• Earthquakes and Structures
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• 제8권4호
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• pp.843-857
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• 2015

System identification is regarded as the most basic technique for structural health monitoring to evaluate structural integrity. Although many system identification techniques extracting mode information (e.g., mode frequency and mode shape) have been proposed so far, it is also desired to identify physical parameters (e.g., stiffness and damping). As for high-rise buildings subjected to long-period ground motions, system identification for evaluating only the shear stiffness based on a shear model does not seem to be an appropriate solution to the system identification problem due to the influence of overall bending response. In this paper, a system identification algorithm using a shear-bending model developed in the previous paper is revised to identify both shear and bending stiffnesses. In this algorithm, an ARX (Auto-Regressive eXogenous) model corresponding to the transfer function for interstory accelerations is applied for identifying physical parameters. For the experimental verification of the proposed system identification framework, vibration tests for a 3-story steel mini-structure are conducted. The test structure is specifically designed to measure horizontal accelerations including both shear and bending responses. In order to obtain reliable results, system identification theories for two different inputs are investigated; (a) base input motion by a modal shaker, (b) unknown forced input on the top floor.

• Smart Structures and Systems
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• 제26권2호
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• pp.253-262
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• 2020

In this paper, a new higher order shear deformation model is developed for static analysis of functionally graded beams with considering porosities that may possibly occur inside the functionally graded materials (FGMs) during their fabrication. The model account for higher-order variation of transverse shear strain through the depth of the beam and satisfies the zero traction boundary conditions on the surfaces of the beam without using shear correction factors. The present work aims to study the effect of the distribution forms of porosity on the bending of simply supported FG beam. Based on the present higher-order shear deformation model, the equations of motion are derived by the principle of virtual works. Navier type solution method was used to obtain displacement and stresses, and the numerical results are compared with those available in the literature. A comprehensive parametric study is carried out to assess the effects of volume fraction index, porosity fraction index, and geometry on the bending of imperfect FG beams. It can be concluded that the proposed model is simple and precise for the resolution of the behavior of flexural FGM beams while taking into account the shape of distribution of the porosity.

• 한국지진공학회논문집
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• 제26권6호
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• pp.227-235
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• 2022

For a member model in nonlinear structural analysis, a lumped plastic model that idealizes its flexural bending, shear, and axial behaviors by springs with the nonlinear hysteretic model is widely adopted because of its simplicity and transparency compared to the other rigorous finite element methods. On the other hand, a challenging task in its numerical solution is to satisfy the equilibrium condition between nonlinear flexural bending and shear springs connected in series. Since the local forces between flexural and shear springs are not balanced when one or both springs experience stiffness changes (e.g., cracking, yielding, and unloading), the additional unbalanced force due to overshooting or undershooting each spring force is also generated. This paper introduces an iterative scheme for numerical solutions satisfying the equilibrium conditions between flexural bending and shear springs. The effect of equilibrium iteration on analysis results is shown by comparing the results obtained from the proposed method to those from the conventional scheme, where the equilibrium condition is not perfectly satisfied.

• Advances in nano research
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• 제5권2호
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• pp.113-126
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• 2017

This paper proposes a new nonlocal higher-order hyperbolic shear deformation beam theory (HSBT) for the static bending and vibration of nanoscale-beams. Eringen's nonlocal elasticity theory is incorporated, in order to capture small size effects. In the present model, the transverse shear stresses account for a hyperbolic distribution and satisfy the free-traction boundary conditions on the upper and bottom surfaces of the nanobeams without using shear correction factor. Employing Hamilton's principle, the nonlocal equations of motion are derived. The governing equations are solved analytically for the edges of the beam are simply supported, and the obtained results are compared, as possible, with the available solutions found in the literature. Furthermore, the influences of nonlocal coefficient, slenderness ratio on the static bending and dynamic responses of the nanobeam are examined.

• Advances in concrete construction
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• 제1권1호
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• pp.1-27
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• 2013

Discrete steel fibres can increase significantly the bending and the shear resistance of concrete structural elements when Steel Fibre Reinforced Concrete (SFRC) is designed in such a way that fibre reinforcing mechanisms are optimized. To assess the fibre reinforcement effectiveness in shallow structural elements failing in bending and in shear, experimental and numerical research were performed. Uniaxial compression and bending tests were executed to derive the constitutive laws of the developed SFRC. Using a cross-section layered model and the material constitutive laws, the deformational behaviour of structural elements failing in bending was predicted from the moment-curvature relationship of the representative cross sections. To evaluate the influence of the percentage of fibres on the shear resistance of shallow structures, three point bending tests with shallow beams were performed. The applicability of the formulation proposed by RILEM TC 162-TDF for the prediction of the shear resistance of SFRC elements was evaluated. Inverse analysis was adopted to determine indirectly the values of the fracture mode I parameters of the developed SFRC. With these values, and using a softening diagram for modelling the crack shear softening behaviour, the response of the SFRC beams failing in shear was predicted.

• Smart Structures and Systems
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• 제22권6호
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• pp.689-697
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• 2018

This paper presents a model of the elastic curve for rectangular beams with straight haunches under uniformly distributed load and moments in the ends considering the bending and shear deformations (Timoshenko Theory) to obtain the deflections and rotations on the beam, which is the main part of this research. The traditional model of the elastic curve for rectangular beams under uniformly distributed load considers only the bending deformations (Euler-Bernoulli Theory). Also, a comparison is made between the proposed and traditional model of simply supported beams with respect to the rotations in two supports and the maximum deflection of the beam. Also, another comparison is made for beams fixed at both ends with respect to the moments and reactions in the support A, and the maximum deflection of the beam. Results show that the proposed model is greater for simply supported beams in the maximum deflection and the traditional model is greater for beams fixed at both ends in the maximum deflection. Then, the proposed model is more appropriate and safe with respect the traditional model for structural analysis, because the shear forces and bending moments are present in any type of structure and the bending and shear deformations appear.

• 콘크리트학회논문집
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• 제14권6호
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• pp.910-921
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• 2002

철근콘크리트 보의 전단거동을 예측하기 위하여 휨모멘트가 고려된 변환각 트러스 모델(TATM)을 제안하였다. 제안된 TATM으로 구한 전단응력-전단변형률 관계는 본 연구에서 수행된 실험결과와 잘 일치하였다. 또한, TATM으로 구한 전단강도는 다양한 전단스팬비와 지점형태 및 단면형태를 가지는 총 170개 실험결과와 비교되었다. TATM에 의한 해석결과는 평균 0.96, 변동계수 11.9 %로서 기존의 트러스 모델에 의한 해석결과보다 실험결과를 더 잘 예측하였으며, 해석결과에 대한 실험결과의 비는 a/d와 η에 관계없이 거의 일정하였다.

• 콘크리트학회논문집
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• 제18권3호
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• pp.379-388
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• 2006

본 연구의 목적은 휨과 전단에 지배 받는 철근콘크리트 보에서 아치작용에 의한 전단기여분을 평가하는 모델을 개발하는 것이다. 전단력은 휨모멘트의 변화률이라는 관계식을 기초로, 분산트러스 이상화 기법을 이용하여 횡단면에서 베르누이(Bernoulli) 휨 평면으로부터 전단변형적합조건을 새롭게 유도하였다. MCFT와 분산트러스 이상화를 통해 전단흐름에 의한 복부전단요소의 전단곡률을 일치시키는 전단변형적합조건을 수립하였다. 전단변형적합조건을 이용하면, 보 전단거동은 타이드아치작용과 보 작용의 두 성분으로 수치적 분해 될 수 있다. 그리고 두 기본 작용의 분해가 가능하기 때문에 전단에 지배받는 보의 내력을 예측할 수 있다. 제안 모델의 유효성은 기존 문헌에 수록된 활용 가능한 실험 자료를 통해 검증하였고, 수행 결과는 예측치와 실험치 사이에서 실질적으로 일치하는 결과를 얻었다. 결과의 정확성으로부터 제안 모델의 합리성을 확신할 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.289-292
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• 2006

In this research, bending shear test of HPFRCC beams is conducted to obtain the shear strength of HPFRCC beams. Parameters are ratio of volume percentage of fibers. Also, the uniaxial tensile test of HPFRCC is conducted to obtain the tensile cracking stress of each parameters. From the uniaxial tensile test result, the shear strength of HPFRCC beams can be calculated by using the preexisting shear analysis model. Then, the shear strengths of bending shear test result and analysis result are compared.

• Structural Engineering and Mechanics
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• 제48권3호
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• pp.351-365
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• 2013

In this paper, unified nonlocal shear deformation theory is proposed to study bending, buckling and free vibration of nanobeams. This theory is based on the assumption that the in-plane and transverse displacements consist of bending and shear components in which the bending components do not contribute toward shear forces and, likewise, the shear components do not contribute toward bending moments. In addition, this present model is capable of capturing both small scale effect and transverse shear deformation effects of nanobeams, and does not require shear correction factors. The equations of motion are derived from Hamilton's principle. Analytical solutions for the deflection, buckling load, and natural frequency are presented for a simply supported nanobeam, and the obtained results are compared with those predicted by the nonlocal Timoshenko beam theory and Reddy beam theories.