DOI QR코드

DOI QR Code

Prediction of Compressive Behavior of FRP-Confined Concrete Based on the Three-Dimensional Constitutive Laws

3차원 구성관계를 고려한 FRP-구속 콘크리트의 압축거동 예측모델

  • Cho Chang-Geun (Research Institute for Disaster Prevention, Kyungpook National University) ;
  • Kwon Min-ho (Engineering Research Institute Dept. of Civil Engineering, GyungSang National University)
  • Published : 2004.08.01

Abstract

The proposed model can predict the compressive behaviors of concrete confined with fiber reinforced polymer (FRP) jacket. To model confining concrete by FRP jackets, the hypoelasticity-based constitutive law of concrete In tri-axial stress states has been presented. The increment of strength of concrete has been determined by the failure surface of concrete in tri-axial states, and its corresponding peak strain is computed by the strain enhancement factor that is proposed in the present study, Therefore, the newly proposed model is a load-dependent confinement model of concrete wrapped by FRP jackets to compare the previous models which are load-independent confinement models. The behavior of FRP jackets has been modeled using the mechanics of orthotropic laminated composite materials in two-dimension. The developed model is implemented into the incremental analysis of compressive tests. The verification study with several different experiments shows that the model is able to adequately capture the behavior of the compression test by including better estimations of the axial responses as well as the lateral response of FRP-confined concrete cylinders.

제안된 모델은 FRP 구속 콘크리트에 대한 압축거동 예측을 위한 것이다. FRP로 구속된 콘크리트의 모델링을 위하여, 3축 응력상태의 콘크리트 아탄성 구성관계를 제시하였다. FRP 구속에 따른 콘크리트 강도 증진은 3축 응력공간의 파괴기준에 따라 결정되며, 이에 대응하는 최대 압축변형률은 본 연구에서 제안된 변형률 증진계수로부터 결정된다. 따라서, 기존의 모델들이 하중단계에 관계없이 구속조건이 초기부터 파괴까지 일정하게 고려되는 반면에, 제안된 모델은 FRP로 구속된 콘크리트의 구속현상을 하중단계에 의존적인 비선형 관계로 제시하였다. FRP 층은 2차원의 적층된 복합재료의 해석에 기초하여 모델링되었다. 개발된 해석모델은 증분법에 의한 압축거동실험에 대한 해석을 수행할 수 있도록 하였다. FRP로 구속된 콘크리트 실린더의 대한 여러 연구자들의 실험 결과와 본 예측모델을 비교한 결과, 제안된 모델은 축방향 변형 뿐만 아니라 횡방향 변형을 포함하여 FRP 층으로 인한 콘크리트의 구속효과의 증진에 관한 거동 특성들을 잘 예측해 주었다.

Keywords

References

  1. Cho, C.G. and Park, M.H, 'Finite Element Prediction of the Influence of Confmement on RC Beamcolumns under Single or IXmble Curvature Bending,' Engineering Structures, Vol.25, 2003, pp.1525~1536 https://doi.org/10.1016/S0141-0296(03)00120-2
  2. Cho, C.G. and Hotta, H, 'A Study on Compressive Strength of Concrete in F1exural Regions of Reinforced Concrete Beams Using Finite Element Analysis,' Structural Engineering and. Mechanics, An International Journal, Vo1.13, No.3, 2002, pp.313~328 https://doi.org/10.12989/sem.2002.13.3.313
  3. Pantazopoulou, S. J. and Mills, R. H., 'Microstructural aspects of the mechanical response of plain concrete, ACI Material Journal, Vol.92, 1995, pp.605-616
  4. Spoelstra, M. R. and Monti, G., 'FRP-confined concrete model,' Journal of Composites for Construdion, ASCE, 1999, No.3, pp.143~150
  5. Saadatmanesh, H., Ehsani, M. R. and Li, M. W., 'Strength and Ductility of Concrete Columns Externally Reinforced with Fiber Composite Straps,' ACI Strudural. Journal, Vo1.91, No.4, 1994, pp.434~447
  6. Hosotani, M., Kawashima, K., and Hoshikuma, J., 'A Stress-Strain Model for Concrete Cylinders Confined by Carbon Fiber Sheets,' Journal of Materials, Concrete Structures, and. Pavement, JSCE, Vo1.39, No. 592, 1993, pp.37~52
  7. Mander, J.B., Priestley, M.J.N, and Park, R, 'Theoretical stress-strain model for confined concrete,' J. Structural Engineering, ASCE, Vol. 114, No.8, 1988, pp.1804~1826
  8. 조창근 외 3인, '다축응력상태의 구성관계에 기초한 FRP 콘크리트 부재의 층분할 단면해석모델', 한국콘크리트학회 논문집, 14권, 6호, 2002, pp.892~899 https://doi.org/10.4334/JKCI.2002.14.6.892
  9. Darwin, D. and Pecknold, D.A., 'Nonlinear biaxial law for concrete,' J. Eng. Mech Div., ASCE, Vol. 103(EM2), 1977, pp.229~241
  10. Saenz, L. P., 'Discussion of equation for the stressstrain curve of concrete by Desayi and Krishman,' Journal of ACI, Vol.61, No.9, 1964, pp.1229~1235
  11. Hsieh, S. S., Ting, E. C., and Chen, W. F., 'An elastic-fracture model for concrete,' ASCE Proc 3d Eng. Mech Div. Spec Conf, 1979, pp.437~440
  12. Selby, R. G., 'Three-climensional constitutive relations for reinforced concrete,' PhD Thesis, University of Toronto, Canada, Toronto, 1993
  13. Minniran, A., and Shahawy, M., 'Behavior of Concrete Columns Confined by Fiber Composites, J. Structural Engineering, ASCE, Vol.123, No.5, 1997, pp.583~590 https://doi.org/10.1061/(ASCE)0733-9445(1997)123:5(583)
  14. Picher, F., Rochette, P., and Labossiere, P., 'Confmement of concrete cylinders with CFRP,' Proc, 1st Int. Conf. on Composites in Infrastructure, H. Saadatmanesh and M. R. Ehsani, eds., University of Arizona, Tucsan, Arizona, 1996, pp.829~841
  15. Kawashima, K., Hosotani, M., and Hoshikuma, J., 'A model for confinement effect for concrete cylinders confined by carbon fiber sheets,' NCEER-NlCEDE Workshop on Earthquake Engineering Frontiers in Transportation Facilities, NCEER State University of New York, Buffalo, N. Y., 1997
  16. Elwi, A. A. and Murray, D. W., 'A 3D hypoelastic concrete constitutive relationship,' Eng. Mech Div, ASCE, Vol.105(EM4), 1979, 623~641
  17. Fam, A. Z. and Rizkalla, S. H., 'Confinement model for axially loaded concrete confined by circular fiber-reinforced polymer tubes,' ACI Structural Journal, Vol.98, No.4, 2001, pp.451~461
  18. Nanni, A. and Bradford, N. M., 'FRP jacketed concrete under uniaxial compression,' Construction and Building Materials, 1995, No.2, pp.115~124