• Composites Research
• /
• 제35권3호
• /
• pp.134-138
• /
• 2022

본 연구에서는 기존 폴리머 콘크리트의 진동 감쇠 효과를 향상시키기 위해 압전 재료 중 하나인 PZT 파우더를 첨가하여 티타늄 파우더/폴리머 콘크리트 복합재료를 제작하였다. 티타늄 파우더는 압전 효과를 이용한 진동특성 변화를 극대화하기 위해 일정한 비율로 유지하였고, PZT 파우더를 첨가하지 않은 시편, PZT 파우더를 2.5 wt%, 5 wt% 첨가한 세 가지 종류의 복합재료 시편을 제작하였으며, 모든 시편에 대해 진동 특성 및 압축 물성 분석을 진행하였다. 그 결과, PZT 파우더 첨가 비율이 높아질수록 티타늄 파우더/폴리머 콘크리트에서 발생한 진동이 전달될 때 압전 효과로 인해 공진주파수에서 전달 함수 Inertance 값이 작아지는 것을 확인하였고, 특히 PZT 파우더 5 wt% 첨가 시편의 경우, 공진주파수에서 Inertance 값은 PZT가 첨가되지 않은 시편에 비해 약 19.3% 감소하는 것으로 나타났다. 시간에 따른 가속도 변화 폭 역시 PZT 파우더가 첨가됨에 따라 크게 감소하는 것으로 나타나 PZT 첨가에 따른 효과를 확인할 수 있었다. 또한, 압축강도 시험을 통해 5 wt%까지의 PZT 첨가에 의한 압축 물성 저하 정도는 미미한 것으로 나타났고, 시편 단면 분석을 통해 파우더가 고르게 분산된 것을 확인하였다.

• 한국공간구조학회논문집
• /
• 제3권3호
• /
• pp.85-93
• /
• 2003

Steel, concrete and their combination materials are the most 6commonly used materials for civil engineering structural systems such as buildings, bridge structures and other structures. Recently, however, fiber reinforced polymer (FRP) composites, a relatively new composite material made of fibers and polymer resins, have been gradually used in structural systems as an alternative structural material. This paper describes a comparison of design strength equations for steel column and FRP composite column based on design philosophies. The safety factors used in allowable stress design (ASD) are relatively higher in FRP structural design than steel structural design. Column critical stress equations of FRP composites column from an experimental study can be represented by Euler elastic buckling equation at the long-range of slenderness, and an exponential form at the short-range of slenderness as defined in Load and Resistance Factor Design (LRFD) of steel column. The column strength of steel and FRP composite columns in large slenderness is independent of material strength, this result verified the elastic buckling equation as derived by Eq. (15) and Eq. (5).

• 콘크리트학회논문집
• /
• 제17권6호
• /
• pp.983-992
• /
• 2005

섬유에 의하여 보강된 철근콘크리트 보의 파괴모드는 섬유가 파단하여 전단강도에 도달하는 경우와 섬유가 파단하기 이전에 전단강도에 도달하는 경우로 나누어진다. 이와 같이 섬유가 파단강도에 도달하지 않는 경우에 두 파괴모드의 전단강도는 상이하다. 섬유가 파단하지 않고 전단강도에 도달할 경우에 보의 전단강도를 예측하기 위하여 섬유의 파단강도를 사용할 수 없으므로 기존의 제안식에서는 섬유강도저감계수를 사용하여 섬유보강 보의 전단강도를 예측하였다. 그러나 기존 제안식의 대부분은 실험결과에 근거한 회귀분석을 통하여 일정한 상수 값에 의하여 섬유강도저감계수를 평가하였으며, 섬유의 도달강도와 밀접한 관계가 있는 콘크리트의 압축강도를 고려하지 않고 있다. 이 연구에서는 변형률의 적합조건을 이용한 트러스모델에 근거하여 섬유보강 보의 파괴모드의 경계점을 구별하고, 이를 이용하여 섬유보강 보의 전단강도를 예측하였다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
• /
• pp.591-596
• /
• 2003

Many studies have dealt with strengthening by epoxy-bonded CFRP(Carbon Fiber Reinforced Polymer) composites. However, the effects of various influencing factors have not been clarified on the behavior of strengthened RC beams. This study was performed to verify the effects of strengthening due to various bond details of externally attached CFRP Composites. In this study, major test parameters include the bond type and the anchor type. The deflections, failure load, strain of reinforcing bar, concrete and CFRP are measured at each loading step. The failure mode and debonding loads(ultimate loads) are analysed from these measured data. According to the test results, all specimens are failed by intermediate flexural crack induced interfacial debonding.

• Steel and Composite Structures
• /
• 제31권2호
• /
• pp.159-172
• /
• 2019

Strengthening of civil infrastructure with advanced composites have recently become one of the most popular methods. The use of Fiber Reinforced Polymer (FRP) strips plates and fabric for strengthening of reinforced concrete structures has well established design guidelines and standards. Research on the application of FRP composites to steel structures compared to concrete structures is limited, especially for shear strengthening applications. Whereas, there is a need for cost-effective system that could be used to strengthen steel high-way bridge girders to cope with losses due to corrosion in addition to continuous demands for increasing traffic loads. In this study, a parametric finite element study is performed to investigate the effect of applying thick CFRP strips diagonally on webs of plate girders on the shear strength of end-web panels. The study focuses on illustrating the effect of several geometric parameters on nominal shear strength. Hence, a formula is developed to determine the enhancement of shear strength gained upon the application of CFRP strips.

• 한국공작기계학회논문집
• /
• 제15권1호
• /
• pp.39-48
• /
• 2006

In this paper, polymer composites based sandwich structures like beams and plates are optimised by using parametric study. The structures are composed of fibre reinforced composites for facial material and resin concrete and PVC foam for core materials. The stacking sequences and thickness of the composites are controlled as major parameters to find out the optimal condition for machine tool components. For the plate structure of machine tool bed composites-skined sandwich structure which has several ribs are proposed to enhance bending stiffnesses in two major directions at the same time. Dynamic robustness of a machine tool structure is investigated using modal analysis. From the results optimal configuration and materials for high precesion machine tools are proposed. And the plate was made of fiber reforced composite material and PVC foam.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
• /
• pp.72-75
• /
• 2004

Carbon Fiber Reinforced Polymer(CFRP) composites are widely applied to strengthen deteriorated concrete structures. This paper presents the experimental results of the performance of reinforced concrete(RC) beams strengthened with externally prestressed CFRP plates. Simple beams with 3 m span length were tested to investigate the effect of prestressing force of CFRP plates on the flexural behavior of externally strengthened RC beams.

• Computers and Concrete
• /
• 제1권4호
• /
• pp.401-416
• /
• 2004

This paper presents investigation of a three-dimensional (3-D) nonlinear finite element model analysis to examine the behavior of reinforced concrete beams strengthened with Carbon Fiber Reinforced Polymer (CFRP) composites to enhance the flexural capacity and ductility of the beams. Three-dimensional nonlinear finite element models were developed between the internal reinforcement and concrete using a smeared relationship. In addition, bond models between the concrete surface and CFRP composite were developed using a smeared bond for general analyses and a contact bond for sensitivity analyses. The results of the FEA were compared with the experimental data on full-scale members. The results of two finite-element bonding models showed good agreement with those of the experimental tests.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
• /
• pp.499-500
• /
• 2009

본 연구에서는 현장 부착강도시험을 통해 콘크리트의 단면복구재로 사용되는 국내 폴리머시멘트 모르타르 제품에 대한 부착강도 특성을 평가하였다. 부착강도시험에는 직접 인발시험기를 적용했으며, 시험결과는 단면복구재에 대한 국내 산업규격의 품질기준에 대한 타당성 검토를 위한 기초자료로 제시한다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1991년도 봄 학술발표회 논문집
• /
• pp.111-116
• /
• 1991

In order to discuss the mechanical properties of carbon fiber reinforced polymer impregnated cement composties with silica powder, experimental studies on CFRC were carried out. The types of fiber used which are in CFRC are PAN-based carbon fiber and Pitch-based carbon fiber. To examine the effects of types, length, contents of carbon fibers and matrices, their properties of fresh and hardened CFRC were tested. According to the test results, compressive, tensile flexural strength of polymer impregnated CFRC were remarkably increased more than that of air cured and autoclaved CFRC. Also, polymer impregnated CFRC were considerably effective in improving thoughness, freezing-thaw resistance and loss of shrinkage compared with air cured and autoclaved CFRC.