• Geomechanics and Engineering
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• 제36권6호
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• pp.545-561
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• 2024

Piled raft foundation has become widely used in the recent years because it can increase bearing capacity of foundation with control settlement. The design for a piled raft in terms vertical load and lateral load need to understands contribution load behavior to raft and pile in piled raft foundation system. The load-bearing behavior of the piled raft, especially concerning lateral loads, is highly complex and challenge to analyze. The complex mechanism of piled rafts can be clarified by using three dimensional (3-D) Finite Element Method (FEM). Therefore, this paper focuses on free-standing head pile group, on-ground piled raft, and embedded raft for the piled raft foundation systems. The lateral resistant of piled raft foundation was investigated in terms of relationship between vertical load, lateral load and displacement, as well as the lateral load sharing of the raft. The results show that both vertical load and raft position significantly impact the lateral load capacity of the piled raft, especially when the vertical load increases and the raft embeds into the soil. On the same condition of vertical settlement and lateral displacement, piled raft experiences a substantial demonstrates a higher capacity for lateral load sharing compared to the on-ground raft. Ultimately, regarding design considerations, the piled raft can reliably support lateral loads while exhibiting behavior within the elastic range, in which it is safe to use.

• Steel and Composite Structures
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• 제32권1호
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• pp.67-77
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• 2019

Pushover analysis captures the behavior of a structure from fully elastic to collapse. In this analysis, the structure is subjected to increasing lateral load with constant gravity one. Neglecting the effects of the higher modes and the changes in the vibration characteristics during the nonlinear analysis are the main obstacles of the proposed lateral load patterns. To overcome these drawbacks, whereas some methods have been presented to achieve updated lateral load distribution, these methods are not precisely capable to predict the response of structures, precisely. In this study, a new method based on optimization procedure is developed to obtain a lateral load pattern for which the difference between the floor displacements of pushover and Nonlinear Dynamic Analyses (NDA) is minimal. For this purpose, an optimization problem is considered and the genetic algorithm is applied to calculate optimal lateral load pattern. Three special moment resisting steel frames with different dynamic characteristics are simulated and their optimal load patterns are derived. The floor displacements of these frames subjected to the proposed and conventional load patterns are acquired and the accuracy of them is evaluated via comparing with NDA responses. The outcomes reveal that the proposed lateral load distribution is more accurate than the previous ones.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.821-828
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• 2011

A significantly larger lateral load and moment are applied on a high speed railway bridge foundation than other bridge foundations. Therefore most of bridge foundations on Honam high speed railway project were designed by high strength steel pipe piles to resist lateral load and moment, which caused the increase of construction costs. In order to perform optimum design, it is important to estimate accurate lateral resistance when designing this type of structure. Lateral load tests were carried out based on the field design data with the purpose of examining the lateral behavioral characteristics of a railway bridge foundation. The standard load test method(ASTM D 3966) was used for field tests by applying twice of design load. Total four load tests were performed on high speed railway bridge foundations with strain gages installed by every 1m along piles to measure load-resistance characteristics under applied lateral loads. The back-calculated P-y curves from strain gages were compared with estimated P-y curves using theoretical methods based on geotechnical investment data. Back-calculated P-y curves from field tests for sand and clay ground conditions were presented in this paper, which are different from theoretical P-y curves. By using the research results of this study, more accurate estimations of pile design under lateral loads can be available for similar geotechnical conditions.

• Geomechanics and Engineering
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• 제28권6호
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• pp.585-598
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• 2022

The monopile-friction wheel hybrid foundation is an innovative solution for offshore structures which are mainly subjected to large lateral eccentric load induced by winds, waves, and currents during their service life. This paper presents an extensive numerical analysis to investigate the lateral load and moment bearing performances of hybrid foundation, considering various potential influencing factors in sand-overlaying-clay soil deposits, with the complex lateral loads being simplified into a resultant lateral load acting at a certain height above the mudline. Finite element models are generated and validated against experimental data where very good agreements are obtained. The failure mechanisms of hybrid foundations under lateral loading are illustrated to demonstrate the effect of the friction wheel in the hybrid system. Parametric study shows that the load bearing performances of the hybrid foundation is significantly dependent of wheel diameter, pile embedment depth, internal friction angle of sand, loading eccentricity (distance from the load application point to the ground level), and the thickness of upper sandy layer. Simplified empirical formulae is proposed based on the numerical results to predict the corresponding lateral load and moment bearing capacities of the hybrid foundation for design application.

• 한국지반환경공학회 논문집
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• 제13권8호
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• pp.57-64
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• 2012

본 연구에서는 모형실험을 실시하여 수평하중 작용 시 무리말뚝의 거동을 평가하였다. 암반을 모사한 콘크리트 블럭에 모형말뚝을 말뚝직경(D)의 1배로 근입시키고, 상부에 모래를 1m 깊이로 포설한 $2{\times}3$ 배열의 무리말뚝에 대하여 모형실험을 실시하였다. 그리고 말뚝길이는 11D, 15D와 20D의 세 종류이다. 각 조건에 대한 모형실험의 결과를 수평하중-변위 곡선으로 나타냈으며, 지반 속에서 발생한 말뚝의 변위를 측정하였다. 모형실험 결과, 말뚝 길이/직경의 비(L/D)가 작아질수록 항복하중은 커지고, 항복하중에서의 수평변위는 증가하는 경향을 나타냈다. 도로교설계기준의 수평변위 기준인 15mm에서의 하중을 비교한 결과, L/D가 11, 15, 20에서의 항복하중은 각각 11.7, 6.2, 3.4kN으로 나타났다. 모든 실험 조건에 대하여 지반 속에서 발생한 말뚝의 수평변위는 거의 직선적으로 나타났고, 모형 말뚝이 콘크리트 블록에 소켓된 지점에서 파괴가 발생하였다.

• 한국지반환경공학회 논문집
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• 제11권9호
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• pp.27-38
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• 2010

모형실험과 유한요소법에 의한 수치해석을 통하여 측방변형지반 속에 설치된 매설관에 작용하는 측방토압을 관찰하였다. 모형실험에서는 모형지반 속에 매설관을 설치한 후 모형지반에 측방변형이 발생될 수 있게 모형실험기를 제작하여 실제 지반에서의 상황을 시뮬레이션하였다. 이 모형실험기는 지반의 변형속도를 여러 가지로 조절할 수 있게 제작하였다. 여러 가지 직경과 형상의 매설관에 대하여 실험을 실시함으로써 이들 요인이 측방토압에 미치는 영향을 조사하였다. 모형실험결과 연약지반의 측방유동으로 인하여 매설관에 작용하는 측방하중은 연약지반의 측방변형속도가 빠를수록 크게 작용하였다. 순간재하 조건에 의한 수치해석 결과는 지반변형속도가 중간 정도 빠르기인 0.3mm/min에서 1.0mm/min 사이의 지반변형속도의 조건에서 실시한 모형실험 결과와 유사하였다. 대부분의 모형실험결과 지반변형량이 작은 시점에서 측방하중의 제1항복이 발생하며 이때까지 탄성변형거동을 보이다가 제2항복에 이르기까지 하중이 한 동안 수렴되는 소성거동을 보였다. 지반변형이 계속하여 증가하면 측방하중도 다시 증가하여 압축거동을 보였다. 그러나 빠른 지반변형속도에서의 실험 결과에서는 항복하중에 도달한 후 수렴과정이 없이 계속하여 하중이 증가하였음을 볼 수 있다. 매설관의 직경이 클수록 측방유동 연약지반 속에 설치된 매설관에 작용하는 측방하중의 크기와 하중증가 속도가 컸으며 초기지반변형에서는 측방하중이 매설관의 직경 및 형상의 영향을 적게 받지만 지반변형량이 증가함에 따라 그 영향이 크게 나타났다.

• 산업기술연구
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• 제26권A호
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• pp.163-171
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• 2006

To evaluate inelastic seismic responses of multi-span-bridge, the equivalent single-degree-of-freedom (ESDOF) methods and the lateral load distributions are applied to the capacity spectrum method(CSM). From the pushover analysis results using the four ESDOF methods and the six types lateral load distributions, the ESDOF method more than lateral load distribution is found to have an important influence upon the pushover analysis. The effects of the higher mode on the bridge seismic behaviors are also increased as the number of pier increase. Therefore, it can be concluded that lateral load distributions and ESDOF methods for reflection of higher mode effects should be considered in the seismic analysis of the bridge structural.

• 콘크리트학회논문집
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• 제11권5호
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• pp.3-10
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• 1999

Earthquake resistant R/C frame structures are generally designed to prevent the columns from plastic hinging. R/C columns under higher axial load or strong earthquake showed a brittle behavior due to the deterioration of strength and stiffness degradation. An experimental study was conducted to examine the behavior and to find the relationship between amounts of lateral reinforcements and compressive strength of ten R/C column specimens subjected to reversed cyclic lateral load and higher axial load. Test results are follows : An increase in the amount of lateral reinforcement results in a significant improvement in both ductility and energy dissipation capacities of columns. R/C columns with sub-tie provide the improved ductility capacity than those with closely spaced lateral reinforcement only. While the load resisting capacity of the high strength R/C columns is higher than the normal strength concrete columns under both an identical ratio of lateral reinforcement, however the ductility capacity of high strength R/C columns is decreased considerably. Therefore, the amounts of lateral reinforcement must be designed carefully to secure the sufficient ductility and economic design of HSC columns under higher axial load.

• 한국산업융합학회 논문집
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• 제4권2호
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• pp.157-166
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• 2001

The purpose of this study is to examine the accuracy of the code provisions on lateral load distribution factors of prestressed concrete girder bridges. Most designers in Korea use the lever method or lateral load distribution formula in the existing design codes. However, the methods do not account for the effect of bridge skew or direction of diaphragm. Therefore, this study analysed the prestressed concrete girder bridge with grillage model for various girder spacings, directions of diaphragms, span lengths, and skews, and compared the results with those of existing design code. It has been found that lateral load distribution factors were proportional to the girder spacing while they were not significantly affected by the change of span length, direction of diaphragm, and skew. For bending moments, lateral load distribution factors from the grillage analysis were 60%~68% of those from Korean bridge design code. Therefore, the code provisions result in very conservative design. For support reactions, however, lateral load distribution factors from the grillage analysis were slightly greater than those from Korean bridge design code. Therefore, the capacity of bearings of the bridge with a large skew should be determined by grillage analysis.

• Steel and Composite Structures
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• 제45권2호
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• pp.175-191
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• 2022

A review of previous studies shows that although there is a considerable difference between buckling loads of structures under follower and non-follower lateral loads, only the buckling load of FGM elliptical cylindrical shell under non-follower lateral load was investigated in the literature. This study is the first to obtain the buckling load of elliptical FGM cylindrical shells under follower lateral load and also make a comparison between buckling loads of elliptical FGM cylindrical shells under follower and non-follower lateral loads. Moreover, this research is the first one to derive the load potential function of elliptical cylindrical shell. In this regard, the FGM cylindrical elliptical shell was modeled using the semi-analytical finite strip method and based on the First Shear Deformation Theory (FSDT). The shell is discretized by strip elements aligned in the longitudinal direction. The Lagrangian and harmonic shape functions were considered in the circumference and longitudinal directions, respectively. The buckling pressure of the shell under follower and non-follower lateral loads was obtained from eigenvalue problem. The results obtained from the model were compared with those presented in the literature to evaluate the validity of the model. A comparison index was defined to compare the buckling loads of the shell under follower and non-follower lateral load. A parametric study was carried out to investigate the effects of material properties and shell geometry characteristics on the comparison index. For the elliptical cylindrical shells with length-to-radius ratio greater than 16 and major-to-minor axis ratio greater than 0.6, the comparison index reaches to more than 20 percent which is significant. Moreover, the maximum difference is about 30 percent in some cases. The results obtained from the parametric study indicate that the buckling load of long elliptical cylindrical shell under non-follower load is not reliable.