• 한국강구조학회 논문집
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• 제26권3호
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• pp.231-240
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• 2014

축방향 인장력을 받는 T-stub은 T-stub과 긴결재의 재료적 물성 특성, T-stub의 기하학적 형상, 긴결재의 직경과 체결력 등의 변화에 의하여 상이한 거동특성을 나타낸다. 이러한 변화의 영향으로 T-stub은 T-stub 플랜지의 휨항복 후 소성파괴, T-stub 필릿부의 휨항복과 긴결재 파단, 긴결재의 파단 등과 같은 세 가지 파괴양상을 나타낸다. 일반적으로 T-stub 플랜지의 두께가 얇고 긴결재의 게이지 거리가 긴 T-stub은 플랜지의 휨항복 후 소성화에 의하여 T-stub 플랜지의 두께가 두껍고 긴결재의 게이지 거리가 짧은 T-stub보다 에너지소산능력이 우수하다. 이 연구는 T-stub 체결에 사용된 긴결재가 T-stub의 에너지소산능력에 미치는 영향을 파악하기 위하여 3차원 비선형 유한요소 해석을 진행하였다. T-stub 해석모델의 긴결재로는 F10T-M20 고장력볼트와 ${\varnothing}19.05mm$(3/4inch)인 SMA 강봉을 모델링하였고, T-stub의 기하학적 형상은 T-stub 필릿부의 휨항복과 긴결재 파단의 파괴를 나타내도록 선택하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제22권1호
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• pp.147-157
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• 2018

철근콘크리트 교량에 대한 대부분의 내진설계기준들은 전체 교량 시스템의 붕괴를 방지하기 위한 성능보장설계를 암시적 또는 명시적으로 적용하고 있다. 이러한 개념 및 규정들을 명시하는 이유는 교량 전체 시스템에 설계지진하중이 작용하는 동안 철근콘크리트 교각들이 완전한 소성회전성능을 발휘할 때까지 구조적인 다른 구성요소들의 취성적인 파괴를 방지하기 위함이다. 이를 위해 철근콘크리트 교량에 대한 내진설계기준들에서는 취성적인 전단파괴를 피하도록 규정하고 있다. 성능보장의 중요한 요소 중의 하나가 교각의 연성거동을 보장하기 위한 전단강도가 충분히 확보되어야 하고 신뢰할 수 있어야 한다. 실험체 8개에 대하여 실험을 수행하였으며 모든 실험체에서 변위비 1.5%에서 다수의 휨-전단 균열이 발생되었고 최종단계까지 균열폭이 증가되었고 균열이 진전되었다. 휨-전단 균열의 각도는 부재 축과 $42^{\circ}{\sim}48^{\circ}$의 범위로 계측되었다. 본 연구에서는 실험에서 계측된 횡방향철근이 부담하는 전단강도에 대한 분석을 중심으로 하였다. 횡방향철근이 부담하는 전단강도, 축력 작용에 의한 전단강도, 콘크리트에 의한 전단강도 등 3요소에 대해 분석하였고 비교하였다. 실험체들의 콘크리트 응력은 도로 교설계기준의 응력한계를 초과하였다.

• Geomechanics and Engineering
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• 제5권2호
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• pp.87-97
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• 2013

In this paper, a novel fibrous material known as axially reinforced braided composite rods (BCRs) have been developed for reinforcement of soils. These innovative materials consist of an axial reinforcement system, comprised of longitudinally oriented core fibres, which is responsible for mechanical performance and, a braided cover, which gives a ribbed surface texture for better interfacial interactions with soils. BCRs were produced using both thermosetting (unsaturated polyester) and thermoplastic (polypropylene) matrices and synthetic (carbon, glass, HT polyethylene), as well as natural (sisal) core fibres. BCRs were characterized for tensile properties and the influence of core fibres was studied. Moreover, BCRs containing carbon fibre in the core composition were characterized for piezoresistivity and strain sensing properties under flexural deformation. According to the experimental results, the developed braided composites showed tailorable and wide range of mechanical properties, depending on the core fibres and exhibited very good strain sensing behavior.

• Structural Engineering and Mechanics
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• 제24권4호
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• pp.447-461
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• 2006

Here, the axisymmetric free flexural vibrations and thermal stability behaviors of functionally graded spherical caps are investigated employing a three-noded axisymmetric curved shell element based on field consistency approach. The formulation is based on first-order shear deformation theory and it includes the in-plane and rotary inertia effects. The material properties are graded in the thickness direction according to the power-law distribution in terms of volume fractions of the constituents of the material. The effective material properties are evaluated using homogenization method. A detailed numerical study is carried out to bring out the effects of shell geometries, power law index of functionally graded material and base radius-to-thickness on the vibrations and buckling characteristics of spherical shells.

• Advances in materials Research
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• 제5권1호
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• pp.35-53
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• 2016

Flexural bending analysis of perfect and imperfect functionally graded materials plates under hygro-thermo-mechanical loading are investigated in this present paper. Due to technical problems during FGM fabrication, porosities and micro-voids can be created inside FGM samples which may lead to the reduction in density and strength of materials. In this investigation, the FGM plates are assumed to have even and uneven distributions of porosities over the plate cross-section. The modified rule of mixture is used to approximate material properties of the FGM plates including the porosity volume fraction. In order the elastic coefficients, thermal coefficient and moisture expansion coefficient of the plate are assumed to be graded in the thickness direction. The elastic foundation is modeled as two-parameter Pasternak foundation. The equilibrium equations are given and a number of examples are solved to illustrate bending response of Metal-Ceramic plates subjected to hygro-thermo-mechanical effects and resting on elastic foundations. The influences played by many parameters are investigated.

• Steel and Composite Structures
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• 제18권1호
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• pp.213-233
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• 2015

A nonlinear finite element analysis (FEA) model is presented for simulating the behaviour of recycled aggregate concrete-filled steel tube (RACFST) beam-columns subjected to constant axial compressive load and cyclically increasing flexural loading. The FEA model was developed based on ABAQUS software package and a displacement-based approach was used. The proposed engineering stress versus engineering strain relationship of core concrete with the effect of recycled coarse aggregate (RCA) replacement ratio was adopted in the FEA model. The predicted results of the FEA model were compared with the experimental results of several RACFST as well as the corresponding concrete-filled steel tube (CFST) beam-columns under cyclic loading reported in the literature. The comparison results indicated that the proposed FEA model was capable of predicting the load versus deformation relationship, lateral bearing capacity and failure pattern of RACFST beam-columns with an acceptable accuracy. A parametric study was further carried out to investigate the effect of typical parameters on the mechanism of RACFST beam-columns subjected to cyclic loading.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2513-2516
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• 2012

This study examined the effects of the epoxidized castor oil (ECO) and $Al_2O_3$ content on the thermal stability and fracture toughness of the diglycidylether of bisphenol-A (DGEBA)/ECO/$Al_2O_3$ ternary composites using a range of techniques. The thermal stability of the composites was decreased by the addition of ECO and $Al_2O_3$ nanoparticles. The fracture toughness of the composites was improved significantly by the addition of ECO and $Al_2O_3$ nanoparticles. The composite containing 3 wt % $Al_2O_3$ nanoparticles showed the maximum flexural strength. Scanning electron microscopy (SEM) revealed tortuous cracks in the DGEBA/ECO/$Al_2O_3$ composites, which prevented deformation and crack propagation.

• Computers and Concrete
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• 제20권2호
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• pp.155-164
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• 2017

During the past decades, development of reinforcing materials caused a revolution in the structure of high strength and high performance cement-based concrete. Among the most important and exciting reinforcing materials, Steel Fiber (SF) becomes a widely used in the recent years. The main reason for addition of SF is to enhance the toughness and tensile strength and limit development and propagation of cracks and deformation characteristics of the SF blended concrete. Basically this technique of strengthening the concrete structures considerably modifies the physical and mechanical properties of plain cement-based concrete which is brittle in nature with low flexural and tensile strength compared to its intrinsic compressive strength. This paper presents an overview of the work carried out on the use of SF as reinforcement in cement-based concrete matrix. Reported properties in this study are fresh properties, mechanical and durability of the blended concretes.

• 콘크리트학회논문집
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• 제12권2호
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• pp.53-62
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• 2000

Under severe lateral loads, ductile moments-resisting reinforced concrete frames will be subjected to large loads and displacements. Thus, large deformation and shear stree are occurred at the beam-column joints which are the most critical region in ductile moments-resisting system. The purpose of this study was to investigate the shear strength of beam-column connection using high strength concrete. Four subassemblies were designed 2/3 scale of read structures and tested. The obtained results are as follows. 1) The transverse beams increase the shear resistance and ductility of joint, 2) The slab was contributed to increase of the flexural capacity of the beam, but was not contributed to increase the joint ductility under cyclic loads. 3) The shear stress factors. given by the ACI code would be modified in evaluating the shear strength of beam-column joints of frame which were constructed with high-strength concrete.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.83-86
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• 2001

This paper presents an investigation of the contribution of fibers in energy absorption during impact and the effect of resin types on properties of the high strength polyethylene (Spectra-900 PE) composite. In high strength polyethylene fiber, main impact energy absorbing mechanism was tensile breakage and deformation of fiber. Two types of resin were examined : Unsaturated polyester (UP) and Epoxy. Tensile and 3-point bending test have been performed to investigate the changes of mechanical properties. In tensile and flexural testes, the Spectra Composite prepregged with UP showed higher properties than Spectra Composite prepregged with epoxy.