• 한국공간구조학회논문집
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• 제5권3호
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• pp.109-115
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• 2005

본 논문에서는 강도를 향상시키기 위하여 탄소섬유쉬트를 압축하여 제작된 탄소섬유 판재을 이용하여 철근 콘크리트 보의 휨내력 향상과 이력거동에 미치는 영향을 규명하기 위하여 실험을 수행하였다. 실험의 주된 변수는 탄소섬유판재의 단면의 크기, 보강전에 철근콘크리트 보의 손상정도이다. 특히 보의 손상정도는 보가 과하중에 의해 손상을 받은 경우를 대상으로 하고 있으며 손상정도는 보의 최대 휨 내력의 30%, 60%, 100%로 하고 있으며 비교를 위하여 손상받지 않은 보도 실험하였다. 얻어진 결론은 탄소섬유판으로 보강한 경우는 보강하지 않은 보에 비해 강도는 상승하나 최대하중점에서의 변형은 감소하고 있으며, 연성에 있어서는 대등한 값을 나타내고 있다.

• Steel and Composite Structures
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• 제33권5호
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• pp.755-765
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• 2019

This study examined geometric and physical nonlinear analyses of beams and arches specifically from rolled profiles used in mining and underground constructions. These profiles possess the ability to create plastic hinges owing to their robustness. It was assumed that displacements in beams and arches fabricated from these profiles were comparable with the size of the structure. It also considered changes in the shape of a rod cross-section and the nonlinearities of the structure. The analyses were based on virtual unit moments, effective flexural rigidity of used open sections, and a secant method. The use of the approach led to a solution for the "after-critical" condition in which deformation increased with decreases in loads. The solution was derived for static determinate beams and static indeterminate arches. The results were compared with results obtained in other experimental tests and methods.

• Design & Manufacturing
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• 제10권2호
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• pp.6-11
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• 2016

Designed patterns of slit are introduced to the uni-directional (UD) prepreg in order to enhance the formability of the carbon/epoxy composites without wrinkling and laddering. Three different types of the slit alignment along the thickness direction are applied to analyse the deformation behavior during the compression moulding process of laminates. Degrees of the slit open and the mechanical strength are evaluated based on the level of the compaction pressure in the course of forming process. Results have shown that the mechanical strength of laminates having slits could attain at least 80% of the conventional ones without slits. However, further studies are required to identify the direct relevance of the slit alignment in laminate to the mechanical properties.

• Structural Engineering and Mechanics
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• 제76권6호
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• pp.737-749
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• 2020

A hybrid bridge deck is proposed, which includes steel bars, concrete and glass-fiber-reinforced-polymer (GFRP) plates with channel sections. The steel bar in the negative moment region can increase the flexural stiffness, improve the ductility, and reduce the GFRP ratio. Three continuous decks with different steel bar ratios and a simply supported deck were fabricated and tested to study the mechanical performance. The failure mode, deflection, strain distribution, cracks and support reaction were tested and discussed. The steel bar improves the mechanical performance of continuous decks, and a theoretical method is proposed to predict the deformation and the shear capacity. The experimental results show that all specimens failed with shear failure in the positive moment region. The increase of steel bar ratio in the negative moment region can achieve an enhancement in the flexural stiffness and reduce the deflection without increasing GFRP. Moreover, the continuous deck can achieve a yield load, and the negative moment can be carried by GFRP plates after the steel bar yields. Finally, a nonlinear analytical method for the deflection calculation was proposed and verified, with considering the moment redistribution, non-cracked sections and nonlinearity of material. In addition, a simplified calculation method was proposed to predict the shear capacity of GFRP-concrete decks.

• Structural Engineering and Mechanics
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• 제76권5호
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• pp.663-674
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• 2020

In this study, partially restrained beam-column moment joints in the weak-axis direction were examined using three large-scale specimens subject to cyclic loading in order to assess the seismic resistance of the joints of low-rise steel structures and to propose joint details based on the test results. The influence of different number of bolts on the moment joints was thoroughly investigated. It was found that the flexural capacity of the joints in the direction of weak axis was highly dependent on the number of high-tension bolts. In addition, even though the flexural connections subjected to cyclic loading was perfectly designed in accordance with current design codes, severe failure mode such as block shear failure could occur at beam flange. Therefore, to prevent excessive deformation at bolt holes under cyclic loading conditions, the holes in beam flange need to have larger bearing capacity than the required tensile force. In particular, if the thickness of the connecting plate is larger than that of the beam flange, the bearing capacity of the flange should be checked for structural safety.

• Structural Engineering and Mechanics
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• 제81권5호
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• pp.539-550
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• 2022

A detailed experimental program was conducted to investigate the flexural behavior of ultra high performance concrete (UHPC) beams reinforced with high strength steel (HSS) rebars with a specified yield strength of 600 MPa via direct tensile test and monotonic four-point bending test. First, two sets of direct tensile test specimens, with the same reinforcement ratio but different yield strength of reinforcement, were fabricated and tested. Subsequently, six simply supported beams, including two plain UHPC beams and four reinforced UHPC beams, were prepared and tested under four-point bending load. The results showed that the balanced-reinforced UHPC beams reinforced with HSS rebars could improve the ultimate load-bearing capacity, deformation capacity, ductility properties, etc. more effectively owing to interaction between high strength of HSS rebar and strain-hardening characteristic of UHPC. In addition, the UHPC with steel rebars kept strain compatibility prior to the yielding of the steel rebar, further satisfied the plane-section assumption. Most importantly, the crack pattern of the UHPC beam reinforced with HSS rebars was prone to transform from single main crack failure corresponding to the normal-strength steel, to multiple main cracks failure under the condition of balanced-reinforced failure, which validated by the conclusion of direct tensile tests cooperated with acoustic emission (AE) source locating technique as well.

• Steel and Composite Structures
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• 제47권5호
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• pp.615-631
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• 2023

Steel corrosion induces structural deterioration of concrete-filled steel tubes (CFSTs), and any potential extreme action on a corroded CFST would pose a severe threat. This paper presents a comprehensive investigation on the lateral impact behaviour of CFSTs suffering from localised pitting corrosion damage. A refined finite element analysis model is developed for the simulation of locally corroded CFSTs subjected to lateral impact loads, which takes into account the strain rate effects on concrete and steel materials as well as the random nature of corrosion pits, i.e., the distribution patterns and the geometric characteristics. Full-range nonlinear analysis on the lateral impact behaviour in terms of loading and deforming time-history relations, nonlinear material stresses, composite actions, and energy dissipations are presented for CFSTs with no corrosion, uniform corrosion and pitting corrosion, respectively. Localised pitting corrosion is found to pose a more severe deterioration on the lateral impact behaviour of CFSTs due to the plastic deformation concentration, the weakened confinement and the reduction in energy absorption capacity of the steel tube. An extended parametric study is then carried out to identify the influence of the key parameters on the lateral impact behaviour of CFSTs with localised pitting corrosion. Finally, simplified design methods considering the features of pitting corrosion are proposed to predict the dynamic flexural capacity of locally pitted CFSTs subjected to lateral impact loads, and reasonable accuracy is obtained.

• Steel and Composite Structures
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• 제49권5호
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• pp.571-585
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• 2023

The application of relatively low volumes of fibres in normal strength concrete has been shown to be of significant benefit when applied to composite slabs with profiled sheet decking. This paper reports on an experimental study aimed at quantifying further potential benefits that may arise from applying ultra-high performance fibre reinforced concrete. To assess performance six simply supported beams were tested under hogging and sagging loading configurations along with three two span continuous beams. Fibre contents are varied from 0% to 2% and changes in strength, deformation, crack width and moment redistribution are measured. At the serviceability limit state, it is shown that the addition of high fibre volumes can significantly enhance member stiffness and reduce crack widths in all beams. At the ultimate limit state it is observed that a transition from 0% to 1% fibres significantly increases strength but that there is a maximum fibre volume beyond which no further increases in strength are possible. Conversely, member ductility and moment redistribution are shown to be strongly proportional to fibre volume.

• Structural Engineering and Mechanics
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• 제53권5호
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• pp.997-1016
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• 2015

The contribution of tensioned concrete between cracks (tension-stiffening) cannot be ignored when analysing deformation of reinforced concrete elements. The tension-stiffening effect is crucial when it comes to adequately estimating the load-deformation response of steel reinforced concrete and the more recently appeared fibre reinforced polymer (FRP) reinforced concrete. This paper presents a unified methodology for numerical modelling of the tension-stiffening effect in steel as well as FRP reinforced flexural members using the concept of equivalent deformation modulus and the smeared crack approach to obtain a modified stress-strain relation of the reinforcement. A closed-form solution for the equivalent secant modulus of deformation of the tensioned reinforcement is proposed for rectangular sections taking the Eurocode 2 curvature prediction technique as the reference. Using equations based on general principles of structural mechanics, the main influencing parameters are obtained. It is found that the ratio between the equivalent stiffness and the initial stiffness basically depends on the product of the modular ratio and reinforcement ratio ($n{\rho}$), the effective-to-total depth ratio (d/h), and the level of loading. The proposed methodology is adequate for numerical modelling of tension-stiffening for different FRP and steel reinforcement, under both service and ultimate conditions. Comparison of the predicted and experimental data obtained by the authors indicates that the proposed methodology is capable to adequately model the tension-stiffening effect in beams reinforced with FRP or steel bars within wide range of loading.

• 한국전산구조공학회논문집
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• 제18권4호통권70호
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• pp.361-372
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• 2005

본 저자의 이전연구(김문영 등, 2004)에서는 2차원 차량 모형과 전단변형 및 회전관성 효과가 고려된 현수교요소와의 상호작용을 고려한 2차원 수직응답에 대한 동적해석을 수행하였다. 본 연구에서는 전단변형 효과와 편심차량의 효과를 알아보는데 목적을 두었다. 이를 위하여 전단변형 및 회전관성 효과가 고려된 3차원 현수교의 수직, 비틂에 대한 고유진동수와 모드형상, 그리고 교량-차량 에너지로부터 라그랑지안식을 이용하여 상호작용을 고려할 수 있는 3차원 운동방정식을 유도한다. 이후 모드중칩법을 이용하여 유도된 운동방정식을 Newmark method를 사용하여 동적해석을 수행한다. 마지막으로 본 연구에서 제시한 이론을 따라 수치해석예제를 수행하여 차량의 동적거동을 분석한다.