• Journal of Institute of Control, Robotics and Systems
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• v.19 no.10
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• pp.915-920
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• 2013

Payload capacity and transition ability are essential for climbing robots to apply the robots to various applications such as inspection and exploration. This paper presents a new climbing robotic platform with multi-link structure of track-wheel modules to enhance payload capacity and transition ability, and its tracking controller design and experimental results. The compliances between track-wheel modules achieve stable internal and external transitions while the large adhesion area of the track-wheel module enhances the payload capacity of the robot. Kinematic model-based tracking controller is designed and implemented for autonomous internal transition, and the gains of the controller are optimized by experimental design. Experiments on the automatic internal transitions are performed and the results guarantee autonomous internal transition with little tracking error.

• International Journal of High-Rise Buildings
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• v.3 no.4
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• pp.297-304
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• 2014

Recently, there have been some reported examples of structural collapse due to gravity, subsequent to damage from accident or an excitation that was not prepared for in the design process. A close view of new concepts, such as a redundancy and key elements, has been taken with the aim of ensuring the robustness of a structure, even in the event of an unexpected disturbance. The author previously proposed a sensitivity index of the vertical load carrying capacity to member disappearance for framed structures. The index is defined as the ratio of the load carrying capacity after a member or a set of an adjacent member disappears, to the original load carrying capacity. The member with the highest index may be regarded as a key element. The concept of bio-mimicry is being applied to various fields of engineering, and tree-shaped structures are sometimes used for the design of building structures. In this study a sensitivity analysis is applied to the irregular-framed structures such as tree-shaped structures.

• Steel and Composite Structures
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• v.13 no.3
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• pp.277-293
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• 2012

The interaction between steel tube and concrete core is the key design considerations for concrete-filled steel tube columns. In a concrete-filled steel tube (CFST) column, the steel tube provides confinement to the concrete core which permits the composite action among the steel tube and the concrete. Due to construction faults and plastic shrinkage of concrete, the debonding separation at the steel-concrete interface weakens the confinement effect, and hence affects the behaviour and bearing capacity of the composite member. This study investigates the axial loading behavior of the concrete filled circular steel tube columns with debonding separation. A three-dimensional nonlinear finite element model of CFST composite columns with introduced debonding gap was developed. The results from the finite element analysis captured successfully the experimental behaviours. The calibrated finite element models were then utilized to assess the influence of concrete strength, steel yield stress and the steel-concrete ratio on the debonding behaviour. The findings indicate a likely significant drop in the load carrying capacity with the increase of the size of the debonding gap. A design formula is proposed to reduce the load carrying capacity with the presence of debonding separation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.5
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• pp.119-125
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• 2017

In this paper, the characteristics and load carrying capacity of square pocket surfaces on a slider bearing are discussed for the thin film effect by the square pocket slider bearing. To study the lubrication, a Reynolds equation is used in this paper for the analysis of the slider bearing characteristics with square pocket surfaces. For numerical analysis, the central differencing scheme finite difference method is used. In a slider bearing with square pocket surfaces, the simulation dependent parameters such as pressure and load carrying capacity of the bearing can be acquired from the independent parameters, the slope of the slider bearing and number of pockets on the upper slider. These results can be acquired by the programmed softwar,e and they can be analyzed and stored in a sequential data file for later analysis. Furthermore, their pressure and load capacity distribution can be displayed easily by using the developed program with the Matlab GUI.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.12
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• pp.858-866
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• 2012

A numerical study was performed to predict the performance of a fin-and-tube condenser. A condenser model was developed and verified by comparing the simulation results with experimental data for a R410A condenser in a residential air-conditioning system. The prediction error was 0.07% and -5.77% for the condenser capacity and pressure drop, respectively. In simulation results, the capacity and pressure drop of the condenser with even air velocity distribution were 0.67% and 12.93% higher than those with uneven distribution of air velocity. It was predicted by the model that the refrigerant distribution at the condenser inlet to the two first passes was not significantly influenced by the air distribution. The simulation results presented that the 1.49% of capacity and 64.6% of pressure drop were reduced by replacing helical microfin tubes with smooth tubes for the condenser.

• YAKHAK HOEJI
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• v.33 no.2
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• pp.111-117
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• 1989

The optimum reaction conditions for the acid consuming capacity of aluminum silicate synthesized from the reaction of sodium silicate solution and potassium aluminum sulfate solution were investigated by Box-Wilson experimental design, and the micromeritic properties were examined by the means of BET $N_2$ adsorption, Hg penetrometer and methylen blue adsorption. The chemical composition of the samples were analyzed by gravitic method. The results were found to be as follows: optimum reaction temperature $54.7^{\circ}C$, both concentrations of reactant soln 15.7%, reactants molar ratio (Al/Si) 0.5 and drying temperature $65.0^{\circ}C$. The acid consuming capacity of the sample prepared by above optimum conditions was 68 ml and the chemical composition was $Al_2O_3{\cdot}3.6SiO_2{\cdot}3H_2O$. The relationship between acid consuming capacity and micromeritic properties could not found in the range of experiments. Therefore, it is assumed that the acid consuming mechanism of aluminum silicate depends on the neutralization of $Al_2O_3$ and buffer action of $SiO_2$ in sample.

• KIEAE Journal
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• v.10 no.5
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• pp.151-157
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• 2010

This study is connected with evaluation of the progressive collapse resisting capacity for sustainable RC super tall building design. As the progressive collapse is not considered in current design codes in Korea, differences between linear static and dynamic analysis based on the GSA guidelines was analyzed for better evaluation, and the analysis model of flat plate system was determined. Finally, the progressive collapse resisting capacity was evaluated for structural system of super tall building. According to this study, the results by linear dynamic analysis were underestimated than the results by linear static analysis. Thus, the dynamic coefficient value of 2 provides conservative approach. The Effective Beam Width's model, currently used in field, is useful for the analysis about lateral force, but this model does not consider the effect of load redistribution by the slab. Hence, finite element analysis considering slab element will be needed for progressive collapse resisting capacity of the flat plate system. Finally, analysis model of 80-story building designed based on KBC(Korea Building Code) shows the weakness against progressive collapse because the DCR value is over 2. Thus, the countermeasure for alternative loading path such as installment of spandrel beam and reinforcements around slab is required to prevent the progressive collapse.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.4
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• pp.3-13
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• 2018

Load bearing capacity of dowel type fasteners loaded perpendicular to the shear plane is determined based on Johansen's yield theory (Johansen, 1949). In case of inclined screws whose axis is no longer perpendicular, the ultimate load of connection increases because of additional axial withdrawal capacity. To calculate load bearing capacity for inclined screws, KBC2016 and Eurocode5 provide design equations using the combination of two effects; axial and bending strength. Although their equations have been validated for a long time, there is still minimal information how to apply them for concrete-CLT joints. Since there are not many test data available, engineers have to make certain assumptions and thus results may look inconsistent in practice. In this paper, authors would like to describe the current approach and assumptions indicated by KBC2016 and Eurocode 5 and how they match the experimental results in terms of shear strength of CLT-concrete connections. To fulfill the objective, several push-out tests were performed on nine different test specimens. Each specimen has different penetration angles and depths. By analyzing load-displacement curves, the maximum shear strength, stiffness, and ductility were obtained. Shear strength values were compared with the current design codes and theoretical equations proposed in this paper. Observations on stiffness and ductility were briefly discussed.

• Steel and Composite Structures
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• v.44 no.3
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• pp.339-351
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• 2022

A mortar-filled rectangular hollow structural section (RHS) can increase a structural section property as well as a compressive buckling capacity of a RHS member. In this study, the tensile performance of newly developed mortar-filled RHS members was experimentally evaluated with various connection details. The major test parameters were the type of end connections, the thickness of cap plates and shear plates, the use of stud bolts, and penetrating bars. The test results showed that the welded T-end connection experienced a brittle weld fracture at the welded connection, whereas the tensile performance of the T-end connection was improved by additional stud bolts inserted into the mortar within the RHS tube. For the end connection using shear plates and penetrating stud bolts, ductile behavior of the RHS tube was achieved after yielding. The penetrating bars increased load carrying capacity of the RHS. Based on the analysis of the load transfer mechanism, the current design code and test results were compared to evaluate the tensile capacity of the RHS tube according to the connection details. Design considerations for the connections of the mortar-filled RHS tubes were also recommended.

• Structural Engineering and Mechanics
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• v.88 no.1
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• pp.25-42
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• 2023

This paper presents a finite element (FE) simulation of eccentrically loaded lightweight aggregate concrete-encased steel (LACES) columns with H-shaped steel sections, analytical equations are also established to estimate the columns' axial and bending moment interaction capacities. The validity of the proposed models is checked by comparing the results with experimental data. Good agreements between the test and proposed models' results are found with acceptable agreements. Moreover, design parameters, including the lightweight aggregate concrete (LWAC) strength, eccentricity, column slenderness ratio, and confinement, are studied using the FE analysis, and their efficiency factors are discussed. The results show that the ultimate axial capacity of the LACES composite columns subjected to eccentric loading is negatively affected by the increase in the columns' height, but it is positively affected by the increase of the confinement. Increasing the eccentricity and columns' height reduced the columns'stiffness. In addition, the ultimate capacity of the LACES column is significantly influenced by the LWAC strength and eccentricity, where the ultimate capacity of the LACES column is significantly increased by increasing LWAC strength, and it is remarkably decreased by increasing the eccentricity. When the eccentricity changed from zero to 70 mm, the ultimate axial capacity and stiffness decreased by 67.97% and 63.56%, respectively.