• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.745-749
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• 2001

The rigid body properties of a structure may be estimated easily if the mass-line of the structure could be taken exactly. However, the exact mass-line cannot be obtained experimentally. In the past years, the modal analysis for which the structure is mounted on the flexible supporter is frequently used to acquire the mass-line. Unfortunately, it is difficult not only to mount the structure but also to decouple the coupled 6 dof mode. If the structure is pended by very long and flexible rope to act free, the rigid-body modes influenced by the rope will be eliminated and the improved mass-line will be obtained. In this paper, the method using the mass-line of F.R.F. for rigid body in free-condition is suggested. The robustness of the suggested method was tested and verified numerically. The experimental results also showed a good agreement with the true value.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.5
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• pp.67-77
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• 2022

Recently, the trend in structural analysis and design is moving towards the development of reliable system. The reliability-based method defines various limit states related to usability and failure, thereby enabling multiple levels of design according to the importance of a structure. Meanwhile, an actual structure is composed of a set of several elements, and particularly, a frame type is composed of a system in which the members are connected each other. At this time, the actual connection between members is in a semi-rigid condition, not in complete rigid or hinged. This semi-rigid is found in several structures, especially in agricultural facilities designed with lightweight materials. In this study, a system reliability analysis technique for frame structure was established, and applied to an analysis of the semi-rigid connection. Various conditions of correlation were applied to reflect the connectivity between members, and through this, the limitations of existing structural analysis method and the behavioral characteristics of structure were analyzed. The failure probability of the frame member component and the overall structure system was significantly different in consideration of the semi-rigid connection. In addition, it was evaluated that the behavior of structure can be more accurately analyzed if the correlation according to the position of members in a system is further investigated.

• Earthquakes and Structures
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• v.7 no.4
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• pp.415-448
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• 2014

A method is presented in this paper to analyze the dynamic response behavior of suspended building structures. The effect of semi-rigid connections that link suspended floors with their supporting structure on structural performance is investigated. The connections, like the restrains in non-structural suspended components, are designed as semi-rigid to avoid pounding and as energy dissipation components to reduce structural response. Parametric study is conducted to assess the dynamic characteristics of suspended building structures with varying connection stiffness and suspended mass ratios. Modal analysis is applied to identify the two distinct sets of vibration modes, pendulum and bearing, of a suspended building structure. The cumulative modal mass is discussed to ensure the accuracy in applying the method of response spectrum analysis by SRSS or CQC modal combination. Case studies indicate that a suspended building having semi-rigid connections and proper suspended mass ratios can avoid local pounding failure and reduce seismic response.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.1
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• pp.7-13
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• 2016

With the increasing running speed of trains, new railway lines in metropolitan areas, and the rising demand for green transportations, the number of underground and tunnel sections are constantly becoming larger, and installations of overhead rigid conductor systems are becoming wider. However, domestic commercial products for overhead rigid conductors are limited to 120 km/h train speeds. In this study, to develop a high-speed (250 km/h) overhead rigid conductor, R-Bar (Rigid Bar), the electrical and mechanical stability was enhanced through the improvement of the cross sectional shape of the R-Bar; the transition structure was also designed for flexibility and natural frequency isolation. In addition, the evaluation of contact forces between a pantograph and the overhead rigid conductor system for 250 km/h train speeds was performed using dynamic analysis.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1557-1568
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• 2015

The nonlinear static analysis of structure, which is under the effect of lateral loads and provides the capacity curve of the structure, is defined as a push-over analysis. Ordinarily, by using base shear and the lateral displacement of target point, the capacity curve is obtained. The speed and ease of results interpretation in this method is more than that of the NRHA responses. In this study, the nonlinear static analysis is applied on the semi-rigid steel gabled frames. It should be noted that the members of this structure are analyzed as a prismatic beam-column element in two states of semi-rigid connections and supports. The gabled frame is modeled in the OpenSees software and analyzed based on the displacement control at the target point. The lateral displacement results, calculated in the top level of columns, are reported. Furthermore, responses of the structure are obtained for various support conditions and the rigidity of nodal connections. Ultimately, the effect of semi-rigid connections and supports on the capacity and the performance point of the structure are presented in separated graphs.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.239-246
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• 1996

Very stiff floor system in a residential-commercial building causes some problems in the numerical analysis procedure due to significant difference in stiffness with adjacent structural elements. Static analysis of structure with a stiff transfer-floor can be peformed approximately in two steps for upper and lower pons for the structure. However, it is impossible to perform dynamic analysis in two steps with separate models. An efficient method for dynamic analysis of a structure with a rigid floor system is proposed in this study. The matrix condensation technique is employed to reduce the degree of freedom for upper and lower parts of the structure and a beam elements with rigid bodies of both ends are introduce to model the rigid floor system. Efficiency end accuracy of the proposed method ore verified through analysis of several example structures.

• The Journal of Korea Robotics Society
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• v.17 no.2
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• pp.209-215
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• 2022

In this paper, a forearm Mechanism design inspired by ligamentous structure of the human body is proposed. The proposed mechanism consists of four rigid bodies and fourteen wires without any mechanical joints. Actually, the mechanism is based on the concept of the tensegrity structure. Therefore, the proposed mechanism has inherently compliant characteristics due to the flexibility of the wires composing the structure. Rigid bodies and wires of the mechanism mimic bones and major ligaments in the forearm of the human. The proposed mechanism is classified as one of the interconnected hybrid flexure systems. The analysis method of the degree of freedom (DOF) of the proposed mechanism is also introduced through analyzing technique of the interconnected hybrid flexure systems, in this paper. Ultimately, the proposed mechanism, whose structure is complicated with rigid bodies and wires, mathematically drives that it has 3-DOFs.

• Steel and Composite Structures
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• v.8 no.4
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• pp.265-280
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• 2008

An investigation on the combined effect of foundation type, foundation flexibility, axial load and PR (semi-rigid) connections on the natural frequencies of steel frames is presented. These effects were investigated using a suitable modified FE program for cases where the foundation flexibility, foundation connectivity, and semi-rigid connections could be treated as equivalent linear springs. The effect of axial load on the natural frequency of a structure was found to be significant for slender structures subjected to high axial loads. In general, if columns of medium slenderness are designed without consideration of axial load effects, the frequency of the structure will be overestimated. Studies on the 3-story Los Angeles PR SAC frame indicate that the assumption of rigid connections at beam-column and column-base interfaces, as well as the assumption of a rigid foundation, can lead to significant errors if simplified design procedures are used. These errors in an equivalent static analysis are expected to lead to even more serious problems when considering the effect of higher modes under a non-linear dynamic analysis.

• Journal of Korean Society of Steel Construction
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• v.12 no.4 s.47
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• pp.375-385
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• 2000

The required connection ductility has been evaluated, considering geometric, material and connection nonlinearity, for 6-story unbraced and 20-story braced steel structures subjected to ultimate lateral load. For material nonlinearity, section moment-curvature relationship and member stiffness matrix have been derived utilizing fiber model and linear flexibility distribution model. In 6-story structure with semi-rigid connections for rigid connection, the required connection ductility is less than that for rigid connection. In 20-story structure, the required connection ductility for semi-rigid connection is almost the same as that for shear connection and the required ductility for rigid connection is larger than that for semi-rigid or shear connection.

• Bulletin of the Korean Chemical Society
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• v.20 no.3
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• pp.285-290
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• 1999

In the present paper, we report a molecular dynamics (MD) simulation study for the structure and dynamics of H+ ions in non-rigid dehydrated H12-A zeolite framework at 298.15 K, using the same method we used in our previous studies of rigid and non-rigid zeolite-A frameworks. It is found that two different structures appear, depending on the choice of the Lennard-Jones parameter (σ) for the H+ ion, as is also observed in the study of rigid dehydrated H12-A zeolite framework, but the ranges of σ are different for the two structures. It is also found that some of the H+ ions exchanged their sites without changing the number of H+ ions at each site. The agreement between experimental and calculated structural parameters for non-rigid dehydrated H12-A zeolite is generally quite good. The calculated IR spectrum by Fourier transform of the total dipole moment auto-correlation function shows two major peaks, one around 2700 cm-1 and the other around 7000 cm-1. The former appears in the calculated IR spectra of non-rigid zeolite-A framework only system and the latter remains unexplained except, perhaps, as an indication of a new formation of a vibrational mode of the framework due to the adsorption of the H+ ions.