• 한국가스학회지
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• 제18권2호
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• pp.10-15
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• 2014

본 연구에서는 원통형 중공롤러를 갖는 와이어 소 머신에 대한 변위와 응력강도 안전성 해석결과를 제시하고 있다. 유한요소법을 사용하여 세 개의 튜브 사이에 Y형상의 편위형 컬럼과 수직형 컬럼을 설치한 중공롤러에서 변형거동과 응력강도 안전성을 높인 중공롤러를 개발하고자 한다. 동일한 직경과 길이를 갖지만, 중량을 달리하는 중공롤러 모델에서 Y 형상의 편위형 및 수직형 중공롤러에 작용하는 변위거동 안전성은 중공롤러의 전체길이에 의해 더 많은 영향을 받는 것으로 나타는데, 이것은 중공롤러의 굽힘 모멘트와 밀접한 관련이 있다. 그러나, 중공롤러의 응력강도는 중량 차이가 크지 않을 경우 절단면의 형상에 의해 더 큰 영향을 받는 것으로 나타났다. 따라서, 중공롤러의 강도안전성을 높이고, 총중량을 낮추기 위해서는 Y형상을 갖는 중공롤러를 사용하는 것이 바람직함을 알 수 있다.

• Steel and Composite Structures
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• 제41권6호
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• pp.887-898
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• 2021

This paper presents a simplified model to capture the nonlinear behavior of steel frames depending on the spread of plasticity method. New interaction formulae were derived to evaluate the plastic strength for I-shaped steel sections under uniaxial bending moment and axial compression load. Also, new empirical formulae were derived to evaluate the tangent stiffness modulus of steel I-shaped cross-sections considering the effect of the residual stresses suggested by the specifications in European Convention for Construction Steelworks (ECCS). The secant stiffness which depends on the tangent modulus is used to evaluate the internal forces. Based on stiffness matrix method, a finite element analysis program was developed for the nonlinear analysis of space steel frames using the derived formulae. Comparison between the proposed model results with those given by the fiber model shows very good agreement. Numerical examples were introduced to verify, check the accuracy, and evaluate the efficiency of the proposed model. The analysis results show that the new proposed model is accurate and able to minimize the solution time.

• 한국강구조학회 논문집
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• 제28권6호
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• pp.467-476
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• 2016

모듈러 건축물에서 모듈러 유닛 사이의 접합은 연결 강판을 이용하여 볼트 접합하는 것이 일반적이다. 건축물의 강도는 가장 약한 부분에 의해 결정되며, 접합부는 부재보다 약한 부분이 될 가능성이 있다. 따라서 모듈러 건축물의 안전성을 확인하기 위해 모듈 내부 기둥-보 접합부의 구조성능뿐 아니라 모듈러 유닛과 유닛 접합부의 구조성능도 평가되어야 한다. 이 연구에서는 각형강관 기둥과 ㄷ형강보가 사용된 모듈이 일자형 접합철물과 십자형 접합철물로 연결된 접합부의 거동을 KBC2009 0722.2.4에 따라 모듈의 폭 방향과 길이 방향에 대해 층간 변위각으로 반복 가력을 제어하는 실험을 통해 조사하였다. 실험결과 모든 실험체는 0.04rad 변위각까지 비교적 안적정인 거동을 보였고, 길이 방향 실험체의 결과가 에너지 흡수능력 면에서 좋은 거동을 보였다. 그러나 일자형 연결 강판이 십자형 연결 강판에 비해 변위각이 커질수록 강성이 저하하고, 기둥의 실제 변위각이 늘어나는 결과를 보였다.

• Computers and Concrete
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• 제30권2호
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• pp.127-141
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• 2022

In this paper, a numerical procedure is proposed for achieving the minimum cost design of reinforced concrete polygonal column cross-sections under compression and biaxial bending. A methodology is developed to integrate the metaheuristic algorithm Quantum Particle Swarm Optimization (QPSO) with an algorithm for the evaluation of the strength of reinforced concrete cross-sections under combined axial load and biaxial bending, according to the design criteria of Brazilian Standard ABNT NBR 6118:2014. The objective function formulation takes into account the costs of concrete, reinforcement, and formwork. The cross-section dimensions, the number and diameter of rebar and the concrete strength are taken as discrete design variables. This methodology is applied to polygonal cross-sections, such as rectangular sections, rectangular hollow sections, and L-shaped cross-sections. To evaluate the efficiency of the methodology, the optimal solutions obtained were compared to results reported by other authors using conventional methods or alternative optimization techniques. An additional study investigates the effect on final costs for an alternative parametrization of rebar positioning on the cross-section. The proposed optimization method proved to be efficient in the search for optimal solutions, presenting consistent results that confirm the importance of using optimization techniques in the design of reinforced concrete structures.

• 한국공작기계학회논문집
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• 제16권6호
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• pp.205-211
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• 2007

In this paper, foam-composite sandwich structures for EDM machine tool components such as column and column block designed by controlling stacking sequences and cross-sectional dimensions of the composite structures. The original column block is a box-shaped structure made of aluminum connecting a column and a Z-stage of the system. This research was focused on the design of efficient column block structure using a foam-composite sandwich structure which have good bending stiffness and damping characteristics to reduce the mass and increase damping ratio of the system. Vibration tests for getting damping ratio with respect to the stacking angle and thickness of the composites were carried out. Finite element analyses for static defection and vibration behaviour were also carried out to find out the appropriate stacking conditions; that is, stacking sequence and rib configuration. From the test and analysis results it was found that composite-foam sandwich structures for the microfactory system can be successful alternatives for high precision machining.

• 한국지진공학회논문집
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• 제19권4호
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• pp.195-205
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• 2015

Various non-seismic tie details are frequently used for one- and two-story small buildings because the seismic demand on their deformation capacities is not relatively significant. To evaluate the effects of the non-seismic tie details on the seismic performance of reinforced concrete columns, six square columns with a cross section of $400{\times}400mm$ and six rectangular columns with a cross section of $250{\times}640mm$ were tested. The anchorage details at both ends and spacing of tie hoops, along with the cross-sectional shape and the magnitude of axial load, were considered as the primary test parameters. Test results showed that square columns had higher stiffness and lower lateral deformation rather than rectangular columns. Both lap spliced tie and U-shaped tie provided comparable or improved seismic performance to $90^{\circ}$ hook tie in terms of maximum strength, ductility, and energy dissipation. The predicted curves with modeling parameters in ASCE41-13 were conservative for test results of lap spliced tie and U-shaped tie specimens since plastic behavior after flexural yielding could not be considered. For economical design, ASCE41-13 should be revised with various test results of tie details.

• Steel and Composite Structures
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• 제34권3호
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• pp.347-359
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• 2020

The objective of this study is to experimentally scrutinize the axial performance of built-up concrete filled steel tube (CFT) columns composed of steel plates. In this case, the main parameters cross section types, compressive strength of filled concrete, and the effect of welding lines. Welded built-up steel box columns are fabricated by connecting two pieces of cold-formed U-shaped or four pieces of L-shaped thin steel plates with continuous penetration groove welding line located at mid-depth of stub column section. Furthermore, traditional square steel box sections with no welding lines are investigated for the comparison of axial behavior between the generic and build-up cross sections. Accordingly, 20 stub columns with thickness and height of 2 and 300 mm have been manufactured. As a result, welding lines in built-up specimens act as stiffeners because have higher strength and thickness in comparison to the plates. Subsequently, by increasing the welding lines, the load bearing capacity of stub columns has been increased in comparison to the traditional series. Furthermore, for specimens with the same confinement steel tubes and concrete core, increment of B/t ratio has reduced the ductility and axial strength.

• Steel and Composite Structures
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• 제39권5호
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• pp.583-598
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• 2021

The composite steel reinforced concrete (SRC) columns have been widely used in Structural Engineering due to their good performances. Many studies have been done on the SRC columns' performances, but they focused on the ordinary types with conventional configurations and materials. In this study, nine new types of steel reinforced lightweight aggregate concrete (SRLAC) short columns with cross-shaped (+shaped and X-shaped) steel section were tested under monotonically axial compressive load; the studied parameters included steel section ratio, steel section configuration, ties spacing, lightweight aggregate concrete (LWAC) strength, and longitudinal bars ratio. From the results, it could be found that the specimens with larger ties ratio, concrete strength, longitudinal bars ratio, and steel section ratio achieved great strength and stiffness due to the excellent interaction between the concrete and steel. The well-confined concrete core could strengthen the steel section. The ductility and toughness of the specimens were influenced by the LWAC strength, steel section ratio, and longitudinal bars ratio; in addition, larger ties ratio with smaller LWAC strength led to better ductility and toughness. The load transfer between concrete and steel section largely depends on the LWAC strength, and the ultimate strength of the new types of SRLAC short columns could be approximately predicted, referring to the codes' formulas of ordinary types of steel reinforced concrete (SRC) columns. Among the used codes, the BS-5400-05 led to the most conservative results.

• Steel and Composite Structures
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• 제38권2호
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• pp.223-239
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• 2021

This paper presents the analytical modeling and finite element (FE) analysis, using ABAQUS software, of the new types of steel reinforced lightweight aggregate concrete (SRLAC) columns with cross-shaped (+shaped and X-shaped) steel section, using proposed three analytical and two FE models in total. The stress-strain material models for different components in the columns, including the confined zones of the lightweight aggregate concrete (LWAC) using three and four concrete zones divisions approaches and with and without taking into account the stirrups reaction effect, are established first. The analytical models for determining the axial load-deformation behavior of the SRLAC columns are drawn based on the materials models. The analytical and FE models' results are compared with previously reported test results of the axially loaded SRLAC columns. The proposed analytical and FE models accurately predict the axial behavior and capacities of the new types of SRLAC columns with acceptable agreements for the load-displacement curves. The LWAC strength, steel section ratio, and steel section configuration affect the contact stress between the concrete and steel sections. The average ratios of the ultimate test load to the three analytical models and FEA model loads, Put /Pa1, Put /Pa2, Put /Pa3, and Put /PFE1, for the tested specimens are 0.96, 1.004, 1.016, and 1.019, respectively. Finally, the analytical parametric studies are also studied, in terms of the effects of confinement, LWAC strength, steel section ratio, and the reinforcement ratio on the axial capacity of the SRLAC column. When concrete strength, confinements, area of steel sections, or reinforcement bars ratio increased, the axial capacities increased.

• 한국강구조학회 논문집
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• 제15권3호
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• pp.251-259
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• 2003

본 논문은 매립형 SRC기둥의 축력과 변형능력과의 관계를 찾아내기 위하여 해석적인 연구를 수행하였다. 해석 모델은 캔틸레버기둥으로 한정하였으며 SRC 기둥의 비탄성 거동에 영향을 미치는 변수들인 철골비, 매립철골형상과 전단스팬과 춤과의 비에 대하여 검토하였다. 일정회전각하에 축력과 반복수평력을 받는 SRC기둥의 안정적 거동을 보장하기 위한 최대한계축력이 있다는 것을 해석결과들은 보여 주고 있다. 반복 횡하중을 받는 기둥이 저항할 수 있는 최대축력은 소요회전각을 보장하는 안정한계축력으로서 정의된다. 해석결과에 따르면 안정한 계축력비는 강재의 강도가 증가함에 따라 콘크리트의 강도가 감소함에 따라 증가하는 것으로 나타났다. 또한 I형 단면이 매립형 철골로 사용될때 철골 단면적이 증가함에 따라 안정한계 축력비는 증가하며, 십자형 단면이 사용되는 경우에는 단면적에 의한 영향이 거의 없었다.