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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Computational Structural Engineering Institute of Korea
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Journal DOI :
The Computational Structural Engineering Institute
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Volume & Issues
Volume 26, Issue 6 - Dec 2013
Volume 26, Issue 5 - Oct 2013
Volume 26, Issue 4 - Aug 2013
Volume 26, Issue 3 - Jun 2013
Volume 26, Issue 2 - Apr 2013
Volume 26, Issue 1 - Feb 2013
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Time-domain Elastic Full-waveform Inversion Using One-dimensional Mesh Continuation Scheme
Kang, Jun Won ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 213~221
DOI : 10.7734/COSEIK.2013.26.4.213
This paper introduces a mesh continuation scheme for a one-dimensional inverse medium problem to reconstruct the spatial distribution of elastic wave velocities in heterogeneous semi-infinite solid domains. To formulate the inverse problem, perfectly-matched-layers(PMLs) are introduced as wave-absorbing boundaries that surround the finite computational domain truncated from the originally semi-infinite extent. To tackle the inverse problem in the PML-truncated domain, a partial-differential-equations(PDE)-constrained optimization approach is utilized, where a least-squares misfit between calculated and measured surface responses is minimized under the constraint of PML-endowed wave equations. The optimization problem iteratively solves for the unknown wave velocities with their updates calculated by Fletcher-Reeves conjugate gradient algorithms. The optimization is performed using a mesh continuation scheme through which the wave velocity profile is reconstructed in successively denser mesh conditions. Numerical results showed the robust performance of the mesh continuation scheme in reconstructing target wave velocity profile in a layered heterogeneous solid domain.
Performance Evaluation of a Time-domain Gauss-Newton Full-waveform Inversion Method
Kang, Jun Won ; Pakravan, Alireza ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 223~231
DOI : 10.7734/COSEIK.2013.26.4.223
This paper presents a time-domain Gauss-Newton full-waveform inversion method for the material profile reconstruction in heterogeneous semi-infinite solid media. To implement the inverse problem in a finite computational domain, perfectly-matchedlayers( PMLs) are introduced as wave-absorbing boundaries within which the domain's wave velocity profile is to be reconstructed. The inverse problem is formulated in a partial-differential-equations(PDE)-constrained optimization framework, where a least-squares misfit between measured and calculated surface responses is minimized under the constraint of PML-endowed wave equations. A Gauss-Newton-Krylov optimization algorithm is utilized to iteratively update the unknown wave velocity profile with the aid of a specialized regularization scheme. Through a series of one-dimensional examples, the solution of the Gauss-Newton inversion was close enough to the target profile, and showed superior convergence behavior with reduced wall-clock time of implementation compared to a conventional inversion using Fletcher-Reeves optimization algorithm.
Installation Analysis of Multibody Systems Dynamics of an Offshore Wind Turbine Using an Offshore Floating Crane
Ku, Nam-Kug ; Ha, Sol ; Kim, Ki-Su ; Roh, Myung-Il ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 233~239
DOI : 10.7734/COSEIK.2013.26.4.233
Recently, a number of wind turbines are being installed due to the increase of interest in renewable, environment-friendly energy. Especially, an offshore wind turbine is being watched with keen interest in that it has no difficulty in securing a site and can get high quality of wind, as compared with a wind turbine on land. The offshore wind turbine is transferred to and installed on the site by an offshore floating crane after it was made in a factory on land such as shipyard. At this time, it is important to secure the safety of the turbine because of its huge size and expensive cost. Thus, a dynamic analysis of the offshore wind turbine which is connedted with the offshore floating crane was performed based on the multibody systems dynamics in this study. As a result. it is shown that the analysis can be applied to verify the safety of a method for the transportation and installation of the offshore wind turbine suspended by the crane.
Experimental Validation of Topology Design Optimization
Cha, Song-Hyun ; Lee, Seung-Wook ; Cho, Seonho ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 241~246
DOI : 10.7734/COSEIK.2013.26.4.241
From the numerical results of density-based topology design optimization, a CAD geometric model is constructed and fabricated using 3D printer to experimentally validate the optimal design. In the process of topology design optimization, we often experience checkerboard phenomenon and complicated branches, which could result in the manufacturing difficulty of the obtained optimal design. Sensitivity filtering and morphology methods are used to resolve the aforementioned issues. Identical volume fraction is used in both numerical and experimental models for precise validation. Through the experimental comparison of stiffness in various designs including the optimal design, it turns out that the optimal design has the highest stiffness and the experimental result of compliance matches very well with the numerical one.
Study on the Applicability of a New Multi-body Dynamics Program Through the Application to the Heave Compensation System
Ku, Nam-Kug ; Ha, Sol ; Roh, Myung-Il ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 247~254
DOI : 10.7734/COSEIK.2013.26.4.247
In this paper, dynamic response analysis of a heave compensation system is performed for offshore drilling operations based on multibody dynamics. With this simulation, the efficiency of the heave compensation system can be virtually confirmed before it is applied to drilling operations. The heave compensation system installed on a semi-submersible platform consists of a passive and an active heave compensator. The passive and active heave compensator are composed of several bodies that are connected to each other with various types of joints. Therefore, to carry out the dynamic response analysis, the dynamics kernel was developed based on mutibody dynamics. To construct the equations of motion of the multibody system and to determine the unknown accelerations and constraint forces, the recursive Newton-Euler formulation was adapted. Functions of the developed dynamics kernel were verified by comparing them with other commercial dynamics kernels. The hydrostatic force with nonlinear effects, the linearized hydrodynamic force, and the pneumatic and hydraulic control forces were considered as the external forces that act on the platform of the semi-submersible rig and the heave compensation system. The dynamic simulation of the heave compensation system of the semi-submersible rig, which is available for drilling operations with a 3,600m water depth, was carried out. From the results of the simulation, the efficiency of the heave compensation system were evaluated before they were applied to the offshore drilling operations. Moreover, the calculated constraint forces could serve as reference data for the design of the mechanical system.
Isogeometric Shape Design Sensitivity Analysis of Mindlin Plates
Lee, Seung-Wook ; Cho, Seonho ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 255~262
DOI : 10.7734/COSEIK.2013.26.4.255
In this paper, a shape design sensitivity analysis(DSA) method is presented for Mindlin plates using an isogeometric approach. The isogeometric method possesses desirable advantages; the representation of exact geometry and the higher order inter-element continuity, which lead to the fast convergence of solution as well as accurate sensitivity results. Unlike the finite element methods using linear shape functions, the isogeometric method considers the exact normal vector and curvature of the CAD geometry, taking advantages of higher order NURBS basis functions. A selective reduced integration(SRI) technique is incorporated to overcome the difficulty of 'shear locking' phenomenon. This simple technique is surprisingly helpful for the accuracy of the isogeometric shape sensitivity without complicated formulation. Through the numerical examples of plate bending problems, the accuracy of the proposed isogeometric analysis method is compared with that of finite element one. Also, the isogeometric shape sensitivity turns out to be very accurate when compared with finite difference sensitivity.
A Numerical Study on the Strain Based Monitoring Method for Lateral Structural Response of Buildings using FBG Sensors
Choi, Se Woon ; Park, Keunhyoung ; Kim, Yousok ; Park, Hyo Seon ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 263~269
DOI : 10.7734/COSEIK.2013.26.4.263
In this study, the strain based monitoring method to evaluate the lateral structural response of buildings is presented and an applicability of the proposed method is confirmed through the numerical study. It is assumed that the fiber Bragg grating(FBG) strain sensor is employed to measure the strain response of members due to the excellent properties such as multiplexing, and higher sampling frequency. These properties of FBG sensors is proper for buildings the a lot of sensors are required to monitor the reponses of those. FBG sensors measure the strain response of vertical members and are employed to calculate the curvatures of members using the measured strain responses. Then the lateral displacement, and lateral acceleration is evaluated based on the curvatures of vertical members. Additionally, these dynamic responses of buildings are used to evaluate the dynamic properties of buildings such as the natural frequencies and mode shapes using the frequency domain decomposition(FDD) method. Through the application of nine-story steel moment frame example structure, it is confirmed that the proposed method is appropriate to evaluate the lateral structural responses and dynamic properties of buildings.
Development of MEMS Inclinometer Sensor System
Ha, Dae Woong ; Kim, Jong Moon ; Park, Hyo Seon ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 271~274
DOI : 10.7734/COSEIK.2013.26.4.271
Inclinometer sensors are widely applied in many fields. Especially in the field of construction of high-rise buildings also measure the horizontal and vertical help has been applied to monitor. Recent micro electro-mechanical system(MEMS) technology with the development of the many sensors have been developed. In this paper, a MEMS inclinometer is based on a MEMS accelerometer. The sensor can measure the angle of inclination using the relationship between static acceleration and gravity acceleration from an accelerometer. From this principle, inclinometer has been developed that has more accurate. The accuracy is proved by the experiment with laser displacement. Results in the experiment express high-accuracy, stability and economics of MEMS inclinometer. In conclusion, wireless MEMS inclinometer sensor is expected to be applicable in the areas of construction and many other industries with accurate and convenient monitoring system.
A Study on the Scalability of Multi-core-PC Cluster for Seismic Design of Reinforced-Concrete Structures based on Genetic Algorithm
Park, Keunhyoung ; Choi, Se Woon ; Kim, Yousok ; Park, Hyo Seon ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 275~281
DOI : 10.7734/COSEIK.2013.26.4.275
In this paper, determination of the scalability of the cluster composed common personal computer was performed when optimization of reinforced concrete structure using genetic algorithm. The goal of this research is watching the potential of multi-core-PC cluster for optimization of seismic design of reinforced-concrete structures. By increasing the number of core-processer of cluster, decreasing of computation time per each generation of genetic algorithm was observed. After classifying the components in singular personal computer, the estimation of the expected bottle-neck phenomenon and comparison with wall-clock time and Amdahl's law equation was performed. So we could obseved the scalability of the cluster appear complex tendency. For separating the bottle-neck phenomenon of physical and algorithm, the different size of population was selected for genetic algorithm cases. When using 64 core-processor, the efficiency of cluster is low as 31.2% compared with Amdahl's law efficiency.
Thermal-Structure Interaction Parallel Fire Analysis for Steel-Concrete Composite Structures under Bridge Exposed to Fire Loading
Yun, Sung-Hwan ; Gil, Heungbae ; Lee, Ilkeun ; Kim, Wooseok ; Park, Taehyo ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 283~292
DOI : 10.7734/COSEIK.2013.26.4.283
The objective of this research is to evaluate of global and local damage for steel-concrete composite structures under highway bridge exposed to fire loading. To enhance the accuracy and efficiency of the numerical analysis, the proposed transient nonlinear thermal structure interaction(TSI) parallel fire analysis method is implemented in ANSYS. To validate the TSI parallel fire analysis method, a comparison is made with the standard fire test results. The proposed TSI parallel fire analysis method is applied to fire damage analysis and performance evaluation for Buchen highway bridge. The result of analysis, temperature of low flange and web are exceed the critical temperature. The deflection and deformation state show good agreement with the fire accident of buchen highway bridge.
Simplified Finite Element Model of an Anchor Bolt Inserted Through Concretes Considering Clamping Forces
Noh, Myung Hyun ; Lee, Sang Youl ; Park, Kyu Sik ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 293~300
DOI : 10.7734/COSEIK.2013.26.4.293
In this study we proposed a simplified finite element model of anchor bolt system inserted through concrete structures considering clamping forces. The three different finite element types using LS-DYNA are applied for numerical efficiency of the anchor bolt modeling. Combined beam and solid elements are used to reflect the tension state at internal part of anchor bolt due to torques. The clamping forces due to torques are considered by introducing a compression for a nut plane modeled by beam elements. The numerical examples show good agreement with different element types. Parametric studies are focused on the various effects of different element types on the induced axial and shear forces of anchor bolts considering clamping forces.
Accuracy Analysis of Parallel Method based on Non-overlapping Domain Decomposition Method
Tak, Moonho ; Song, Yooseob ; Jeon, Hye-Kwan ; Park, Taehyo ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 301~308
DOI : 10.7734/COSEIK.2013.26.4.301
In this paper, an accuracy analysis of parallel method based on non-overlapping domain decomposition method is carried out. In this approach, proposed by Tak et al.(2013), the decomposed subdomains do not overlap each other and the connection between adjacent subdomains is determined via simple connective finite element named interfacial element. This approach has two main advantages. The first is that a direct method such as gauss elimination is available even in a singular problem because the singular stiffness matrix from floating domain can be converted to invertible matrix by assembling the interfacial element. The second is that computational time and storage can be reduced in comparison with the traditional finite element tearing and interconnect(FETI) method. The accuracy of analysis using proposed method, on the other hand, is inclined to decrease at cross points on which more than three subdomains are interconnected. Thus, in this paper, an accuracy analysis for a novel non-overlapping domain decomposition method with a variety of subdomain numbers which are interconnected at cross point is carried out. The cause of accuracy degradation is also analyze and establishment of countermeasure is discussed.
Development of Abutment-H pile Connection for Large Lateral Displacements of Integral Abutment Bridges
Kim, Woo Seok ; Lee, Jaeha ; Park, Taehyo ;
Journal of the Computational Structural Engineering Institute of Korea, volume 26, issue 4, 2013, Pages 309~318
DOI : 10.7734/COSEIK.2013.26.4.309
Abutment-to-pile connection in an integral abutment bridge is vulnerable to lateral displacement induced by thermal movement of the superstructure. However, previous researches have merely focused on the connection. In order to improve the performance of the connection, new abutment-to-pile connection designs were proposed based on quasi-static nonlinear finite element model. The reinforcement detail specified in PennDOT DM4 and HSS tube were barely effective in controlling crack growing but spiral rebar effectively performed to delay crack growth as well as absorbing energy capacity. However, it was found that delaying cracking and strengthening the connection also caused the high lateral load in superstructures. Consequently, shape of HP pile were modified to introduce plastic hinge of the HP pile for reducing the lateral load in superstructures. Connections with modified HP pile significantly prevented crack propagations under the lateral displacement.