• Title, Summary, Keyword: OpenSees

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Seismic performance of a resilient low-damage base isolation system under combined vertical and horizontal excitations

  • Farsangi, Ehsan Noroozinejad;Tasnimi, Abbas Ali;Yang, T.Y.;Takewaki, Izuru;Mohammadhasani, Mohammad
    • Smart Structures and Systems
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    • v.22 no.4
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    • pp.383-397
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    • 2018
  • Traditional base isolation systems focus on isolating the seismic response of a structure in the horizontal direction. However, in regions where the vertical earthquake excitation is significant (such as near-fault region), a traditional base-isolated building exhibits a significant vertical vibration. To eliminate this shortcoming, a rocking-isolated system named Telescopic Column (TC) is proposed in this paper. Detailed rocking and isolation mechanism of the TC system is presented. The seismic performance of the TC is compared with the traditional elastomeric bearing (EB) and friction pendulum (FP) base-isolated systems. A 4-storey reinforced concrete moment-resisting frame (RC-MRF) is selected as the reference superstructure. The seismic response of the reference superstructure in terms of column axial forces, base shears, floor accelerations, inter-storey drift ratios (IDR) and collapse margin ratios (CMRs) are evaluated using OpenSees. The results of the nonlinear dynamic analysis subjected to multi-directional earthquake excitations show that the superstructure equipped with the newly proposed TC is more resilient and exhibits a superior response with higher margin of safety against collapse when compared with the same superstructure with the traditional base-isolation (BI) system.

Seismic response of bridge pier supported on rocking shallow foundation

  • Deviprasad, B.S.;Dodagoudar, G.R.
    • Geomechanics and Engineering
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    • v.21 no.1
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    • pp.73-84
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    • 2020
  • In the seismic design of bridges, formation of plastic hinges plays an important role in the dissipation of seismic energy. In the case of conventional fixed-base bridges, the plastic hinges are allowed to form in the superstructure alone. During seismic event, such bridges may be safe from collapse but the superstructure undergoes significant plastic deformations. As an alternative design approach, the plastic hinges are guided to form in the soil thereby utilizing the inevitable yielding of the soil. Rocking foundations work on this concept. The formation of plastic hinges in the soil reduces the load and displacement demands on the superstructure. This study aims at evaluating the seismic response of bridge pier supported on rocking shallow foundation. For this purpose, a BNWF model is implemented in OpenSees platform. The capability of the BNWF model to capture the SSI effects, nonlinear behavior and dynamic loading response are validated using the centrifuge and shake table test results. A comparative study is performed between the seismic response of the bridge pier supported on the rocking shallow foundation and conventional fixed-base foundation. Results of the study have established the beneficial effects of using the rocking shallow foundation for the seismic response analysis of the bridge piers.

Pushover analysis of gabled frames with semi-rigid connections

  • Shooshtari, Ahmad;Moghaddam, Sina Heyrani;Masoodi, Amir R.
    • Steel and Composite Structures
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    • v.18 no.6
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    • pp.1557-1568
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    • 2015
  • The nonlinear static analysis of structure, which is under the effect of lateral loads and provides the capacity curve of the structure, is defined as a push-over analysis. Ordinarily, by using base shear and the lateral displacement of target point, the capacity curve is obtained. The speed and ease of results interpretation in this method is more than that of the NRHA responses. In this study, the nonlinear static analysis is applied on the semi-rigid steel gabled frames. It should be noted that the members of this structure are analyzed as a prismatic beam-column element in two states of semi-rigid connections and supports. The gabled frame is modeled in the OpenSees software and analyzed based on the displacement control at the target point. The lateral displacement results, calculated in the top level of columns, are reported. Furthermore, responses of the structure are obtained for various support conditions and the rigidity of nodal connections. Ultimately, the effect of semi-rigid connections and supports on the capacity and the performance point of the structure are presented in separated graphs.

Characteristics of Interior Noise of High Speed Trains in Tunnels (터널에서의 고속차량 차내 소음 특성)

  • Lee Chan-Woo;Kim Jae-Chul
    • Proceedings of the KSR Conference
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    • pp.479-484
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    • 2005
  • Comparison it analyed the tunnel travelling hour interior noise arresting quality of the inside and outside of the country high-speed vehicle from the research which it sees. In the interior sound arresting comparison objective vehicle of the tunnel travelling hour KTX vehicle from the research which it sees and it limited by the TGV vehicle of France and the ICE vehicle og Germany and the Shinkansen vehicle of Japan comparison it analyzed the interior sound arresting from the open field and the tunnel line. The tunnel passage hour interior sound arresting problem of the domestic KTX vehicle follows in the concreate track tunnel the ballast track tunnel and the interior sound arresting quality is appearing different.

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THE GALACTIC OPEN CLUSTER NGC 6531 (M21)

  • PARK BYEONG-GON;SUNG HWANKYUNG;KANG YONG HEE
    • Journal of The Korean Astronomical Society
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    • v.34 no.3
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    • pp.149-155
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    • 2001
  • UBV RI and H$\alpha$ photometry has been performed for the open cluster NGC 6531. A total of 56 bright main sequence (MS) members were selected from their positions in photometric diagrams. We also classified 7 pre-main sequence (PMS) stars and 6 PMS candidates with Ha: emission from H$\alpha$ photometry. We determined a reddening of < E(B - V) >= 0.29 $\pm$ 0.03 and a distance modulus of Vo - Mv = 10.5 for the cluster. From the comparison of our photometric results to theoretical evolution models, we derived a MS turnoff age of 7.5 Myr and a PMS age spread of $\~$4 Myr. The IMF slope $\Gamma$, calculated in the mass range of 0.45 $\le$ log m $\le$ 1.35 is a steep value of $\Gamma$ = -1.8 $\pm$ 0.6.

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Nonlinear Seismic Response Analysis for Shallow Soft Soil Deposits (낮은 심도의 연약지반에 대한 비선형 지진응답해석)

  • Park, Hong-Gun;Kim, Dong-Kwan;Lee, Kyung-Koo;Kim, Dong-Soo
    • Journal of the Earthquake Engineering Society of Korea
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    • v.14 no.5
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    • pp.1-12
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    • 2010
  • This study presents a finite element analysis method that can accurately evaluate the nonlinear behaviour of structures affected by shallow soft subsoils and the soil-structure interaction. A two-dimensional finite element model that consists of a structure and shallow soft subsoil was used. The finite element model was used for a nonlinear time domain analysis of the OpenSees program. A parametric study was performed to investigate the effects of soil shear velocities, earthquake input motions, soft soil depth, and soil-structure interaction. The result of the proposed nonlinear finite element analysis method was compared with the result of an existing frequency domain analysis method, which is frequently used for addressing nonlinear soil behavior. The result showed that the frequency domain analysis, which uses equivalent secant soil stiffness and does not address the soil-structure interaction, significantly overestimated the response of the structures with short dynamic periods. The effect of the soil-structure interaction on the response spectrum did not significantly vary with the foundation dimensions and structure mass.

A Program Development for Prediction of Negative Skin Friction on Piles by Consolidation Settlement (압밀침하를 고려한 말뚝의 부마찰력 예측 프로그램 개발)

  • Kim, Hyeong-Joo;Mission, Jose Leo C.
    • Journal of the Korean Geotechnical Society
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    • v.25 no.9
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    • pp.5-17
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    • 2009
  • The microcomputer program PileNSF (Pile Negative Skin Friction) is developed by the authors in a graphical user interface (GUI) environment using $MATLAB^{(R)}$ for predicting the bearing capacity of a pile embedded in a consolidating ground by surcharge loading. The proposed method extends the one-dimensional soil-pile model based on the nonlinear load transfer method in OpenSees to perform an advanced one-dimensional consolidation settlement analysis based on finite strain. The developed program has significant features of incorporating Mikasa's finite strain consolidation theory that accounts for reduction in the thickness of the clay layer as well as the change of the soil-pile interface length during the progress of consolidation. In addition, the consolidating situation of the ground by surcharge filling after the time of pile installation can also be considered in the analysis. The program analysis by the presented method has been verified and validated with several case studies of long-term test on single piles subjected to negative skin friction. Predicted results of negative skin friction (downdrag and dragload) as a result of long from consolidation settlement are shown to be in good agreement with measured and observed case data.

A Parallel Axial-Flexural Hinge Model for Nonlinear Dynamic Progressive Collapse Analysis of Welded Steel Moment Frames (용접 철골모멘트골조의 비선형 동적 연쇄붕괴해석을 위한 병렬 소성힌지 모델의 개발)

  • Lee, Cheol Ho;Kim, Seon Woong;Lee, Kyung Koo
    • Journal of Korean Society of Steel Construction
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    • v.21 no.2
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    • pp.155-164
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    • 2009
  • In this study, a computationally efficient parallel axial-flexural plastic hinge model is proposed for nonlinear dynamic progressive collapse analysis of welded steel moment frames. To this end, post-yield flexural behavior and the interaction of bending moment and axial force of the double-span beams in the column's missing event was first investigated by using material and geometric nonlinear parametric finite element analysis. A piece-wise linear parallel point hinge model that captures the moment-axial tension interaction was then proposed and applied to nonlinear dynamic progressive collapse analysis of welded steel moment frames with the use of the OpenSees Program. The accuracy as well as the efficiency of the proposed model was verified based on the inelastic dynamic finite element analysis results. The importance of including the catenary action effects for proper progressive collapse resistant analysis and design was also emphasized.