• Title, Summary, Keyword: pseudo-dynamic test

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Comparison of Acceleration-Compensating Mechanisms for Improvement of IMU-Based Orientation Determination (IMU기반 자세결정의 정확도 향상을 위한 가속도 보상 메카니즘 비교)

  • Lee, Jung Keun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.9
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    • pp.783-790
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    • 2016
  • One of the main factors related to the deterioration of estimation accuracy in inertial measurement unit (IMU)-based orientation determination is the object's acceleration. This is because accelerometer signals under accelerated motion conditions cannot be longer reference vectors along the vertical axis. In order to deal with this issue, some orientation estimation algorithms adopt acceleration-compensating mechanisms. Such mechanisms include the simple switching techniques, mechanisms with adaptive estimation of acceleration, and acceleration model-based mechanisms. This paper compares these three mechanisms in terms of estimation accuracy. From experimental results under accelerated dynamic conditions, the following can be concluded. (1) A compensating mechanism is essential for an estimation algorithm to maintain accuracy under accelerated conditions. (2) Although the simple switching mechanism is effective to some extent, the other two mechanisms showed much higher accuracies, particularly when test conditions were severe.

Pseudo-Static Behaviors of U-shaped PSC Girder with Wide Flanges (확폭플랜지를 갖는 U형 프리스트레스 거더의 유사정적거동)

  • Rhee, In-Kyu;Lee, Joo-Beom;Kim, Lee-Hyeon;Park, Joo-Nam;Kwak, Jong-Won
    • Proceedings of the KSR Conference
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    • pp.993-999
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    • 2008
  • A girder height limitation is the critical parameter for rapid construction of bridge deck and construction space limitation especially in urban area such as high population area and high density habitats. A standard post-tensioned I-shaped concrete girder usually demands relatively higher girder height in order to retain sufficient moment arm between compression force and tensile force. To elaborate this issue, a small U-shaped section with wide flanges can be used as a possible replacement of I-shaped standard girder. This prestressed concrete box girder allows more flexible girder height adjustment rather than standard I-shaped post-tensioned girder plus additional torsion resistance benefits of closed section. A 30m-long, 1.7m-high and 3.63m-wide actual small prestressed concrete box girder is designed and a laboratory test for its static behaviors by applying 6,200kN amount of load in the form of 4-point bending test was performed. The load-deflection curve and crack patterns at different loading stage are recorded. In addition, to extracting the dynamic characteristics such as natural frequency and damping ratio of this girder, several excitation tests with artificial mechanical exciter with un-symmetric mass are carried out using operational frequency sweep-up. Nonlinear finite element analysis of this 4 point bending test under monotonic static load is investigated and discussed with aids of concrete damaged plasticity formulation using ABAQUS program.

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Similitude Law on Material Non-linearity for Seismic Performance Evaluation of RC Columns (RC기둥의 내진성능평가를 위한 재료비선형 상사법칙)

  • Lee, Do-Keun;Cho, Jae-Yeol
    • Journal of the Korea Concrete Institute
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    • v.22 no.3
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    • pp.409-417
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    • 2010
  • This paper discusses a series of experiments including material improvement in order to ensure quality of grouting for the post-tensioned structure. In prestressed concrete, grouting refers to the construction procedure of filling empty space of duct enclosing with strands using cementitious material, To date, adequate quality control of the grouting has not been established in Korea because the relationship between the grouting and durability of post-tensioned structure is not well-recognized. The Korean standard does not consider the important material characteristic, wick effect, which is caused by strands in the ducts and current standard testing method unlikely quantify reasonable material segregation. As a result, the grout material, which meets the current material standards, may exhibit excessive bleeding water or shrinkage during construction. In this study, international codes and standards related to grouting were surveyed. The ratio of constituents and novel admixtures were suggested to meet equivalently with these standards. Performance of this enhanced grout was compared to common domestic grout using the international standard testing method. A series of mock-up specimens considering geometry of PC beam was constructed and grout flow pattern was observed as the grout was injected. It was observed that the grouting performance was highly influenced by material properties and filling characteristic can be varied depending on geometry of ducts.

Analysis of PRC regeneration algorithm performance in dynamic environment by using Multi-DGPS Signal (다중 DGPS 신호를 이용한 동적 환경에서의 PRC 재생성 알고리즘 성능분석)

  • Song Bok-Sub;Oh Kyung-Ryoon;Kim Jeong-Ho
    • The KIPS Transactions:PartA
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    • v.13A no.4
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    • pp.335-342
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    • 2006
  • As PRC linear interpolation algorithm is applied after analysed and verified in this paper, the unknown location of a user can be identified by using PRC information of multi-DGPS reference station. The PRC information of each GPS satellite is not varying rapidly, which makes it possible to assume that PRC information of each GPS satellite varies linearly. So, the PRC regeneration algorithm with linear interpolation can be applied to improve the accuracy of finding a user's location by using the various PRC information obtained from multi-DGPS reference station. The desirable PRC is made by the linear combination with the known position of multi-DGPS reference station and PRC values of a satellite using signals from multi-DGPS reference station. The RTK-GPS result was used as the reference. To test the performance of the linearly interpolated PRC regeneration algorithm, multi-channel DGPS beacon receiver was built to get a user's position more exactly by using PRC data of maritime DGPS reference station in RTCM format. At the end of this paper, the result of the quantitative analysis of the developed navigation algorithm performance is presented.

A Study on the Seismic Performance of Energy-Dissipating Sacrificial Devices for Steel Plate Ginder Bridges (강합성 거더교에 적용된 희생부재형 에너지소산장치의 내진성능에 관한 연구)

  • Cho, Kwang-Il;Gwak, Pil-Bong;Mha, Ho-Seong;Kim, Sang-Hyo
    • Journal of the Earthquake Engineering Society of Korea
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    • v.11 no.3
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    • pp.87-96
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    • 2007
  • A new Energy-Dissipating Sacrificial Device (EDSD) is developed for steel plate girders, which can effectively dissipate the energy stored in the structures during seismic actions. To verify the performance of the EDSD, various seismic responses of a sample bridge with the EDSD are analyzed in terms of energy, member forces and deformation. The full scale model tests are conducted to certify the performance of the EDSD when it is applied on existing bridges. Using the improved hysteretic model of the sacrificial member, the seismic analysis for an example bridge is performed. The results show that the proposed EDSD under seismic excitations can significantly decrease the energy stored in the bridge structures and reduce the relative displacements of each superstructure to the ground. The EDSD is also found to function as a structural fuse under strong ground motions, sacrificing itself to absorb the excessive energy. Consequently, economical enhancement of the seismic performance of bridges can be achieved by employing the newly developed energy-dissipating sacrificial device.