• Title/Summary/Keyword: unbraced

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Classification system for figid and semi-rigid connection (강·반강 철골 접합부의 분류체계에 관한 연구)

  • Jang, Mee;Lee, Sang Sup;Mun, Tae Sup
    • Journal of Korean Society of Steel Construction
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    • v.13 no.4
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    • pp.351-361
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    • 2001
  • The connections are classified as rigid, semi+rigid, or pinned. There are two classification systems, EC3 adn Bjorhovede et al., representatively. The EC3 boundary between rigid and semi-rigid connections is in on the whole restrictive in term of the stiffness as well as the moment capacity of connections. The boundary specified by Bjorhovede et al. may not be sufficient to assure the behavior of rigid frames in some cases. In this study, it is proposed the new classification system for steel connection that depends on the reduction factor(R) of critical buckling load for unbraced semi-rigid frame expressed by the stiffness ratio($\rho$) of beam to column and the stiffness ratio(k) of connection to beam. Finally, it is examined by experimental data that new classification criteria provides a practical boundary compared wit hteh existing classifications.

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Experimental Study on the Buckling Behavior of Cold-formed Steel Warren Truss (냉간성형강 평트러스 시스템의 좌굴 거동에 관한 실험 연구)

  • Park, Wan Soon;Kim, Gap Deuk
    • Journal of Korean Society of Steel Construction
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    • v.14 no.6
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    • pp.747-754
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    • 2002
  • Cold-formed steel truss system was reviewed in order to improve the various problems associated with the steel floor joist system, such as the structural deficiency caused by web punching and others. Two types of floor truss system using cold-formed steel were reviewed during this research project, including the square end type(SE type) and underslung type(EE type). The strctural behavior was analyzed using the AISI design criteria and various bending tests. Test results show that the SE type floor truss proved to be more efficient than the EE type when it is subjected to concentrated load, and that the unbraced length of the floor truss about the weak axis has much importance on the buckling strength of the floor truss. Test results indicate that their values surpass the calculated values predicated through the AISI design criteria.

Application of Direct Analysis Method Considering Initial Imperfection Limitation (초기변형 허용값을 고려한 직접해석법 적용)

  • Kim, Hee Dong
    • Journal of Korean Society of Steel Construction
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    • v.25 no.5
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    • pp.487-495
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    • 2013
  • As the first step to suggest effective ways of using direct analysis method considering current situations of construction fields in Korea, analytical approach is used to verify direct analysis method which adapts initial imperfection limitation of Korean specification of building construction. The main analytical variables are size of frames, axial load ratio, axial load distribution, value of notional loads, location of notional loads, and applied method of notional loads. The results show that the use of initial imperfection limitation of Korean specification, L/700 is suitable, and the recommendable method to use direct analysis method is applied notional loads based on L/700 as minimum lateral load at each story, even if B2 is less than 1.5 and lateral loads exist.

3-D Frame Design Using Second-Order Plastic-Hinge Analysis Accounting for Lateral Torsional Buckling (횡비틀림좌굴을 고려하는 2차 소성힌지해석을 이용한 3차원 강뼈대 구조물 설케)

  • 김승억;박주수
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.15 no.1
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    • pp.117-126
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    • 2002
  • In this paper, 3-D fame design using second-orders plastic-hinge analysis accounting for lateral torsional buckling is developed. This analysis accounts for material and geometric nonlinearities of the structural system and its component members. Moreover, the problem associated with conventional second-order plastic-hinge analyses, which do not consider the degradation of the flexural strength caused by lateral torsional buckling, is overcome. Efficient ways of assessing steel frame behavior including gradual yielding associated with residual stresses and flexure, second-order effect, and geometric imperfections are presented. In this study, a model consisting of the unbraced length and cross-section shape is used to account for lateral torsional buckling. The proposed analysis is verified by the comparison of the LRFD results. A case studs shows that lateral torsional buckling is a very crucial element to be considered in second-order plastic-hinge analysis. The proposed analysis is shown to be an efficient reliable tool ready to be implemented into design practice.

The Eigenvalues and Their Relationships for the Rectangular Frame (4각형 골조의 고유치와 고유치 간의 관계)

  • Lee, Soo-Gon;Kim, Soon-Cheol;Song, Chang-Young;Song, Sang-Yong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.9 no.3
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    • pp.139-150
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    • 2005
  • Finite element method is applied to the determinations of the two eigenvalues(the elastic critical load and the natural frequence of lateral vibrations) of single story-3 equal bay rectangular frame. The analysis parameters are taper parameter ${\alpha}$ for column, and beam span to column height ratio, ${\beta}$ and second moment area ratio of beam to column, ${\Upsilon}$. Support condition at the column base and sway condition at the column top are also considered in the stability analysis of frame. The changes in the coefficient of eigenvalue are represented by algebraic function of analysis parameter. The coefficients estimated by the proposed algebraic function show good agreement with those determined by finite element method, which suggest the design aid role of the proposed function. By increasing the column axial forces step by step, the corresponding frequencies are also determined, which makes one examine or confirm the relationship suggested by other studies.

Measurement of Structural Properties of PLA Filament as a Supplier of 3D Printer (3D 프린터에 공급되는 PLA 필라멘트의 물성치 측정)

  • Choi, Won;Woo, Jae-Hyeong;Jeon, Jeong-bae;Yoon, Seong-soo
    • Journal of The Korean Society of Agricultural Engineers
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    • v.57 no.6
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    • pp.141-152
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    • 2015
  • Most of agricultural structures are consisted of complex components and exposed to various boundary conditions. There have been no ways to express those structures exactly for model experiment. As an alternative, 3D printer can produce any type of solid model. However, there are limited informations related to structural experiments using 3D printer. The object of this study gives the basic informations to structural engineers who try to use 3D printer for model experiment. When PLA was used as a supplier for 3D printer, the outcomes showed less heat deformation to compare with ABS. To test the material properties, two kinds of experiments (three-point flexibility test and compression test) were executed using universal testing machine. In three-point flexibility test, plastic hinge and its deformation were developed as observed in material such as steel. The behavior was in a linear elastic state, and elastic bending modulus and yield force were evaluated. In the compression test using unbraced columns with hinge-hinge boundary condition, the constant yield forces were observed regardless of different lengths in all columns with same section size, whereas the compressive elastic modulus was increased as the length of column was increased. The suggested results can be used for model experiments of various agricultural structures consisted of single material.

The Study on the Placements of Brace Members Using Optimum Seismic Design of Steel Frames (강골조 구조물의 내진 최적설계에 의한 브레이스 부재 배치에 관한 연구)

  • Kim, Ki-Wook;Park, Moon-Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.9 no.1
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    • pp.111-119
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    • 2005
  • This study presents continuous and discrete optimum design algorithm and computer programs for unbraced and braced steel frame structures under earthquake loads. The program, which is avaliable to perform structural analysis and optimum design, continuous and discrete, simultaneously is developed. And the program adopts various braced types, Untraced, Z-braced(V), Z-braced(inverse-V), X-braced(A), X-braced(B), X-braced(C) and K-braced, in steel structures with static loads and seismic effects. The objectives in this optimization are to minimize the total weight of steel, and design variables, based on the ultimate strength requirements of AISC-ASD specifications, the serviceability requirements and allowable story drift requirements of ATC-3-06, and various constraints. The purpose is to present proper braced type for seismic effects by comparing and analysing results of various cases.

Numerical Analysis of Inelastic Lateral Torsional Buckling Strength of HSB800 Steel Plate Girder with Monosymmetric Section (일축대칭단면 HSB800 강재 플레이트거더의 비탄성 횡비틂좌굴강도의 해석적 평가)

  • Park, Yong Myung;Lee, Kun Joon;Choi, Byung Ho;Hwang, Min O
    • Journal of Korean Society of Steel Construction
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    • v.25 no.2
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    • pp.153-164
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    • 2013
  • In this paper, lateral-torsional buckling(LTB) strength of HSB800 high strength steel plate girder with monosymmetric section under uniform moment was evaluated by nonlinear analysis. The unbraced length in inelastic LTB range was considered for the sections whose smaller or larger flange is in compression with slender, noncompact and compact web. Analyses of SM490 steel girders were first performed with the single-panel and three-panel model to judge the validity of the constructed models by comparing those results with Eurocode 3, AASHTO and AISC codes. By using the same models, LTB strength of HSB800 girder was evaluated and it was found that the sections whose smaller flange is in compression with noncompact flange-slender/noncompact web could not reach the flexural strength of the design codes.

[Retracted]Analysis of Minimum Penetrated Depth of Pile bent of IPM Bridge ([논문철회]토압분리형 일체식 교대 교량의 파일벤트에 대한 최소근입깊이 해석)

  • Kim, Hongbae;Kim, Taesu;Park, Jongseo;Han, Heuisoo
    • Journal of the Korean GEO-environmental Society
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    • v.18 no.5
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    • pp.45-53
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    • 2017
  • IPM bridge was developed to revise the problems of IAB bridge by Nam et al, (2016). This research conducted the p-y analysis to examine the parameter traits among the protruded length (H), penetrated length (L) of pile bent and soil conditions. From the results, the maximum bending moment happened in the top segment of pile bent, because it is integrated to the upper structure. Also, the maximum shear force was shown in the boundary of the sand and weathered soil zones according to the analysis soil conditions. The maximum member force and unbraced length is converged when the ratio (L/H) of protruded length (H) and penetrated length (L) is 1.0. The larger material force is happened, if the pile bent is penetrated shallowly compared to the protruded length. The definite inflection points were shown in the horizontal displacement curve from the p-y analysis, also the smaller penetrated length made the curve grade slower.

Optimum Design of Braced Steel Framed Structures Considering Soil Condition Under Earthquake Loads (지반조건을 고려한 브레이스된 강골조 구조물의 내진 최적설계)

  • Park, Moon-Ho;Kim , Ki-Wook;Lee , Seung-Jo;Park , Jung-Hwal
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.4
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    • pp.97-107
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    • 2006
  • This study is structural analysis and continuous, discrete optimum design of braced steel frame structures under earthquake loads considering soil condition. The program which is able to perform simultaneously structural analysis and continuous, discrete optimum design, it is applied steel frame structures using unbraced, Z-braced, and X-braced types and analyze the program about static loads and seismic loads. The purpose of this study is to present proper braced type for seismic effects by comparing and analyzing results of analytic method about various cases using specially Newmark-Hall design spectrum, ATC design spectrum and ATC equivalent static analysis and finding minimum weight and design variables which satisfy the ultimate strength requirements of AISC-ASD specifications, the serviceability requirements and allowable story drift requirements of ATC-3-06 and various constraints.