• Journal of Korean Association for Spatial Structures
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• v.20 no.4
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• pp.93-100
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• 2020

In this study, structural characteristics were analyzed by combining gravity load and lateral loads such as seismic loads through static analysis of example structures, and the static characteristics of the twisted structure according to the plane rotation angle were also analyzed. Example structures were selected as regular structure, and twisted structures; 1.0, 2.0, and 3.0 degree angle of rotation per story, and static analysis was performed by the load combination case 1 and case 2. As a result the story drift ratio of the twisted-shaped structure also increased as the plane rotation angle per story increased. The eccentricity according to the load combination was the highest in the lower stories of all analysis models, and the eccentricity was found to be larger as the rotation angle decreased. The twisted-shaped structure was more responsible for the bending moment of the column than the regular structure, and the vertical member axial force of all analysis models was almost similar.

• Journal of Advanced Marine Engineering and Technology
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• v.12 no.3
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• pp.29-42
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• 1988

With the Hertzian contact theory, it is possible to determine the bearing load distributing pattern among the balls and rollers and also variations of the load-displacement relationships for rolling elements contacting raceways according to bearing clearance, load distribution, contact forces and dimensions of bearing components (i.e diameter of raceway and rolling elements), etc. In this paper the calculation theories of contact load and normal approach between two raceways under radial load are reviewed, and compared these calculation results with those of experimental results. A new calculation theory for elastic displacement of outer-race of ball bearing under radial load is developed by authors by application of energy method, which is independent on the effects of roughness, bending or eccentricity of bearing with driving shaft, and is effective in measuring the location of its defect.

• Tribology and Lubricants
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• v.17 no.2
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• pp.116-123
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• 2001

A theoretical analysis has been undertaken to show the influence of bearing geometry on the steady state characteristics of air lubricated spherical tilting pad bearings. The geometry variations considered are the number of pads, the eccentricity ratio, the direction of load, and the preloading. Dynamic characteristic equations are derived with pad assembly method.

• Tribology and Lubricants
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• v.33 no.4
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• pp.153-167
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• 2017

The aim of this study is to find the change in trend in the eccentricities of two journal bearings supporting the crankshaft of a single cylinder engine and the degree of misalignment of the shaft. We analyze the change in oil film thickness considering the wear scar under mixed-elasto-hydrodynamic lubrication regime at potential wear regions. For this, we first calculate the central eccentricities of the two journal bearings by using the mobility method. Then we calculate the outer end eccentricity by using the geometry of the bearings. Further, the tilting angle and degree of misalignment of the shaft are calculated by using the eccentricities of the two bearings. We show that the eccentricity of bearing #1, on which higher load is applied, increases at the beginning of the start-up cycle and during the coast-down cycle. However, the eccentricity of bearing #2, on which lower load is applied, decreases at the beginning of the start-up cycle and increases during the coast-down cycle. From the results of the analysis of oil film thickness, we show that the mixed-elasto-hydrodynamic lubrication regime for a misaligned shaft is at the initial stages of the start-up cycle for both bearing #1 and #2 and at the final stage of the coast-down cycle for only bearing #1.

• Earthquakes and Structures
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• v.8 no.2
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• pp.463-484
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• 2015

Modern codes for earthquake resistant building design require consideration of the so-called accidental design eccentricity, to account for torsional response caused by several factors not explicitly considered in design. This provision requires that the mass centres in the building floor be moved a certain percentage of the building's dimension (usually 5%) along both the x and y axes and in both positive and negative directions. If one considers also the spatial combinations of the two component motion in a dynamic analysis of the building, the number of required analyses and combinations increases substantially, causing a corresponding work load increase for practicing structural engineers. Another shortcoming of this code provision is that its introduction has been based primarily on elastic results from investigations of oversimplified, hence questionable, one story building models. This problem is addressed in the present paper using four groups of eccentric braced steel buildings, designed in accordance with Eurocodes 3 (steel) and 8 (earthquake design), with and without accidental eccentricities considered. The results indicate that although accidental design eccentricities can lead to somewhat reduced inelastic response demands, the benefit is not significant from a practical point of view. This leads to suggestions that accidental design eccentricities should probably be abolished or perhaps replaced by a simpler and more effective design provision, at least for torsionally stiff buildings that constitute the vast majority of buildings encountered in practice.

• Structural Engineering and Mechanics
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• v.67 no.6
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• pp.671-682
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• 2018

The effect of earthquake induced torsion, due to mass eccentricities, is investigated with the objective of providing practical design guidelines for minimizing the torsional response of building structures. Current code provisions recommend performing three dimensional static or dynamic analyses, which involve shifting the centers of the floor masses from their nominal positions to what is called an accidental eccentricity. This procedure however may significantly increase the design cost of multistory buildings, due to the numerous possible spatial combinations of mass eccentricities and it is doubtful whether such a cost would be justifiable. This paper addresses this issue on a theoretical basis and investigates the torsional response of asymmetric multistory buildings in relation to their behavior when all floor masses lie on the same vertical line. This approach provides an insight on the overall seismic response of buildings and reveals how the torsional response of a structure is influenced by an arbitrary spatial combination of mass eccentricities. It also provides practical guidelines of how a structural configuration may be designed to sustain minor torsion, which is the main objective of any practicing engineer. A parametric study is presented on 9-story common building types having a mixed-type lateral load resisting system (frames, walls, coupled wall bents) and representative heightwise variations of accidental eccentricities.

• Computers and Concrete
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• v.13 no.2
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• pp.291-308
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• 2014

A nonlinear, three-dimensional finite element analysis was conducted on six intermediate L-shaped spandrel beams using the "ANSYS Civil FEM" program. The beams were constructed and tested in the laboratory under eccentric concentrated load at mid-span to obtain a combined loading case: torsion, bending, and shear. The reinforcement case parameters were as follows: without reinforcement, with longitudinal reinforcement only, and reinforced with steel bars and stirrups. All beams were tested under two different combined loading conditions: T/V = 545 mm (high eccentricity) and T/V = 145 mm (low eccentricity). The failure of the plain beams was brittle, and the addition of longitudinal steel bars increased beam strength, particularly under low eccentricity. Transverse reinforcement significantly affected the strength at high eccentricities, that is, at high torque. A program can predict accurately the behavior of these beams under different reinforcement cases, as well as under different ratios of combined loadings. The ANSYS model accurately predicted the loads and deflections for various types of reinforcements in spandrel beams, and captured the critical crack regions of these beams.

• Journal of Korean Association for Spatial Structures
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• v.22 no.1
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• pp.33-40
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• 2022

When the center of stiffness and the center of mass of the structure differ under the seismic load, torsion is caused by eccentricity. In this study, an analysis model was modeled in which the positions of the core and the plane rotation axis of a 60-story torsional atypical structure with a plane rotation angle of 1 degree per floor were different. The structural behavior of the analysis model was analyzed, and the earthquake response behavior of the structure was analyzed based on the time history analysis results. As a result, as the eccentricity of the structure increased, the eccentricity response was amplified in the high-rise part, and the bending and torsional behavior responses were complex in the low-order vibration mode. As a result of the analysis, the maximum displacement and story drift ratio increased due to the torsional behavior. The maximum story shear force and the story absolute maximum acceleration showed similarities for each analysis model according to the shape of the vibration mode of the analysis model.

• Transactions of the Korean Society of Mechanical Engineers
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• v.3 no.1
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• pp.35-41
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• 1979

In order to improve the load capacity of externally pressurized air-lubeicatedjournal bearings, a new type(doubly-stepped type) bearing was revised and experimented. Through the results of experiment, the load capacity of doubly-stepped bearings was discussed and compared with equivalent conventional circular journal bearings. Results were obtained for speed up to 18000rpm and for supply pressure ratio(Ps/Pa) 4.8,6,7. Compared with equivalent conventional bearings, doubly-stepped bearings resultd a high gain in load capacity. It is also shown that the increasing rate of load capacith increases with decreasing the eccentricity ratio. Furthermore, the increasing rate is higher in the case of great clearanceratio than small dleatance ratio of doubly-stepped bearings. Such an increase in load capacity is confirmed by pressure distributions in the bearings.

• Computational Structural Engineering
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• v.9 no.4
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• pp.135-140
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• 1996

Single angle or channel with thin-walled open section can be used as compression member for example as web member in truss. In this case the inevitable eccentricity due to fabrication is commonly neglected in structural design. However eccentricity effect should be considered in the member design, especially in case of compression member. The critical loads of compression members that buckle by twisting or by a combination of bending and twisting are to be determined by solving governing differential equations. In this paper, the investigations are limited to the rolled channels([), equal-leg angles(L), lipped channels(C) and the applied loads are assumed to have some eccentricities.