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Strength prediction of rotary brace damper using MLR and MARS

  • Mansouri, I.;Safa, M.;Ibrahim, Z.;Kisi, O.;Tahir, M.M.;Baharom, S.;Azimi, M.
    • Structural Engineering and Mechanics
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    • v.60 no.3
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    • pp.471-488
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    • 2016
  • This study predicts the strength of rotary brace damper by analyzing a new set of probabilistic models using the usual method of multiple linear regressions (MLR) and advanced machine-learning methods of multivariate adaptive regression splines (MARS), Rotary brace damper can be easily assembled with high energy-dissipation capability. To investigate the behavior of this damper in structures, a steel frame is modeled with this device subjected to monotonic and cyclic loading. Several response parameters are considered, and the performance of damper in reducing each response is evaluated. MLR and MARS methods were used to predict the strength of this damper. Displacement was determined to be the most effective parameter of damper strength, whereas the thickness did not exhibit any effect. Adding thickness parameter as inputs to MARS and MLR models did not increase the accuracies of the models in predicting the strength of this damper. The MARS model with a root mean square error (RMSE) of 0.127 and mean absolute error (MAE) of 0.090 performed better than the MLR model with an RMSE of 0.221 and MAE of 0.181.

Locating and identifying model-free structural nonlinearities and systems using incomplete measured structural responses

  • Liu, Lijun;Lei, Ying;He, Mingyu
    • Smart Structures and Systems
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    • v.15 no.2
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    • pp.409-424
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    • 2015
  • Structural nonlinearity is a common phenomenon encountered in engineering structures under severe dynamic loading. It is necessary to localize and identify structural nonlinearities using structural dynamic measurements for damage detection and performance evaluation of structures. However, identification of nonlinear structural systems is a difficult task, especially when proper mathematical models for structural nonlinear behaviors are not available. In prior studies on nonparametric identification of nonlinear structures, the locations of structural nonlinearities are usually assumed known and all structural responses are measured. In this paper, an identification algorithm is proposed for locating and identifying model-free structural nonlinearities and systems using incomplete measurements of structural responses. First, equivalent linear structural systems are established and identified by the extended Kalman filter (EKF). The locations of structural nonlinearities are identified. Then, the model-free structural nonlinear restoring forces are approximated by power series polynomial models. The unscented Kalman filter (UKF) is utilized to identify structural nonlinear restoring forces and structural systems. Both numerical simulation examples and experimental test of a multi-story shear building with a MR damper are used to validate the proposed algorithm.

A Study on Endurance Test Mode Generation of Powertrain System Using Multi-Objective Optimization (다목적 최적화 기법을 이용한 동력장치의 실차 내구시험모드 생성에 관한 연구)

  • Lee, Jeonghwan;Sung, Younghwa;Lee, Byoungyong
    • Journal of the Korea Institute of Military Science and Technology
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    • v.21 no.5
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    • pp.614-622
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    • 2018
  • Based on army operating road profile, the endurance test of military vehicle aims to reproduce the similar loading conditions with mixture of proving ground tracks. It is so called as endurance test mode and its optimal generation is important to meet high reliability of endurance test. In this paper, proving ground optimization is proposed to achieve a close match to the target profile. Several performance measures such as torque-revolution counts or transmission ratio for the powertrain system can be considered as one of the objective functions. However, the one-side optimal endurance test mode may give the poor solution in the whole system point of view. To incorporate several goals simultaneously, this paper employs multi-objective optimization technique to generate endurance test mode. One of the most widely used method, weighted-sum method is applied here and the case study is discussed.

Development of Centrifugal Compressors in an 1.2MW Industrial Gas Turbine(I)-Aerodynamic Design and Analysis- (1.2MW급 산업용 가스터빈 원심압축기 개발(1)- 공력설계해석 -)

  • Jo, Gyu-Sik;Lee, Heon-Seok;Son, Jeong-Rak
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.8
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    • pp.2707-2720
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    • 1996
  • The aerodynamic design of the two-stages of centrifugal compressors in an 1.2MW industrial gas turbine is completed with the application of numerical analyses. The final shape of an intake, the axial guide vanes and a return channel is determined using several interactions between design and two-dimensional turbulent flow analysis, focused on the minimum loss of internal flows. The one-dimensional turbulent flow analysis, focused on the minimum loss of internal flows. The one-dimensional design and prediction of aerodynamic performances for the compressors are performed by two different methods; one is a method with conventional loss models, and the other a method with the two-zone model. The combination methods of the Betzier curves generate three-dimensional geometric shapes of impeller blades which are to be checked with a careful change of aerodynamic blade loadings. The impeller design is finally completed by the applications of three-dimensional compressible turbulent flow solvers, and the effect of minor change of design of the second-stage channel diffuser is also studied. All the aerodynamic design results are soon to the verified by component performance tests of prototype centrifugal compressors.

Flexural Performance of Activated Hwangtoh Concrete Beam (활성 황토 콘크리트 보의 휨 성능)

  • Lee, Nam-Kon;Hwang, Hye-Zoo;Park, Hong-Gun
    • Journal of the Korea Concrete Institute
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    • v.22 no.4
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    • pp.567-574
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    • 2010
  • As a eco-friendly material, Hwangtoh(red clay) has been studied for a partial or complete replacement of portland cement. Most of existing studies focused on the mechanical properties of the Hwangtoh concrete including the compressive strength, drying shrinkage, creep. In the present study, the flexural capacity of the beams made with the Hwangtoh concrete was tested. One of the concrete tested consisted of activated Hwangtoh replacing 20% of the cement. The other consisted 100% activated Hwangtoh replacing all the cement. The simple beams were tested under two point static loading. The flexural strength, cracking moment, deflection, and ductility were compared with those of the beams made with ordinary portland cement concrete.

Measurement of Pile Load Transfer using Optical Fiber Sensors (광섬유 센서에 의한 말뚝 하중전이 측정)

  • 오정호;이원제;이우진
    • Proceedings of the Korean Geotechical Society Conference
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    • 1999.10a
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    • pp.397-404
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    • 1999
  • It is essential to measure load transfer mechanism of pile to check the appropriateness of assumptions made for design purpose and to continuously monitor the behavior of pile foundation. Through many attempts to monitor the behavior of super-structure in civil engineering area using several optical fiber sensors have been made, application of optical fiber sensor technology on pile foundation has not been tried up to now. Load transfer of model piles during compression loading was measured by optical fiber sensors and compared with the measurement by strain gauges. Fiber Bragg Grating(FBG) sensor system was used since it has many advantages, such as easy multiplexing, high sensitivity, and simple fabrication. Besides the model pile tests, uniaxial tension test of steel bar and compression tests of mortar specimen were carried out to evaluate the performance of FBG sensors in embedded environments. The shift of refilming wavelength due to the strain in FBG sensor is converted to the strain at sensor location and the dependence between them is 1.28 pm/${\mu}$ strain. FBG sensors embedded in model pile showed a better survivability than strain gauges. Measured results of load transfer by both FBG sensors and strain gauges were similar, but FBG sensors showed a smoother trend than those by strain gauge. Based on the results of model pile test, it was concluded that the use of FBG sensor for strain measurement in pile has a great potential for the analysis of pile load transfer.

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Experimental Research on Aerodynamic Instabilities in a Multi Stage Transonic Axial Compressor (다단 천음속 압축기의 유동 불안정성에 관한 실험적 연구)

  • Kang, Young-Seok;Park, Tae-Choon;Hwang, Oh-Sik;Lim, Hyung-Soo;Yang, Soo-Seok
    • The KSFM Journal of Fluid Machinery
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    • v.15 no.2
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    • pp.12-19
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    • 2012
  • This study presents unsteady and unstable characteristics of three stage transonic axial compressor, developed by Korea Aerospace Research Institute. As approaching to the unstable operating region at the 103% design speed of the compressor, a modal type stall precursor appears in front of highly loaded 3rd rotor row at first, and it propagates to the upstream. On the contrary, actual stall cell initiates from the stall precursor in front of the 1st rotor row, and it propagates to the downstream of the compressor. After the stall region reached the 3rd stage and stall cell rotates circumferentially about 360 deg, it develops to one dimensional compressor surge mode. It shows a mild surge behaviour with 3~4 Hz frequency. From the test data, it can be suggested that there is a priority to give an optimum blade loading distributions to construct a multi stage transonic axial compressor stages either to secure more stable compressor operating ranges, or to maximize the compressor efficiency.

Life Prediction of Automotive Vehicle's W/H System Using Finite Element Analysis (차량용 와이어하네스의 유한요소해석을 이용한 대변형 내구수명 예측)

  • Kim, Byeong-Sam;Kang, Ki-Jun;Park, Kyoung-Woo;Noh, Kwang-Doo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.18 no.1
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    • pp.139-144
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    • 2010
  • In the automotive electronic industry, the development of vehicle's door wiring harness (W/H) system for new applications is driven continuously for the low-cost and the high strength performance for electronic components. The problem of the fatigue strength estimation for materials and components containing natural defects, inclusions, or inhomogeneities is of great importance both scientifically and industrially. This article gives some insight into the dimensioning process with special focus on the fatigue analysis of wiring harness (W/H) in vehicle's door structures. The results from endurance tests using slim test specimens were compared with the results from FEM for predicted fatigue life. The expectation for the life of components is affected by the microstructural features with complex stress state arising from the combined service loading and residual stresses.

An Experimental Study on the Determination of Exterior Orientation Parameters with GPS/INS (GPS/INS에 의한 외부표정요소 결정에 관한 경험적 연구)

  • 한상득;조규전;이재원
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.22 no.1
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    • pp.53-62
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    • 2004
  • This paper deals with a new approach to acquire the exterior orientation parameters based on GPS(Global Positioning System) in combination with IMU(Inertial Measuring Unit), which enables us to achieve the same accuracy with minimal ground control points comparing to the conventional photogrammetric method. To prove the possibility of practical use of GPS/INS photogrammetry, a survey flight was conducted loading with all necessary photographing systems. The observed data set by GPS/IMU were analyzed and verified :he accuracy performance of kinematic GPS, and also compared to those of conventional photogrammetry in various points of view.

A Ship Scheduling Model for Raw Material Transportation with Yard Storage Constraints in a Steel Mill (재고수준을 고려한 제철원료 수송을 위한 선박 일정계획 수립 모형)

  • Seong, Deok-Hyun;Suh, Min-Soo;Kim, Sang-Won;Kim, Woo-Jin
    • Journal of Information Technology Services
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    • v.10 no.3
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    • pp.49-59
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    • 2011
  • A ship scheduling model is presented for the raw material transportation problem with yard storage constraints in a steel mill. The problem is formulated as 0, 1 mixed integer programming considering such constraints as loading port conditions, ship size and hold capacity, unloading conditions, and yard storage space. In addition, inventory related constraints including safety stock are taken into consideration to support the continuous operations of steel making process. The proposed model has been implemented and applied successfully to a real world problem, and its results show the improvement of performance compared to the traditional method. For example, the arrival dates of ships are determined satisfying the constraints. The total inventory level is minimized at the stock yard as a result. Also, the safety inventory level is always kept at the planning stage, and the standard deviation of total inventory level is reduced significantly. Further research is expected to develop efficient heuristics to have a better response time for even larger scale problems.