• Title, Summary, Keyword: Buckling

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Structural Safely Analysis of a Modified 1-2W Type Greenhouse Enhanced for Culturing Paprika (착색단고추 재배용 1-2W형 개조온실 구조의 안정성 검토)

  • Suh, Won-Myung;Choi, Man-Kwon;Bae, Yong-Han;Lee, Jong-Won;Yoon, Yong-Cheol
    • Protected Horticulture and Plant Factory
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    • v.17 no.3
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    • pp.197-203
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    • 2008
  • This study was performed to check the structural safety of modified 1-2W Greenhouses to be utilized fur growing Paprika. This type of greenhouse was derived from being remodeled by enhancing the column height of conventional 1-2W type greenhouses. According to the results of structural analysis performed by SAP-2000, there was not significant change in critical snow depth in spite of increasing the column height of 1.2 m by welding. But the critical wind velocities were shown to be $26.0\sim4l.0m/s$, which were $3\sim18%$ lower wind velocities compared with those critical velocities estimated for typical type of 1-2W greenhouse. Under the wind loads, those maximum section forces such as shear force, axial force, and bending moment, together with the deformed frame shape of strained greenhouse, were almost similar in both typical type and modified type. Maximum bending moment of column was found at eave's height of column on windward side. Under the snow loads, those maximum section forces such as shear farce, axial force, and bending moment, together with the deformed frame shape of strained greenhouse, were almost similar in both typical type and modified type. Maximum section forces except axial force was found at eave's height of column. Maximum axial force was found at inner column. Soil bearing capacity together with the total foundation resistance against wind upheaval was found to be consistently safe enough to resist to both wind load and snow load.

Performance Evaluation of Steel Moment Frame and Connection including Inclined Column (경사기둥을 포함한 철골모멘트 골조 및 접합부의 성능평가)

  • Kim, Yong-Wan;Kim, Taejin;Kim, Jongho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.26 no.3
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    • pp.173-182
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    • 2013
  • The building design projects which are being proceeded nowadays pursue a complex and various shape of structures, escaping from the traditional and regular shape of buildings. In this new trend of the architecture, there rises a demand of the research in the structural engineering for the effective realization of such complex-shaped buildings which disassembles the orthogonality of frames. As a distinguished characteristics of the buildings in a complex-shape, there frequently are inclined columns included in the structural frame. The inclined column causes extra axial force and bending moment at the beam-column connection so it is necessary to assess those effects on the structural behavior of the frame and the connection by experiment or analysis. However, with comparing to the studies on the normal beam-column connections, the inclined column connections have not been studied sufficiently. Therefore, this study evaluated the beam-column connections having an inclined column using nonlinear and finite element analysis method. In this paper, steel moment frames having inclined columns were analyzed by the nonlinear pushover analysis to check the global behavior and beam-column connection models were analyzed by the finite element analysis to check the buckling behavior and the fracture potentials.

Initial Imperfection and Axial Strength of Struts with Octagonal Hollow Section fabricated from HR Plate (열연강판 팔각강관 버팀보의 초기편심과 축방향 압축강도)

  • Jo, Jae Byung
    • Journal of Korean Society of Steel Construction
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    • v.27 no.1
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    • pp.23-30
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    • 2015
  • Developed in this study were Octagonal-hollow-section(OHS) struts, whose compressive strengths against flexural and local buckling is higher than H-shape or rectangular-hollow-section(RHS) struts with the same unit weight. OHS members are also advantageous in handling and storing compared to circular hollow sections(CHS). OHS members were fabricated from HR Plates by cold forming and fillet welding. 5 numbers of 20m long OHS struts were assembled, each of which consist of two 9.6m long OHS member and two end connection elements made of cast iron. The compressive strength of the OHS strut was evaluated by comparing the test results, design codes and FEM analysis each other. Test results show that all of the struts have almost same or larger compressive strength than Korean Road Bridge Design Code(KRBDC) (2012). The initial imperfections can be estimated by using measured strains and are turned out to be less than L/450 for all the struts tested. The results of FEM analysis show that the variation of initial imperfection has less effects on the compressive strength for struts with vertical surcharge than for those with self-weight only, while the strength decreases as the initial imperfection increases. As the result of this study, the allowable initial imperfection for 20m long OHS struts is recommended to be less than L/350 on job sites.

Flexural Tensile Strength of CJP Groove Welded Joints Connecting Thick HSA800 Plates (HSA800 후판재의 완전용입 맞댐용접부 휨-인장강도 실험)

  • Lee, Cheol Ho;Kim, Dae Kyung;Han, Kyu Hong;Park, Chang Hee;Kim, Jin Ho;Lee, Seung Eun;Kim, Do Hwan
    • Journal of Korean Society of Steel Construction
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    • v.26 no.5
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    • pp.407-418
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    • 2014
  • As a continuing work of previously conducted standard tension tests, full-scale flexural tests were conducted in this study to assess the structural performance the CJP groove welded joints connecting thick HSA800 plates. Two welding electrodes were available at the time of this experimental research; one was GMAW-based electrode A and the other FCAW-based electrode B. Three full-scale box-type beam specimens with single bevel- and V-groove CJP welded joints were fabricated from 60mm and 25mm thick HSA800 plates according to the AWS-prequalified groove welded joint details. In designing the specimens, all possible limit states like local and lateral torsional buckling were carefully controlled in order to induce flexural plastic yielding or eventual joint fracture. All the CJP joints made by both welding electrodes showed satisfactory performance and were able to transfer the tensile flange forces higher than that corresponding to the measured tensile strength of HSA800 flange plates. However, it should be noted that, during fabrication, serious concerns about the welding efficiency and workability of the GMAW-based electrode were raised by a certified welder. The fracture occurred at the unbeveled (or vertical) interface between the weldment and the base metal when the GMAW-based electrode was used in the single-bevel joint, implying the possibility of insufficient melting. Thus, the FCAW-based electrode B is again recommended as the choice of welding electrode for HSA800 plates. The limited test data of this study implies that the V-groove CJP joint should be used in favor of the single bevel CJP joint, if possible.

Experimental Study on the Confinement Effect of Headed Cross Tie in RC Column Subjected to Cycling Horizontal Load (철근콘크리트 기둥에서 반복횡력에 대한 헤드형 횡보강근의 구속효과에 대한 실험연구)

  • Seo, Soo Yeon;Ham, Ju Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.16 no.5
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    • pp.1-10
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    • 2012
  • This paper presents an experimental result and suggests the confinement effect of headed cross tie in reinforced concrete(RC) columns subjected to cycling horizontal loads under constant axial load. Five RC columns specimens were manufactured, taking confined type of transverse reinforcement, whether or not using cross tie, end detail of cross tie (hooked or headed), and axial stress in column as major variables, Cyclic horizontal load applied to the columns under constant axial stress and the effect of cross tie to structural capacity of column was evaluated from the test. The column without cross tie failed showing bending deformation of hoop with crack in core concrete at low horizontal load while the column with cross tie showed quite improved strength and ductility by suppressing bending deformation of hoop as well as buckling of longitudinal bar at once even after crack in core concrete. At high lateral displacement, the column with hooked cross tie showed the failure pattern loosing the confining force of cross tie since the $90^{\circ}$ hooked part of cross tie was stretched out and the cracked core concrete lumps were came off. However, the column with headed cross tie showed very stable behavior since the head of cross tie effectively confined the hoop and longitudinal bars even at high lateral displacement.

Compressive Strength and Residual Stress Evaluation of Stub Columns Fabricated of High Strength Steel (고강도강재 단주의 압축강도 및 잔류응력 평가)

  • Lee, Cheol-Ho;Kim, Dae-Kyung;Han, Kyu-Hong;Kim, Jin-Ho;Lee, Seung-Eun;Ha, Tae-Hyu
    • Journal of Korean Society of Steel Construction
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    • v.24 no.1
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    • pp.23-34
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    • 2012
  • In this study, stub columns subjected to concentrical and eccentrical loads were tested to check the applicability of the current local stability criteria (KBC2009, AISC2005) to 800MPa high-strength steel (HSA800). The key test variables in the concentrically loaded tests included the plate-edge restraints and the width-to-thickness ratio normalized by the yield strength of steel. Specimens made of ordinary steel (SM490) were also tested for comparative purposes. Eccentrically loaded stub column tests were conducted for a range of the P-M combinations by controlling the loading eccentricity. All the concentrically loaded specimens with non-compact and slender sections developed sufficient strengths according to the current local stability criteria. All the eccentrically loaded specimens with non-compact H sections also exhibited a sufficient P-M interaction strength that was even higher than that of compact H- section counterparts. Residual stresses were also measured by using the non-destructive indentation method to demonstrate their dependency or independency on the steel material's yield strength. The measured results of this study also indicated that the magnitude of residual stresses bears no strong relation to the yield strength of the steel material.

Cyclic Loading Test for TSC Beam - PSRC Column Connections (TSC 합성보 - PSRC 합성기둥 접합부에 대한 주기하중 실험)

  • Hwang, Hyeon Jong;Eom, Tae Sung;Park, Hong Gun;Lee, Chang Nam;Kim, Hyoung Seop
    • Journal of Korean Society of Steel Construction
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    • v.25 no.6
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    • pp.601-612
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    • 2013
  • In the present study, details of the TSC beam-to-PSRC column connection for low and middle seismic zones were developed. For ease construction, the top and bottom flanges of the steel section of the TSC beam were discontinuous at the joint face on purpose, while the web passes through the joint. Thus, tensile resistance of the top and bottom flanges is not considered in the calculation of nominal strength of the connection. Cyclic loading tests on two interior connections and an exterior connection were performed to verify the seismic performance. The test parameter for two interior connections was the depth of the TSC beams: 600 and 700 mm including the slab depth. The test results showed that the nominal strength of the connections predicted by KBC 2009 correlated well with the test results. The connection specimens exhibited relatively good deformation and energy dissipation capacities, greater than the requirements for the ordinary and intermediate moment frames. Ultimately, the connection specimens were failed at the story drift ratios of 3.0 to 4.0 % due to local buckling and tensile fracture of the web of the TSC beam passing through the joint. By modifying the existing provisions of ASCE, the joint shear strength of the TSC beam-PSRC column connection was evaluated.

Experimental Study on Flexural Structural Performance of Sinusoidal Corrugated Girder (파형 웨브주름 보의 휨성능에 관한 실험적 연구)

  • Kim, Jong Sung;Chae, Il Soo
    • Journal of Korean Society of Steel Construction
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    • v.27 no.6
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    • pp.503-511
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    • 2015
  • In long span steel structure, the plate girder reinforced with stiffeners are commonly used. When choosing the cross section with deep depth of girder as well as narrow width, however, out of plane buckling can be a problem due to web slenderness. In an effort to solve this issue, current study determined the applicability of using corrugated web girder with deep depth as bending member, which is generally being utilized in both factory and warehouse nationwide. To accomplish this, we performed the loading test of H-shaped beam with sinusoidal corrugated web. Corrugated web CP-2.3 specimen exhibited 12% less maximal bending strength but CP-3.2 specimen exerted 24% increase in strength compared to plate web P-4.5. this result indicates that corrugated web provides enough strength even with unfavorable width-thickness ratio of plate. And bending as well as shear strength estimated by the Eurocode (EN 1993-1-5) were compared with both bending strength by loading test and shear strength estimated by KBC2009. In case of eurocode, increase in plate thickness did not help in bending performance improvement. moreover, shear performance was sensitive to the thickness of the web folds and the shape of the web plate.

Analysis Study on Fire Performance with Internal Anchored Concrete Filled Steel Tube Columns According to Percent of Steel-Fibers (강섬유 콘크리트 혼입율에 따른 내부앵커형 콘크리트 충전기둥 내화성능에 관한 해석적 연구)

  • Kim, Sun Hee;Yom, Kong Soo;Kim, Yong Hwan;Choi, Sung Mo
    • Journal of Korean Society of Steel Construction
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    • v.28 no.1
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    • pp.23-34
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    • 2016
  • Concrete filled steel tube system has two major advantages. First, the confinement effect of steel tube improves the compressive strength of concrete. Second, the load capacity and deformation capacity of members are improved because concrete restrains local buckling of steel tube. It does, however, involve workability problem of using stud bolts or anchor bolts to provide composite effect for larger cross-sections. While the ribs inside the columns are desirable in terms of compressive behavior, they cause the deterioration in load capacity upon in-plane deformation resulting from thermal deformation. Since the ribs are directly connected with the concrete, the deformation of the ribs accelerates concrete cracking. Thus, it is required to improve the toughness of the concrete to resist the deformation of the ribs. Welding built-up tubular square columns can secure safety in terms of fire resistance if the problem are solved. This study focuses on mixing steel fiber in the concrete to improve the ductility and toughness of the columns. In order to evaluate fire resistance performance, loaded heating test was conducted with 8 specimens. The behavior and thermal deformation capacity of the specimens were analyzed for major variables including load ratio. The reliability of heat transfer and thermal stress analysis model was verified through the comparison of the results between the test and previous study.

Seismic Performance of Circular RC Columns Retrofitted Using Ductile PET Fibers (고연성 PET 섬유로 보강된 철근콘크리트 원형 기둥의 내진성능)

  • Vachirapanyakun, Sorrasak;Lim, Myung-Kwan;Choi, Dong-Uk
    • Journal of the Korea Concrete Institute
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    • v.28 no.3
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    • pp.289-298
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    • 2016
  • An experimental research was performed using fibers for the purpose of retrofitting existing reinforced concrete circular columns. Glass fiber (GF) and polyethylene terephthalate (PET) were used as well as combined GF+PET (HF). PET has high tensile strength (over 600 MPa) and high ductility (about 15%), but has very low elastic modulus (about 1/6 of GF). A total of four columns was tested against laterally applied reverse cyclic load: control column, GF-, PET-, and HF-strengthened columns. All columns retrofitted using fibers demonstrated improved moment capacity and ductility. Moment capacity of GF-, PET-, and HF-strengthened columns was 120%, 107%, and 120% of the control column, respectively. Drift ratio of all retrofitted columns also increased by 63 ~ 83% over the control column. The final failure mode of the control column was main bar buckling. The final failure mode of the GF- and HF-strengthened columns was GF rupture while that of the PET-strengthened column was main bar rupture in tension. No damage was observed for PET at the ultimate stage due to excellent strain capacity intrinsic to PET. Current test results indicate that PET can be effectively used for seismic retrofit of RC columns. It is noted that the durability characteristics of PET needs to be investigated in the future.