• Title/Summary/Keyword: axial force effect

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Nonlinear response of the pile group foundation for lateral loads using pushover analysis

  • Zhang, Yongliang;Chen, Xingchong;Zhang, Xiyin;Ding, Mingbo;Wang, Yi;Liu, Zhengnan
    • Earthquakes and Structures
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    • v.19 no.4
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    • pp.273-286
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    • 2020
  • The pile group foundation is widely used for gravity pier of high-speed railway bridges in China. If a moderate or strong earthquake occurs, the pile-surrounding soil will exhibit obvious nonlinearity and significant pile group effect. In this study, an improved pushover analysis model for the pile group foundation with consideration of pile group effect is presented and validated by the quasi-static test. The improved model uses simplified springs to simulate the soil lateral resistance, side friction and tip resistance. PM (axial load-bending moment) plastic hinge model is introduced to simulate the impact of the axial force changing of pile group on their elastic-plastic characteristics. The pile group effect is considered in stress-stain relations of the lateral soil resistance with a reduction factor. The influence factors on nonlinear characteristics and plastic hinge distribution of the pile group foundation are discussed, including the pier height, longitudinal reinforcement ratio and stirrup ratio of the pile, and soil mechanical parameters. Furthermore, the displacement ductility factor, resistance increase factor and yielding stiffness ratio are provided to evaluate the seismic performance of soil-pile system. A case study for the pile group foundation of a railway simply supported beam bridge with a 32 m-span is conducted by numerical analysis. It is shown that the ultimate lateral force of pile group is not determined by the yielding force of the single one in these piles. Therefore, the pile group effect is essential for the seismic performance evaluation of the railway bridge with pile group foundation.

Effect of Anchorage on Strength of Precast R/C Beam-Column Joints

  • Kim, Kwangyeon
    • Architectural research
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    • v.2 no.1
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    • pp.55-60
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    • 2000
  • Recently, there is a great demand for precast reinforced concrete (RC) construction methods on the purpose of simplicity in construction. Nishimatsu Construction Company has developed a construction method with precast reinforced concrete members in medium-rise building. In this construction method, how to joint precast members, especially the anchorage of the main bar of beam, is important problem. In this study, the structural performance of exterior joints with precast members was investigated. The parameters of the test specimens are anchorage type of the main bar of beam (U-shape anchorage or anchorage plate) and the ratio of the column axial force to the column strength. Specimens J-3 and J-4 used U-shape anchorage and the ratio of the column axial force of specimen J-4 was higher. On the other hand, specimens J-5 and J-6 used anchorage plate, and the anchorage lengths are 15d and 18d, respectively. Experimental results are summarized as follows; 1) For the joints with beam flexural failure mode, it was found that the maximum strength of specimen with anchorage plate is equal to or larger than that of specimen with conventional U-shaped anchorage if the anchorage length of more than 15d would be ensured, 2) Each specimen shows stable hysteretic curves and there were no notable effects on the hysteretic characteristics and the maximum strength caused by the anchorage method of beam main bar and the difference of column axial stress level.

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Influence of shear on seismic performance and failure mode of RC piers (전단이 RC 교각의 지진성능 및 파괴모드에 미치는 영향)

  • Lee, Do-Hyeong
    • The Journal of Engineering Research
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    • v.6 no.1
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    • pp.53-63
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    • 2004
  • In this paper, influence of shear on the seismic performance and failure mode of reinforced concrete piers subjected to earthquake loading is investigated. Comparative study has been carried out for reinforced concrete column tests to verify the shear-axial interaction model presented in this paper. Comparison shows that predicted shear hysteretic response agrees well with the test results. Also conducted is a nonlinear time-history analysis of a reinforced concrete bridge damaged by the Kobe earthquake using the current development. Displacement response for piers reveals that maximum displacement is considerably increased due to the effect of shear coupled with axial force variation, which leads to overall stiffness degradation and period elongation. It is therefore concluded that the response considering both shear and axial force gives better explanation regarding the seismic damage evaluation of reinforced concrete bridge piers.

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A new and simple analytical approach to determining the natural frequencies of framed tube structures

  • Mohammadnejad, Mehrdad;Kazemi, Hasan Haji
    • Structural Engineering and Mechanics
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    • v.65 no.1
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    • pp.111-120
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    • 2018
  • This paper presents a new and simple solution for determining the natural frequencies of framed tube combined with shear-walls and tube-in-tube systems. The novelty of the presented approach is based on the bending moment function approximation instead of the mode shape function approximation. This novelty makes the presented solution very simpler and very shorter in the mathematical calculations process. The shear stiffness, flexural stiffness and mass per unit length of the structure are variable along the height. The effect of the structure weight on its natural frequencies is considered using a variable axial force. The effects of shear lag phenomena has been investigated on the natural frequencies of the structure. The whole structure is modeled by an equivalent non-prismatic shear-flexural cantilever beam under variable axial forces. The governing differential equation of motion is converted into a system of linear algebraic equations and the natural frequencies are calculated by determining a non-trivial solution for the system of equations. The accuracy of the proposed method is verified through several numerical examples and the results are compared with the literature.

Effect of groundwater level change on piled raft foundation in Ho Chi Minh City, Viet Nam using 3D-FEM

  • Kamol Amornfa;Ha T. Quang;Tran V. Tuan
    • Geomechanics and Engineering
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    • v.32 no.4
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    • pp.387-396
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    • 2023
  • Ground subsidence, which is a current concern that affects piled raft foundations, has occurred at a high rate in Ho Chi Minh City, Viet Nam, due primarily to groundwater pumping for water supply. In this study, the groundwater level (GWL) change affect on a piled raft foundation was investigated based on the three-dimensional finite element method (3D-FEM) using the PLAXIS 3D software. The GWL change due to global groundwater pumping and dewatering were simulated in PLAXIS 3D based on the GWL reduction and consolidation. Settlement and the pile axial force of the piled raft foundation in Ho Chi Minh subsoil were investigated based on the actual design and the proposed optimal case. The actual design used the piled foundation concept, while the optimal case applied a pile spacing of 6D using a piled raft concept to reduce the number of piles, with little increased settlement. The results indicated that the settlement increased with the GWL reduction, caused by groundwater pumping and dewatering. The subsidence started to affect the piled raft foundation 2.5 years after construction for the actual design and after 3.4 years for the optimal case due to global groundwater pumping. The pile's axial force, which was affected by negative skin friction, increased during that time.

Dynamic Characteristics of the Radial Clearance Flow between Axially Oscillating Rotational Disk and Stationary Disk

  • Horiguchi, Hironori;Ueno, Yoshinori;Takahashi, Koutaro;Miyagawa, Kazuyoshi;Tsujimoto, Yoshinobu
    • International Journal of Fluid Machinery and Systems
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    • v.2 no.2
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    • pp.147-155
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    • 2009
  • Dynamic characteristics of the clearance flow between an axially oscillating rotational disk and a stationary disk were examined by experiments and computations based on a bulk flow model. In the case without pressure fluctuations at the inlet and outlet of the clearance, parallel and contracting flow paths had an effect to stabilize the axial oscillation of the rotating disk. The enlarged flow path had an effect to destabilize the axial oscillation due to the negative damping and stiffness for outward and inward flows, respectively. It was shown that the fluid force can be decomposed into the component caused by the inlet or outlet pressure fluctuation without the axial oscillation and that due to the axial oscillation without the inlet or outlet pressure fluctuation. A method to predict the stiffness and damping coefficients is proposed for general cases when the device is combined with an arbitrary flow system.

Moment-curvature hysteresis model of angle steel frame confined concrete columns

  • Rong, Chong;Tian, Wenkai;Shi, Qingxuan;Wang, Bin;Shah, Abid Ali
    • Structural Engineering and Mechanics
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    • v.83 no.1
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    • pp.19-29
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    • 2022
  • The angle steel frame confined concrete columns (ASFCs) are an emerging form of hybrid columns, which comprise an inner angle steel frame and a concrete column. The inner angle steel frame can provide axial bearing capacity and well confining effect for composite columns. This paper presents the experimental and theoretical studies on the seismic behaviour of ASFCs. The experimental study of the 6 test specimens is presented, based on the previous study of the authors. The theoretical study includes two parts. One part establishes the section analysis model, and it uses to analyze section axial force-moment-curvature. Another part establishes the section moment-curvature hysteresis model. The test and analysis results show that the axial compression ratio and the assembling of steel slabs influence the local buckling of the angle steel. The three factors (axial compression ratio, content of angle steel and confining effect) have important effects on the seismic behaviour of ASFCs. And the theoretical model can provide reasonably accurate predictions and apply in section analysis of ASFCs.

An analysis of cutting force according to specific force coefficients (비절삭저항 상수 변화에 따른 절삭력 분석)

  • Kim, Jong-Do;Yoon, Moon-Chul
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.13 no.2
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    • pp.108-116
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    • 2014
  • Considering the run-out effect and cutting force coefficients, the cutting force profile of half immersion end-milling was analyzed in detail. The effects of three specific cutting-force coefficients and three edge-force coefficients are verified. Through a detailed investigation, it is proved that the radial cutting force coefficients and are the major factors which increase the cutting forces Fx and Fy in end-milling. However, the axial cutting force coefficients have no influence on the force Fx and Fy changes in end-milling. Also, the analyzed end-milling force model shows good consistency with the actual measured force with regard to Fx and Fy. Thus, this model can be used for the prediction of the force history in end-milling with run-out, and it incurs a different force history with different start and exit immersion angles as well as holding effects.

Study of Effect of tunnelling on pile group - Numerical Analysis (터널 굴착이 무리말뚝거동에 미치는 영향에 대한 수치해석연구)

  • Woo, Seung-Je;Choi, Go-Ny;Yoo, Chung-Sik
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.09b
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    • pp.96-103
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    • 2010
  • This paper presents of effect of tunneling on pile group of being operated bridge using Three-dimensional numerical modeling to study the effect of coordination of tunneling location under discontinuous group pile. In order to find idealistic tunneling location that causes settlement, change of stress on the piles and movement of soil at a minimum, a fully coupled 3D finite element model is adopted. The study contains pile settlement, axial force on each piles in the group, axial displacement of piles and soil behaviour caused by tunneling. Based on the result some insights into the pile behavior due to tunneling obtained from numerical analysis were mentioned and discussed.

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