be derived based on this analytical model. This research can also be used for dynamic modeling and vibration isolation performance analysis of a vibration isolation platform based on this bellows-type fluid viscous damper. Originality/value This paper proposed a simplified model of damping element in bellows-type fluid viscous damper, which can be used to analyze hydraulic stiffness in this damper and it was found that this damper showed stable hydraulic stiffness in the medium- and high-frequency domains.

Investigation of partially bonded fiber-reinforced elastomeric isolators (PB-FREIs) with nominal vertical tensile loads

2019 ◽  
Vol 46 (8) ◽  
pp. 669-676 ◽  
Author(s):  
Niel C. Van Engelen ◽  
Michael J. Tait ◽  
Dimitrios Konstantinidis
Keyword(s):  
Seismic Isolation ◽  
Low Cost ◽  
Compressive Load ◽  
Polymer Fibers ◽  
Experimental Investigations ◽  
Loading Conditions ◽  
Fiber Reinforced ◽  
Conventional Steel ◽  
Tensile Forces ◽  
The Cost

Unbonded fiber-reinforced elastomeric isolators (FREIs) were initially proposed as a potential low-cost alternative to conventional steel-reinforced elastomeric isolators (SREIs). FREIs are similar to SREIs but comparatively lightweight as the steel components from SREIs have been replaced with polymer fibers in FREIs. Subsequent experimental investigations identified that unbonded FREIs have desirable characteristics for seismic isolation due to the unbonded application and fiber reinforcement. The unbonded application removes mechanical fasteners, relying on friction to transfer horizontal loads, further reducing the cost. However, the unbonded application also introduces limitations, being susceptible to slip in certain loading conditions and being incapable of resisting tensile forces. In this paper, the concept of partially bonded FREIs (PB-FREIs), a proposed solution to these limitations, is further investigated experimentally with nominal vertical tensile loads. It is shown that PB-FREIs can achieve similar properties to an unbonded FREI with a vertical compressive load.

The Influence of Tangential Roller Pressure on the Stability of Circular Saw Blade

2014 ◽  
Vol 614 ◽  
pp. 32-35 ◽  
Author(s):  
Ming Song Zhang ◽  
Yi Zhang ◽  
Jian Jun Ke ◽  
Xiao Wei Li ◽  
Lian Bing Cheng
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Symmetric Model ◽  
The Finite Element Method ◽  
Circular Saw ◽  
The Face ◽  
Circular Saw Blade ◽  
Cyclic Symmetric ◽  
The Stability ◽  
Saw Blade

The finite element method was used to study tangential roller method impact on the stability of circular saw blade. Using 30 ° cyclic symmetric model is analyzed. The results show that the tension of the saw blade is not the same, and tensioning effect is different, when the tangential roller pressure is not same. At the same time, after tangential roller, the face run out of saw blade is small, which show that the smoothness of tangential roller is better.

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