• Title, Summary, Keyword: dynamic analyses

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Seismic Analysis of Tunnel in Transverse Direction Part II: Evaluation of Seismic Tunnel Response via Dynamic Analysis (터널 횡방향 지진해석 Part II: 동적해석을 통한 터널의 지진응답 예측)

  • Park, Du-Hee;Shin, Jong-Ho;Yun, Se-Ung
    • Journal of the Korean Geotechnical Society
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    • v.26 no.6
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    • pp.71-85
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    • 2010
  • Dynamic analyses of tunnels are widely performed in practice in Korea. Accurate performance of a dynamic analysis is very difficult, requiring appropriate application of lower and lateral boundary conditions, deconvolution, constitutive model, and selection of dynamic soil properties etc. Lack of a systematic guideline on how to perform the dynamic analysis makes it even more difficult to perform an analysis. In addition, dynamic analyses are not needed in most cases and pseudo-static analyses are more than adequate. However, they are performed without a clear understanding on the need for the dynamic analysis and differences between the two methods. In this study, firstly, a guideline for correctly performing a 2D dynamic analysis is developed. Secondly, the differences in the tunnel responses using dynamic and pseudo-static analyses are discussed and compared. The results show that the discrepancies between the dynamic and static analyses are not significant for most cases. It is therefore recommended that the dynamic analyses be performed at tunnel portal, very soft ground, or in cases where spatial variation of the ground motion needs to be considered in the seismic analysis of tunnels in transverse direction.

A Case Study on Verification of Inverse Calculation of Dynamic Properties of Rockfill Zone using Microearthquake Records (댐 계측지진 활용 사력죤 물성 역산법 검증 사례 연구)

  • Ha, Ik-Soo;Oh, Byung-Hyun
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.759-764
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    • 2010
  • In this study, from the comparison of the results obtained by 3 dimensional dynamic analyses using the inverse-calculated properties and those by calculating using the real earthquake records, the inverse calculation method for obtaining the dynamic properties of rockfill materials was verified. The fundamental frequency of the dam was determined by analyzing the response spectrum of observed records. By repeated dynamic analyses for various shear moduli of rockfill material, the shear moduli in the rockfill zone that satisfy the relationship between the fundamental frequency obtained by analysis of the observed records and that by numerical analyses were determined. Using the determined shear moduli, the 3 dimensional dynamic analyses for the dam were carried out and the result were compared with the real response characteristics on the crest of the dam.

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Nonlinear Subgrade Model-Based Comparison Study between the Static and Dynamic Analyses of FWD Nondestructive Tests (노상의 비선형 모델에 근거한 비파괴 FWD 시험에 있어 정적과 동적 거동의 비교연구)

  • Mun, Sungho
    • International Journal of Highway Engineering
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    • v.19 no.1
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    • pp.73-80
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    • 2017
  • PURPOSES : This paper presents a comparison study between dynamic and static analyses of falling weight deflectometer (FWD) testing, which is a test used for evaluating layered material stiffness. METHODS: In this study, a forward model, based on nonlinear subgrade models, was developed via finite element analysis using ABAQUS. The subgrade material coefficients from granular and fine-grained soils were used to represent strong and weak subgrade stiffnesses, respectively. Furthermore, the nonlinearity in the analysis of multi-load FWD deflection measured from intact PCC slab was investigated using the deflection data obtained in this study. This pavement has a 14-inch-thick PCC slab over fine-grained soil. RESULTS: From case studies related to the nonlinearity of FWD analysis measured from intact PCC slab, a nonlinear subgrade model-based comparison study between the static and dynamic analyses of nondestructive FWD tests was shown to be effectively performed; this was achieved by investigating the primary difference in pavement responses between the static and dynamic analyses as based on the nonlinearity of soil model as well as the multi-load FWD deflection. CONCLUSIONS : In conclusion, a comparison between dynamic and static FEM analyses was conducted, as based on the FEM analysis performed on various pavement structures, in order to investigate the significance of the differences in pavement responses between the static and dynamic analyses.

Seismic response of vertical shafts in multi-layered soil using dynamic and pseudo-static analyses

  • Kim, Yongmin;Lim, Hyunsung;Jeong, Sangseom
    • Geomechanics and Engineering
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    • v.21 no.3
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    • pp.269-277
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    • 2020
  • In this study, numerical analyses were conducted to investigate the load transfer mechanisms and dynamic responses between the vertical shaft and the surrounding soil using a dynamic analysis method and a pseudo-static method (called response displacement method, RDM). Numerical solutions were verified against data from the literature. A series of parametric studies was performed with three different transient motions and various surrounding soils. The results showed that the soil stratigraphy and excitation motions significantly influenced the dynamic behavior of the vertical shaft. Maximum values of the shear force and bending moment occurred near an interface between the soil layers. In addition, deformations and load distributions of the vertical shaft were highly influenced by the amplified seismic waves on the vertical shaft constructed in multi-layered soils. Throughout the comparison results between the dynamic analysis method and the RDM, the results from the dynamic analyses showed good agreement with those from the RDM calculated by a double-cosine method.

Analysis of Dynamic Responses for Steel Box Girder and I-girder Bridges under Train Loads (강합성 상자형교 및 소수주형 I형 거더교의 철도차량에 대한 동특성 해석)

  • Choi, Dong-Ho;Na, Ho-Sung;Ahn, Gi-Chul;Kim, Ok-Yeon
    • Proceedings of the KSR Conference
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    • pp.954-959
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    • 2011
  • The intensity of train load in the railway bridges is relatively large and continues to repeat. Also, the speed of vehicles is very fast. For these reasons, analyses for dynamic response under train load are necessary in the railway bridges. In other words, the dynamic characteristics of steel-composite bridges under train loads should be investigated considering effects of dynamic responses such as vibrations, repeated displacements and acceleration of bridge members. Therefore, in this study, static and dynamic analyses for the steel box girder bridges and I-girder bridges are carried out. Based on analyses results, we investigated and compared dynamic response considering the impact factors of domestic and foreign design specifications.

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On the System Development for the railway vehicle dynamic analysis based on integrated process environments (프로세스 통합 환경 기반의 철도차량 동역학 해석시스템 구축)

  • Huh Young-Cheol;Han Hyung-Suk;Lee Jae-Kyung;Kim Byung-Hyun
    • Proceedings of the KSR Conference
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    • pp.140-145
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    • 2005
  • The dynamic performances of railway vehicles, such as ride comfort, stability and safety, have the opposite characteristics of response each other according to design changes of suspensions. For this reasons, it is necessary that multidisciplinary engineers join in design processes of the suspensions so as to satisfy the requirements of dynamic performance with design constraints. Sometimes iterative dynamic analyses are required so many times during the design processes. In this paper, the development of integrated process environments and the dynamic analyses of railway vehicles based on the environments are presented. Using agent and wrapping technologies, process managements about the work process and design parameters were set up under the distributed computing environments. Also, dynamic analyses on the sample railway vehicle were carried out and the efficiency and improvement in future work were discussed as results.

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Assessment of nonlinear static and incremental dynamic analyses for RC structures

  • Oncu, Mehmet Emin;Yon, Merve Sahin
    • Computers and Concrete
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    • v.18 no.6
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    • pp.1195-1211
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    • 2016
  • In this study, seismic behaviour of reinforced concrete buildings using the pushover and incremental dynamic analysis method was investigated. A numerical study was performed for a reinforced concrete frame building. Pushover analysis according to uniform and triangular load shapes and incremental dynamic analyses were performed for selected building. For the nonlinear analysis, three ground motion records were selected to ensure compatibility with the design spectrum defined in the Turkish Seismic Code. The maximum response, dynamic pushover curve, capacity curves, interstorey drifts and moment rotation curves for various element ends of the selected building were obtained. Results were compared each other and good correlation was obtained between the dynamic analyses envelope with static pushover curves for the building.

Analytical and experimental modal analyses of a highway bridge model

  • Altunisik, Ahmet Can;Bayraktar, Alemdar;Sevim, Baris
    • Computers and Concrete
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    • v.12 no.6
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    • pp.803-818
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    • 2013
  • In this study, analytical and experimental modal analyses of a scaled bridge model are carried out to extract the dynamic characteristics such as natural frequency, mode shapes and damping ratios. For this purpose, a scaled bridge model is constructed in laboratory conditions. Three dimensional finite element model of the bridge is constituted and dynamic characteristics are determined, analytically. To identify the dynamic characteristics experimentally; Experimental Modal Analyses (ambient and forced vibration tests) are conducted to the bridge model. In the ambient vibration tests, natural excitations are provided and the response of the bridge model is measured. Sensitivity accelerometers are placed to collect signals from the measurements. The signals collected from the tests are processed by Operational Modal Analysis; and the dynamic characteristics of the bridge model are estimated using Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods. In the forced vibration tests, excitation of the bridge model is induced by an impact hammer and the frequency response functions are obtained. From the finite element analyses, a total of 8 natural frequencies are attained between 28.33 and 313.5 Hz. Considering the first eight mode shapes, these modes can be classified into longitudinal, transverse and vertical modes. It is seen that the dynamic characteristics obtained from the ambient and forced vibration tests are close to each other. It can be stated that the both of Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are very useful to identify the dynamic characteristics of the bridge model. The first eight natural frequencies are obtained from experimental measurements between 25.00-299.5 Hz. In addition, the dynamic characteristics obtained from the finite element analyses have a good correlation with experimental frequencies and mode shapes. The MAC values obtained between 90-100% and 80-100% using experimental results and experimental-analytical results, respectively.

The soil effect on the seismic behaviour of reinforced concrete buildings

  • Yon, Burak;Calayir, Yusuf
    • Earthquakes and Structures
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    • v.8 no.1
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    • pp.133-152
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    • 2015
  • This paper investigates the soil effect on seismic behaviour of reinforced concrete (RC) buildings by using the spread plastic hinge model which includes material and geometric nonlinearity of the structural members. Therefore, typical reinforced concrete frame buildings are selected and nonlinear dynamic time history analyses and pushover analyses are performed. Three earthquake acceleration records are selected for nonlinear dynamic time history analyses. These records are adjusted to be compatible with the design spectrum defined in Turkish Seismic Code. Interstory drifts and damages of selected buildings are compared according to local soil classes. Also, capacity curves of these buildings are compared with maximum responses obtained from nonlinear dynamic time history analyses. The results show that, soil class influences the seismic behaviour of reinforced concrete buildings, significantly.

Sensitivity Analysis on the Seismic Responses of the Reactor Structures (원자로구조물의 지진응답 민감도해석)

  • Lee, J. H.;Kim, J. B.;Koo, G. H.;Kim, J. I.;Yoo, B.;Choi, S.
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.183-190
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    • 1993
  • The seismic response of the reactor structures depends on the dynamic charact-eristics of the structures and the input earthquake loadings. The stuctural integ-rity of the reactor internal components can be verified by the dynamic response analyses to implement the effects of the design loadings like earthquakes. The sensitivity analyses of the dynamic characteristics for the analytical model of reactor structures considering the possible variations of the stiffnesses of the CSB upper flange and the snubber were performed to improve the dynamic characteri-stics of the structures against seismic loading. And to enhance the structural design margin of the reactor internal components the nonlinear time history analyses were attempted for the modified analytical model, and the results were compared between the reference model and the modified ones.

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