• Title/Summary/Keyword: rise-to-span ratio

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Free Vibrations of Non-Circular Arches with Elastic Supports (탄성지점을 갖는 변화곡률 아치의 자유진동)

  • Oh, Sang-Jin;Kim, Gwon-Sik;Park, Kwang-Kyou
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.340-343
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    • 2007
  • The differential equations governing free, in-plane vibrations of non-circular arches with the translational (radial and tangential directions) and rotational springs at the ends, including the effects of rotatory inertia, shear deformation and axial deformation, are solved numerically using the corresponding boundary conditions. The lowest four natural frequencies for the parabolic geometry are calculated over a range of non-dimensional system parameters: the arch rise to span length ratio, the slenderness ratio, and the translational and rotational spring parameters.

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A numerical investigation of seismic performance of large span single-layer latticed domes with semi-rigid joints

  • Zhang, Huidong;Han, Qinghua
    • Structural Engineering and Mechanics
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    • v.48 no.1
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    • pp.57-75
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    • 2013
  • It is still inadequate for investigating the highly nonlinear and complex mechanical behaviors of single-layer latticed domes by only performing a force-based demand-capacity analysis. The energy-based balance method has been largely accepted for assessing the seismic performance of a structure in recent years. The various factors, such as span-to-rise ratio, joint rigidity and damping model, have a remarkable effect on the load-carrying capacity of a single-layer latticed dome. Therefore, it is necessary to determine the maximum load-carrying capacity of a dome under extreme loading conditions. In this paper, a mechanical model for members of the semi-rigidly jointed single-layer latticed domes, which combines fiber section model with semi-rigid connections, is proposed. The static load-carrying capacity and seismic performance on the single-layer latticed domes are evaluated by means of the mechanical model. In these analyses, different geometric parameters, joint rigidities and roof loads are discussed. The buckling behaviors of members and damage distribution of the structure are presented in detail. The sensitivity of dynamic demand parameters of the structures subjected to strong earthquakes to the damping is analyzed. The results are helpful to have a better understanding of the seismic performance of the single-layer latticed domes.

A Study on Buckling Characteristics of 2-way Grid Single-Layer Domes Considering Rigidity-Effect of Roofing Covering Materials (지붕마감재 강성효과를 고려한 2방향 그리드 단층돔의 좌굴특성에 관한 연구)

  • Park, Sang-Hoon;Suk, Chang-Mok;Jung, Hwan-Mok;Kwon, Young-Hwan
    • Journal of Korean Association for Spatial Structures
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    • v.2 no.1 s.3
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    • pp.85-92
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    • 2002
  • Two way grid single-layer domes are of great advantage in fabrication and construction because of the simple fact that they have only four members at each junction. But, from a point of view of mechanics, the rectangular latticed pattern gives rise to a nonuniform rigidity-distribution in the circumferential direction. If the equivalent rigidity is considered in the axial direction of members, the in-plane equivalent shearing rigidity depends only on the in-plane bending rigidity of members and its value is very small in comparison to that of the in-plane equivalent stretching rigidity. It has a tendency to decrease buckling -strength of dome considerably by external force. But it is possible to increase buckling strength by the use of roofing covering materials connected to framework. In a case like this, shearing rigidity of roofing material increases buckling strength of the overall structure and can be designed economically from the viewpoint of practice. Therefore, the purpose of this paper, in Lamella dome and rectangular latticed dome that are a set of 2-way grid dome, is to clarify the effects of roofing covering materials for increasing of buckling strength of overall dome. Analysis method is based on FEM dealing with the geometrically nonlinear deflection problems. The conclusion were given as follows: 1. In case of Lamella domes which have nearly equal rigidity in the direction of circumference, the rigidity of roofing covering materials does not have a great influence on buckling-strength, but in rectangular latticed domes that has a clear periodicity of rigidity, the value of its buckling strength has a tendency to increase considerably with increasing rigidity of roofing covering materials 2. In case of rectangular latticed domes, as rise-span-ratio increases, models which is subjected to pressure -type-uniform loading than vertical-type-uniform loading are higher in the aspects of the increasing rate of buckling- strength according to the rate of shear reinforcement rigidity, but in case of Lamella dome, the condition of loading and rise-span-ratio do not have a great influence on the increasing rate of buckling strength according to the rate of shear reinforcement rigidity.

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Models for Hydration Heat Development and Mechanical Properties of Ultra High Performance Concrete (초고성능 콘크리트의 수화발열 및 역학적 특성 모델)

  • Cha, Soo-Won;Kim, Ki-Hyun;Kim, Sung-Wook;Park, Jung-Jun;Bae, Sung-Geun
    • Journal of the Korea Concrete Institute
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    • v.22 no.3
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    • pp.389-397
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    • 2010
  • Concrete has excellent mechanical properties, high durability, and economical advantages over other construction materials. Nevertheless, it is not an easy task to apply concrete to long span bridges. That's because concrete has a low strength to weight ratio. Ultra high performance concrete (UHPC) has a very high strength and hence it allows use of relatively small section for the same design load. Thus UHPC is a promising material to be utilized in the construction of long span bridges. However, there is a possibility of crack generation during the curing process due to the high binder ratio of UHPC and a consequent large amount of hydration heat. In this study, adiabatic temperature rise and mechanical properties were modeled for the stress analysis due to hydration heat. Adiabatic temperature rise curve of UHPC was modeled superposing 2-parameter model and S-shaped function, and the Arrhenius constant was determined using the concept of equivalent time. The results are verified by the mock-up test measuring the temperature development due to the hydration of UHPC. In addition, models for mechanical properties such as elastic modulus, tensile strength and compressive strength were developed based on the test results from conventional load test and ultrasonic pulse velocity measurement.

Free Vibrations of Arches in Rectangular Coordinates (직교좌표계에 의한 아치의 자유진동)

  • Lee, Byoung-Koo;Lee, Tae-Eun;Ahn, Dae-Soon;Kim, Young-Il
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11b
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    • pp.971-976
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    • 2002
  • The differential equations governing free vibrations of the elastic arches with unsymmetric axis are derived in rectangular coordinates rather than in polar coordinates, in which the effect of rotatory inertia is included. Frequencies and mode shapes are computed numerically for parabolic arches with both clamped ends and both hinged ends. Comparisons of natural frequencies between this study and SAP 2000 are made to validate theories and numerical methods developed herein. The convergent efficiency is highly improved under the newly derived differential equations in Rectangular coordinates. The lowest four natural frequency parameters are reported, with and without the rotatory inertia, as functions of three non-dimensional system parameters: the rise to chord length ratio, the span length to chord length ratio, and the slenderness ratio. Also typical mode shapes of vibrating arches are presented.

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The Instability Behavior of Shallow Sinusoidal Arches(1) : Classification of Static Buckling According to Shape Characteristics (얕은 정현형 아치의 불안정 거동에 관한 연구(1) : 형상특성에 따른 정적좌굴의 분류)

  • 김승덕;박지윤;권택진
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.12 no.3
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    • pp.407-415
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    • 1999
  • There are two kinds of instability phenomena for shell-type structures which are snap-through and bifurcation buckling. These are very sensitive according to the shape characteristics including rise-span ratio and especially shape initial imperfection. In this study, the equilibrium path of shallow sinusoidal arches supported by hinges at both ends is investigated to grasp the instability behavior of shell-type structures with initial imperfection. The Galerkin method is used to get the nonlinear discretized equation of governing differential equation considering geometric nonlinearity of arches and the perturbation method is also used to transform the nonlinear equation to incremental form.

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ANALYSIS OF MULTPLE SHELL STRUCTURES SUBJECTED TO LATERAL LOADS (횡력을 받는 합성 쉘 구조의 해석)

  • 이평수
    • Computational Structural Engineering
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    • v.2 no.2
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    • pp.73-83
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    • 1989
  • A computer program, MSSLL, was developed for the analysis of the "Multiple Shell Subjected to Lateral Loads" by utilizing 2-dimensional finite elements in a 3-dimensional global assemblage with 6 DOF at each nodal point. In this program, substructuring procedure with frontal solver was introduced in the solution procedure to save both human and computer resource when the whole structure consists of repeated identical substructures. Some of the results obtained by MSSLL were compared with the existing solutions by other methods. The effect of rise to span-length ratio was investigated for the behavior of the multiple conical shell with 8 substructures subjected to seismic loads by performing a parametric study.

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A Study on the Buckling Characteristics of Double-Layer Latticed Domes whose Boundary Configuration are Elliptical (경계부 형상이 타원형인 복층 래티스 돔의 좌굴 특성에 관한 연구)

  • Seo, Young-Ill;Kwun, Ik-No;Kwun, Taek-Jin
    • Journal of Korean Association for Spatial Structures
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    • v.2 no.3 s.5
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    • pp.71-79
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    • 2002
  • The purpose of this paper is to study the buckling characteristics of elliptical latticed domes under conservative loading conditions. The latticed domes are usually designed in geometrically spherical shape. For this type of latticed domes, many researchers have researched and even the simplified estimation codes for the buckling load level have been available. However, geometrically elliptical latticed domes have been often constructed, and show different buckling characteristics following with geometrical parameters as rise-to-span ratio and so on. Therefore, it is necessary to investigate the general tendency of buckling characteristics of the elliptical latticed domes. In this paper, to find out some buckling characteristics of elliptical latticed domes, height, boundary configuration and gap are used as the shape coefficients. For each model with different parameters, the eigen values and the buckling loads are evaluated.

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The Regularization Algorithm of Configuration for Geodesic Borne (지오데식 돔의 형상 균일화 알고리즘)

  • 한상을;이효천;이지연
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2003.10a
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    • pp.340-347
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    • 2003
  • The aim of regularization of a structural configuration is to obtain a structure that consists of elements with identical or nearly identical length. And it is also possible to modify the configuration in a manner that the size of the elements vary in accordance with a specified pattern. For practical purpose, geodesic dome is cut off at a suitable place in order to make it fit on horizontal. Inevitably this pattern effects a change of element lengths. The purpose of this study is to verify a method for regularization of structural configuration by genetic algorithms and modify the element lengths of the dome. As a result of regularization of domes with various rise-span ratio, modified configurations have more regular element lengths and are more economical than initial configurations.

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A Study on the Variation of Streambeds Surrounding the Piers according to the Established Patterns of Hydraulic Structures (수공구조물 설치 형태에 따른 교각주변의 하상변동에 관한 연구)

  • Ahn, Seung-Seop;Moon, Sang-Cheol;Lee, Hyo-Jung;Song, In-Ryeol
    • Proceedings of the Korea Water Resources Association Conference
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    • 2009.05a
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    • pp.714-717
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    • 2009
  • As part of a new riverside development project, various types of bridges and covering bridges were constructed in natural river estuary; and these structures got in the way of the flow of the river, which has resulted in a topographical change in natural river estuary, decrease in the gross sectional area of flow, and rise of water level. As a result, surrounding areas are suffering from damages due to overflowing of river over the bank. This study was designed to provide basic data for efficient design of structures, by examining resistance and characteristics in the surrounding areas of bridges based on changes in the span length ratio.

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