• 한국터널지하공간학회 논문집
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• 제20권4호
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• pp.671-686
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• 2018

최근 경주, 포항 인근에서 지진이 발생하여 대도시의 초고층 빌딩과 그에 인접한 지하구조물의 내진해석에 대한 사회적 요구가 증가하고 있다. 그러나 기존에 수행되어 왔던 대부분 내진해석 연구는 초고층 빌딩과 지하구조물을 개별적으로 분석하여 구조물간 동적 상호거동 연구가 부족한 실정이다. 따라서 본 연구에서는 기반암과 표층으로 이루어진 지반에 건물과 인접 지하구조물이 설치된 복합지하시설물을 대상으로 지반과 구조물을 동시에 고려한 동적해석을 수행하였다. 특히 신뢰도를 높이기 위해 유사정적해석을 추가로 수행하여 동적해석 결과와 비교 분석하였다. 종합적으로 복합시설물에 대한 SSI 해석 시 인접 지하구조물을 고려하는 것이 보다 보수적인 방법이라고 결론 내렸다.

• 한국전산구조공학회논문집
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• 제32권6호
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• pp.367-374
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• 2019

논문에서는 수직방향 지진입력에 의한 지반-구조물 상호작용 효과가 기초 종류에 따라 LNG 저장탱크의 지진응답에 미치는 효과를 분석하였다. 이를 위하여 직경 71m인 LNG 탱크와 기반암 위 점토지반의 깊이가 30m인 지반조건을 고려하였다. 그리고 기초형식으로 네 가지(얕은 기초, 말뚝지지 전면기초, 말뚝기초(지표면 접촉식, 부유식)를 고려하였다. 지반의 비선형성은 자유장 지반에 대하여 등가선형화기법으로 고려되었다. 또한, 말뚝기초의 시공과정에서 발생하는 동다짐 효과에 대해서도 분석하였다. SSI 해석을 위하여 진동수영역 해석프로그램인 KIESSI-3D를 이용하였다. 지반-구조물 상호작용 해석을 통해 LNG 저장탱크의 외조 벽체 쉘의 응력을 구하였다. 해석결과로부터 다음과 같은 결론을 얻을 수 있었다: (1) 얕은 기초에서 외조탱크의 수직응력은 SSI 효과로 인하여 고정기초응답 보다 작았다. (2) 말뚝으로 지지된 기초에서 말뚝으로 인해 기초의 수직강성이 커지고 방사감쇠가 작아질 수 있기 때문에 SSI 응답이 고정기초응답 보다 커질 수 있다. (3) 동다짐 효과는 수직지진에 의한 LNG 저장탱크의 응답에 미치는 영향이 매우 작았다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1997년도 봄 학술발표회 논문집
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• pp.19-26
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• 1997

In this paper, two dimensional analytical infinite elements which can include multiple wave components to model a underlying half-space are developed. Since these elements are expressed clearly and simply using Legendre polynomials of frequencies in frequency domain, these are very economical and efficient in computing the responses of strip foundations in frequency domain and are easily transformed for SSI analysis in time domain. To prove the behavior of the proposed two dimensional analytical infinite elements, vertical, horizontal, and rocking compliances of a rigid strip foundation in layered soils are analyzed and compared with those of Tzong ' Penzie $n^{(17)}$ and with those which calculated by numerical infinite elemen $t^{(1)}$ in frequency domain, and good agreements are noticed between them. As an application for a further study, a new scheme for SSI analysis in time domain are proposed and verified by comparing the displacement responses of the soil with a underlying rock due to a rectangular impulse loading with those of a soil modeled extended FE meshes.soil modeled extended FE meshes.

• 한국전산구조공학회논문집
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• 제29권5호
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• pp.377-388
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• 2016

이 연구는 기초의 묻힘이 면진 원전구조물의 응답에 미치는 효과를 지표기초와 비교하여 평가하였다. 면진장치의 비선형성을 고려한 비선형 SSI 해석은 진동수영역해석과 시간영역해석의 복합법인 경계반력법(BRM)을 이용하여 수행하였다. BRM 해석모델은 BRM을 이용한 등가선형 SSI 해석결과를 재래의 주파수영역 SSI 해석결과와 비교함으로 검증하였다. 마지막으로 비선형 SSI해석에 의한 묻힌기초 모델의 면진장치의 변위 및 구조물 응답을 지표기초의 해석결과와 비교하였다. 비교결과, 면진장치의 변위응답은 묻힌기초효과를 고려할 경우 감소할 수 있음을 알 수 있었다.

• Earthquakes and Structures
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• 제7권3호
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• pp.349-365
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• 2014

The dynamic response of structures under extremely short duration dynamic loads is of great concern nowadays. This paper investigates structures' response as well as the associated structural damage to explosive loads considering and ignoring the supporting soil flexibility effect. In the analysis, buildings are modeled by two alternate approaches namely, (1) building with fixed supports, (2) building with supports accounting for soil-flexibility. A lumped parameter model with spring-dashpot elements is incorporated at the base of the building model to simulate the horizontal and rotational movements of supporting soil. The soil flexibility for various shear wave velocities has been considered in the investigation. In addition, the influence of variation of lateral natural periods of building models on the obtained response and peak response time-histories besides damage indices has also been investigated under blast loads with different peak over static pressures. The Dynamic response is obtained by solving the governing equations of motion of the considered building model using a developed Matlab code based on the finite element toolbox CALFEM. The predicted results expressed in time-domain by the building model incorporating SSI effect are compared with the corresponding model results ignoring soil flexibility effect. The results show that the effect of surrounding soil medium leads to significant changes in the obtained dynamic response of the considered systems and hence cannot be simply ignored in damage assessment and response time-histories of structures where it increases response and amplifies damage of structures subjected to blast loads. Moreover, the numerical results provide an understanding of level of damage of structure through the computed damage indices.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 가을 학술발표회논문집
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• pp.361-368
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• 2000

This paper demonstrates how nonlinear soil behavior in a soil-structure interaction system can be realistically incorporated by using a hybrid method in a nonlinear time-domain analysis. The hybrid method employs a general-purpose nonlinear finite element program coupled with a linear SSI program for the unbounded layered soil medium In order to verify the validity and applicability of the hybrid method, nonlinear earthquake response analyses are carried out for the Hualien free-field problem, in which the ground and underground accelerations were measured during several earthquake events, and for a 2-D subway station. It is found that the nonlinear earthquake responses predicted for the Hualien free-field using the hybrid method compare very well with the observed responses whereas the subway station example gives reasonable results.

• Structural Engineering and Mechanics
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• 제33권4호
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• pp.529-537
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• 2009

A key parameter in the design of a laterally loaded pile is the determination of its performance level. Performance level of a pile is usually expressed as the maximum head deflection and bending moment. In general, uncertainties in the performance of a pile originates from many factors such as inherent variability of soil properties, inadequate soil exploration programs, errors taking place in the determination of soil parameters, limited calculation models as well as uncertainties in loads. This makes it difficult for practicing engineers to decide for the reliability of laterally loaded piles both in cohesive and cohesionless soils. In this paper, limit state functions and consequent performance functions are obtained for single concrete piles to predict the maximum bending moment, a widely accepted design criterion along with the permissible pile head displacement. Analyses were made utilizing three dimensional finite element method and soil-structure-interaction (SSI) effects were accounted for.

• Structural Engineering and Mechanics
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• 제49권1호
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• pp.1-22
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• 2014

A seismic evaluation is made of the response to horizontal ground shaking of cantilever retaining walls using the finite element model in three dimensional space whose verification is provided analytically through the modal analysis technique in case of the assumptions of fixed base, complete bonding behavior at the wall-soil interface, and elastic behavior of soil. Thanks to the versatility of the finite element model, the retained medium is then idealized as a uniform, elastoplastic stratum of constant thickness and semi-infinite extent in the horizontal direction considering debonding behavior at the interface in order to perform comprehensive soil-structure interaction (SSI) analyses. The parameters varied include the flexibility of the wall, the properties of the soil medium, and the characteristics of the ground motion. Two different finite element models corresponding with flexible and rigid wall configurations are studied for six different soil types under the effects of two different ground motions. The response quantities examined incorporate the lateral displacements of the wall relative to the moving base and the stresses in the wall in all directions. The results show that the wall flexibility and soil properties have a major effect on seismic behavior of cantilever retaining walls and should be considered in design criteria of cantilever walls. Furthermore, the results of the numerical investigations are expected to be useful for the better understanding and the optimization of seismic design of this particular type of retaining structure.

• Structural Engineering and Mechanics
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• 제75권2호
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• pp.175-191
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• 2020

In this study, multi-story structures are actively controlled using metaheuristic algorithms. The soil conditions such as dense, normal and soft soil are considered under near-fault ground motions consisting of two types of impulsive motions called directivity effect (fault normal component) and the flint step (fault parallel component). In the active tendon-controlled structure, Proportional-Integral-Derivative (PID) type controller optimized by the proposed algorithms was used to achieve a control signal and to produce a corresponding control force. As the novelty of the study, the parameters of PID controller were determined by different metaheuristic algorithms to find the best one for seismic structures. These algorithms are flower pollination algorithm (FPA), teaching learning based optimization (TLBO) and Jaya Algorithm (JA). Furthermore, since the influence of time delay on the structural responses is an important issue for active control systems, it should be considered in the optimization process and time domain analyses. The proposed method was applied for a 15-story structural model and the feasible results were found by limiting the maximum control force for the near-fault records defined in FEMA P-695. Finally, it was determined that the active control using metaheuristic algorithms optimally reduced the structural responses and can be applied for the buildings with the soil-structure interaction (SSI).

• Earthquakes and Structures
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• 제7권1호
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• pp.83-99
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• 2014

This study is devoted to estimate higher-mode effects for multi-story structures with considering soil-structure interaction subjected to decomposed parts of near-fault ground motions. The soil beneath the super-structure is simulated based on the Cone model concept. Two-dimensional structural models of 5, 15, and 25-story shear buildings are idealized by using nonlinear stick models. The ratio of base shears for the soil-MDOF structure system to those obtained from the equivalent soil-SDOF structure system is selected as an estimator to quantify the higher-mode effects. The results demonstrate that the trend of higher-mode effects is regular for pulse component and has a descending variation with respect to the pulse period, whereas an erratic pattern is obtained for high-frequency component. Moreover, the effect of pulse component on higher modes is more significant than high-frequency part for very short-period pulses and as the pulse period increases this phenomenon becomes vice-versa. SSI mechanism increases the higher-mode effects for both pulse and high-frequency components and slenderizing the super-structure amplifies such effects. Furthermore, for low story ductility ranges, increasing nonlinearity level leads to intensify the higher-mode effects; however, for high story ductility, such effects mitigates.