• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.12
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• pp.1077-1085
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• 2016

Linear roller bearing (LRB) is an important mechanical element that is widely used in precise positioning systems that are subjected to large loads. This paper presents a new model for estimating the displacement of an LRB subjected to external forces. For this purpose, assuming that the linear motion block (LM block) is rigid, the equilibrium conditions for the LRB were obtained by solving the equilibrium equations of the rollers and the rigid LM block using the iterative Newton-Raphson method. The contact loads between the rollers and raceways were determined considering the profiled rollers. Then, the structural deformations of the LM block, subjected to the contact loads from the rigid LM block model, were computed using a finite element model for the LM block. The displacements of the LRB were then determined by superposition of the rigid LM block displacements on the induced displacements due to the structural deformations of the LM block. The proposed method was verified through comparison with a program by the bearing manufacturer.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.49-57
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• 2019

Recently, the use of deep deck plate has been increased in various structures, such as underground parking lots, logistics warehouses, because it can reduce construction periods and labor costs. In this study, a newly developed Double Deck (D-deck) plate which can leads to save story heights has been introduced, and experimental tests on a total of five D-deck plates under construction loads have been carried out to investigate their structural performance at construction stage. The loads were applied by sands and concrete to simulate the actual distributed loading conditions, and the vertical deflection of D-Deck and the horizontal deformation of web were measured and analyzed in detail. As a result, it was confirmed that all the D-decks showed very small vertical deflection of less than 5.34 mm under construction loads, which satisfies the maximum deflection limit of L / 180. In addition, the D-Deck plate was found to have a sufficient rigidity to resist construction loads in a stable manner.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.8
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• pp.905-911
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• 2012

To establish a floating offshore wind turbine simulation model, a tension leg platform is added to an onshore wind turbine. The wind load is calculated by using meteorological administration data and a power law that defines the wind velocity according to the height from the sea surface. The wind load is applied to the blade and wind tower at a regular distance. The relative Morison equation is employed to generate the wave load. The rated rotor speed (18 rpm) is applied to the hub as a motion. The dynamic behavior of a 2-MW floating offshore wind turbine subjected to the wave excitation and wind load is analyzed. The flexible effects of the wind tower and the blade are analyzed. The flexible model of the wind tower and blade is established to examine the natural frequency of the TLP-type offshore wind turbine. To study the effect of the flexible tower and blade on the floating offshore wind turbine, we modeled the flexible tower model and flexible tower-blade model and compared it with a rigid model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.5
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• pp.487-495
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• 2012

The yaw control, a major part of the wind turbine, is closely related to the efficiency of electric power production and the mechanical load. The yaw error, which results from the nacelle not being appropriately aligned in the wind direction, not only decreases the power output but also reduces the lifetime of the wind turbine as a result of large fatigue loads. However, the yawing rate cannot be increased indefinitely because of constraints on mechanical loads. This paper investigates the characteristics of an active yaw control system, the basic principle of the system, and mechanical loads around the yaw axis during yawing.

• Journal of Korean Society of Steel Construction
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• v.19 no.1
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• pp.129-137
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• 2007

In this study, the elastic out-of-plane buckling load and the effective length factor of X-bracing systems were studied. Points of the intersection of diagonals were modeled as a rigid connection or a pinned connection depending on the connection method of diagonals. The boundary condition of the intersection influences the buckling load of X-bracing systems. For each boundary condition of the intersection, effective out-of-plane length factors of X-bracing systems were derived as a function of the length ratio of tension and compression diagonals $L_P$/$L_T$, the applied force ratio of tension and compression diagonals T/P, and the Euler buckling load ratio of tension and compression diagonals $P_{ET}$/$P_{EP}$. The proposed effective out-of-plane length factors of X-bracing systems were compared with the results of previous researchers and those of the finite element analysis and their properties were verified. Finally, the effects of the boundary condition of the intersection on the out-of-plane buckling load of X-bracing systems were investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1187-1191
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• 2011

In this paper, the development of an adjustable load limiter is presented, which is a component of the seat belt. The adjustable load limiter is loaded at different levels for varied weights and heights of occupant. The recent regulation FMVSS 208 demands strict safety standards for different percentiles of dummy size. In this work, high- and low-level load conditions are proposed according to dummy scale and thoracic injury criteria. The suggested load conditions were verified by performing a sled test using the benchmark model. A dual-level load limiter has been developed on the basis of these tests. Experiments were conducted on the product performance, and finite element analysis was carried out; the results confirmed the points for improvement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3C
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• pp.105-111
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• 2012

Bucket foundations, which are used in the foundations of offshore wind turbines, should be able to withstand large amounts of horizontal and moment loads. Tripod bucket foundation, which combines three single buckets, has been used to increase horizontal and moment capacities. This study performed numerical analysis using ABAQUS (2010), to analyze the group effect and the bearing capacity of a tripod bucket in clay. Parametric studies were performed varying the bucket spacing ratio S/D (S=spacing between the centers of the bucket and the tower; D=diameter of the bucket) and depth ratio L/D (L=embedded length of skirt). The applied constitutive models were a linear elastic perfectly plastic model with Tresca yield criteria for normally consolidated clay and an elastic model for buckets. Loading in the vertical, horizontal, and moment directions was simulated with an increase in each movement at a reference point. The bearing behavior and the capacities of a single and a tripod bucket were compared. Capacity evaluation method of the tripod bucket was suggested using the capacity of a single bucket.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.4
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• pp.883-891
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• 1990

본 연구에서는 항공기 구조용 재료로서 널리 사용되고 고장력 7075-T73 알루 미늄합금을 준비하고, 균열깊이 a/W변화에 따른 단일과대하중후의 지연현상을 기준응 력확대계수범위 .DELTA.K$_{b}$ 및 과대하중비 %O.L. 과 함께 검토하였다.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.1
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• pp.78-85
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• 1992

This experiment was carried out to investigate the heritabilities, phenotypic correlation, genetic correlation and path-coefficients for desirable characters on the lodging related traits. Characters, that had high relation degree with field lodging degree, were rice-straw length, Wl /P, W/I, Wl /d, L, Wl / A, W/l, P, W $s^2$/ $l^4$ etc. Breaking strength appear negative correlation having an intention to field lodging. The second inertia moment of culm diameter trunk (branch), cross section area, rice-straw thickness and trunk cross section didn't appear negative coefficient with field lodging. It is considered that rice-straw length, leaf dry weight and lodging index, because of high heritability, become selection index of characters for breeding. In direct, indirect effect, and right rice-straw wall thickness appear largest( $P_{7y}$=0.6904), the next is the order of leaf dry weight( $P_{3y}$=0.2848), root dry weight ( $P_{1y}$=0.2658), culm diameter ( $P_{6y}$=-0.2280), and negative relation appear the order of rice-straw length ( $P_{5y}$=-0.9640) and stem dry weight( $P_{2y}$=-0.7072), therefore, the smaller culm length and stem dry weight, the stronger to lodging. to lodging.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6A
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• pp.625-639
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• 2009

Experimental and analytical studies are performed on the mechanical behavior of concrete-filled tubular(CFT) truss girders for different f/L ratios. Bending tests are conducted on two CFT truss girder specimens to determine fundamental structural characteristics such as the strength and deformation properties. Nonlinear material models for CFT members subjected to an axial compressive force are compared in this paper by using the nonlinear finite element program, ABAQUS. Previous researchers have proposed several nonlinear stress-strain models of confined concrete. In this study, the nonlinear analyses are performed applying several stress-strain models for confined concrete proposed by Mander, Sakino, Han, Susantha and Ellobody, and the results are compared with the experimental results in terms of load-deflection and load-strain relationships. Based on the comparisons of the load-deflection relationships, the models proposed by Mander and Susantha provide a maximum load about 12.0~13.8% higher and that by Sakino gives a maximum load about 7.6% higher than the experimental results. The models proposed by Han and Ellobody give a maximum load only about 0.2~1.2% higher than the test results, showing the best agreement among the proposed stress-strain models. However, the load-strain relations predicted by the existing models generally provide conservative results exhibiting larger strains than the experimental data.