• Structural Engineering and Mechanics
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• 제62권6호
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• pp.759-769
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• 2017

The effect of central axial load on natural frequencies of various thin-walled beams, are investigated by some researchers using different methods such as finite element, transfer matrix and dynamic stiffness matrix methods. However, there are situations that the load will be off centre. This type of loading is called eccentric load. The effect of the eccentricity of axial load on the natural frequencies of asymmetric thin-walled beams is a subject that has not been investigated so far. In this paper, the mentioned effect is studied using exact dynamic stiffness matrix method. Flexure and torsion of the aforesaid thin-walled beam is based on the Bernoulli-Euler and Vlasov theories, respectively. Therefore, the intended thin-walled beam has flexural rigidity, saint-venant torsional rigidity and warping rigidity. In this paper, the Hamilton‟s principle is used for deriving governing partial differential equations of motion and force boundary conditions. Throughout the process, the uniform distribution of mass in the member is accounted for exactly and thus necessitates the solution of a transcendental eigenvalue problem. This is accomplished using the Wittrick-Williams algorithm. Finally, in order to verify the accuracy of the presented theory, the numerical solutions are given and compared with the results that are available in the literature and finite element solutions using ABAQUS software.

• 대한토목학회논문집
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• 제28권4A호
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• pp.465-474
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• 2008

일반적으로, 보-기둥 부재로 구성된 강뼈대구조물의 설계는 개별부재의 유효좌굴길이를 고려하여 설계기준에서 제시한 안정성 평가식을 적용하고 있다. 그러나 이 방법은 구조물에서 상대적으로 작은 압축력이 적용되는 부재에서는 유효좌굴길이가 커지는 문제가 발생하게 된다. 이러한 문제를 극복하고자 본 연구에서는 대상 구조물의 초기결함(initial imperfection)을 고려한 2차 탄성해석법을 제시한다. 이 방법은 탄성좌굴 고유치해석으로 산정된 좌굴모드 및 좌굴고유치, 개별부재의 축력을 이용하여, 가장 작은 무차원 세장비를 가진 부재를 선정하고, 그 부재에 대하여 기하적, 재료적인 효과가 고려된 설계기준의 기준강도곡선으로부터 좌굴모드에 대한 증폭량을 산정한다. 이렇게 결정된 증폭량을 대상 구조물의 좌굴모드에 증폭시켜 2차 탄성해석을 수행하고, 개별부재의 안정성을 평가한다. 본 방법의 타당성을 확인하기 위하여, 8층 및 4층으로 이루어진 평면 강뼈대구조물에 적용시키고, 설계기준에서 제시하는 안정성 평가법과 비교한다.

• 한국공간구조학회논문집
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• 제22권1호
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• pp.17-24
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• 2022

Currently, the construction trend of high-rise structures is changing from a cube-shaped box to a free-form. In the case of free-form structures, it is difficult to predict the behavior of the structure because it induces torsional deformation due to inclined columns and the eccentricity of the structure by the horizontal load. For this reason, it is essential to review the stability by considering the design variables at the design stage. In this paper, the position of the weak vertical member was analyzed by analyzing the behavior of the structure according to the change in the core position of the twisted high-rise structures. In the case of the shear wall, the shear force was found to be high in the order of proximity to the center of gravity of each floor of the structure. In the case of the column, the component force was generated by the axial force of the outermost beam, so the bending moment was concentrated on the inner column with no inclination.

• Structural Engineering and Mechanics
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• 제9권3호
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• pp.289-304
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• 2000

This study discusses on the experimental and analytical results of the global buckling tests, carried out on aluminum alloy double layer space grids composed of tubular members, ball joints and connecting bolts at the member ends, with the purpose of demonstrating the effectiveness of a simplified analysis method using an equivalent slenderness ratio for the members. Because very few experiments have been carried out on this type of aluminum space grids, the buckling behavior is investigated experimentally over the post buckling regions using several space grid specimen with various values for the member slenderness ratio. The observed behavior duping the experiments is compared with the analytically obtained results. The comparison is made based on two different schemes; one on the plastic hinge method considering a bending moment-axial force interaction for members and the other on a method using an equivalent slenderness ratio. It is confirmed that the equivalent slenderness method can be effectively applied, even in the post buckling regions, once the effects of the rotational rigidity at the ball joints are appropriately evaluated, because the rigidity controls the buckling behavior. The effectiveness of the equivalent slenderness method will be widely utilized for estimation of the ultimate strength, even in post buckling regions for large span aluminum space grids composed of an extreme large number of nodes and members.

• 한국전산구조공학회논문집
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• 제18권1호
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• pp.79-91
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• 2005

본 논문에서는 프리스트레스를 이용한 가시설 공법(IPS)에 적용되는 띠장의 거동의 해석 및 설계절차에 대한 연구를 수행하였다. 띠장에 초기장력이 도입되는 구조계는 탄성지반위에 놓인 보이론에 의하여 부재력이 산출되고, 토압에 의한 부재력은 장력을 부정정력으로 취하여 부정정 구조해석을 통하여 띠장의 축력 및 휨모멘트를 계산하였다. 지반은 압축력 전담요소, 케이블은 인장력 전담요소를 사용하여 등분포 토압 및 편토압을 받는 띠장의 전산해석을 수행하였다. 기존의 가시설 설계에 적용되는 토압을 적용하여 IPS 띠장설계를 실시하였고, 긴장력과 설계토압에 의한 축력과 휨모멘트를 계산하여 축응력과 휨응력을 도출하고 합성응력검토를 수행하였다.

• Steel and Composite Structures
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• 제32권6호
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• pp.717-729
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• 2019

A horizontal cyclic test was carried out to study the seismic performance of lightweight aggregate concrete filled steel tube (LACFST). The constitutive and hysteretic model of core lightweight aggregate concrete (LAC) was proposed for finite element simulation. The stress and strain changes of the steel tube and concrete filled inside were measured in the experiment, and the failure mode, hysteresis curve, skeleton curve, and strain curve of the test specimens were obtained. The influence of axial compression ratio, diameter-thickness ratio and material strength were analysed based on finite element model. The results show that the hysteresis curve of LACFST indicated favourable ductility, energy dissipation, and seismic performance. The LACFST failed when the concrete in the bottom first crushed and the steel tube then bulged, thus axial force imposed by prestressing was proved to be feasible. The proposed constitutive model and hysteretic model of LAC under the constraint of its steel tube was reliable. The bearing capacity and ductility of the specimen increase significantly with increasing thickness of the steel tube. The bearing capacity of the member improves while the ductility and energy dissipation performance slightly decreased with the increasing strength of the steel and concrete.

• 한국지반공학회논문집
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• 제38권11호
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• pp.119-135
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• 2022

본 논문에서는 대심도 가설 흙막이 벽체의 내진안전성을 검토하기 위해 평균재현주기 2,400년 수준(0.220g)을 목표로 Northridge(1994), Kobe(1995), 인공지진파 그리고 2.5Hz 정현파 총 네 가지 지진파를 가진하는 동적원심모형실험을 수행하였다. 원심모형실험은 대심도 굴착현장을 대상을 모사하였다. 모형지반은 상대밀도 55% 건조사질토지반으로 조성하였고, 모형벽체는 심도 24.8m의 지하연속벽 흙막이벽체와 중구경 강관 지보재로 보강된 공법을 모사하였다. 흙막이 시스템은 기반암 가속도가 배면지반, 벽체 상단과, 기반암 근처 하단부에서 증폭되었고, 중앙부에서는 상대적으로 감쇠되는 경향을 보였다. 벽체 전체최대휨모멘트와 지보재 전체최대축력이 유발되는 시점의 부재력을 정지상태 부재력과 비교하였다. 그 결과, 벽체 휨모멘트는 정모멘트와 부모멘트가 최대 10.1%, 36.2% 증가하였으며, 축력은 하단 지보재에서 최대 70% 증가하였다. 또한, Mononobe-Okabe(M-O) 동적토압이론과 Seed-Whitman(S-W) 동적토압이론을 활용한 등가정적해석을 수행하여 실험결과와 비교하였다. M-O 이론 등가정적해석이 휨모멘트 동적증가분을 과소평가하고, S-W 이론 등가정적해석은 과대평가하였다.

• 한국안전학회지
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• 제34권2호
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• pp.34-39
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• 2019

Vinyl house consists of main rafter, lateral member, clamps and polyethylene film. Many vinyl houses are used in the countryside to grow vegetables. These vinyl houses have occasionally been collapsed due to heavy snowfall in winter. Many farmers get a lot of economical damages, if vinyl houses are collapsed. So it is most important to built a safe vinyl house that can withstand heavy snowfall. In this study, a structural analysis was performed on three types of vinyl houses(07-single-01, 10-single-04, 12-single-01). In addition, the structural analysis of the three types of vinyl houses provided axial forces, flexural moment, and combined stress. For these three types of vinyl houses, structural safety was reviewed by obtaining the combined stress ratio by the strength design method. This structural review showed that the specifications for the vinyl house proposed in the design are not safe. Especially, the result of increasing the design snow load by 15 percent and 30 percent showed that the vinyl house structure constructed as a standard for vinyl house was a more dangerous structure. Therefore, it is necessary to revise regulations such as increasing the thickness of rafters or widening the gap in order to make vinyl houses structurally safe for heavy snowfall in the future, and to devise diverse methods to make vinyl houses that are structurally safe.

• 한국지반신소재학회논문집
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• 제15권3호
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• pp.67-76
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• 2016

교대는 토압을 받는 구조체로 뒤채움의 재질 및 부설방법, 다짐정도, 배수시설 등에 따라 교대에 미치는 영향이 민감한 구조물이다. 하지만 보통 실무에서는 경험치인 내부마찰값을 $30{\sim}35^{\circ}$를 적용하고 있는 실정으로 뒤채움재의 물성치값을 현실에 맞도록 합리적인 값의 설정이 필요하다고 할 수 있다. 본 논문에서는 교대높이 12m로 가정하고 직접기초의 교대를 최소안전율을 기반하여 절 성토 표준단면을 선정하여 내부마찰각의 변화에 따른 외적안정성분석와 부재력 검토하여 공사비를 비교하였다. 그 결과 내부마찰각에 따라 교대단면 축소 등으로 인한 공사비용 절감효과는 약 2.2%~8.4% 감소하였다.

• 국제초고층학회논문집
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• 제3권1호
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• pp.21-33
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• 2014

The tied braced frame (TBF) system was developed to achieve uniform seismic inelastic demand along the height of multi-storey eccentrically braced steel frames. A modular tied braced frame (M-TBF) configuration has been recently proposed to reach the same objective while reducing the large axial force demand imposed on the vertical tie members connecting the link beams together in TBFs. M-TBFs may however experience variations in storey drifts at levels where the ties have been removed to form the modules. In this paper, the possibility of reducing the discontinuity in displacement response of a 16-storey M-TBF structure by introducing energy dissipating (ED) devices between the modules is examined. Two M-TBF configurations are investigated: an M-TBF with two 8-storey modules and an M-TBF with four 4-storey modules. Three types of ED devices are studied: friction dampers (FD), buckling restrained bracing (BRB) members and self-centering energy dissipative (SCED) members. The ED devices were sized such that no additional force demand was imposed on the discontinuous tie members. Nonlinear response history analysis showed that all three ED systems can be used to reduce discontinuities in storey drifts of M-TBFs. The BRB members experienced the smallest peak deformations whereas minimum residual deformations were obtained with the SCED devices.