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Antoine E. Naaman,김민경,이차돈 中央大學校 建設環境硏究所 1998 環境科學硏究 Vol.9 No.1
Recently, application of composite materials such as fiber reinforced concretes(FRC) and fiber reinforced plastics(FRP) in conjunction with conventional structural components have been of the main research areas. A proper use of advanced composite materials requires understanding their resistance mechanism and failure mode when they are applied to structures or their components, This can be achieved either experimentally or analytically. In modeling , due consideration must be given to the different constitutive behaviors of composite beams, various possible combinations of placement of composite materials, and reasonable reproduction of overall behavior of composite structures. The analytical model is developed in order to predict the nonlinear flexural responses of various beams including boned and unbonded prestressed concrete beams which contain advanced composite materials either in matrices or in reinforcing bars. The block concept is developed, which can be regarded as an intermediate modeling method between the couple method with one block and the layered method with multiple sliced layers in a section. The concept is adopted for its effectiveness in considering cementitious composite matrices cast in part as blocks in a beam section. In order ot find a particular deflection point of a beam under load, solutions to the 2N-variables(top and bottom strains at each section along beam axis having N sections for analysis) are found numerically by using approximate N-force equilibrium equations and N-moment equilibrium equations. The model can successfully predict the flexural behavior of variously reinforced concrete beams with composite materials as well as strengthened beam with FRP sheets at their soffit.
Dong-Joo Kim,Antoine E. Naaman,Sherif El-Tawil 한국콘크리트학회 2009 International Journal of Concrete Structures and M Vol.3 No.2
This paper provides a brief summary of the performance of an innovative slip hardening twisted steel fiber in comparison with other fibers including straight steel smooth fiber, high strength steel hooked fiber, SPECTRA (high molecular weight polyethylene) fiber and PVA fiber. First the pull-out of a single fiber is compared under static loading conditions, and slip ratesensitivity is evaluated. The unique large slip capacity of T-fiber during pullout is based on its untwisting fiber pullout mechanism, which leads to high equivalent bond strength and composites with high ductility. Due to this large slip capacity a smaller amount of T-fibers is needed to obtain strain hardening tensile behavior of fiber reinforced cementitious composites. Second, the performance of different composites using T-fibers and other fibers subjected to tensile and flexural loadings is described and compared. Third, strain rate effect on the behavior of composites reinforced with different types and amounts of fibers is presented to clarify the potential application of HPFRCC for seismic, impact and blast loadings.
Kim, Dong-Joo,Naaman, Antoine E.,El-Tawil, Sherif Korea Concrete Institute 2009 International Journal of Concrete Structures and M Vol.3 No.2
This paper provides a brief summary of the performance of an innovative slip hardening twisted steel fiber in comparison with other fibers including straight steel smooth fiber, high strength steel hooked fiber, SPECTRA (high molecular weight polyethylene) fiber and PVA fiber. First the pull-out of a single fiber is compared under static loading conditions, and slip rate-sensitivity is evaluated. The unique large slip capacity of T-fiber during pullout is based on its untwisting fiber pullout mechanism, which leads to high equivalent bond strength and composites with high ductility. Due to this large slip capacity a smaller amount of T-fibers is needed to obtain strain hardening tensile behavior of fiber reinforced cementitious composites. Second, the performance of different composites using T-fibers and other fibers subjected to tensile and flexural loadings is described and compared. Third, strain rate effect on the behavior of composites reinforced with different types and amounts of fibers is presented to clarify the potential application of HPFRCC for seismic, impact and blast loadings.