• Title, Summary, Keyword: axial ratio

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Experimental study on fire performance of axially-restrained NSC and HSC columns

  • Wu, Bo;Li, Yi-Hai
    • Structural Engineering and Mechanics
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    • v.32 no.5
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    • pp.635-648
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    • 2009
  • This paper describes fire performance of eight axially restrained reinforced concrete (RC) columns under a combination of two different load ratios and two different axial restraint ratios. The eight RC columns were all concentrically loaded and subjected to ISO834 standard fire on all sides. Axial restraints were imposed at the top of the columns to simulate the restraining effect of the rest of the whole frame. The axial restraint was effective when the column was expanding as well as contracting. As the results of the experiments have shown, the stiffness of the axial restraint and load level play an important role in the fire behaviors of both HSC and NSC columns. It is found that (a) the maximum deformations during expanding phase were influenced mostly by load ratio and hardly by axial restraint ratio, (b) For a given load ratio, axial restraint ratio had a great impact on the development of axial deformation during contraction phase beyond the initial equilibrium state, (c) increasing the axial restraint increased the value of restraint force generated in both the NSC and HSC columns, and (d) the development of column axial force during the contracting and cooling phase followed nearly parallel trend for columns under the same load ratio.

Axial compression ratio limit values for steel reinforced concrete (SRC) special shaped columns

  • Chen, Zongping;Xu, Jinjun;Chen, Yuliang;Xue, Jianyang
    • Steel and Composite Structures
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    • v.20 no.2
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    • pp.295-316
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    • 2016
  • This paper presents the results of experimental investigation, numerical calculation and theoretical analysis on axial compression ratio limit values for steel reinforced concrete (SRC) special shaped columns. 17 specimens were firstly intensively carried out to investigate the hysteretic behavior of SRC special shaped columns subjected to a constant axial load and cyclic reversed loads. Two theories were used to calculate the limits of axial compression ratio for all the specimens, including the balanced failure theory and superposition theory. It was found that the results of balanced failure theory by numerical integration method cannot conform the reality of test results, while the calculation results by employing the superposition theory can agree well with the test results. On the basis of superposition theory, the design limit values of axial compression ratio under different seismic grades were proposed for SRC special shaped columns.

Compressive performance of RAC filled GFRP tube-profile steel composite columns under axial loads

  • Ma, Hui;Bai, Hengyu;Zhao, Yanli;Liu, Yunhe;Zhang, Peng
    • Advances in concrete construction
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    • v.8 no.4
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    • pp.335-349
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    • 2019
  • To investigate the axial compressive performance of the recycled aggregate concrete (RAC) filled glass fiber reinforced polymer (GFRP) tube and profile steel composite columns, static loading tests were carried out on 18 specimens under axial loads in this study, including 7 RAC filled GFRP tube columns and 11 RAC filled GFRP tube-profile steel composite columns. The design parameters include recycled coarse aggregate (RCA) replacement percentage, profile steel ratio, slenderness ratio and RAC strength. The failure process, failure modes, axial stress-strain curves, strain development and axial bearing capacity of all specimens were mainly analyzed in detail. The experimental results show that the GFRP tube had strong restraint ability to RAC material and the profile steel could improve the axial compressive performance of the columns. The failure modes of the columns can be summarized as follow: the profile steel in the composite columns yielded first, then the internal RAC material was crushed, and finally the fiberglass of the external GFRP tube was seriously torn, resulting in the final failure of columns. The axial bearing capacity of the columns decreased with the increase of RCA replacement percentage and the maximum decreasing amplitude was 11.10%. In addition, the slenderness ratio had an adverse effect on the axial bearing capacity of the columns. However, the strength of the RAC material could effectively improve the axial bearing capacity of the columns, but their deformability decreased. In addition, the increasing profile steel ratio contributed to the axial compressive capacity of the composite columns. Based on the above analysis, a formula for calculating the bearing capacity of composite columns under axial compression load is proposed, and the adverse effects of slenderness ratio and RCA replacement percentage are considered.

Study on the performance of concrete-filled steel tube beam-column joints of new types

  • Liu, Dianzhong;Li, Hongxian;Ren, Huan
    • Computers and Concrete
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    • v.26 no.6
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    • pp.547-563
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    • 2020
  • In this paper, the influence of axial compression ratio on the mechanical properties of new type joints of side span of rectangular concrete-filled steel tubular column-H-type steel beam is studied. Two new types of side-span joints of rectangular concrete-filled steel tubular column-H-type steel beam are designed and quasi-static tests of five new type joints with 1:2 scale reduction ratios are performed. The axial compression ratio of joint JD1 is 0.3, 0.4 and 0.5, and the axial compression ratio of joint JD2 is 0.3 and 0.5. In the joint test, different axial forces were applied to the top of the column according to different axial compression ratios, and low-cyclic reciprocating load was applied on the beam. The stress and strain distribution, beam and column deformation, limit state, failure process, failure mechanism, stiffness degradation, ductile deformation and energy dissipation capacity of the joint were measured and analyzed. The results show that: with the increase of axial compression ratio, the ultimate bearing capacity of the joint decreases slightly, the plastic deformation decreases, and the stiffness and ductility decrease. According to the energy dissipation curve of the specimen, the equivalent damping coefficient also increases with the increase of axial compression ratio in a certain range, indicating that the increase of axial compression ratio can improve the seismic performance of the joint to a certain extent. The finite element method is used to simulate the joint test, and the test results are in good agreement with the simulation results.

Axial Force of a V-Belt CVT -Experimental Study- (V-벨트 CVT의 축력해석 II -실험적 연구-)

  • 김광원;김현수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.5
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    • pp.847-854
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    • 1989
  • Axial force of a V-belt CVT is investigated experimentally. The experimental results on speed ratio-torque-axial force show good agreement with the theoretical results that were obtained in the previous work. It is also found that torque capacity of the V-belt CVT increases as the axial force and the speed ratio increase. Impending slip which occurs at the maximum torque is determined via experiments for various speed ratios. Based on the impending slip region, and the theoretical curves for the speed ratio-torque-axial force relationship, an actual operating criteria for the V-belt CVT is obtained. It is suggested to use the actual operating criteria with the theoretical equations as a basic design formula for the V-belt CVT.

A Numerical Study on the Drag of Axial Cylinder (종축 실린더의 항력에 대한 수치 해석적 연구)

  • Lee, Hyun-Bae;Choi, Jung-Kyu;Kim, Hyoung-Tae
    • Journal of the Society of Naval Architects of Korea
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    • v.49 no.6
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    • pp.512-520
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    • 2012
  • In this study, the numerical analysis for the flows around an axial cylinder is carried out in order to investigate the basic characteristics of drag of blunt body. A variation of drag and flow separation for the axial cylinder is investigated according to the length-diameter ratio. Also, the flow separation around the head is removed by rounding-off the front edge of the body to analyze the effect of drag reduction. Most of the drag turns out to be a pressure drag component and the variation of drag is caused by the change of pressure and velocity which is affected strongly by the flow separation at the edges of the axial cylinder. Especially, it is found that the pressure drag component acting on the back of axial cylinder, as known as the base drag, mainly changes the drag. As the length-diameter ratio of axial cylinder increases, the drag sharply decreases and the minimum is shown when the length-diameter ratio is about 2.4. Also, as the length-diameter ratio increases further above 2.4, the drag increases at a slower rate. The pressure drag is almost constant when the length-diameter ratio is greater than 8, but the increase of friction drag component is the reason for the increase of the drag. When flow separation is removed completely at the front edge of the axial cylinder, the pressure drag component is reduced to 12~17%, but the total drag is reduced to only 17%~32% due to the friction drag component that increases linearly proportional to the length-diameter ratio.

Study on axial compressive behavior of quadruple C-channel built-up cold-formed steel columns

  • Nie, Shaofeng;Zhou, Tianhua;Liao, Fangfang;Yang, Donghua
    • Structural Engineering and Mechanics
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    • v.70 no.4
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    • pp.499-511
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    • 2019
  • In this study, the axial compressive behavior of novel quadruple C-channel built-up cold-formed steel columns with different slenderness ratio was investigated, using the experimental and numerical analysis. The axial compressive capacity and failure modes of the columns were obtained and analyzed. The finite element models considering the geometry, material and contact nonlinearity were developed to simulate and analyze the structural behavior of the columns further. There was a great correlation between the numerical analyses and test results, which indicated that the finite element model was reasonable and accurate. Then influence of, slenderness ratio, flange width-to-thickness ratio and screw spacing on the mechanical behavior of the columns were studied, respectively. The tests and numerical results show that due to small slenderness ratio, the failure modes of the specimens are generally local buckling and distortional buckling. The axial compressive strength and stiffness of the quadruple C-channel built-up cold-formed steel columns decrease with the increase of maximum slenderness ratio. When the screw spacing is ranging from 150mm to 450mm, the axial compressive strength and stiffness of the quadruple C-channel built-up cold-formed steel columns change little. The axial compressive capacity of quadruple C-channel built-up cold-formed steel columns increases with the decrease of flange width-thickness ratio. A modified effective length factor is proposed to quantify the axial compressive capacity of the quadruple C-channel built-up cold-formed steel columns with U-shaped track in the ends.

Parametric study on eccentrically-loaded partially encased composite columns under major axis bending

  • Begum, Mahbuba;Driver, Robert G.;Elwi, Alaa E.
    • Steel and Composite Structures
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    • v.19 no.5
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    • pp.1299-1319
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    • 2015
  • This paper presents a detailed parametric study, conducted using finite element tools to cover a range of several geometric and material parameters, on the behaviour of thin-walled partially encased composite (PEC) columns. The PEC columns studied herein are composed of thin-walled built-up H-shaped steel sections with concrete infill cast between the flanges. Transverse links are provided between the opposing flanges to improve resistance to local buckling. The parametric study is confined to eccentrically-loaded columns subjected to major axis bending only. The parameters that were varied include the overall column slenderness ratio (L/d), load eccentricity ratio (e/d), link spacing-to-depth ratio (s/d), flange plate slenderness ratio (b/t) and concrete compressive strength ($f_{cu}$). The overall column slenderness ratio was chosen to be the primary variable with values of 5, 10 and 15. Other parameters were varied within each case of L/d ratio. The effects of the selected parameters on the behaviour of PEC columns were studied with respect to the failure mode, peak axial load, axial load versus average axial strain response, axial load versus lateral displacement response, moment versus lateral displacement behaviour and the axial load-moment interaction diagram. The results of the parametric study are presented in the paper and the influences of each of the parameters investigated are discussed.

Plastification procedure of laterally-loaded steel bars under a rising temperature

  • Huang, Zhan-Fei;Tan, Kang-Hai;England, George L.
    • Structural Engineering and Mechanics
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    • v.35 no.6
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    • pp.699-715
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    • 2010
  • This paper investigates the structural responses of axially restrained steel beams under fire conditions by a nonlinear finite element method. The axial restraint is represented by a linear elastic spring. Different parameters which include beam slenderness ratio, external load level and axial restraint ratio are investigated. The process of forming a mid-span plastic hinge at the mid-span under a rising temperature is studied. In line with forming a fully plastic hinge at mid-span, the response of a restrained beam under rising temperature can be divided into three stages, viz. no plastic hinge, hinge forming and rotating, and catenary action stage. During catenary action stage, the axial restraint pulls the heated beam and prevents it from failing. This study introduces definitions of beam limiting temperature $T_{lim}$, catenary temperature $T_{ctn}$ and warning time $t_{wn}$. Influences of slenderness ratio, load level and axial restraint ratio on $T_{lim}$, $T_{ctn}$ and $t_{wn}$ are examined.

A Study on Development for Joint of Concrete Filled Steel Tube Column and P.C Reinforced Concrete Beam(2) -The Behaviors Properties of Joint with Key Parameter, such as Strength of Concrete, size of Panel Zone and Axial Force ratio- (콘크리트 충전강관 기둥과 PC 철근 콘크리트 보 접합부의 개발에 관한 연구(2) -콘크리트 강도, 판넬죤의 크기, 축력비를 변수로 한 접합부의 거동 특성-)

  • Park, Jung Min;Lee, Sung Jo;Kim, Wha Jung
    • Journal of Korean Society of Steel Construction
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    • v.9 no.1
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    • pp.107-120
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    • 1997
  • The purpose of this study is to develop composite structural system which is to have versatility in plan design and to improve economical efficieney, to maximise structural capacity than existing structural system. In this viewpoint, it was investigated to the properties of structural behaviors for i oint consisting of concrete filled steel square tube column and P.C reinforced concrete beam through a series of hysteretic behavior experiment. In the previous report, researched to the properties of joints with key parameters. such as Axial Force ratio and section types. From the based on previous results, this study investigated the properties of this joints with key parameters, such as strength of concrete, size of panel zone and Axial Force ratio. The obtained results are summarised as follows. (1) Investigating for the failure mode of the beam-to-column joint, the specimens of S,LL and LH series(except for L5H) presented flexural failure mode. (2) The initial stiffness of joint was increasd as the decrease of axial force ratio and increase of the concrete strength. (3) The rotation resisting capacity was effective as the increment of the concrete strength and decrement of the axial force ratio. (4) The emprical formula to predict the ultimate capacity of joint model to introduce decrease coefficient according to the axial force ratio to superimpose shearing strength of steel web(H section) and bending strength of reinforced concrete beam was expected.

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