• Title, Summary, Keyword: pseudo-dynamic test

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Displacement Ductility Evaluation of Earthquake Experienced RC Bridge Piers with 2.5 Aspect Ratio (지진을 경험한 형상비 2.5 RC 교각의 내진 변위 연성도 평가)

  • 정영수;박창규;이은희
    • Journal of the Earthquake Engineering Society of Korea
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    • v.7 no.3
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    • pp.79-88
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    • 2003
  • For the construction of PC bridge piers the implementation of 1992 seismic provisions, longitudinal steels were practically lap-spliced in the plastic hinge region. Experimental investigation was conducted ductility of evaluate the seismic earthquake-experienced reinforced concrete columns with 2,5 aspect ratio. Six test specimens were mode with test parameters: confinement ratios, lap splices, and retrofitting FRP materials. They were damaged under series of artificial earthquakes that could be compatible in Korean peninsula. Directly after the pseudo-dynamic test, damaged columns were retested under inelastic reversal cyclic loading simultaneously under a constant axial load, P=0.1f$\_$ck/A$\_$g/. Residual seismic performance of damaged columns was evaluated and compared to that of the corresponding original columns. Test results show that PC bridge piers with lap-spliced longitudinal steels appeared to fail at low ductility. This was due to the debonding of the lap splice, which resulted from insufficient development of the longitudinal steels. The specimens externally wrapped with composite FRP straps in the potential plastic hinge region indicated significant improvement both in flexural strength and displacement ductility.

Seismic Performance Evaluation of RC Bridge Piers with Limited Ductility by the Pseudo-Dynamic Test (한정연성 철근콘크리트 교각의 유사동적 실험에 의한 내진 성능 평가)

  • Chung, Young-Soo;Park, Chang-Kyu;Park, Jin-Young
    • Journal of the Korea Concrete Institute
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    • v.15 no.5
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    • pp.705-714
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    • 2003
  • Even though Korean peninsula is located in regions of moderate seismic risks, current seismic design provisions of the roadway bridge design code have adopted the AASHTO code which is based on the requirements for high seismic regions. The objective of this research is to investigate the seismic performance of circular reinforced concrete (RC) bridge piers with limited ductility, which may be desirable in low or moderate seismic regions, such as in Korea. Four test specimens were designed and constructed. The reference specimen was designed with longitudinal steel ratio as 1.01% and the confinement reinforcement ratio as 0.13% without considering earthquake, and three other test specimens were designed in accordance with a limited-ductility concept as 0.3% for the confinement steel ratio. This confinement ratio is 0.32 times of minimum lateral reinforcement specified in current seismic design provisions, and 2.3 times of lateral reinforcement required in nonseismic design provisions. The pseudo-dynamic test was carried out to evaluate the seismic performance of full-scale specimens in size of 1.2m diameter and 4.8m height. Judging from the experiment, the reference specimen was not satisfactory for the demand displacement ductility ${\mu}$=5.0, but three limited-ductility specimens appeared to have the displacement ductility of more than 5.

Similitude Law on Small Scaled RC Model for Seismic Performance Evaluation Tests (내진성능평가실험을 위한 철근콘크리트 축소모형 상사법칙)

  • Lee, Do-Keun;Cho, Jae-Yeol
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.455-456
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    • 2009
  • Although pseudo-dynamic test and shaking table test have been performed using small scale models to evaluate the seismic performance of RC structures, researches on similitude law are not sufficient. This study presents a reasonable similitude law for improvement of economical efficiency and reliability.

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A Discussion on the Definitions of Seismic Coefficient for Gravity Quay Wall in Korea (국내 중력식 안벽의 수평지진계수 산정 방법에 대한 고찰)

  • Lee, Moon Gyo;Jo, Seong Bae;Cho, Hyung Ik;Park, Heon Joon;Kim, Dong Soo
    • Journal of the Earthquake Engineering Society of Korea
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    • v.21 no.2
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    • pp.77-85
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    • 2017
  • Pseudo-static approach has been conventionally applied for the design of gravity quay walls. In this method, the decision to select an appropriate seismic coefficient ($k_h$) is an important one, since $k_h$ is a key variable for computing an equivalent pseudo-static inertia force. Nonetheless, there is no unified standard for defining $k_h$. Likewise, port structure designers in Korea have a difficulty in choosing an appropriate $k_h$ definition, as there are conflicts in how $k_h$ is defined between the existing seismic code of port structures and the proposed new one. In this research, various seismic design codes for port structures were analyzed to compare the definitions of the seismic coefficient. The results were used for the proposing a unified seismic coefficient definition. Further, two dynamic centrifuge tests were performed with different wall heights (5 m, 15 m) to clarify the reference point of peak acceleration used in determination of $k_h$ according to the wall height. Results from dynamic centrifuge experiments showed that correction factors for the peak ground acceleration considering both the wall height and allowable displacement are needed to calculate $k_h$.

Seismic performance evaluation of circular composite columns by shaking table test (진동대 실험을 통한 원형 합성 기둥의 내진 성능 평가)

  • Shim, Chang-Su;Chung, Young-Soo;Park, Ji-Ho;Park, Chang-Young
    • Journal of the Earthquake Engineering Society of Korea
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    • v.11 no.5
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    • pp.71-81
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    • 2007
  • For the design of composite bridge piers, detail requirements for the reinforcements is not clear to satisfy the required seismic performance. Composite bridge piers were suggested to reduce the sectional dimensions and to enhance the ductility of the columns under earthquake loadings. In this paper, five specimens of concrete encased composite columns of 400mm diameter with single core steel were fabricated to investigate the seismic performance of the composite columns. Shaking table tests and a Pseudo-Dynamic test were carried out and structural behavior of small-scaled models considering near-fault motions was evaluated. Test parameters were the pace of the transverse reinforcement, lap splice of longitudinal reinforcement and encased steel member sections. The displacement ductility from shaking table tests was lower than that from the pseudo-dynamic test. Limited ductile design and 50% lap splice of longitudinal reinforcement reduced the displacement ductility. Steel ratio showed significant effect on the ultimate strength. Lap splice and low transverse reinforcements reduced the displacement capacity. The energy dissipation capacity of composite columns did not show significant difference according to details.

Rocking behavior of bridge piers with spread footings under cyclic loading and earthquake excitation

  • Hung, Hsiao-Hui;Liu, Kuang-Yen;Chang, Kuo-Chun
    • Earthquakes and Structures
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    • v.7 no.6
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    • pp.1001-1024
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    • 2014
  • The size of spread footings was found to be unnecessarily large from some actual engineering practices constructed in Taiwan, due to the strict design provisions related to footing uplift. According to the earlier design code in Taiwan, the footing uplift involving separation of footing from subsoil was permitted to be only up to one-half of the foundation base area, as the applied moment reaches the value of plastic moment capacity of the column. The reason for this provision was that rocking of spread footings was not a favorable mechanism. However, recent research has indicated that rocking itself may not be detrimental to seismic performance and, in fact, may act as a form of seismic isolation mechanism. In order to clarify the effects of the relative strength between column and foundation on the rocking behavior of a column, six circular reinforced concrete (RC) columns were designed and constructed and a series of rocking experiments were performed. During the tests, columns rested on a rubber pad to allow rocking to take place. Experimental variables included the dimensions of the footings, the strength and ductility capacity of the columns and the intensity of the applied earthquake. Experimental data for the six circular RC columns subjected to quasi-static and pseudo-dynamic loading are presented. Results of each cyclic loading test are compared against the benchmark test with fixed-base conditions. By comparing the experimental responses of the specimens with different design details, a key parameter of rocking behavior related to footing size and column strength is identified. For a properly designed column with the parameter higher than 1, the beneficial effects of rocking in reducing ductility and the strength demand of columns is verified.

A Study on the Earthquake Response Characteristics of Steel Frames with Metallic Damper (강재 댐퍼를 부착한 철골조의 지진응답특성에 관한 연구)

  • Lee, Seung-Jae;Park, Jae-Seong;Oh, Sang-Hoon
    • Journal of the Korean Association for Spatial Structures
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    • v.11 no.2
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    • pp.119-127
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    • 2011
  • The purpose of this study is to propose damper system which is easy to design, which can ensure against risks, and to verify earthquake response characteristics. For this study, the pseudo dynamic earthquake response tests carried out for steel frames with metallic damper. As a result, in case of using the metallic damper as a vibration control device proposed by this study, the damper having higher stiffness than main-structure turned to the state of plasticity by little displacement has been proved to be able to absorb earthquake energy.

ON-LINE PSEUDO-DYNAMIC NETWORK TESTING ON BASE-ISOLATED BRIDGE USING INTERNET AND WIRELESS INTERNET (유무선 인터넷을 이용한 면진 교량의 온라인 네트워크 실험)

  • Park, D-U;Yun, C-B;Lee, J-W;K. Nagata;E. Watanabe;K. Sugiura
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.33-40
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    • 2004
  • 본 논문에서는 한국과 일본에 위치한 여러 연구기관들 사이에서 수행된 온라인 네트워크 유사동적 실험결과에 대해 나타내었다. 예제 구조물로는 4경간 연속의 면진 교량을 이용하였다. 실험 장비를 보유하고있는 두 연구기관에서 면진 장치의 비선형 거동에 대한 실험을 수행하고 각 실험 결과를 조합하여 전체구조의 동적 해석을 수행하였다. 본 논문에서는 먼저 인터넷을 이용한 두 가지 데이터 전송기법을 이용하여 두 기법의 효율성을 비교, 분석하였다. 또한 최근 국내에 위치한 두 연구기관 사이에서 수행된 실험 결과에 대해 논의하였다. 마지막으로 유선과 무선 인터넷을 이용한 온라인 실험 기법에 대하여 나타내었다. 그 결과, 온라인 네트워크 실험에 소요된 실험 시간은 데이터 전송 기법과 실험장비에 따라 매 시간 단계의 데이터 전송에 0.2-15초, 각 연구기관의 유사동적 실험에 1-10초의 시간이 소요되어 매우 큰 폭으로 변화함을 알 수 있었다. 또한 무선 인터넷을 이용한 온라인 실험의 경우, 뛰어난 이동성과 인터넷 보안성 등과 같은 여러 가지 장점을 가지고 있음을 알 수 있었다.

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ON-LINE PSEUDO-DYNAMIC NETWORK TESTING ON BASE-ISOLATED BRIDGE USING WEB-BASED JAVA MONITORING SYSTEM (자바 모니터링 서버를 이용한 면진교량의 온라인 네트워크 유사동적 실험)

  • Park, D.U.;Yun, C.B.;Lee, J.W.;Nagata, K.;Watanabe, E.;Sugiura, K.
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.477-486
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    • 2005
  • 본 논문에서는 한국과 일본에 위치한 여러 연구기관들 사이에서 수행된 온라인 네트워크 유사동적 실험 결과에 대해 나타내었다.예제 구조물로는 4경간 연속의 면진 교량을 이용하였다. 실험 장비를 보유하고 있는 두 연구기관에서 면진 장치의 비선형 거동에 대한 실험을 수행하고 각 실험 결과를 조합하여 전체 구조의 동적 해석을 수행하였다. 본 논문에서는 먼저 인터넷을 이용한 두 가지 데이터 전송기법을 이용하여 두 기법의 효율성을 비교, 분석하였다. 또한 최근 국내에 위치한 두 연구기관 사이에서 수행된 실험 결과에 대해 논의하였다. 본 연구에서는 상대 연구기관의 실험 상황 및 수행된 실험 결과의 효율적인 모니터링을 위하여 웹 기반의 자바 모니터링 시스템을 개발하였다. 마지막으로 유선과 무선 인터넷을 이용한 온라인 실험 기법에 대하여 나타내었다. 그 결과, 온라인 네트워크 실험에 소요된 실험 시간은 데이터 전송 기법과 실험장비에 따라 매 시간 단계의 데이터 전송에 0.2-15초, 각 연구기관의 유사동적 실험에 1-10초의 시간이 소요되어 매우 큰 폭으로 변화함을 알 수 있었다. 또한 무선 인터넷을 이용한 온라인 실험의 경우, 뛰어난 이동성과 인터넷 보안성 등과 같은 여러 가지 장점을 가지고 있음을 알 수 있었다.

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Shake Table Response and Analysis of RC Bridge Piers with Lap-Spliced Steel under NFGM (주철근 겹침이음된 RC교각의 근단층지반운동에 대한 진동대 응답과 분석)

  • Chung, Young-Soo;Park, Chang-Young;Hong, Hyun-Ki;Park, Ji-Ho;Shim, Chang-Su
    • Journal of the Korea Concrete Institute
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    • v.20 no.4
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    • pp.451-458
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    • 2008
  • The near-fault ground motion (NFGM) is characterized by a single long period velocity pulse of large magnitude. NFGM's have been observed in recent strong earthquakes, Izmit Turkey (1999), Kobe Japan (1995), Northridge USA (1994), etc. These strong earthquakes have caused considerable damage to infrastructures because the epicenter was close to the urban area, called as NFGM. Extensive research for the near-fault ground motion (NFGM) have been carried out in strong seismic region, but limited research have been done for NFGM in low or moderate seismic regions because of very few records. The purpose of this study is to investigate and analyze the effect of near-fault ground motions on reinforced concrete (RC) bridge piers with lap-spliced longitudinal reinforcing steels. The seismic performance of four RC bridge piers under near-fault ground motions was investigated on the shake table. In addition, a RC bridge pier is subjected to pseudo-dynamic loadings. Test results showed that large residual displacements were observed in RC bridge piers under NFGM. RC specimens on the shake table failed at relatively low displacement ductility, compared with the displacement ductility of RC bridge pier subjected to pseudo-dynamic loadings.