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3차원 시간이력해석을 통한 매설가스배관 종방향 지진응답 예측을 위한 경험적 설계법의 적용성 평가
곽형주,박두희,이장근,강재모 한국지반공학회 2015 한국지반공학회논문집 Vol.31 No.9
Longitudinal strain is an important component of seismic design for buried pipelines. A design procedure which determines the wavelength from site natural period and shear wave velocity of the soil layer and closed-form solutionsof pipelines under a harmonic motion is typically used in design. However, the applicability of the procedure has not yet been thoroughly investigated. In this paper, displacement-time histories extracted from 1D site response analysesare used in 3D shell-spring model to accurately predict the response of pipelines. The results are closely compared to those from the design procedure. The area of interest is East Siberia. Performing a site response analysis to determinesite specific displacement time history is highlighted. The site natural period may be used to predict the predominant period of the acceleration time history, but cannot be used to estimate the predominant period of the displacement timehistory. If an accurate estimate of the predominant period of the displacement time history is provided, it is demonstrated that the design equation can be successfully used to predict the response of pipelines.
곽형주(Hyungjoo Kwak),박두희(Duhee Park),이장근(Jangguen Lee),강재모(Jaemo Kang) 한국지반환경공학회 2015 한국지반환경공학회논문집 Vol.16 No.9
이 연구에서는 사실적인 매설관의 종방향 지진 응답특성을 규명하기 위하여 3차원 시간 이력해석이 가능한 쉘-스프링 수치모델을 구축하였으며 지진파 입사방향, 2방향 재하의 영향을 평가하였다. 조화운동을 적용한 결과, 이의 주기는 큰 영향을 주는 것으로 나타났다. 이는 주기가 감소할수록 매설관의 곡률이 증가하며 응답이 증가하기 때문인 것으로 판단된다. 입사방향의 영향을 평가하기 위하여 매설관 축 방향, 수평평면, 그리고 수직평면으로 운동을 재하 하였다. 매설관 축 방향으로 하중을 재하할 경우 휨 변형만을 유발하므로 응답이 매우 작게 계산되었다. 수평 및 수직평면에서 매설관 축 방향과 45°로 재하 하는 경우 축방향 변위가 응답에 지배적인 영향을 주는 것으로 나타났다. 또한 2방향 재하 시, 휨 변형만을 유발하는 요소의 영향이 극히 작으므로 1방향으로만 재하 하는 경우와 결과가 유사하게 계산되었다. 계측기록을 재하 하는 경우에도 응답은 유사하게 계산되었고 1방향 및 2방향 해석의 결과는 크게 다르지 않은 것으로 나타났다. 결과적으로 매설관의 종방향 지진 응답은 축 방향 변위를 유발하는 1방향 재하만으로도 충분히 정확하게 예측할 수 있을 것으로 판단된다. In this paper, a 3D shell-spring model that can perform time history analysis of buried pipelines is used to evaluate the effect of the incident direction of the earthquake motion. When applying harmonic motions, it is shown that the period of vibration has pronounced influence on the response of buried pipelines. With decrease in the period, the curvature of the pipeline and corresponding response are shown to increase. To evaluate the effect of the incident angle, the motions are applied in the direction of the pipleline, horizontal, and vertical planes. When the motion is applied parallel to the direction of the pipeline, it only induces bending strains and therefore, the response is the lowest. Under motions subjected in horizontal and vertical planes at an angle of 45° from the longitudinal axis of the buried pipeline, the axial deformation is shown to contribute greatly to the response of the pipelines. When imposing two-components simultaneously, the calculated response is similar to the case where only single-component is imposed. It is because one component only induces bending strain, resulting in very small increase in the response. The trend of the response is shown to be quite similar for recorded motions. Therefore, it is concluded that use of a single-component is sufficient for estimation of the longitudinal response of buried pipelines.
박두희,곽형주,강재모,이용국 한국지반공학회 2014 한국지반공학회논문집 Vol.30 No.10
The thickness of permafrost in Eastern Siberia is from 200 to 500 meters. The seasonally frozen layer can vary from0 to 4m depending on ground temperature and its location. The shear wave velocity varies from 80m/s in summer to1500m/s in winter depending on soil type. When melted, large impedence will occur due to the difference betweenthe shear wave velocity of seasonally frozen soil and that of permafrost layer. Large displacement may occur at theboundary of the melted and the frozen layer, and this phenomenon should be considered in a seismic design. In thisresearch, one-dimensional equivalent linear analyses were performed to investigate the effects of the seasonally frozenlayer on ground amplification characteristics. Soil profiles of Yakutsk and Chara in Eastern Siberia were selected fromgeotechnical reports. 20 recorded ground motions were used to evaluate the effect of input motions. As the thicknessof seasonally frozen layer and the difference in the shear wave velocity increases, the amplification is shown to increase. Peat, very soft organic soil widely distributed throughout Eastern Siberia, is shown to cause significant ground motionamplification. It is therefore recommended to account for its influence on propagated motion.