비정질 마이크로 강섬유 복합체 적용 콘크리트 보의 거동 및 설계

Abstract

Concrete in tension has many shortcomings such as in brittleness, low tensile strength, and crack localization. Many researchers have studied about mixed fibers with concrete in order to improve the cracking and brittle characteristics in the properties of concrete. In this research, as an high-performance fiber cementitious composites, Amorphous Micro Steel Fiber (AMSF) cementitious composites is newly developed. By applying the AMSF composites, concrete members can be improve in bending and shear capacities. The amorphous micro steel fiber is more light and flexible than the general steel fibers such as the bundrex steel fiber. The AMSFs were good when mixing with concrete or mortar in the quality of dispersibility. The direct tensile and shear tests of the AMSF composites were conducted to evaluate the high-ductile tensile strain, tensile strength, and shear strength varying with the fiber volume fraction. From the test results, design tensile and shear strengths of the AMSF composites were newly proposed varying with the fiber volume fraction. By applying AMSF composites, a series of bending and shear tests of AMSF and reinforced concrete composite beams were conducted to compare with a general reinforced concrete beam in order to evaluate bending and shear performances of the AMSF composites in the beams. The beam specimens were manufactured as two types by the failure mechanism of bending and shear, and as four types by fiber types such as Bundrex steel fibers, 15 mm AMSF, and 30 mm AMSF. From experiment of beams, it was shown that AMSF and reinforced concrete composite beams gave good performances not only in improving bending and shear strength of the beams but also in minimizing failures by crack localization from bending and shear. The proposed design bending and shear strengths of AMSF and reinforced concrete composite beams were well matched with the measured strength of the tested beams.