• Tribology and Lubricants
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• 제17권1호
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• pp.22-27
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• 2001

This paper presents an analysis of eccentricity ratio of rolling piston using mobility method which is a powerful tool for analyzing dynamically-loaded journal bearings with efficiency and applicability. And, we investigate influences of design parameters (discharge pressure, radial clearance, rotational velocity of shaft, and eccentricity of compressor) on bearing load and eccentricity ratio. The results show that the discharge pressure, radial clearance and rotational velocity of shaft have significant influence on eccentricity ratio, and the discharge pressure and eccentricity of compressor have influence on bearing load.

• Earthquakes and Structures
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• 제9권2호
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• pp.391-413
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• 2015

Damage of torsionally coupled buildings situated on soil sites has been reported in literature, however no site-specific studies are available for torsionally coupled buildings having site characteristics as a parameter. Effect of torsion is being accounted in seismic codes by the provision of design eccentricity where the dynamic to static eccentricity ratio is a parameter. In this paper, a methodology to determine dynamic to static eccentricity ratio of torsionally coupled buildings has been demonstrated for Delhi region for two torsionally coupled buildings on three soil sites. The variations of average and standard deviations of frame shears for stiff and flexible edges are studied for four eccentricity ratios for the two buildings for the three sites. From the limited studies made, it is observed that the dynamic to static eccentricity ratios observed for site-specific earthquakes are different from Indian seismic code specified value, hence a proposal is made to include a comment in Indian seismic code. Methodology proposed in this paper can be adopted for any region, for the estimation of dynamic to static eccentricity ratio for site specific earthquake.

• Earthquakes and Structures
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• 제23권3호
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• pp.283-295
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• 2022

Seismic design codes permit the use of Equivalent Static Analysis of buildings considering torsional eccentricity e with dynamic amplification factors on structural eccentricity and some accidental eccentricity. Estimation of e in buildings is not addressed in codes. This paper presents a simple approximate method to estimate e in RC Moment Frame and RC Structural Wall buildings, which required no detailed structural analysis. The method is validated by 3D analysis (using commercial structural analysis software) of a spectrum of building. Results show that dynamic amplification factor should be applied on torsional eccentricity when performing Response Spectrum Analysis also. Also, irregular or mixed modes of oscillation arise in torsionally unsymmetrical buildings owing to poor geometric distribution of mass and stiffness in plan, which is captured by the mass participation ratio. These irregular modes can be avoided in buildings of any plan geometry by limiting the two critical parameters (normalised torsional eccentricity e/B and Natural Period Ratio 𝜏 =T_𝜃/T, where B is building lateral dimension, T_𝜃 uncoupled torsional natural period and T uncoupled translational natural period). Suggestions are made for new building code provisions.

• 한국자동차공학회논문집
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• 제5권5호
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• pp.157-169
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• 1997

The effects of intake port eccentricity on the characteristics of in-cylinder swirl ratio in a 4-valve diesel engine having the two intake ports; one is a helical intake port and the other is a tangential intake port were investigated by using the ISM(impulse swirl meter) in steady flow test rig. Swirl ratio($R_s$) and mean flow coefficient($C_{f(mean)}$) with valve eccentricity ratio($N_y$) and axial distance(Z/B) were measured. As the results from this experiment, the characteristics of in-cylinder swirl ratio formed by a 4-valve cylinder head were largely affected by intake port eccentricity. There is a difference in the mass flowrate through the two intake ports, and the mass flowrate through the tangential intake port is 19% more than that of the helical intake port. Therefore, we could know that the effects of the mass flowrate ratio through each intake port besides intake port shape should be conidered.

• 한국공간구조학회논문집
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• 제1권1호
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• pp.117-124
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• 2001

In Single-layer latticed domes with rectangular network which is composed of ring of circumferential direction and rafter of longitudinal direction, that is, rib domes, if we use the cross-membered junction's method for the advantage in fabrication and construction, the eccentricity is occurred in the nodal point of crossing members. This paper is aimed at investigating the buckling characteristics for the effect of eccentricity according to rise-span ratios and distance of eccentricity. Analysis method is based on FEM dealing with the geometrically nonlinear deflection problems. The conclusion were given as follows: 1. The maximum decreasing ratio of buckling strength due to the junction's eccentricity is about 60% in models of this paper. 2. In the increasing ratio of buckling strength for rise-span ratio, that of Type 3 models is larger than that of type 2 models. On the other hand, that of Type 2 mode is larger than that of Type 3 for eccentricity-distance. 3. In the viewpoint of the value of buckling strength, that of Type 2 models is larger than that of type 3 models. The effect of the junction's rigidity on buckling strength is not great for overall models. Therefore if we use the cross-membered junction's method for the advantage in fabrication and construction, the method of Type 2 will have the great advantage of that of Type 3.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1142-1148
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• 2006

The floating ring seal which is used in the high pressure turbo pump is frequently used in the oxidizer pump and the fuel pump of the turbo pump of the liquid propulsion rocket, because it is able to minimize clearance to decrease the leakage flow rate. But, floating ring seal has a tendency to increase the force which caused instability of system as the eccentricity ratio increases. In this paper, we devised design of floating ring seal which decrease contact area between floating and supporting ring. Modified floating ring seal has a tendency to decrease the eccentricity ratio compare with original floating ring seal. The whirl frequency ratio which is able to distinguish stability of system decrease compare with original floating ring seal

• Earthquakes and Structures
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• 제8권5호
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• pp.1069-1089
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• 2015

This paper presents average numerical results of 2128 nonlinear dynamic finite element (FE) analyses of lightweight acceleration-sensitive non-structural components (NSCs) attached to the floors of one-bay three-storey reinforced concrete (RC) primary structures (P-structures) with different eccentricity ratios. The investigated parameters include the NSC to P-structure vibration period ratio, peak ground acceleration, P-structure eccentricity ratio, and NSC damping ratio. Appropriate constitutive relationships were used to model the behaviour of the RC P-structures. The NSCs were modelled as vertical cantilevers fixed at their bases with masses on the free ends and varying lengths so as to match the vibration periods of the P-structures. Full dynamic interaction was considered between the NSCs and P-structures. A set of seven natural bi-directional ground motions were used to evaluate the seismic response of the NSCs. The numerical results show that the acceleration response of the NSCs depends on the investigated parameters. The accelerations of the NSCs attached to the flexible sides of the P-structures increased with the increase in peak ground acceleration and P-structure eccentricity ratio but decreased with the increase in NSC damping ratio. Comparison between the FE results and Eurocode 8 (EC8) predictions suggests that, under tuned conditions, EC8 provisions underestimate the seismic response of the NSCs mounted on the flexible sides of the plan-irregular RC P-structures.

• Structural Engineering and Mechanics
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• 제83권1호
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• pp.45-51
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• 2022

The need to account for accidental torsion in seismic design is no longer debatable, however, the seismic codes' requirement for accidental eccentricity has recently faced criticism. In order to get as close to real conditions as possible, this study investigated the impact of accidental torsion in symmetric RC multistory buildings caused by one of its many sources, the torsional earthquake component, and compared the results to those obtained by using the accidental eccentricity recommended by the codes (shifting the center of mass). To cover a wide range of frequencies and site conditions, two types of torsion seismic components were used: a recorded torsion accelerogram and five others generated using translation accelerograms. The main parameters that govern seismic responses, such as the number of stories (to account for the influence of all modes of vibration) and the frequency ratio (Ω) variation, were studied in terms of inter-story drift and displacement responses, as well as torsional moment. The results show that the eccentricity ratio of 5% required by most codes for accidental torsion should be reexamined and that it is prudent for computer analysis to use the static moment approach to implement the accidental eccentricity while waiting for new seismic code recommendations on the subject.

• Structural Engineering and Mechanics
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• 제13권6호
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• pp.671-694
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• 2002

This paper presents theoretical investigation on the cross correlation between torsional vibration ($u_{\theta}$) and translation vibration ($u_x$) of asymmetrical structure under white noise excitation. The formula reveals that the cross correlation coefficient (${\rho}$) is a function of uncoupled frequency ratio (${\Omega}={\omega}_{\theta}/{\omega}_x$), eccentricity, and damping ratio (${\xi}$). Simulations involving acceleration records from fifteen different earthquakes show correlation coefficients results similar to the theoretical correlation coefficients. The uncoupled frequency ratio is the dominating parameter to ${\rho}$; generally, ${\rho}$ is positive for ${\omega}_{\theta}/{\omega}_x$ > 1.0, negative for ${\omega}_{\theta}/{\omega}_x$ < 1.0, and close to zero for ${\omega}_{\theta}/{\omega}_x$ = 1.0. When the eccentricity or damping ratio increases, ${\rho}$ increases moderately for small ${\Omega}$ (< 1.0) only. The relation among $u_x$, $u_{\theta}$ and corner displacement are best presented by ${\rho}$; a simple way to hand-calculate the theoretical dynamic corner displacements from $u_x$, $u_{\theta}$ and ${\rho}$ is proposed as an alternative to dynamic analysis.

• KSTLE International Journal
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• 제2권1호
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• pp.1-11
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• 2001

The influence of aerated oil on a high-speed journal bearing is examined by classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. With changing eccentricity ratio, it is investigated the effects of air bubbles on the performance of a high-speed plain journal bearing. Just at the moderate eccentricity ratios, even if the involved aeration levels are not so severe and the entrained air bubble sizes are not so small, it is found that the bearing load and friction force may be changed so visibly for the high speed bearing operation.