• Earthquakes and Structures
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• 제22권2호
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• pp.203-218
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• 2022

In this paper, quasi-static tests were carried out on three prefabricated reinforced concrete column-steel beam (RCS) sub-assemblages with floor slabs and one comparison specimen without floor slab. The effects of axial compression and floor slab on the seismic performance were studied, and finite element simulations were conducted using ABAQUS. The results showed that the failure of prefabricated RCS sub-assemblages with floor occurred as a joint beam and column failure mode, while failure of sub-assemblages without floor occurred due to beam plastic hinge formation. Compared to the prefabricated RCS sub-assemblages without floor slab, the overall stiffness of the sub-assemblages with floor slab was between 19.2% and 45.4% higher, and the maximum load bearing capacity increased by 26.8%. However, the equivalent viscosity coefficient was essentially unchanged. When the axial compression ratio increased from 0.24 to 0.36, the hysteretic loops of the sub-assemblages with floor became fuller, and the load bearing capacity, ductility, and energy dissipation capacity increased by 12.1%, 12.9% and 8.9%, respectively. Also, the initial stiffness increased by 10.2%, but the stiffness degradation accelerated. The proportion of column drift caused by beam end plastic bending and column end bending changed from 35% and 46% to 47% and 36%, respectively. Comparative finite element analyses indicated that the numerical simulation outcomes agreed well with the experimental results.

• Earthquakes and Structures
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• 제12권6호
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• pp.603-617
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• 2017

This paper presents investigation into the behavior of beam-column joints, with the joint region concrete being replaced by steel fiber reinforced concrete (SFRC) and by ultra-high performance concrete (UHPC). A total of ten beam-column joint specimens (BCJ) were tested experimentally to failure under monotonic and cyclic loading, with the beam section being subjected to flexural loading and the column to combined flexural and axial loading. The joint region essentially transferred shear and axial stresses as received from the column. Steel fiber reinforced concrete (SFRC) and ultra-high performance concrete (UHPC) were used as an innovative construction and/or strengthening scheme for some of the BCJ specimens. The reinforced concrete specimens were reinforced with longitudinal steel rebar, 18 mm, and some specimens were reinforced with an additional two ties in the joint region. The results showed that using SFRC and UHPC as a replacement concrete for the BCJ improved the joint shear strength and the load carrying capacity of the hybrid specimens. The mode of failure was also converted from a non-desirable joint shear failure to a preferred beam flexural failure. The effect of the ties in the SFRC and UHPC joint regions could not be observed due to the beam flexural failure. Several models were used in estimating the joint shear strength for different BCJ specimens. The results showed that the existing models yielded wide-ranging values. A new concept to take into account the influence of column axial load on the shear strength of beam-column joints is also presented, which demonstrates that the recommended values for concrete tensile strength for determination of joint shear strength need to be amended for joints subject to moderate to high axial loads. Furthermore, finite element model (FEM) simulation to predict the behaviour of the hybrid BCJ specimens was also carried out in an ABAQUS environment. The result of the FEM modelling showed good agreement with experimental results.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.206-211
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• 1999

The purpose of this study is to investigate the natural frequencies and mode shapes of beam-columns on the non-homogeneous foundaion. The beam model is based on the classical Bernoulli-Euler beam theory. The linear foundation modulus is chosen as the non-homogeneous foundation in this study . The differentidal equation goeverning free vibrations of such beam-columns subjected to axial load is derived and solved numerically for calculting the natural frquencies and mode shapes. In numerical fivekinds of end constraint are considered, and the lowest four natural frquencies and corresponding mode shape are obtained as the non-dimensional forms.

• 항공우주기술
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• 제3권2호
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• pp.149-159
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• 2004

축방향 인장 및 압축하중을 받는 점탄성층을 갖는 복합재료 적층보의 동력학적 거동을 해석하였다. 개선된 지그재그 보이론과 지배방정식에 기초한 기하학적 상관식을 이용하여 점탄성층을 갖는 복합재료 적층보를 모델링하였고 이에 기초한 보 유한요소를 개발하였다. 축방향 인장 및 압축하중하의 고유진동수와 감쇠계수는 복소수 유일법을 이용하여 계산하였다. 축방향 인장 및 압축하중이 고유진동수 및 감쇠계수에 미치는 영향을 조사하였다.

• Structural Engineering and Mechanics
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• 제55권2호
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• pp.281-298
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• 2015

In this study, nonlinear transverse vibrations of tensioned Euler-Bernoulli nanobeams are studied. The nonlinear equations of motion including stretching of the neutral axis and axial tension are derived using nonlocal beam theory. Forcing and damping effects are included in the equations. Equation of motion is made dimensionless via dimensionless parameters. A perturbation technique, the multiple scale methods is employed for solving the nonlinear problem. Approximate solutions are applied for the equations of motion. Natural frequencies of the nanobeams for the linear problem are found from the first equation of the perturbation series. From nonlinear term of the perturbation series appear as corrections to the linear problem. The effects of the various axial tension parameters and different nonlocal parameters as well as effects of different boundary conditions on the vibrations are determined. Nonlinear frequencies are estimated; amplitude-phase modulation figures are presented for simple-simple and clamped-clamped cases.

• Steel and Composite Structures
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• 제27권4호
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• pp.401-416
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• 2018

Composite beams with web openings are vulnerable to Vierendeel bending failure. The available methods provide quite conservative estimates of Vierendeel bending resistance. An alternative design method to compute the resistance was proposed in this study, based on quadratic nonlinear interactions of normalized shear force, axial force and Vierendeel bending moment. The interactions of the top and bottom Tee section must satisfy mutual conditions to prevent the Vierendeel failure. The normalized shear force and Vierendeel bending moment of the composite part were used instead in the top Tee interaction. The top Tee axial force was computed based on force equilibrium. Based on a rigid-plastic model, the composite resistance is estimated using an effective slab width of the vertical shear resistance. On using the proposed method, nonlinear reductions due to shear loads and axial forces are not required, in contrast to prior methods. The proposed method was validated against experiments from literature. The method limitations and accuracy as well as the Vierendeel behavior were investigated by finite element simulations, with varied composite beam parameters. The proposed design loads are less conservative than earlier estimates and deviate less from the simulations.

• 대한기계학회논문집A
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• 제31권2호
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• pp.231-236
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• 2007

This paper presents the effect of the center of the series on convergence in solving vibration problems by Differential Transformation Method(DTM) to the transverse vibration of the Euler-Bernoulli beam under varying axial force. The governing differential equation of the transverse vibration of the Euler-Bernoulli beam under varying axial force is derived. The concepts of DTM were briefly introduced. Numerical calculations are carried out and compared with previously published results. The effect of the center of the series on convergence in solving the problem by DTM is discussed.

• Advances in nano research
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• 제14권6호
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• pp.521-525
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• 2023

This paper concerned with the vibration of double walled carbon nanotubes (CNTs) as continuum model based on Timoshenko-beam theory. The vibration solution obtained from Timoshenko-beam theory provides a better presentation of vibration structure of carbon nanotubes. The natural frequencies of double-walled CNTs against half axial wave mode are investigated. The frequency decreases on decreasing the half axial wave mode. The shape of frequency arcs is different for various lengths. It is observed that model has produced lowest results for C-F and highest for C-C. A large parametric study is performed to see the effect of half axial wave mode on frequencies of CNTs. This numerically vibration solution delivers a benchmark results for other techniques. The comparison of present model is exhibited with previous studies and good agreement is found.

• 한국전산구조공학회논문집
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• 제25권2호
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• pp.129-138
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• 2012

이 연구는 조합하중을 받는 변단면 변화곡선 보의 기하 비선형 수치해석 방법에 관한 연구이다. 보의 좌단은 회전지점이고 우단은 마찰이 없는 활동(滑動)지점으로 지지되어 있어 하중이 작용하면 보의 축방향 길이가 증가하여 평형상태를 이룬다. 조합하중은 회전지점에 작용하는 모멘트 하중과 집중하중을 고려하였다. 보의 단면은 휨 강성이 부재축을 따라 함수적으로 변화하는 변단면으로 선택하였다. 이러한 보의 비선형 거동을 지배하는 연립 미분방정식을 Bernoulli-Euler 보 이론으로 유도하였다. 이 미분방정식을 반복법으로 수치해석하여 보의 정확탄성곡선을 산정하였다. 이 연구의 이론을 검증하기 위하여 실험실 규모의 실험을 실행하였다.

• Smart Structures and Systems
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• 제21권1호
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• pp.53-64
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• 2018

Nondestructive testing methods are required to assess the condition of civil structures and formulate their maintenance programs. Axial force identification is required for several structural members of truss bridges, pipe racks, and space roof trusses. An accurate evaluation of in situ axial forces supports the safety assessment of the entire truss. A considerable redistribution of internal forces may indicate structural damage. In this paper, a novel compressive force identification method for prismatic members implemented using static deflections is applied to steel beams. The procedure uses the Euler-Bernoulli beam model and estimates the compressive load by using the measured displacement along the beam's length. Knowledge of flexural rigidity of the member under investigation is required. In this study, the deflected shape of a compressed steel beam is subjected to an additional vertical load that was short-term measured in several laboratory tests by using fiber Bragg grating-differential settlement measurement (FBG-DSM) sensors at specific cross sections along the beam's length. The accuracy of midspan deflections offered by the FBG-DSM sensors provided excellent force estimations. Compressive load detection accuracy can be improved if substantial second-order effects are induced in the tests. In conclusion, the proposed method can be successfully applied to steel beams with low slenderness under real conditions.