• Title/Summary/Keyword: Elastic Soil

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Seismic Performance Evaluation of the Underground Utility Tunnel by Response Displacement Method and Response History Analysis (응답변위법과 응답이력해석법을 이용한 지중 공동구의 내진성능 평가)

  • Kwon, Ki-Yong;Lee, Jin-Sun;Kim, Yong-Kyu;Youn, Jun-Ung;Jeong, Soon-Yong
    • Journal of the Korean Geotechnical Society
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    • v.36 no.11
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    • pp.119-133
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    • 2020
  • Underground utility tunnel, the most representative cut and cover structure, is subjected to seismic force by displacement of the surrounding soil. In 2020, Korea Infrastructure Safety Corporation has published "Seismic Performance Evaluation Guideline for Existing Utility Tunnel." This paper introduces two seismic evaluation methods, RDM (Response Displacement Method) and RHA (Response History Analysis) adopted in the guide and compares the methods for an example of an existing utility tunnel. The test tunnel had been constructed in 1988 and seismic design was not considered. RDM is performed by single and double cosine methods based on the velocity response spectrum at the base rock. RHA is performed by finite difference analysis that is able to consider nonlinear behavior of soil and structure together in two-dimensional plane strain condition. The utility tunnel shows elastic behavior for RDM, but shows plastic hinge for RHA under the collapse prevention level earthquake.

The Study on the Development and the Applicability of Consolidation Analysis Program Considering the Creep Strain (Creep 변형을 고려한 압밀해석 프로그램의 개발과 적용성 분석)

  • Kim, Su-Sam;Jeong, Seung-Yong;An, Sang-Ro
    • Geotechnical Engineering
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    • v.14 no.5
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    • pp.129-142
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    • 1998
  • This research is focused on the inducement of the constitutive equation considering the creep strain component and on the development of a finite element method program. The purpose of this research was to contribute to the design of construction structures or to the construction management in soft clay ground through predicting the long-term strain of construction structures reasonably bused on the above program. Modified Cam Clay model was adopted to describe the elastic-plastic behavior of clayey soil. And in the calculation of the creep sprain, the secondary coefficient of consolidation C. was applied for considering the volumetric creep element and the constants m, $\alpha$, A were rosed by the empirical creep equation proposed by Singh 8E Mitchell for considering the deviatoric creep element. To examine the reliability of the program which is developed in this study, the estimated values by this program were compared with the theoretical solution and the experimental results. And the applicability of the developed program was found to be reliable from the sensitive analysis of each parameters used in this study. According to the results obtained from the application of the program on the field measurement data, the estimated values by the program were found with be consistent with the actual values. And from the analysis of the displacement of embankments, the case of considering the creep behavior induced much fower errors than the case of neglecting it. But the results obtained from considering the volumetric creep behavior only were slightly underestimated the results from considering the deviator creep behavior showed the slightly overestimated values. Therefore, it remains the task of further studios to develop the laboratory test devices to obtain the reliable creep parameters, and to select the appropriate soil parameters, etc.

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Evaluation of Seismic Performance of Pile-supported Wharves with Batter Piles through Response Spectrum Analysis (응답스펙트럼해석을 통한 경사말뚝이 설치된 잔교식 안벽의 내진성능 평가)

  • Yun, Jung-Won;Han, Jin-Tae;Kim, JongKwan
    • Journal of the Korean Geotechnical Society
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    • v.37 no.12
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    • pp.57-71
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    • 2021
  • The pile-supported wharf is the port structure in which the upper deck is supported by piles or columns. By installing batter piles in this structure, horizontal load such as earthquake loads can be partially delivered as axial forces. The codes suggests using the response spectrum analysis as a preliminary design method for seismic design of pile-supported wharf, and suggests modeling the piles using virtual fixed points or soil spring methods for this analysis. Recently, several studies have been conducted on pile-supported wharves composed of vertical piles to derive a modeling method that appropriately simulates the dynamic response of structures during response spectrum analysis. However, studies related to the response spectrum analysis of pile-supported wharves with batter piles are insufficient so far. Therefore, this study performed the dynamic centrifuge model test and response spectrum analysis to evaluate the seismic performance according to the modeling method of pile-supported wharves with batter piles. As a result of test and analysis, it is confirmed that modeling using the Terzaghi (1955) constant of horizontal subgrade reaction (nh) most appropriately simulates the actual response in the case of the pile-supported wharf with batter piles.

Site-Investigation of Underground Complex Plant Construction by Seismic Survey and Electrical Resistivity (탄성파 및 전기비저항을 활용한 지하복합 플랜트 건설 후보지 탐사)

  • Kim, Namsun;Lee, Jong-Sub;Kim, Ki-Seog;Kim, Sang Yeob;Park, Junghee
    • Journal of the Korean Geotechnical Society
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    • v.38 no.10
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    • pp.49-60
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    • 2022
  • Underground urbanization appears to be a promising solution in response to the shortage of construction sites in the above-ground space. In this context, an accurate evaluation of a construction site ensures the long-term performance of geosystems. This study characterizes potential sites for complex plants built in underground space using geophysical methods (i.e., seismic refraction exploration and electrical resistivity survey) and in situ tests (i.e., standard penetration tests (SPTs) and downhole tests). SPTs are conducted in nine boreholes BH-1-BH-9 to estimate the groundwater level and vertical distribution of geological structures. The seismic refraction method enables us to obtain the elastic wave velocity and thickness of each soil layer for each cross-sectional area. An electrical resistivity survey conducted using the dipole array method provides the electrical resistivity profiles of the cross-sectional area. Data obtained using geophysical techniques are used to assess the classification of the soil layer and bedrock, particularly the fracture zone. This study suggests that geotechnical information using in situ tests and geophysical methods are useful references to design an underground complex plant construction.

A Study on the Ground Input Motion for Seismic Analysis of Structures (구조물의 내진 해석을 위한 지반 입력운동의 산정에 관한 연구)

  • Lee, In-Moo;Song, Tae-Won;Huh, Young
    • Geotechnical Engineering
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    • v.5 no.3
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    • pp.5-18
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    • 1989
  • The ground input motions used for seismic analysis of structures are studied in this paper, The one-dimensional wave propagation theory, the simple transfer function by Elsabee and Morray, and the finite element method that can account for the effect of scattering field, respectively, are used to get the ground input motions, and the results by these methods are compared among others. The responses of structures are also computed by both finite element analysis and elastic half space analysis, using the ground input motions obtained by the different methods mentioned above, and the computed results are analyzed. In addition, the parameteric study Is performed to analyze the effect of the increase of soil stiffness on the response of structures, and on that of the ground input motions. The responses of structures obtained are compared with the results obtained using the Building Code on seismic analysis for structures in Korea. The results of this study show that the ground input motions obtained without considering the effect of scattering field was 2 times larger than those with scattering effect, concluding that the effect of scattering field may not be ignored when obtains the ground input motion.

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A Study on the Dynamic Behavior of a Various Buried Pipeline (각종 매설관의 동적거동에 관한 연구)

  • Jeong, Jin-Ho;Lim, Chang-Kyu;Joeng, Du-Hwoe;Kook, Seung-Kyu
    • Journal of the Earthquake Engineering Society of Korea
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    • v.10 no.4 s.50
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    • pp.15-24
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    • 2006
  • This work reports the results of our study on the dynamic response of various buried pipelines depending on their boundary conditions. We have studied behavior of the buried pipelines both along the axial and the transverse direction. The buried pipelines are modeled as beams on elastic foundation while the seismic wave as a ground displacement in the form of a sinusoidal wave. The natural frequency, its mode, and the effect of parameters have been interpreted in terms of free vibration. In order to investigate the response on the ground wave, the resulting frequency and the mode shape obtained from the free vibration have been utilized to derive the mathematical formula for the forced vibration. The natural frequency varies most significantly by the soil stiffness and the length of the buried pipelines in the case of free vibration. The effects of the propagation direction and velocity and the frequency of ground wave on the dynamic responses of concrete, steel, and FRP pipes have been analyzed and then dynamic responses depending on the type of pipes have been compared. Through performing dynamic analyser for various boundary conditions and estimation of the location of maximum strain has been estimated for the type of pipes and boundary conditions.

Freezing and Bearing Capacity Characteristics of Road Foundations under Temperature Condition (온도조건에 의한 도로하부 지반의 동결 및 지지력 특성)

  • Shin, Eun-Chul;Kim, Sung-Hwan;Park, Jeong-Jun
    • Journal of the Korean Geotechnical Society
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    • v.28 no.3
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    • pp.5-14
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    • 2012
  • In the current design codes for anti-freezing layer, the thickness of anti-freezing layer is calculated by freezing depth against the temperature condition. Therefore, they have a tendency of over-design and uniform thickness without the considerations of thermal stability, bearing capacity and frost susceptibility of materials. So, it is essential for studying the appropriateness and bearing capacity of road foundation materials as well as their seasonal and mechanical properties to take an appropriate and reasonable design of the road structure system. In this paper, the freezing and bearing capacity characteristics of typical road foundation materials were evaluated in the large scale laboratory test. LFWD (light falling weight deflectometer) was used to determine the change of elastic modulus ($E_{LFWD}$) caused by to the frost heave and thaw. Furthermore, the influence of crushed natural aggregate on the freezing of the subgrade soil was studied to verify the function and effectiveness of the anti-freezing layer.

Conditional mean spectrum for Bucharest

  • Vacareanu, Radu;Iancovici, Mihail;Pavel, Florin
    • Earthquakes and Structures
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    • v.7 no.2
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    • pp.141-157
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    • 2014
  • The Conditional Mean Spectrum represents a powerful link between the seismic hazard information and the selection of strong ground motion records at a particular site. The scope of the paper is to apply for the city of Bucharest for the first time the method to obtain the Conditional Mean Spectrum (CMS) presented by Baker (2011) and to select, on the basis of the CMS, a suite of strong ground motions for performing elastic and inelastic dynamic analyses of buildings and structures with fundamental periods of vibration in the vicinity of 1.0 s. The major seismic hazard for Bucharest and for most of Southern and Eastern Romania is dominated by the Vrancea subcrustal seismic source. The ground motion prediction equation developed for subduction-type earthquakes and soil conditions by Youngs et al. (1997) is used for the computation of the Uniform Hazard Spectrum (UHS) and the CMS. The disaggregation of seismic hazard is then performed in order to determine the mean causal values of magnitude and source-to-site distance for a particular spectral ordinate (for a spectral period T = 1.0 s in this study). The spectral period of 1.0 s is considered to be representative for the new stock of residential and office reinforced concrete (RC) buildings in Bucharest. The differences between the Uniform Hazard Spectrum (UHS) and the Conditional Mean Spectrum (CMS) are discussed taking into account the scarcity of ground motions recorded in the region of Bucharest and the frequency content characteristics of the recorded data. Moreover, a record selection based on the criteria proposed by Baker and Cornell (2006) and Baker (2011) is performed using a dataset consisting of strong ground motions recorded during seven Vrancea seismic events.

Anlysis and Design of Wale in Innovative Prestressed Support(IPS) System (혁신적 프리스트레스트 가시설(IPS)공법에 적용되는 띠장의 설계 및 해석)

  • Kim, Sung-Bo;Han, Man-Yop;Kim, Moon-Young;Kim, Nak-Kyung;Ji, Tea-Sug
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.18 no.1
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    • pp.79-91
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    • 2005
  • The behaviors and design procedures of wale in innovative prestressed support(IPS) system are presented in this paper. Using the theory of the beam on elastic foundation, the member forces of the wale under initial pretension are evaluated. Choosing cable tensions as redundant forces, member forces subjected to earth pressure are calculated by the statically indeterminate analysis. The computer analysis model under uniform and non-uniform earth pressure is constructed using beam element for the IPS wale, tension-only element for cable, and compression-only element for soil. Axial forces and bending moments of IPS wale under initial pretension and design earth pressure are calculated. The combined stresses due to these axial force and bending moment are estimated to satisfy the design formula.

Characteristics of Bearing Capacity and Stress Concentration of Clay Ground Improved with Sand Compaction Piles (SCP 보강 점성토 지반의 지지력 및 응력분담특성)

  • Yoo Nam-Jae;Park Byung-Soo;Jeong Gil-Soo;Koh Kyung-Hwan;Kim Ji-Sung
    • Journal of the Korean Geotechnical Society
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    • v.21 no.1
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    • pp.81-91
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    • 2005
  • This paper is the results of experimental and numerical works on the investigating design factors influencing the bearing capacity, the ratio of stress concentration, and the failure mechanism of the clay ground improved with sand compaction piles (SCP). In order to find the behavior of the clay ground improved with SCP, extensive centrifuge model experiments were carried out for each of the SCP replacement ratio of 20, 40, and $70\%$, the non-plastic fine contents in sand of 5, 10, and $15\%$, and the ratio of the improved width to the loaded area (W/B) of 1, 2, and 3. The commertially available software of FEM, CRISP, was used to analyze test results by performing numerical estimations. In these numerical analyses the sand compaction piles and the clay ground were simulated as a linear elastic and plastic constitutive model and the modified Cam-clay model, based on Critical State Soil Mechanics, respectively.