• Steel and Composite Structures
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• v.49 no.5
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• pp.517-532
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• 2023

Tower structures have been widely used in communication and transmission engineering. The failure of joints is the leading cause of structure failure, which make it play a crucial role in tower structure engineering. In this study, the aluminum alloy three tube tower structure is taken as the prototype, and the middle joint of the tower was selected as the research object. Three different stainless steel-aluminum alloy composite joints (SACJs), denoted by TA, TB and TC, were designed. Finite element (FE) modeling analysis was used to compare and determine the TC joint as the best solution. Detail requirements of fasteners in the TC stainless steel-aluminum alloy composite joint (TC-SACJ) were designed and verified. In order to systematically and comprehensively study the mechanical properties of TC-SACJ under multi-directional loading conditions, the full-scale experiments and FE simulation models were all performed for mechanical response analysis. The failure modes, load-carrying capacities, and axial load versus displacement/stain testing curves of all full-scale specimens under tension/compression loading conditions were obtained. The results show that the maximum vertical displacement of aluminum alloy tube is 26.9mm, and the maximum lateral displacement of TC-SACJs is 1.0 mm. In general, the TC-SACJs are in an elastic state under the design load, which meet the design requirements and has a good safety reserve. This work can provide references for the design and engineering application of aluminum alloy tower structures.

• Journal of the Korea Safety Management & Science
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• v.14 no.4
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• pp.93-105
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• 2012

The purpose of this study was to investigate drivers' postures in different car pedal systems and skilled levels under fatigue. Twenty four subjects participated in this experiment. For three-dimensional analyses, six cameras (Proreflex MCU-240, Qualisys) were used to acquire raw data. The parameters were calculated and analyzed with Visual-3D. In conclusion, ROAs of two leg-pedal system were less than one leg pedal system by pattern analysis. Through statistical tests, skilled levels have effects on ROAs(X, Y, Z) of ankle joint at breaking a pedal and ROAs(Y, Z) of ankle joint at accelerating a pedal. Also, car pedal systems have effects on ROAs(Y, Z) of ankle joint, and ROA(Z) of knee joint at accelerating a pedal. In addition, skilled levels and car pedal systems (cross effects) have an effect on ROA(Z) of ankle joint. These findings suggested that we should improve a present single pedal system.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.738-743
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• 2006

Falling rocks are classed by the collapse to wide meaning. it is a kinds of earth disaster that has happen every year. Falling rocks are defined as blocks which had fallen from the cliff. It is caused by the relaxation of discontinuous structures like as a joint, a foliation, a bedding, and so on. Usually, the Relaxation of blocks from the rock face is happened by various kinds factors that are acted as a complex. Sometimes, the tree can be a factor of the weakness or relaxation of rock blocks and a cause of the falling rock.

• Structural Engineering and Mechanics
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• v.3 no.2
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• pp.135-144
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• 1995

Since structural systems may fail in any one of several failure modes, computation of system reliability is always difficult. A method using numerical quadrature for computing structural system reliability with either one or more than one failure mode is presented in this paper. Statistically correlated safety margin equations are transformed into a group of uncorrelated variables and the joint density function of these uncorrelated variables can be generated by using the Maximum Entropy Method. Structural system reliability is then obtained by integrating the joint density function with the transformed safety domain enclosed within a set of linear equations. The Gaussian numerical integration method is introduced in order to improve computational accuracy. This method can be used to evaluate structural system reliability for Gaussian or non-Gaussian variables with either linear or nonlinear safety boundaries. It is also valid for implicit safety margins such as computer programs. Both the theory and the examples show that this method is simple in concept and easy to implement.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.401-412
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• 2013

Multi-stage shear test has been performed using joint specimens of gneiss, granite and shale to investigate the influence of micro-scale asperity change on the shear strength of joint plane. For each shear test asperity degradation characteristics of joint specimens of different joint surface strength have been analyzed by utilizing the optimum asperity parameter which can reflect the sequential asperity degradation. Elevation of joint surface profile has been measured and both the changes of asperity parameters and micro-scale asperity distribution have been investigated. Two distinctive variation modes of cohesion and friction angle have been delineated and major cause of shear strength parameter change has been analyzed by considering the micro-scale asperity angle change resulting from the abrasion, fracturing and regeneration of micro-scale asperities. Effects of micro-scale asperity variation on the joint shear strength have been also investigated.

• Journal of the Korean Institute of Gas
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• v.21 no.5
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• pp.70-76
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• 2017

The standards related to the "Urban Gas Business Act" and the "Safety Control and Business Regulation of Liquefied Petroleum Gas Act" prescribe the separation distance between gas piping joint excluding welded joints and electric equipments(electric switch, watt meter, breaker, connector, etc). The "Korea Electro technical Regulation" also prescribes the distance between gas piping joints and electric equipments in accordance with the gas related standards. In case of the standards related to the "Urban Gas Business Act", the distance criteria stipulated in the standard of supplying facilities are different from those stipulated in the standard of using facilities. In this study, we have conducted pilot test on the possible ignition distance from the piping joint when LP gas is leaked from the point. We have also examined the adequacy of current standards on the separation distance between gas piping joint and electric equipments. As a result of the tests, we have found that ignition is able to occur at a distance of 30 cm as stipulated in the current standards or more when LP gas is leaked from the joint of the pipe. Therefore, we have made a decision that the criteria for separation distance between gas piping joint and electric equipment specified in the current standards related to the "Urban Gas Business Act" and the "Safety Control and Business Regulation of Liquefied Petroleum Gas Act" is appropriate.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.1
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• pp.51-56
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• 2007

The K-joint is one of the commonly applied element in offshore structures. Due to its structural configuration, the stress concentration occurs in the joint. Considering the important effect to the structural safety and the design optimization, a design guideline is strongly required. The main variables determining the configuration of K-joint including ${\alpha},\;{\beta},\;{\gamma},\;{\tau}$ and ${\theta}$ are closely investigated to find the individual effect to the Stress to K-joint. The maximum Stress of joint has been differed as per the variation of parameters. The parametric study has been numerically carried out and compare with the experimental data.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.33-38
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• 2022

As the intense heat continues, many cases of highway pavement blow up and bridge expansion joints damages have been inspected. Especially, Expansion joint closure of bridges is an important problem that can threat the safety of the bridge structure or reduce long-term durability. This paper proposed a structural analysis method for bridges having expansion joint closure and structural analysis was performed to verify the effects according to bridge types. Analysis bridges were divided into four types: concrete and steel bridges, shallow and piled foundations. To induce the situation of abutments and bridge decks are jammed, the following loads were additionally considered; lateral flow pressure, pavement expansion by alkali-aggregate reaction, creep settlement of backfill. The structural analysis method was verified by comparing the structural analysis results with the actually measured joint gap data. In addition, behavioral analysis due to joint closure was conducted to confirm the change in safety ratio by type of superstructure as the axial force increased.

• The Journal of Korea Robotics Society
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• v.3 no.4
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• pp.315-322
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• 2008

A new soft finger mechanism using a spring as a backbone is proposed in this work. It is a 4 DOF mechanism that consists of a spring and 3 cylinders, which behave like joints with 3 up-and-down rotations and 1 left-and-right rotation. To control each joint, cylinders have small holes in their cross-sectional areas, and wires of different length are penetrated into these holes. We can control each joint by pulling the corresponding wire. The forward kinematics is solved by using the geometry of mechanism. And the relationship (Jacobian) between the linear velocity of the wires and the joint angular rate is obtained. A virtual simulator is developed to test the validity of the kinematic model. In the experiment, first, the position control is conducted by tracking a given trajectory. Second, to verify the flexibility and safety, we show that the soft finger deflects in a safe manner, in spite of the collision with environment.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.92-95
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• 2004

This study proposes an industrial rehabilitation robot system which can exercise two joints in 3 dimensional spaces. The robot kinematics analysis and the results of studies on each joint for the rehabilitation robot could verify possibility of rehabilitation motion to exercise a joint. The force and torques sensor not only measures a rehabilitation performance of subjects between the abnormal limb and the manipulator, but also carries out an important function of safety device to prevent accidents. Also, limit sensors and emergency stop switch are used for high safety in this system. In this real test, the possibility of rehabilitation robot system is evaluated by C&R ARM I which is similar to upper-limb.