• Title/Summary/Keyword: constant axial load

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Effect of tube area on the behavior of concrete filled tubular columns

  • Gupta, P.K.;Verma, V.K.;Khaudhair, Ziyad A.;Singh, Heaven
    • Computers and Concrete
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    • v.15 no.2
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    • pp.141-166
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    • 2015
  • In the present study, a Finite Element Model has been developed and used to study the effect of diameter to wall thickness ratio (D/t) of steel tube filled with concrete under axial loading on its behavior and load carrying capacity. The model is verified by comparing its findings with available experimental results. Influence of thickness and area of steel tube on strength, ductility, confinement and failure mode shapes has been studied. Strength enhancement factors, load factor, confinement contribution, percentage of steel and ductility index are defined and introduced for the assessment. A parametric study by varying length and thickness of tube has been carried out. Diameter of tube kept constant and equals to 140 mm while thickness has been varied between 1 mm and 6 mm. Equations were developed to find out the ultimate load and confined concrete strength of concrete. Variation of lateral confining pressure along the length of concrete cylinder was obtained and found that it varies along the length. The increase in length of tubes has a minimal effect on strength of tube but it affects the failure mode shapes. The findings indicate that optimum use of materials can be achieved by deciding the thickness of steel tube. A better ductility index can be obtained with the use of higher thickness of tube.

Modelling inelastic hinges using CDM for nonlinear analysis of reinforced concrete frame structures

  • Rajasankar, J.;Iyer, Nagesh R.;Prasad, A. Meher
    • Computers and Concrete
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    • v.6 no.4
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    • pp.319-341
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    • 2009
  • A new formulation based on lumped plasticity and inelastic hinges is presented in this paper for nonlinear analysis of Reinforced Concrete (RC) frame structures. Inelastic hinge behaviour is described using the principles of Continuum Damage Mechanics (CDM). Member formulation contains provisions to model stiffness degradation due to cracking of concrete and yielding of reinforcing steel. Depending on its nature, cracking is classified as concentrated or distributed. Concentrated cracking is accounted through a damage variable and its growth is defined based on strain energy principles. Presence of distributed flexural cracks in a member is taken care of by modelling it as non-prismatic. Plasticity theory supported by effective stress concept of CDM is applied to describe the post-yield response. Nonlinear quasi-static analysis is carried out on a RC column and a wide two-storey RC frame to verify the formulation. The column is subjected to constant axial load and monotonic lateral load while the frame is subjected to only lateral load. Computed results are compared with those due to experiments or other numerical methods to validate the performance of the formulation and also to highlight the contribution of distributed cracking on global response.

Buckling and Vibration of Laminated Composite Non-Circular Cylindrical Shells (비원형 단면을 가진 적층복합재료원통셸의 좌굴 및 진동해석)

  • 이영신;안상균;이우식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.5
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    • pp.807-819
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    • 1989
  • Buckling and vibration of laminated non-circular cylindrical shells with constant thickness and simply supported boundary condition is considered. Governing equations are derived based on the Donnell and Flugge shell theory and Galerkin method is applied for the numerical analysis. Comparisons are made between present results and others. Variations of frequency parameter and buckling load parameter on the change of stacking angle, eccentricity parameter and shell theories are investigated. Conclusion of this study is as follows: (1) General solutions of buckling and vibration of laminated non-circular cylindrical shell are obtained. (2) Frequency parameter is decreased as the initial axial load is increased. (3) In general, frequency and buckling load parameter of laminated non-circular cylindrical shells are decreased as increasing of eccentricity parameter and stacking angle.

Dynamic characteristics of elastic beams subjected to traffic loads

  • Tang, Chia-Chih;Wang, Yang-Cheng
    • Structural Engineering and Mechanics
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    • v.13 no.2
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    • pp.211-230
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    • 2002
  • The objective of this study is to investigate the dynamic behavior of elastic beams subjected to moving loads. Although analytical methods are available, they have limitations with respect to complicated structures. The use of computer technology in recent years is an effective way to solve the problem; thus using the latest technology this study establishes a finite-element solution procedure to investigate dynamic behaviors of a typical elastic beam having a set of constant geometric properties and various span lengths. Both the dead load of the beam and traffic load are applied in which the traffic load is considered a concentrated moving force with various traveling passage speeds on the beam. Dynamic behaviors including deflection, shear, and bending moment due to moving loads are obtained by both analytical and finite element methods; for simple structures, they have an excellent agreement. The numerical results show that based on analytical methods the fundamental mode is good enough to estimate the dynamic deflection along the beam, but is not sufficient to simulate the total response of the shear force or the bending moment. The linear dynamic behavior of the elastic beams subjected to multiple exciting loads can easily be found by linear superposition, and the geometric nonlinear results caused by large deformation and axial force of the beam are always underestimated with only a few exceptions which are indicated. In order to make the results useful, they have been nondimensionalized and presented in graphical form.

Seismic Behavior of High-Strength Reinforced Concrete Bridge Columns (고강도 철근콘크리트 교각의 내진 거동)

  • Hwang Sun-Kyoung;Lee Chin-Ok;Ryu Hyo-Jin;Yun Hyun-Do;Lim Byung-Hoon
    • Journal of the Korea Concrete Institute
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    • v.17 no.4 s.88
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    • pp.505-511
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    • 2005
  • This experimental investigation was conducted to examine the seismic performance of reinforced concrete bridge columns. The columns were subjected to a constant axial load and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research were the volumetric ratios of transverse reinforcement (ps=0.96, 1.44 percent) and axial load ratios (P/Po=0.05, 0.1, 0.2) and concrete strengths (35, 60MPa). Test results showed that bridge columns with $44\%$ higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-02 showed ductile behavior. For bridge columns with axial load ratio(P/Po) less than 0.2, the ratio of $M_{max}\;over\;M_{ACI}$, nominal moment capacity predicted by ACI 318-02 provisions, was consistently greater than 1 with approximately a $20\%$ margin of safety.

Investigating the Influence of Rate Dependency and Axial Force on the Seismic Performance Evaluation of Isolation Bearing (면진받침의 내진성능평가를 위한 실험 시 속도의존성과 수직하중의 영향)

  • Minseok Park;Yunbyeong Chae;Chul-Young Kim
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.27 no.6
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    • pp.22-29
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    • 2023
  • In the evaluation of seismic performance for structural materials and components, the loading rate and axial force can have a significant impact. Due to time-delay effects between input and output displacements, It is difficult to apply high-rate displacement in cyclic tests and hybrid simulations. Additionally, the difficulty of maintaining a consistent vertical load in the presence of lateral displacement has limited fast and real-time tests performed while maintaining a constant vertical load. In this study, slow, fast cyclic tests and real-time hybrid simulations were conducted to investigate the rate dependency and the influence of vertical loads of Isolation Bearing. In the experiment, the FLB System including an Adaptive Time Series (ATS) compensation and a state estimator was constructed for real-time control of displacement and vertical load. It was found that the vertical load from the superstructure and loading rate can have a significant impact on the strength of the seismic isolation bearing and its behavior during an earthquake. When conducting experiments for seismic performance evaluation, they must be implemented to be similar to reality. This study demonstrates the excellent performance of the system built and used for seismic performance evaluation and enables accurate and efficient seismic performance evaluation.

Experimental studies on behaviour of tubular T-joints reinforced with grouted sleeve

  • Jiang, Shouchao;Guo, Xiaonong;Xiong, Zhe;Cai, Yufang;Zhu, Shaojun
    • Steel and Composite Structures
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    • v.23 no.5
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    • pp.585-596
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    • 2017
  • Tubular joints have been widely used in offshore platforms and space structures due to their merits such as easy fabrication, aesthetic appearance and better static strength. For existing tubular joints, a grouted sleeve reinforced method was proposed in this paper. Experimental tests on five tubular T-joints reinforced with the grouted sleeve and two conventional tubular T-joints were conducted to investigate their mechanical behaviour. A constant axial compressive force was applied to the chord end to simulate the compressive state of the chord member during the tests. Then an axial compressive force was applied to the top end of the brace member until the collapse of the joint specimens occurred. The parameters investigated herein were the grout thickness, the sleeve length coefficient and the sleeve construction method. The failure mode, ultimate load, initial stiffness and deformability of these joint specimens were discussed. It was found that: (1) The grouted sleeve could change the failure mode of tubular T-joints. (2) The grouted sleeve was observed to provide strength enhancement up to 154.3%~172.7% for the corresponding un-reinforced joint. (3) The initial stiffness and deformability were also greatly improved by the grouted sleeve. (4) The sleeve length coefficient was a key parameter for the improved effect of the grouted sleeve reinforced method.

Repair and Strengthening Methods for Concrete Structures using Sprayed Fiber Reinforced Polymers - Strengthening performance of Reinforced Concrete Shear Columns - (Sprayed FRP 공법에 의한 콘크리트 구조물의 보수.보강법 개발에 관한 연구 - 철근콘크리트 전단기둥의 보강성능 평가 -)

  • Lee, Kang-Seok;Byeon, In-Hee;Son, Young-Sun;Lee, Moon-Sung;Li, Cheng-Hao;Lee, Li-Hyung
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.137-140
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    • 2006
  • In this study, a seismic performance of reinforced concrete columns strengthened by a sprayed fiber reinforced polymer (SFRP) is investigated. For this purpose, six column specimens approximately scaled into 2/3, are designed and tested under a constant axial load, 10% of the nominal axial strength of column, and pseudo-static reversed cyclic lateral loading system. Four specimens are strengthened by Sprayed FRP using different combinations of short fibers (carbon or glass fiber) and resins (epoxy or vinyl esther). For comparison, the test investigated in this study also includes a specimen strengthened using carbon fiber reinforced polymer (CFRP), and also a control specimen without strengthening. The results revealed that specimens strengthened using SFRP showed a improved structure behavior, compared to control specimen, in terms of strength, ductility, lateral drift capacity, and energy-absorbtion capacity. In addition, compared to the specimen strengthened using CFRP, Sprayed FRP-strengthened specimens reasonably showed a equivalent seismic performance.

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Influence of loading condition and reinforcement size on the concrete/reinforcement bond strength

  • Turk, Kazim;Caliskan, Sinan;Sukru Yildirim, M.
    • Structural Engineering and Mechanics
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    • v.19 no.3
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    • pp.337-346
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    • 2005
  • The paper reports on a study of bond strength between reduced-water-content concrete and tensile reinforcement in spliced mode. Three different diameters (12, 16 and 22 mm) of tensile steel were spliced in the constant moment zone, where there were two bars of same size in tension. For each diameter of reinforcement, a total of nine beams ($1900{\times}270{\times}180mm$) were tested, of which three beams were with no axial force (positive bending) and the other six beams were with axial force (combined bending). The splice length was selected so that bars would fail in bond, splitting the concrete cover in the splice region, before reaching the yield point. It was found that there was a considerable size effect in the experimental results, i.e., as the diameter of the reinforcement reduced the bond strength and the deflection recorded at the midspan increased significantly, whilst the stiffness of the beams reduced. It was also found for all reinforcement sizes that higher bond strength and stiffness were obtained for beams tested in combined bending than that of the beams tested in positive bending only.

In-plane seismic performance of masonry wall retrofitted with prestressed steel-bar truss

  • Hwang, Seung-Hyeon;Kim, Sanghee;Yang, Keun-Hyeok
    • Earthquakes and Structures
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    • v.19 no.6
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    • pp.459-469
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    • 2020
  • An external prestressed steel-bar truss unit was developed as a new strengthening technology to enhance the seismic performance of an in-plane masonry wall structure while taking advantage of the benefits of a prestressed system. The presented method consists of six steel bars: two prestressed vertical bars to introduce a prestressing force on the masonry wall, two diagonal bars to resist shear deformation, and two horizontal bars to maintain the configuration. To evaluate the effects of this new technique, four full-scale specimens, including a control specimen, were tested under combined loadings that included constant-gravity axial loads and cyclic lateral loads. The experimental results were analyzed in terms of the shear strength, initial stiffness, dissipated energy, and strain history. The efficiency of the external prestressed steel-bar truss unit was validated. In particular, a retrofitted specimen with an axial load level of 0.024 exhibited a more stable post behavior and higher energy dissipation than a control specimen with an observed complete sliding failure. The four vertical bars of the adjacent retrofitting units created a virtual column, and their strain values did not change until they reached the peak shear strength. The shear capacity of the masonry wall structure with external prestressed steel-bar truss units could be predicted using the model suggested by Yang et al.