• Title, Summary, Keyword: 휨 변형

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The Effect of Axial Force on the Behavior and Average Crack Spacing of Reinforced Concrete Flexural Member (축력이 철근콘크리트 휨부재의 거동과 평균 균열간격에 미치는 영향)

  • 양은익;김진근;이성태;임전사랑
    • Magazine of the Korea Concrete Institute
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    • v.9 no.4
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    • pp.207-214
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    • 1997
  • This study was performed to verify the effect of axial force due to restraint on the mechanical behavior and the average crack spacing of the reinforced concrett. ilexural menlbers. For. this purpose, the flexural sttvngt.h and rigidity werc experimentally investigated undcl. axially rcstmined and unr.est.rainrd conditions. Furthermore , the average crack spacing was also checkcd for the axilly restrained contlit.ion. Thc test results showd that the flexual strength and rigidity of t,he restrained beam were higher. than those of the unrestrained beam. The major. factors affecting on the average crack spacing were steeel stress, axial force, cicumference of reinforcing bar and effective tension arm of concrete. However. the concrete compressive strength was minor effect. Including thesc factors, a prediction equation for the average crack spacing of the restrained member was proposed.

A C Finite Element of Thin-Walled Laminated Composite I-Beams Including Shear Deformation (전단변형을 고려한 적층복합 I형 박벽보의 C유한요소)

  • Baek, Seong-Yong;Lee, Seung-Sik
    • Journal of Korean Society of Steel Construction
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    • v.18 no.3
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    • pp.349-359
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    • 2006
  • This paper presents a new block stiffness matrix for the analysis an orthogonal Cartesian coordinate system. The displacement fields are defined using the first order shear deformable beam theory. The longitudinal displacement can be expressed as the sum of the projected plane deformation of the cross-section due to Timoshenko's beam theory and axial warping deformation due to modified Vlasov's thin-waled beam theory. The derived element takes into account flexural shear deformation and torsional warping deformation. Three different types of beam elements, namely, the two-noded, three-noded, and four-noded beam elements, are developed. The quadratic and cubic elements are found to be very efficient for the flexural analysis of laminated composite beams. The versatility and accuracy of the new element are demonstrated by comparing the numerical results available in the literature.

Analytical Study on Ductility Index of Reinforced Concrete Flexural Members (철근 콘크리트 휨부재의 연성지수에 관한 해석적 연구)

  • Lee, Jae Hoon
    • Journal of The Korean Society of Civil Engineers
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    • v.14 no.3
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    • pp.391-402
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    • 1994
  • One of the most important design concept for reinforced concrete structures is to achieve a ductile failure mode, and also moment redistribution for economic design is possible in case that adequate ductility is provided. Flexural ductility index is, therefore, used as a reference for possibility of moment redistribution as well as for prediction of flexural behavior of designed R.C. structures. Ductility index equations, however, provide approximate values due to the linear concrete compressive stress assumption at the tension steel yielding state. Theoretically more exact ductility index is calculated by a numerical analysis with the realistic stress-strain curves for concrete and steel to be compared with the result from tire ductility index equations. Variation of ductility index for the selected variables and the reasonable maximum tension steel ratio for doubly reinforced section are investigated. A moment-curvature curve model is also proposed for future research on moment redistribution.

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An Experimental Study on Flexural Behavior of Beams Reinforced with Zinc-Coated Rebar (아연코팅 철근콘크리트 보의 휨 거동 실험 연구)

  • Yang, In-Hwan;Kim, Kyong-Chul
    • Journal of the Korea Concrete Institute
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    • v.26 no.3
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    • pp.299-306
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    • 2014
  • Coating is one of the methods used to solve the problem of corrosion of reinforcement in concrete structures. There are few research reported in the literature regarding the effect of zinc-coating on flexural behavior compared to epoxy coating. The objective of this study was to determine whether zinc-coated rebar adversely affects flexural behavior. Concrete beams reinforced with black or zinc-coated steel were tested in flexure. The test variables included the presence of rebar surface coating with zinc, steel ratio used and cover depth. The study concentrated on comparing crack pattern, crack width, deflection and strain. The ultimate flexural capacity of beams reinforced with zinc-coated bars was not different from that of black steel reinforced beams. The results from deflection and crack width measurements were indicative of no significant variation for the different rebar surface conditions. In addition, it was found that load-strain curve of beam reinforced with zinc-coated steel was similar to that of beam reinforced with zinc-coated steel. Therefore, the test results indicated that the use of zinc-coated rebar had no adverse effect on flexural behavior compared to the use of black rebar.

Two-Stage Design Optimization of an Automotive Fog Blank Cover for Enhancing Its Injection Molding Quality (자동차용 안개등 커버의 사출성형 품질 향상을 위한 2 단계 설계 최적화)

  • Park, Chang-Hyun;Ahn, Hee-Jae;Choi, Dong-Hoon;Pyo, Byung-Gi
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.8
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    • pp.1097-1103
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    • 2010
  • Injection pressure, an important factor in the filling procedure, should be minimized to enhance injection molding quality. In addition, warping deformation and weld lines, which are representative failures, should be avoided to enhance injection molding quality. To improve injection molding quality, the design procedure for an automotive fog blank cover is divided into two stages. In the first stage, we optimally obtain injection molding process variables that minimize injection pressure and warping deformation by using design of experiments, approximation and optimization techniques equipped in PIAnO (Process Integration, Automation and Optimization), a commercial PIDO (Process Integration and Design Optimization) tool. Then, we determine the thickness of the automotive fog blank cover that enables us to avoid generating weld lines. The design results we obtain in this study are found far better than those of the initial design, which demonstrates the effectiveness of our design method.

Estimation of Orthotropic Flexural Rigidities Considering the Deformed Shape for a Plate Stiffened with Rectangular Ribs (변형 형상을 고려한 평강 리브 보강판의 직교이방성 휨강성 산정)

  • Chu, Seok Beom;Im, Kwan Hyuk
    • Journal of Korean Society of Steel Construction
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    • v.19 no.6
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    • pp.621-632
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    • 2007
  • The purpose of this study was the estimation and formulation of orthotropic flexural rigidities considering the deformed shape for a plate stiffened with rectangular ribs. Analytical results of methods modifying the flexural rigidity of the x-direction, the y-direction or both directions were compared at the center, the x-directional quarter point and the y-directional quarter point of stiffened plates loaded at the center. The composite method modifying the flexural rigidity of both directions improves the accuracy compared with the other methods. Moreover, the ratio of modified coefficients for each directional rigidity can be expressed as a function corresponding to each dimension of stiffened plates. The application of modified coefficient functions to various types of stiffened plates with different boundary conditions, aspect ratios and rib arrangement shows that the increment of the error ratio is small compared with examples of this study and the application of proposed functions shows more accurate results than previous methods modifying the flexural rigidity. Therefore, by using the modified coefficient functions proposed in this study, the orthotropic plate analysis of plates stiffened with rectangular ribs can easily achieve more accurate displacement results.

Transient Analysis of High-rise Wall-Frame Structures with Outriggers under Seismic Load (초고층 전단벽-골조 아웃리거 구조시스템의 지진하중에 대한 시간이력해석)

  • Kim, Jin Man;Choe, Eun Hui;Park, Dae Gyu;Lee, Jae Hong
    • Journal of Korean Society of Steel Construction
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    • v.20 no.2
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    • pp.303-312
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    • 2008
  • In this paper, the seismic behavior of shear wal-frame systems is analyzed. The governing equations of the wall-frame systems with outrigger truss are formulated through the continuum approach and the whole structure is idealized as a shear-flexural cantileverwith rotational spring. The effect of shear deformation and flexural deformation of the wall-frame and outrigger trusses are considered and incorporated in the formulation of the wall-frame structures with and without outriggers are compared by using finite element analysis incorporated with the Newmark-${\beta}$ method. Numerical results are obtained and compared with the finite element package MIDAS. The proposed method is found to be simple and efficient, and provides reason ably accurate results in the early design stage of tall building structures.

Cracking Behavior and Flexural Performance of RC Beam with Strain Hardening Cement Composite and High-Strength Reinforcing Bar (고강도 철근과 변형경화형 시멘트복합체를 사용한 보의 균열거동 및 휨 성능)

  • Jang, Seok-Joon;Kang, Su-Won;Yun, Hyun-Do
    • Journal of the Korea Concrete Institute
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    • v.27 no.1
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    • pp.37-44
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    • 2015
  • This paper describes the effect of strain hardening cement composite (SHCC) material on structure performance of reinforced concrete (RC) beams with high-strength reinforcing bar. Also, this paper explores the structure application of SHCC in order to mitigation cracking damage and improve the ductility of flexural RC members. The prediction model for flexural strength of doubly reinforced SHCC beams are investigated in this study. To achieve the these objectives, a total of 6 rectangular beam specimens were tested under four point monotonic loading condition. The main parameters included the types of cement composite and reinforcing bar. Test results indicated that reinforced beam specimens with SHCC material were improved the structure performances and damage characteristics. Specifically, replacement of conventional high-strength concrete with SHCC materials has the potential of high-strength steel bar as flexural reinforcement on RC members. It is remarkable that suggested method of reinforced SHCC beams with high-strength reinforcing bar could be used usefully to the structure design.

Flexural Behavior of Glass Fiber Reinforced Plastic Pipes (유리섬유 강화 플라스틱관의 휨거동에 관한 연구)

  • 장동일;고재원
    • Magazine of the Korea Concrete Institute
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    • v.5 no.3
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    • pp.187-194
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    • 1993
  • 본 논문에서는 유리섬유의 적층수, 유리섬유의 배향각도에 대한 유리섬유 강화 플라스틱(Glass Fiber Reinforced Plastics ; GFRP)의 인장거동 변화를 고찰하고, 이들의 상관관계를 규명하기 위하여 일련의 GFRP 시험체에 대하여 인장실험을 수행하였다. 시험체는 폭12.5mm, 길이 60mm크기로 일정하게 제작하였으며, 시험체에 대하여 인장실험을 수행하였다. 시험체 제작시 유리섬유로 적층수는 14, 22, 30층, 유리섬유의 배향각도는 0$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$로 하였다. 인장실험시 각 시험체의 파괴양상, 극한하중 및 하중변화에 대한 인장변형율을 조사하였고, 이들 결과를 토대로 유리섬유의 적층수와 배향각도에 따른 GFRP의 극한하중, 응력-변형율 선도 및 탄성계수 등을 비교 분석하였다. 한편 본 논문에서는 유리섬유의 적층수, 직경 변화에 따른 GFRP관의 파괴거동을 고찰하기 위하여 4점 재하법에 의한 GFRP관의 휨파괴실험을 수행하였다. 실험에 사용된 시험체는 길이 1200mm로 하였으며, 유리섬유의 적층수를 30, 35, 40층, 관의 직경을 50, 100, 150mm로 하였다. 파괴실험시 각 시험체의 하중변화에 대한 휨 변형율, 중앙점 처짐량 및 항복하중을 측정하였고, 이들 결과를 토대로 유리섬유으 적층수와 관의 직경에 따라 GFRP관의 항복하중 및 파괴에너지를 비교 분석 하였으며, 항복시 파괴에너지를 추정할 수 있는 제안식을 유도하였다.

Flexural Analysis of Reinforced Concrete Members Strengthened with FRP Systems Based on Strength Method (FRP 시스템으로 보강한 철근콘크리트 부재의 휨 해석)

  • Cho, Baik-Soon;Kim, Seong-Do;Cheung, Jin-Hwan
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.2
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    • pp.175-186
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    • 2006
  • Strength method for determining nominal moment capacity of reinforced concrete members is also assumed to be suitable for strengthened members with FRP system. If the internal tensile forces of the strengthened member from steel and FRP is insufficient, the FRP system strain might become greater than its ultimate tensile strain which makes the strength method a contradiction and unapplicable. The experimental results of 27 strengthened beams with carbon fiber sheets which have relatively lower tensile forces from steel and FRP show that not only concrete compressive strain is lower than 0.003 but also measured ultimate moment was lower than nominal moment using the strength method.