• Composites Research
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• 제17권2호
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• pp.9-14
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• 2004

본 연구는 FRP 보강 콘크리트 슬래브의 휨거동에 관한 이론적 연구로서 FRP 보강 콘크리트 슬래브를 구조적 직교이방성판으로 간주하고 고전적 직교이방성판이론에 따른 휨해석 및 유한요소해석을 수행하였다. FRP 보강 콘크리트 슬래브를 직교이방성판으로 모델링하기 위해서는 각 하중한대별로 실제 구조물의 거동에 부합하는 직교이방성판의 휨강성을 결정하는 것이 중요하다. 본 연구에서는 탄성등가법을 적용하여 FRP 보강 콘크리트 슬래브와 등가인 직교이방성판의 휨강성을 결정하였으며, 탄성등가법에 의해 결정된 휨강성을 사용하여 유한요소해석 수행을 위한 강성행렬의 결정방법을 제안하였다. 또한, 이론식에 의한 해석결과와 제안된 강성행렬을 사용하여 해석한 유한요소해석 결과를 실험결과와 비교하였다.

• Structural Engineering and Mechanics
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• 제10권4호
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• pp.337-357
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• 2000

Analytical formulations and solutions for the first time, to the stability analysis of a simply supported composite and sandwich plates based on a higher order refined theory, developed by the first author and already reported in the literature are presented. The theoretical model presented herein incorporates laminate deformations which account for the effects of transverse shear deformation, transverse normal strain/stress and a nonlinear variation of inplane displacements with respect to the thickness coordinate - thus modelling the warping of transverse cross sections more accurately and eliminating the need for shear correction coefficients. The equations of equilibrium are obtained using the Principle of Minimum Potential Energy (PMPE). The comparison of the results using this higher order refined theory with the available elasticity solutions and the results computed independently using the first order and the other higher order theories developed by other investigators and available in the literature shows that this refined theory predicts the critical buckling load more accurately than all other theories considered in this paper. New results for sandwich laminates are also presented which may serve as a benchmark for future investigations.

• Structural Engineering and Mechanics
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• 제84권3호
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• pp.361-373
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• 2022

This paper examines the flexural performance of concrete beams reinforced with glass fibre-reinforced polymer (GFRP) bars under fatigue loading. Experiments were carried out on concrete beams of size 1500×200×100 mm reinforced with 10 mm and 13 mm diameter GFRP bars under fatigue loading. Experimental investigations revealed that fatigue loading affects both strength and serviceability properties of GFRP reinforced concrete. Experimental results indicated that (i) the concrete beams experienced increase in deflection with increase in number of cycles and failed suddenly due to snapping of rebars and (ii) the fatigue life of concrete beams drastically decreased with increase in stress level. Analytical model presented a procedure for predicting the deflection of concrete beams reinforced with GFRP bars under cyclic loading. Deflection of concrete beams was computed by considering the aspects such as stiffness degradation, force equilibrium equations and effective moment of inertia. Nonlinear finite element (FE) analysis was performed on concrete beams reinforced with GFRP bars. Appropriate constitutive relationships for concrete and GFRP bars were considered in the numerical modelling. Concrete non linearity has been accounted through concrete damage plasticity model available in ABAQUS. Deflection versus number of cycles obtained experimentally for various beams was compared with the analytical and numerical predictions. It was observed that the predicted values are comparable (less than 20% difference) with the corresponding experimental observations.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.245-248
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• 2008

최근 세계적으로 FRP 복합재료를 이용한 다양한 연구가 진행 중에 있다. 본 연구 과제중 가격 경쟁력을 위해 유리 섬유를 이용한 신개념의 FRP+콘크리트 합성 거더 모듈을 제안하고 장경간 교량에 적용될 수 있도록 하중 재하실험을 수행한 바 있다. 실험 결과 콘크리트 충진으로 인하여 성능이 현저하게 개선되는 것으로 평가되었다. 본 연구에서는 소형화된 모듈의 FRP+콘크리트 합성거더에 대하여 거동을 해석하고 실험결과와 비교, 분석하였다. 또한, 큰 단면을 위해 모듈화된 FRP 거더 4개를 연결하여 어떠한 거동을 보이는지 예측해 보았다. 해석을 위해 FRP 거더면끼리는 충분한 접촉강도를 가지고 있으므로 완전 부착으로 가정하였다. 그 결과 콘크리트가 충진되지 않은 FRP 거더는 처짐 허용량을 초과하였지만, 콘크리트가 충진된 FRP 거더는 상대적으로 적은 처짐량을 보여 주여 충진된 FRP거더를 실제 구조물에 사용되더라도 추가 보완 연구를 통해 처짐으로 인한 사용성의 문제를 해결 할 수 있을 것으로 사료된다.

• Steel and Composite Structures
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• 제47권6호
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• pp.709-728
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• 2023

Experimental and analytical studies were conducted to clarify the influencing mechanisms of the longitudinal reinforcement on performance of axially loaded Reinforced Concrete-Filled Steel Tube (R-CFST) short columns. The longitudinal reinforcement ratio was set as parameter, and 10 R-CFST specimens with five different ratios and three Concrete-Filled Steel Tube (CFST) specimens for comparison were prepared and tested. Based on the test results, the failure modes, load transfer responses, peak load, stiffness, yield to strength ratio, ductility, fracture toughness, composite efficiency and stress state of steel tube were theoretically analyzed. To further examine, analytical investigations were then performed, material model for concrete core was proposed and verified against the test, and thereafter 36 model specimens with four different wall-thickness of steel tube, coupling with nine reinforcement ratios, were simulated. Finally, considering the experimental and analytical results, the prediction equations for ultimate load bearing capacity of R-CFSTs were modified from the equations of CFSTs given in codes, and a new equation which embeds the effect of reinforcement was proposed, and equations were validated against experimental data. The results indicate that longitudinal reinforcement significantly impacts the behavior of R-CFST as steel tube does; the proposed analytical model is effective and reasonable; proper ratios of longitudinal reinforcement enable the R-CFSTs obtain better balance between the performance and the construction cost, and the range for the proper ratios is recommended between 1.0% and 3.0%, regardless of wall-thickness of steel tube; the proposed equation is recommended for more accurate and stable prediction of the strength of R-CFSTs.

• Steel and Composite Structures
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• 제34권6호
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• pp.803-818
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• 2020

Semi-rigid connections with blind bolts could solve the difficulty that traditional high strength bolts were unavailable to splice a steel/composite beam to a closed section column. However, insufficient investigations have focused on the performance of semi-rigid connection to square concrete filled double-skin steel tubular (CFDST) columns. In this paper, a component model was developed to evaluate the mechanical behavior of semi-rigid composite connections to CFDST columns considering the stiffness and strength of column face in compression and column web in shear which were determined by the load transfer mechanism and superstition method. Then, experimental investigations on blind bolted composite joints to square CFDST columns were conducted to validate the accuracy of the component model. Dominant failure modes of the connections were analyzed and this type of joint behaved semi-rigid manner. More importantly, strain responses of CFDST column web and tubes verified that stiffness and strength of column face in compression and column web in shear significantly affected the connection mechanical behavior owing to the hollow part of the cross-section for CFDST column. The experimental and analytical results showed that the CFDST column to steel-concrete composite beam semi-rigid joints could be employed for the assembled structures in high intensity seismic regions.

• Advances in materials Research
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• 제6권3호
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• pp.257-278
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• 2017

A simple closed-form solution to calculate the interfacial shear and normal stresses of retrofitted concrete beam strengthened with thin composite plate under mechanical loads including the creep and shrinkage effect has been presented in this paper. In such plated beams, tensile forces develop in the bonded plate, and these have to be transferred to the original beam via interfacial shear and normal stresses. Consequently, debonding failure may occur at the plate ends due to a combination of high shear and normal interfacial stresses. These stresses between a beam and a soffit plate, within the linear elastic range, have been addressed by numerous analytical investigations. Surprisingly, none of these investigations has examined interfacial stresses while taking the creep and shrinkage effect into account. In the present theoretical analysis for the interfacial stresses between reinforced concrete beam and a thin composite plate bonded to its soffit, the influence of creep and shrinkage effect relative to the time of the casting, and the time of the loading of the beams is taken into account. Numerical results from the present analysis are presented both to demonstrate the advantages of the present solution over existing ones and to illustrate the main characteristics of interfacial stress distributions.

• 한국지반환경공학회 논문집
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• 제8권3호
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• pp.51-57
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• 2007

강우시의 비탈면 설계에서는 강우특성변화에 따라 지하수위가 지표면에 위치하는 것으로 가정한다. 또한, 안정성 검토는 비탈면 설계시 대절토 비탈면을 대상으로 수행하는 반면, 안정성 검토가 수행되지 않는 비탈면에 대해서는 설계기준에 규정된 표준 경사가 적용된다. 강화된 지하수위 적용기준에도 불구하고 강우시 비탈면의 규모와 관계없이 비탈면 붕괴가 지속적으로 발생되고 있다. 붕괴원인을 조사하기 위하여 본 연구에서는 지반 조건별로 건기시와 우기시에 대하여 국내 시방기준에서 제안하고 있는 토사 비탈면의 표준경사에 대하여 안정성을 검토하였다. 시방기준에서 제시된 비탈면 표준경사는 건기시나 우기시 모두 안정해야 함에도 불구하고, 검토 결과는 많은 경우에서 기준 안전율이 얻어지지 않는 것으로 나타났다. 건기시의 경우는 전체 검토대상 조건에 대하여 약 50% 이상, 우기시의 경우 약 65% 이상이 기준 안전율을 만족하지 못하였다. 이러한 결과를 바탕으로 본 논문은 현 설계기준의 문제점을 지적하고 대책수립을 위한 방안을 제안하고 있다.

• 전기의세계
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• 제14권1호
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• pp.5-12
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• 1965

In the designs of the sensitive electronic devices such as phase sensitive detector, X-ray diffractometer, and neutron diffractometers, we must take into account the geometrical factors in a coil systems and extraneous stray fields. Input wave forms in such a sensitive electronic devices are often altered by the influence of these factors. Since the magnitude of the stray fields is generally very small, this affection may be removed by applying a good shielding but it is not ease to remove the affection from a geometrical factor. This affection must be however calculated by the theoretical methods and analytical solution in the equation of these factors. The fundamental purpose of this paper lie in the theoretical calculations and practical measurements of the geometrical factor in the coil systems, finite solenoid, and four point prove. In the heoretical calculations, the geometrical factors in the coil systems were calculated by applying the elliptic functions and in the contact points were calculated by applying the elliptic functions and in the contact points were calculated by applying the eigen functions and the infinite series. The measurements were carried out by using the sensitive electronic device made from author's design, as shown in the Fig. 9. The result of this work has verified the essential correctness of theoretical investigations and measuring techniques of geometrical factors on the design of sensitive electronic devices. It also has several advantages such that: (1) all the data obtained may give effective data to designer to work on the field of sensitive electronic devices or microelectronic devices, (2) it has evidently explained the characteristics of electrical investigations and physical definition, and has removed the conventional error of geometrical factors in the coil systems and contact points.

• Structural Engineering and Mechanics
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• 제52권6호
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• pp.1085-1098
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• 2014

Plastic mechanism analysis of structures subjected to large deformation has long been used in order to determine collapse mechanisms of steel structures, and the energy absorbed in plastic deformation during such collapses. In this paper the technique is applied to vehicle roof structures that undergo large plastic deformation as a result of rollover crashes. The components of such roof structures are typically steel spot-welded hat-type sections. Ten different deformation mechanisms are defined from investigations of real-world rollover crashes, and an analytical technique to determine the plastic collapse load and energy absorption of such mechanisms is determined. The procedure is presented in a generic manner, such that it may be applied to any vehicle structure undergoing a rollover induced collapse. The procedure is applied to an exemplar vehicle, in order to demonstrate its application in determining the energy absorbed in the deformation of the identified collapse mechanisms. The procedure will be useful to forensic crash reconstructionists, in order to accurately determine the initial travel velocity of a vehicle that has undergone a rollover and for which the post-crash vehicle deformation is known. It may also be used to perform analytical studies of the collapse resistance of vehicle roof structures for optimisation purposes, which is also demonstrated with an analysis of the effect of varying the geometric and material properties of the roof structure components of the exemplar vehicle.