• Computers and Concrete
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• 제31권1호
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• pp.53-69
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• 2023

The rotational stiffness of a semi-rigid beam-to-column connection plays an important role in the reduction of the second-order effects in the precast concrete skeletal frames. The aim of this study is to present a detailed nonlinear finite element study to reproduce the experimental response of a semi-rigid precast beam-to-column connection composed by corbel, dowel bar and continuity tie bars available in the literature. A parametric study was carried using four arrangements of the reinforcing tie bars in the connection, including high ratio of the continuity tie bars passing around the column in the cast-in-place concrete. The results from the parametric study were compared to analytical equations proposed to evaluate the secant rotational stiffness of beam-to-column connections. The good agreement with the experimental results was obtained, demonstrating that the finite element model can accurately predict the structural behaviour of the beam-to-column connection despite its complex geometric configuration. The secant rotational stiffness of the connection was good evaluated by the analytical model available in the literature for ratio of the continuity tie bars of up to 0.69%. Precast beam-to-column connection with a ratio of the continuity tie bars higher than 1.4% had the secant stiffness overestimated. Therefore, an adjustment coefficient for the effective depth of the crack at the end of the beam was proposed for the analytical model, which is a function of the ratio of the continuity tie bars.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.470-473
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• 2006

Past experiences from recent earthquakes indicate that shear failures of beam-column connections were one of the main reasons causing significant damages and collapses of RC structures subjected to earthquake loadings. Many researchers and engineers have conducted to propose an effective way to improve the joint shear strength of RC connections. This paper presents an analytical model for the RC exterior beam-column joints strengthened with CFRP sheets. In the analytical model, the effect of shear behavior of the RC beam-column joint, bond slip of the beam longitudinal reinforcements and CFRP sheets were considered and incorporated into the non-linear structural analysis program. Final analytical results were compared with those from the experiment of eight exterior RC beam-column specimens. The analytical results showed that the developed connection model is very useful to investigate the hysteretic joint behavior and overall load-displacement response of the RC beam-column connections strengthened with CFRP sheets.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.884-889
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• 2003

Based on the reinterpretation of the well-known relationship between shear and the rate of change of bending moment in a reinforced concrete beam subject to combined shear and moment loads, the shortcomings of present truss models are discussed. The core of the theory is that a new perspective on the shear strength can be gained by viewing the internal stress filed in terms of the superposition of two base components of shear resistance; arch action and beam action. The arch action can be designed using the simple truss having curved compression chord, while the beam action between the two chords can be modeled using a parallel chord truss with MCFT or RA-STM. The compatibility of deformation associated to the two action is taken into account by employing a characteristic factor a. The new model was examined by the Stuttgart beam shear tests, and the results show that the present approach provides good estimates of stirrup contribution and concrete contributions.

• Steel and Composite Structures
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• 제21권4호
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• pp.805-827
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• 2016

A new type of precast CFST column to RC beam braced frame is proposed in this paper. A series of shake table tests were conducted to excite a one-third scale six-story model for investigating the global seismic performance of this type of structure against earthquake actions. Particular emphasis was given to its dynamic property, global seismic responses and failure path. Correspondingly, a numerical model built on the basis of fiber-beam-element model, multi-layer shell model and element-deactivation method was developed to simulate the seismic performance of the prototype structure. Numerical results were compared with the measured values from shake table tests to verify the validity and reliability of the numerical model. The results demonstrated that the proposed novel precast CFST column to RC beam braced frame performs excellently under strong earthquake excitations; the "strong CFST column-weak RC beam" and "strong connection-weak member" anti-seismic design principles can be easily achieved; the maximum deflections of precast CFSTC-RCB braced frame satisfied the deflection limitations proposed in national code; the numerical model can properly simulate the dynamic property and responses of the precast CFSTC-RCB braced frame that are highly concerned in engineering practice.

• 전산구조공학
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• 제10권1호
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• pp.213-223
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• 1997

복잡한 구조물의 거동을 해석하는 데 있어서 초기 설계단계에서 부터 쉘요소를 사용하여 해석하는 것은 많은 시간과 경비가 요구된다. 이에 경비절감의 측면에서 쉘구조물을 단순 보구조물에 의해 모델링함에 의해 분석하고자 하는 연구가 진행되어왔다. 본 연구에서는 단순화된 보구조물의 결합부에 고려하기 위한 유연도를 나타내는 굽힘회전강성을 결정하는 방법을 제안하고, 제안된 방법을 통해 얻어진 결합부에서의 유연도을 보구조물의 결합부에 적용하여 비선형해석을 수행한다. 수치해석 결과로 쉘구조물에서 나타나는 기하학적 비선형거동을 결합부에서 유연도를 고려하는 단순 보구조물에 의해 작은 오차의 범위안에서 기술할 수 있었다.

• 한국태양에너지학회 논문집
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• 제39권4호
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• pp.11-24
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• 2019

The total solar irradiation on horizontal surfaces is separated into the beam and diffuses components. Although horizontal global irradiance is a commonly measured parameter for many sites, horizontal diffuse irradiance is not so readily obtainable. For such sites that measure global irradiation alone, a simple but reasonably accurate method is required to estimate diffuse irradiance from its global counterpart. This study investigates the applicability of correlation coefficients models correlating hourly diffuse and beam fraction and hourly clearness index in Daejeon. The three diffuse to global correlation coefficients models (Orgill and Holland model, CIBSE Guide J model, and Erbs et al. model) are selected and the three modified beam to global correlation coefficients models are generated. MBE, RMSE, r-squared of Daejeon and Daejeon boundary site-fitted models are compared with the case of original coefficients. The comparison result shows that the beam and diffuse to global solar irradiation correlation coefficients models with boundary site-fitted coefficients are best suitable for Daejeon. Further researches will be conducted to find the boundary site-fitting method using measured data of other cities and correlation coefficients models using solar altitude, cloud cover, and sunshine duration.

• Structural Engineering and Mechanics
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• 제69권2호
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• pp.205-219
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• 2019

This paper analyzes nonlinear free vibration of the circular nano-tubes made of functionally graded materials in the framework of nonlocal strain gradient theory in conjunction with a refined higher order shear deformation beam model. The effective material properties of the tube related to the change of temperature are assumed to vary along the radius of tube based on the power law. The refined beam model is introduced which not only contains transverse shear deformation but also satisfies the stress boundary conditions where shear stress cancels each other out on the inner and outer surfaces. Moreover, it can degenerate the Euler beam model, the Timoshenko beam model and the Reddy beam model. By incorporating this model with Hamilton's principle, the nonlinear vibration equations are established. The equations, including a material length scale parameter as well as a nonlocal parameter, can describe the size-dependent in linear and nonlinear vibration of FGM nanotubes. Analytical solution is obtained by using a two-steps perturbation method. Several comparisons are performed to validate the present analysis. Eventually, the effects of various physical parameters on nonlinear and linear natural frequencies of FGM nanotubes are analyzed, such as inner radius, temperature, nonlocal parameter, strain gradient parameter, scale parameter ratio, slenderness ratio, volume indexes, different beam models.

• Journal of Astronomy and Space Sciences
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• 제7권2호
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• pp.113-123
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• 1990

전자 beam이 중성 plasma계에 들어왔을 때의 상호작용을 이차원 정전 model을 사용하여 수치계산을 한 결과 beam의 밀도변화에 따라 상호작용이 큰 변화를 보이는 것으로 나타났다. beam 전자의 밀도가 주변 전자의 밀도보다 낮을 때는 많은 양의 beam들이 주변 plasma와의 상호작용을 통해 위상공간에서 vortex 구조를 보이며 입사지역으로부터 멀리 진행할 수 있었던 반면 beam 전자들의 밀도가 높을 때는 대부분의 beam 전자들이 입사지역으로 되돌아오는 희귀전류를 형성하였다. 이 때 자기장의 게기에 따라 전자보다 훨씬 질랴이 큰 ion들이 가속될 수도 있으며 전자들의 전파와 상호작용의 양상이 크게 바뀔 수 있는 것으로 나타났다.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1661-1666
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• 2003

The purpose of this study is to develop the simplified model of the crankshaft in the large marine engine for dynamic analysis. Because the actual engine system is under complex dynamic loading condition and it has multi-cylinder, the dynamic analysis is purchased at a high computation cost. In spite of this burden, the dynamic analysis must be perfonned to assure structural integrity of operating marine engine. Therefore, simplification of the analytic model is necessary for dynamic analysis. Beam-mass model, which is generated with the section property method, is the model simplified effectively. Section property method can provide desired section information by optimization technique. By applying beam-mass model to the crankshaft in the large marine engine, the usefulness of the proposed method was proven.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.553-560
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• 2001

Recently, ultrasonic testing simulation has becomes very important in the field of nondestructive evaluation due to its unique capability of providing testing signals without real inspection. The ultrasonic testing simulation requires three elementary models including the transducer beam radiation model, the flaw scattering model, and the reception model. In the present work, we briefly describe an approach to develop the ultrasonic testing model together with its elementary models with the multi-gaussian beam model. Based on this approach, we developed ultrasonic testing simulation program with MATLAB. The performance of the developed program is demonstrated by the predicting of ultrasonic signals from two types of flaws, circulars crack and spheres.