• Steel and Composite Structures
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• v.24 no.3
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• pp.339-349
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• 2017

In this paper, a conventional refined plastic hinge analysis is improved to account for the effects of local buckling and lateral-torsional buckling. The degradation of flexural strength caused by these effects is implicitly considered using practical LRFD equation. The second-order effect is captured using stability functions to minimize modeling and solution time. An incremental-iterative scheme based on the generalized displacement control method is employed to solve the nonlinear equilibrium equations. A computer program is developed to predict the second-order inelastic behavior of space steel frames. To verify the accuracy and efficiency of the proposed program, the obtained results are compared with the existing results and those generated using the commercial finite element package ABAQUS. It can be concluded that the proposed program proves to be a reliable and effective tool for daily use in engineering design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.10
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• pp.1598-1608
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• 1997

Based on the application of te theory of conjugate approximations and the Loubignac's iterative method in a local region, a method to improve the stress filed in a displacement-formulated finite element solution has been proposed. The validity of the proposed method has been tested through two examples : a thick cylinder under internal pressure loading and an infinite plate with a central circular hole subjected to uniaxial tension. As a result of analysis of the examples, it was found that the stress field obtained for the local region model by the proposed method approximates well for the whole domain model. In addition, it was found that because of a significant decrease in the computing time to obtain the improved stress field, the proposed method is efficient and useful for the detailed stress analysis in local regions.

• Structural Engineering and Mechanics
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• v.80 no.6
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• pp.737-747
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• 2021

The objective of seismic resilience is to maintain or rapidly restore the function of a building after an earthquake. An efficient tilt mechanism at the member level is crucial for the restoration of the main structure function; however, the damage resistance of the members should be the main focus. In this study, through a comparison with the classical Flamant theory of local loading in the elastic half-space, an elastomechanical solution for the axial-stress distribution of a reinforced-concrete (RC) rocking column was derived. Furthermore, assuming that the lateral displacement of the rocking column is determined by the contact surface rotation angle of the column end and bending and shear deformation of the column body, the load-lateral displacement mechanical model of the RC rocking column was established and validated through a comparison with finite-element simulation results. The axial-compression ratio and column-end strength were analyzed, and the results indicated that on the premise of column damage resistance, simply increasing the axial-compression ratio increases the lateral loading capacity of the column but is ineffective for improving the lateral-displacement capacity. The lateral loading and displacement of the column are significantly improved as the strength of the column end material increases. Therefore, it is feasible to improve the working performance of RC rocking columns via local reinforcement of the column end.

• Structural Engineering and Mechanics
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• v.63 no.2
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• pp.251-257
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• 2017

A local damage identification method using measured structural static displacement is proposed in this study. Based on the residual force vector deduced from the static equilibrium equation, residual strain energy (RSE) is introduced, which can localize the damage in the element level. In the case of all the nodal displacements are used, the RSE can localize the true location of damage, while incomplete displacement measurements are used, some suspicious damaged elements can be found. A model updating method based on static displacement response sensitivity analysis is further utilized for accurate identification of damage location and extent. The proposed method is verified by two numerical examples. The results indicate that the proposed method is efficient for damage identification. The advantage of the proposed method is that only limited static displacement measurements are needed in the identification, thus it is easy for engineering application.

• Journal of Aerospace System Engineering
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• v.15 no.6
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• pp.1-9
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• 2021

In this study, a new design of an extension-type actuator (ExACT) is proposed based on a chevron structure with displacement amplification mechanisms by local heating. ExACT comprises diamond-shaped displacement amplification structures (DASs) containing axially oriented V-shaped chevron beams, a support bar that restricts lateral heat deformation, and a loading slot for thin-film heaters. On heating the thin film heater, the diamond-shaped DASs undergo thermal expansion. However, lateral expansion is restricted by the support bar, leading to displacement amplification in the axial direction. The performance parameters of ExACT such as temperature distribution and extended displacement is calculated using thermo-mechanical analysis methods with the finite element method (FEM) tool. Subsequently, the ExACTs are fabricated using a polymer-based 3D printer capable of reproducing complex structures, and the performance of ExACTs is evaluated under various temperature conditions. Finally, the performance evaluation results were compared with those of the FEM analysis.

• Korean Journal of Applied Biomechanics
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• v.14 no.2
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• pp.139-152
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• 2004

Two subjects, an expert and a novice, were carefully selected based upon their foot speed. Three dimensional videography was used in the assessment of roundhouse kicking of the Tae-kwon-Do. The local reference frames were imbedded at the trunk, pelvis, thigh and shank. Anatomical angular displacement at the joints were measured by projecting the upper segment's local axes to the lower segment's local reference planes. The local axes again projected to the global reference frames and absolved each segment's movement. The peaks of the anatomical angular displacement curve assessed as the countermovements and the angular movements of the segments in the global space absolved in light of the occurrence of the countermovements. The expert showed larger and more countermovements than the novice at the all segments. The counterrnovement occured more clearly at the trunk than the hip and knee joint and during the preparative movement phase. These countermovements occurrence were due to either by turning upper or lower segments and controlled by the turning direction and sequence of the two nearby segments. It was revealed that the countermovements of the trunk during the preparative movement phase was the important factor of the power kicking.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.13-18
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• 2013

Experimental studies were carried out to investigate the interactions between the propagating flame fronts and different multiple obstacles within an explosion chamber. The explosion chamber is 600 mm in height, $700{\times}700mm^2$ in cross-section and has a H/L value of 0.86. Three different multiple obstacles with the blockage ratio of 0.43 were replaced within the chamber. The results showed that relatively higher local flame displacement speed was observed with the triangular obstacle while the lower was observed with the circular one. It was found that the local flame displacement speeds behind the obstacle were largely dependent on the obstacle types. It was also found that as the flame interacted with the flow field generated behind the obstacle, the probability density functions(PDFs) of the local flame displacement speed were extensively distributed toward higher speeds.

• Structural Engineering and Mechanics
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• v.13 no.2
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• pp.135-154
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• 2002

This paper presents the convected material frame approach to study the nonlinear behavior of inelastic frame structures. The convected material frame approach is a modification of the co-rotational approximation by incorporating an adaptive convected material frame in the basic definition of the displacement vector and strain tensor. In the formulation, each discrete element is associated with a local coordinate system that rotates and translates with the element. For each load increment, the corresponding strain-displacement and nodal force-stress relationships are defined in the updated local coordinates, and based on the updated element geometry. The rigid body motion and deformation displacements are decoupled for each increment. This modified approach incorporates the geometrical nonlinearities through the continuous updating of the material frame geometry. A generalized nonlinear function is used to derive the inelastic constitutive relation and the kinematic hardening is considered. The equation of motion is integrated by an explicit procedure and it involves only vector assemblage and vector storage in the analysis by assuming a lumped mass matrix of diagonal form. Several numerical examples are demonstrated in close agreement with the solutions obtained by the ANSYS code. Numerical studies show that the proposed approach is capable of investigating large deflection of inelastic planar structures and providing an excellent numerical performance.

• Korean Journal of Construction Engineering and Management
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• v.24 no.2
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• pp.70-78
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• 2023

Inclinometer has several problems of 1)difficulty installing inclinometer casing, 2) measuring 2D local lateral displacement of retaining wall, 3) measurement by manpower. To solve such problems, a 2D LiDAR sensor-based retaining wall displacement measurement system was developed in previous studies. The purpose of this study is to select a displacement analysis algorithm to be applied in the retaining wall displacement measurement system. As a result of the displacement analysis algorithm selection, the M3C2 (Multiple Model to Model Cloud Comparison) algorithm with a displacement estimation error of 2mm was selected as the displacement analysis algorithm. If the M3C2 algorithm is applied in the system and the reliability of the displacement analysis result is secured through several field experiments. Convenient management of the displacement for the retaining wall is possible in comparison with the current measurement management.

• Journal of Korea Multimedia Society
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• v.17 no.8
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• pp.937-945
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• 2014

Multi-modal biometric system can use another biometric trait in the case of having deficiency at a biometric trait. It also has an advantage of improving the performance of personal identification by using multiple biometric traits, so studies on new biometric traits have continuously been performed. The inner face of finger is a relatively new biometric trait. It has two major features of knuckle lines and wrinkles, which can be used as discriminative features. This paper proposes a finger identification method based on displacement vector to effectively process some variation appeared in contactless hand image. At first, the proposed method produces displacement vectors, which are made by connecting corresponding points acquired by matching each pair of local block. It then recognize finger by measuring the similarity among all the detected displacement vectors. The experimental results using pubic CASIA hand image database show that the proposed method may be effectively applied to personal identification.