• Structural Engineering and Mechanics
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• 제10권6호
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• pp.603-619
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• 2000

Analysis of a framed structure for vertical vibration requires a lot of computational efforts because large number of degrees of freedom are generally involved in the dynamic responses. This paper presents an efficient modeling technique for vertical vibration utilizing substructuring technique and super elements. To simplify the modeling procedure each floor in a structure is modeled as a substructure. Only the vertical translational degrees of freedom are selected as master degrees of freedom in the inside of each substructure. At the substructure-column interface, horizontal and rotational degrees of freedom are also included considering the compatibility condition of slabs and columns. For further simplification, the repeated parts in a substructure are modeled as super elements, which reduces computation time required for the construction of system matrices in a substructure. Finally, the Guyan reduction technique is applied to enhance the efficiency of dynamic analysis. In numerical examples, the efficiency and accuracy of the proposed method are demonstrated by comparing the response time histories and the analysis time.

• 대한기계학회논문집
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• 제17권10호
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• pp.2457-2466
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• 1993

A simple method is presented for determining transient responses of locally nonlinear structures using substructure eigenproperties and Lagrange multiplier technique. Although the method is based upon the mode synthesis formulation procedure, the equations of the combined whole structure are not constructed compared with the conventional methods. Lagrange multi-pliers are used to enforce the conditions of geometric compatibility between the substructure interfaces and they are treated as external forces on each substructure itself. Substructure eigenvalue problem is defined with the substructure interface free of fixed. The transient analysis is based upon the recurrence discrete-time state equations and offers the simplicity of the Euler integration method without requiring small time increment and iterative solution procedure. Numerical examples reveal that the method is very accurated and efficient in calculating transient responses compared with the direct numerical integration method.

• Earthquakes and Structures
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• 제17권1호
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• pp.101-113
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• 2019

Earthquake-induced pounding is one of the major reasons for structural failure in earthquake prone cities. An accurate description of the pounding phenomenon of two buildings requires the consideration of systems with a large number of degrees of freedom including adequate contact impact formulations. In this paper, firstly, a node to surface formulation for the realization of state-of-the-art pounding models for structural beam elements is presented. Secondly, a hierarchical substructure technique is introduced, which is adapted to the structural pounding problem. The numerical accuracy and efficiency of the method, especially for the contact forces, are verified on an academic example, applying four different impact elements. Error estimations are carried out and compared with the classical modal truncation method. It is demonstrated that the hierarchical substructure method is indeed able to significantly speed up the numeric integration procedure by preserving a required level of accuracy.

• 소음진동
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• 제7권6호
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• pp.993-1000
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• 1997

This paper presents a new technique of mathematical treatment using a finite element model for analyzing the vibration of the towed line array. Since the towed line array has the axisymmetricity, axisymmetric elements are used in finite element modeling for the towed array structure. The fluid-structure interaction is also considered. The array consists of a series of identical substructures which can include internal structures such as spacers, hydrophones and ropes. That periodicity of substrucutres permits the substructure synthesis technique using characteristic wave guide for analyzing the response of towed array system. This synthesis technique can reduce the cost of computing the array response. It is suggested that a response of towed array can be computed by the finite element method and substructure synthesis technique using wave guide. Several experiments for towed array were performed to verify the present computation technique. The predicted vibration for the towed array shows good agreement with the measured result.

• 전산구조공학
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• 제7권3호
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• pp.143-152
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• 1994

슈퍼요소를 이용한 구조해석은 항공기나 선박등 대형구조물의 해석에서 장점을 가지며 하드웨어의 제한된 조건속에서 효과적인 결과를 준다. 본 논문에서는 고정된 타이벡(ite back) 상태에서 세게 최대의 5000톤, 회전 상태에서 3000톤을 들어 올릴수 있는 크레인선의 구조 안전성 검토를 위하여 슈퍼요소로 분할된 부분 구조물 해석을 다루었으며, 효과적인 부분구조화(substructuring)과정과 독특한 하중추출방법 및 유한요소 모델링 기법을 제시하고 있다. 또한 해석결과에 근거한 실질적인 구조물의 총괄적 국부보강방법을 보여주고 있다. 대형 크레인선의 구조해석적용 연구를 통하여 부분구조기법의 효율성을 확립하였으며 이러한 해석기법을 통하여 새로운 형태의 유사한 구조물에 대한 해석지침을 제시하고 있다.

• The Journal of Advanced Prosthodontics
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• 제6권4호
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• pp.253-258
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• 2014

PURPOSE. To compare marginal and internal gaps of zirconia substructure of single crowns with those of three-unit fixed dental prostheses. MATERIALS AND METHODS. Standardized Co-Cr alloy simulated second premolar and second molar abutments were fabricated and subsequently duplicated into type-III dental stone for working casts. After that, all zirconia substructures were made using $Lava^{TM}$ system. Marginal and internal gaps were measured in 2 planes (mesial-distal plane and buccal-palatal plane) at 5 locations: marginal opening (MO), chamfer area (CA), axial wall (AW), cusp tip (CT) and mid-occlusal (OA) using Replica technique. RESULTS. There were significant differences between gaps at all locations. The $mean{\pm}SD$ of marginal gap in premolar was $43.6{\pm}0.4{\mu}m$ and $46.5{\pm}0.5{\mu}m$ for single crown and 3-unit bridge substructure respectively. For molar substructure the $mean{\pm}SD$ of marginal gap was $48.5{\pm}0.4{\mu}m$ and $52.6{\pm}0.4{\mu}m$ for single crown and 3-unit bridge respectively. The largest gaps were found at the occlusal area, which was $150.5{\pm}0.5{\mu}m$ and $154.5{\pm}0.4{\mu}m$ for single and 3-unit bridge premolar substructures respectively and $146.5{\pm}0.4{\mu}m$ and $211.5{\pm}0.4{\mu}m$ for single and 3-unit bridge molar substructure respectively. CONCLUSION. Independent-samples t-test showed significant differences of gap in zirconia substructure between single crowns and three-unit bridge (P<.001). Therefore, the span length has the effect on the fit of zirconia substructure that is fabricated using CAD/CAM technique especially at the occlusal area.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1993년도 춘계학술대회논문집; 한국과학연구소, 21 May 1993
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• pp.52-56
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• 1993

An efficient method is presented for determining transient responses of locally nonlinear structures using substructure eigenproperties and Lagrange multiplier technique. The method is based upon the mode synthesis formulation procedure, but does not construct the equations of motion of the combined whole structure compared with the conventional methods. For modal bases of each linear substructure, either fixed or free interface modes can be employed. The transient analysis is based upon the recurrence discrete-time state equations and offers the simplicity of the Euler integration method without requiring small time increment and iterative solution procedure. Numerical examples reveal that the method is very accurate and efficient in calculating transient responses compared with the direct numerical integration method.

• Structural Engineering and Mechanics
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• 제88권3호
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• pp.263-271
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• 2023

Base isolation is a widely used technique for the seismic control of structures as it reduces the structural seismic demand. However, displacement of the isolation layer is not economically feasible in congested urban areas. To resolve the issue, an innovative system is proposed here to isolate both horizontally at the base and vertically in the upper portion of the structure. A simplified linear three degree-of-freedom (3DOF) model of the system that considers the mass and stiffness ratios of the substructure has been introduced and analyzed in MATLAB by spectrum analysis. The 3DOF model results revealed that, when the period of the soft substructure reaches 2.5 times that of the stiff substructure, the isolation and the lower substructure responses decrease by 65% and 51%, respectively. Time-history analysis of a MDOF system at three frequency ratios under a wide range of ground motions indicated that, at the expense of accepting a certain large drift by the soft substructure in the upper portion of the structure, base isolation displacement can be decreased by 10%.

• The Journal of Advanced Prosthodontics
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• 제2권3호
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• pp.65-70
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• 2010

Large oro-facial defects result from cancer treatment consequences in serious functional as well as cosmetic deformities. Acceptable cosmetic results usually can be obtained with a facial prosthesis. However, retention of a large facial prosthesis can be challenging because of its size and weight. This article describes prosthetic rehabilitation of a 57-year-old man having a right lateral mid-facial defect with intraoral-extraoral combination prosthesis. A modified technique to fabricate a hollow substructure in heat-polymerizing polymethyl-methacrylate to support silicone facial prosthesis was illustrated. The resultant facial prosthesis was structurally durable and light in weight facilitating the retention with magnets satisfactorily. This technique is advantageous as there is no need to fabricate the whole prosthesis again in case of damage of the silicone layer because the outer silicone layer can be removed and re-packed on the substructure if the gypsum-mold is preserved.

• 한국생산제조학회지
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• 제18권4호
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• pp.355-361
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• 2009

In this paper, an analysis technique is presented for performing the effective design of bus structure. Sensitivity analysis is carried out for the natural frequency of component structures consisting of bus B.I.W. Local vibration modes of substructure, which large affect on the global vibration mode of the bus B.I.W., are obtained through the sensitivity analysis technique using the mathematical chain rule. And also the design variables, which are determined from the sensitivity analysis, are redesigned through optimum design process. The proposed analysis technique shows that the bus structure can be effectively designed considering the vibration characteristics.