• Earthquakes and Structures
• /
• 제21권6호
• /
• pp.641-652
• /
• 2021

Digging well foundation has been widely used in railway bridges due to its good economy and reliability. In other instances, bridges with digging well foundation still have damage risks during earthquakes. In this study, a new type of digging well foundation with prefabricated roots was proposed to reduce earthquake damage of these bridges. Quasi-static tests were conducted to investigate the failure mechanism of the root digging well foundation, and then to analyze seismic behaviors of the new type well foundation. The testing results indicated that these prefabricated roots could effectively limit the rotation and uplift of the digging well foundation and increase the lateral bearing capacity of the digging well foundation. The elastic critical load and ultimate load can be increased by 69% and 36% if prefabricated roots were added in the digging well foundation. The prefabricated roots drived more soil around the foundation to participate in working, the stiffness of the bridge pier with root digging well foundation was improved. Moreover, the root participation could improve the energy dissipation capacity of soil-foundation-pier interaction system. The conclusions obtained in this paper had important guiding significance for the popularization and application of the digging well foundation with prefabricated roots in earthquake-prone zones.

• Earthquakes and Structures
• /
• 제21권6호
• /
• pp.563-576
• /
• 2021

The rocking foundation is effective for reducing structural seismic demand and avoiding overdesign of the foundation. It is crucial to evaluate the performance of rocking foundations because they cause plastic hinging in the soil. In this study, to derive optimized ground motion intensity measures (IMs) for rocking foundations, the efficiency of IMs correlated with engineering demand parameters (EDPs) was estimated through the coefficient determination using a physical modeling database for rocking shallow foundations. Foundation deformations, the structural horizontal drift ratio, and contribution in drift from foundation rotation and sliding were selected as crucial EDPs for the evaluation of rocking foundation systems. Among 15 different IMs, the peak ground velocity exhibited the most efficient parameters correlated with the EDPs, and it was discovered to be an efficient ground motion IM for predicting the seismic performance of rocking foundations. For vector regression, which uses two IMs to present the EDPs, the IMs indicating time features improved the efficiency of the regression curves, but the correlation was poor when these are used independently. Moreover, the ratio of the column-hinging base shear coefficient to the rocking base shear coefficient showed obvious trends for the accurate assessment of the seismic performance of rocking foundation-structure systems.

• 전산구조공학
• /
• 제1권1호
• /
• pp.103-112
• /
• 1988

본 연구에서는 기초의 uplift의 영향을 고려하여 지진하중에 대한 건축구조물의 동적 거동을 예측하는 효율적인 방법을 제안하였다. 기초와 지반의 관계에 대한 모델에는 Winker 모델과 Two-Spring 모델이 있다. Winker 모델에 의한 해석방법은 정확하기는 하나 계산 시간이 오래 걸리고 복잡하다는 단점이 있다. 본 연구에서 Winker 모델을 보다 정확하게 나타낼 수 있고 해석이 간편하며 효율적인 등가 Two-Spring 모델(S-모델)을 제안하였다. S 모델은 기초에 정적하중이 작용했을 때의 기초 중앙의 모멘트와 회전각의 비선형 관계를 간단한 5개의 선형적인 관계로 나타냄으로써 유도되며, S모델에 의한 동적해석 결과는 Winker 모델에 의한 해석 결과와 잘 일치하였다.

• 한국강구조학회 논문집
• /
• 제13권1호
• /
• pp.91-100
• /
• 2001

본 연구에서는 스팬의 중간지점에 신축 스프링과 회전 스프링을 가지며 Pasternak지반 위에 놓인 Timoshenko보-기둥에 대한 유한 요소법을 이용하여 안정해석을 한 것이다. 이 유한요소법에 의하여 얻어진 해는 신축스프링과 회전스프링, 전단지반이 없는 Timoshenko보-기둥의 경우에 대하여 기존해와 비교되었다. 동적안정해석에 의해 스팬 중간지점에 신축 및 회전 스프링을 가진 Pasternak지반 위해 놓인 Timoshenko보-기둥의 동적안정영역을 결정하였다.

• Structural Engineering and Mechanics
• /
• 제33권4호
• /
• pp.447-484
• /
• 2009

The spatially coupled buckling, in-plane, and lateral bucking analyses of thin-walled Timoshenko curved beam with non-symmetric, double-, and mono-symmetric cross-sections resting on elastic foundation are performed based on series solutions. The stiffness matrices are derived rigorously using the homogeneous form of the simultaneous ordinary differential equations. The present beam formulation includes the mechanical characteristics such as the non-symmetric cross-section, the thickness-curvature effect, the shear effects due to bending and restrained warping, the second-order terms of semitangential rotation, the Wagner effect, and the foundation effects. The equilibrium equations and force-deformation relationships are derived from the energy principle and expressions for displacement parameters are derived based on power series expansions of displacement components. Finally the element stiffness matrix is determined using force-deformation relationships. In order to verify the accuracy and validity of this study, the numerical solutions by the proposed method are presented and compared with the finite element solutions using the classical isoparametric curved beam elements and other researchers' analytical solutions.

• Structural Engineering and Mechanics
• /
• 제37권5호
• /
• pp.489-507
• /
• 2011

The dynamic response of a Timoshenko beam on a tensionless Pasternak foundation is investigated by assuming that the beam is subjected to a concentrated harmonic load at its middle. This action results in the creation of lift-off regions between the beam and the foundation that effect the character of the response. Although small displacements for the beam and the foundation are assumed, the problem becomes nonlinear since the contact/lift-off regions are not known at the outset. The governing equations of the beam, which are coupled in deflection and rotation, are obtained in both the contact and lift-off regions. After removing the coupling, the essentials of the problem (the contact regions) are determined by using an analytical-numerical method. The results are presented in figures to demonstrate the effects of some parameters on the extent of the contact lengths and displacements. The results are also compared with those of Bernoulli-Euler, shear, and Rayleigh beams. It is observed that the solution is not unique; for a fixed value of the frequency parameter, more than one solution (contact length) exists. The contact length of the beam increases with the increase of the frequency and rotary-inertia parameters, whereas it decreases with increasing shear foundation parameter.

• 한국지진공학회논문집
• /
• 제28권4호
• /
• pp.165-170
• /
• 2024

This study investigated the impact of soil-structure interaction on multi-degree-of-freedom structures using the shallow-foundation Winkler model, known as the BNWF model. The model's period was determined through eigenvalue analysis and compared to results obtained from FEMA's formula. Results indicated that considering the soil, the structure's period increased by up to 8.7% compared to the fixed-base model, aligning with FEMA's calculations. Furthermore, with adequate ground acceleration, roof displacement increased by 3.4% to 3.8%, while base shear decreased by 4% to 10%. However, roof displacement and base shear increased in some earthquake scenarios due to spectral shape effects in regions with extended structural periods. Foundation damping effects, determined through the foundation's moment-rotation history, grew with higher ground acceleration. This suggests that accounting for period elongation and foundation damping can enhance the seismic design of multi-degree-of-freedom structures.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 추계 학술발표회
• /
• pp.598-604
• /
• 2010

The drilled pier foundation is widely used to support transmission line structures due to its simplicity of construction. When this foundation type is used in conjunction with a single shaft or H-frame structure, it is subjected to a high overturning moment, combined with modest vertical and shear loads. Since the length and diameter of drilled piers are often governed by a maximum permissible deflection, many drilled piers being installed today are very conservatively designed. In this study, Nine prototype field-tests (1/8 scale) have been conducted in order to determine the vertical and lateral resistance of drilled pier foundation for single pole structures. These test results reveal the test piers behaved essentially as rigid bodies in soil (6D) and the center of rotation of the pier were typically 0.6~0.4 of the pier depth below ground surface. Test results also show the relationship between the applied load and the deflection at the top of the pier is highly nonlinear.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
• /
• pp.1087-1094
• /
• 2008

The drilled pier foundation is widely used to support transmission line structures due to its simplicity of construction. When this foundation type is used in conjunction with a single shaft or H-frame structure, it is subjected to a high overturning moment, combined with modest vertical and shear loads. Since the length and diameter of drilled piers are often governed by a maximum permissible deflection, many drilled piers being installed today are very conservatively designed. In this study, Five prototype field-tests (1/8 scale) have been conducted in order to determine the lateral resistance of drilled pier foundation for single pole structures. These test results reveal the test piers behaved essentially as rigid bodies in soil (6D) and the center of rotation of the pier were typically 0.6~0.4 of the pier depth below ground surface. Test results also show the relationship between the applied load and the deflection at the top of the pier is highly nonlinear.

• 한국지반환경공학회 논문집
• /
• 제22권10호
• /
• pp.31-36
• /
• 2021

풍력발전기 기초의 누적 회전각과 침하량을 예측하는 것은 매우 중요하다. 하지만 반복하중에 따른 버킷기초의 장기거동을 분석하는 연구는 거의 이루어지지 않았다. 본 연구에서는 사질토 지반에 설치된 버킷기초의 다양한 3차원 유한요소해석을 수행하였다. 반복 삼축압축시험으로부터 도출된 강성감소 경험식을 수치모델에 사용자 서브루틴으로 적용하여 해석을 수행하였다. 강성감소 모델을 사용하여 버킷기초의 누적 회전각을 산정하였으며, 반복하중 작용 시 거동에 영향을 주는 주요인자에 대한 분석이 이루어졌다.