• 국제강구조저널
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• 제18권4호
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• pp.1440-1463
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• 2018

The Wagner coefficient is a key parameter used to describe the inelastic lateral-torsional buckling (LTB) behaviour of the I-beam, since even for a doubly-symmetric I-section with residual stress, it becomes a monosymmetric I-section due to the characteristics of the non-symmetrical distribution of plastic regions. However, so far no theoretical derivation on the energy equation and Wagner's coefficient have been presented due to the limitation of Vlasov's buckling theory. In order to simplify the nonlinear analysis and calculation, this paper presents a simplified mechanical model and an analytical solution for doubly-symmetric I-beams under pure bending, in which residual stresses and yielding are taken into account. According to the plate-beam theory proposed by the lead author, the energy equation for the inelastic LTB of an I-beam is derived in detail, using only the Euler-Bernoulli beam model and the Kirchhoff-plate model. In this derivation, the concept of the instantaneous shear centre is used and its position can be determined naturally by the condition that the coefficient of the cross-term in the strain energy should be zero; formulae for both the critical moment and the corresponding critical beam length are proposed based upon the analytical buckling equation. An analytical formula of the Wagner coefficient is obtained and the validity of Wagner hypothesis is reconfirmed. Finally, the accuracy of the analytical solution is verified by a FEM solution based upon a bi-modulus model of I-beams. It is found that the critical moments given by the analytical solution almost is identical to those given by Trahair's formulae, and hence the analytical solution can be used as a benchmark to verify the results obtained by other numerical algorithms for inelastic LTB behaviour.

• 콘크리트학회논문집
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• 제24권2호
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• pp.185-193
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• 2012

이 연구에서는 인접한 보에 소성힌지가 발생하기 전에 접합부에서 전단파괴가 발생하는 내부 보-기둥 접합부의 전단강도를 평가하기 위해서 식을 제안하였다. ACI와 AIJ의 기존 기준식은 콘크리트의 압축강도만을 고려하여 평가하지만 제안식은 트러스 작용 또한 고려하고 있다. 제안식은 콘크리트의 연화효과를 반영하기 위해 적용하는 콘크리트 유효압축계수를 구할 때 수직, 수평 철근을 고려하여 접합부의 전단강도를 평가한다. 그 결과, $V_{test}/V_{cal}$의 평균은 1.14, 변동계수는 20%이고 ACI와 AIJ에 의한 평가보다 비교적 향상된 결과를 보였다. $V_{test}/V_{cal}$는 각 방향의 철근비에 따라 비슷한 경향을 보이고 있음을 알 수 있다.

• 대한기계학회논문집A
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• 제23권11호
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• pp.2007-2013
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• 1999

A Newly proposed control methodology applied to the aeroelastic system experiencing flutter is investigated and its performance is verified experimentally. The flexible cantilever beam slicked with piezofilm sensor and piezoceramic actuator is modelled in physical domain. Dynamic moment equation for the system is derived via Ito's stochastic differential equation and F-P-K equation. Also system's characteristics in stochastic domain is analyzed simultaneously. LQG controller is designed and used in physical and stochastic domain. It is shown experimentally that the vibration of beam is controlled effectively by designed LQG controller in physical domain. By comparing the result with that of LQG controller designed in stochastic domain, it is shown that the new control method, called Heo-stochastic control technique, has better performance as a controller.

• 한국구조물진단유지관리공학회 논문집
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• 제26권6호
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• pp.222-229
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• 2022

외부 긴장재를 사용하는 PSC I 보는 외부긴장재의 복합 거동으로 해석적인 예측이 어렵다. 이러한 점을 고려하여 단면 보강용 외부 긴장강선의 사용으로 인한 휨 성능을 검증하고, 하중으로 인한 외부 강선의 응력증가량 식을 제안하여 식의 검토를 위하여 실험적 연구를 수행하였다. 검증을 위해 외부 강선의 유·무에 따른 두 개의 실험체를 제작하여 정적 하중 재하실험을 실시하였다. 실험의 연구 데이터를 비교 분석한 결과, 단면 보강용 외부 긴장강선의 사용으로 인하여 휨 성능이 증가하였다. 또한, 제안한 외부 강선의 응력증가량식을 사용하여 휨 강도를 산정한 결과값과 실험적 데이터를 비교한 결과 두 값이 거의 일치하였다. 결과적으로 단면 보강용 외부 긴장 강선으로 보강한 PSC I 보 휨 성능의 향상을 입증하였고, 제안된 응력증가량 식이 타당하였다.

• 한국정밀공학회지
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• 제15권12호
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• pp.194-201
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• 1998

The beam rotating actuator has been developed. It can be utilized to improve the data transfer rate for the optical disk systems, Newly developed laser beam rotating actuator is applied to put multi-beam spots on more than one track on the optical disk simultaneously. The beam rotating actuator is made of piezoelectric ceramic bimorph as the form of cantilever, Piezoelectric actuators with high resolution, high stiffness and fast frequency response are widely assembled in micropositioning applications. Therefore, the actuator has above 50Hz natural frequency. Beam array is rotated using the dove prism in the end of beamrotator. The dynamic equation of beam rotating actuator is derived theoretically. The actuator is designed on the ground of this analysis. The performance of the beam rotating actuator is verified as the dynamics frequency performance is measured using the dynamic analyzer and sensor.

• 한국정밀공학회지
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• 제17권5호
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• pp.154-159
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• 2000

A multi-beam optical disk drive is presented as a method for improving the effective data transfer rate by increasing the beam spot number formed on an optical disk. The beam rotating actuator is necessary for putting multi-beam on more than one track. The beam rotating actuator is made up of piezoelectric material, high stiffness wire hinge and dove prism. The actuator has good frequency response above 1KHz and suitable operational range. The dynamic equation for the actuator is derived.

• 한국자동차공학회논문집
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• 제12권5호
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• pp.146-153
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• 2004

Torsion beam rear suspension has been widely adopted to the rear suspension of vehicle by reason of simple structure and cost competitiveness. Since the kinematic characteristics of torsion beam rear suspension are determined by elastic behavior of torsion beam, quasi-static analysis based on finite element modeling of torsion beam has been conducted to obtain the kinematic parameters of torsion beam rear suspension. In this paper, simple kinematic equations with rear geometric parameters are derived to predict the kinematic behavior of torsion beam rear suspension. The suspension design parameters such as roll center height, roll stiffness, roll steer and roll camber can be easily obtained with the kinematic equations. The suggested kinematic equations are validated from comparison with the test results and solution offered by ADAMS. The suspension design parameters varied with the position of torsion beam are discussed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.481-486
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• 2002

A precast concrete beam which is larger than the limits of domestic transportation regulation in weight, length, and volume is divided into three parts, transported separately, and erected with a composite beam by post-tensioning in site. Shear tests are performed on the post-tensioned composite segmental beam models with 1/2 scale. The jacking force and the ratio of area of shear key to beam section are major experimental variables. Nine shear strength are resulted from the tests with two variables. Rational equation for estimation of shear strength are obtained from the regression analysis on test results.

• Structural Engineering and Mechanics
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• 제2권1호
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• pp.113-123
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• 1994

A method for computing the elastic buckling prestressing force of a post-tensioned composite steel-concrete tee-beam is presented. The method is based on a virtual work formulation, and incorporates the restraint provided by the concrete slab to the buckling displacements of the steel beam. The distortional buckling solutions are shown to be given by a quadratic equation. The application of the analysis to calculation buckling strengths is given, based on codified rules for beam-columns. Conclusions are then drawn on the importance of distortional buckling when a post-tensioned composite beam is stressed during jacking.

• Smart Structures and Systems
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• 제22권1호
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• pp.105-120
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• 2018

In this paper, the nonlinear free and forced vibration responses of sandwich nano-beams with three various functionally graded (FG) patterns of reinforced carbon nanotubes (CNTs) face-sheets are investigated. The sandwich nano-beam is resting on nonlinear Visco-elastic foundation and is subjected to thermal and electrical loads. The nonlinear governing equations of motion are derived for an Euler-Bernoulli beam based on Hamilton principle and von Karman nonlinear relation. To analyze nonlinear vibration, Galerkin's decomposition technique is employed to convert the governing partial differential equation (PDE) to a nonlinear ordinary differential equation (ODE). Furthermore, the Multiple Times Scale (MTS) method is employed to find approximate solution for the nonlinear time, frequency and forced responses of the sandwich nano-beam. Comparison between results of this paper and previous published paper shows that our numerical results are in good agreement with literature. In addition, the nonlinear frequency, force response and nonlinear damping time response is carefully studied. The influences of important parameters such as nonlocal parameter, volume fraction of the CNTs, different patterns of CNTs, length scale parameter, Visco-Pasternak foundation parameter, applied voltage, longitudinal magnetic field and temperature change are investigated on the various responses. One can conclude that frequency of FG-AV pattern is greater than other used patterns.