Feasibility Study of Steel Fibers as a Substitute for Transverse Reinforcement in New RC Columns

There are several advantages of reinforced concrete. For example, reinforced concrete is durable. Also, the buildings built by reinforced concrete are easy to conserve and maintain the structure. Moreover, the cost is low to build the buildings with reinforced concrete. It is a trend that people start to build high-rise buildings. The higher the building is, the more axial load of the columns at the bottom sustain. If the high- rise buildings are built with the traditional RC structure, the lower floors’ dimension must be enlarged. Therefore, in 1988, New RC project was proposed in Japan. The purposes of the project were increasing the strength of the construction materials and reducing the amount of the materials. With high strength material, the size of columns’ dimension is decreased, also the available space of buildings is increased.
However, the brittleness is the disadvantage of the high strength materials. Once the maximum concrete strength is reached, the construction will immediately be destroyed. Besides, Taiwan is located in a seismic belt, so the toughness is required for most of the buildings. The higher the toughness, the more it can reduce the strength caused by the earthquake. In order to increase the toughness in a traditional construction, adding new materials is one of the methods. According to the references, the toughness and the shear resistance in concrete materials are increased by adding the steel fiber into concrete. Also, the amount of the transverse steel is reduced and the process of tying steel cage is simplified. Moreover, adding the steel fiber can not only prevent the early cover spalling, but also restrain the cracks’ development that may cause immediate destruction.
The performance of high-strength steel fiber reinforced concrete columns under the condition of double curvature cyclic loading test is investigated in this study. The study can be divided into two parts. The first part is using the same designed strength to compare the differences between the original concrete and steel fiber concrete. The second part is the feasibility of substitution of the steel fiber for transverse steel based on the method that enlarging the spacing between transverse steel. Furthermore, not only the regression between the toughness of RC columns and the toughness of steel fiber RC columns was proposed in the study, but also the prediction formula. In addition, the relationship between the confinement effect that built by the prediction formula and the cyclic loading test is proposed in the study.