Recently, as the atypical buildings increase due to the development of building technology, the consideration of the torsional moment in the design of the structure increase. In addition, when the structure is damaged in the out-of-plane direction by any external load and long-term deformation in the RC structure, the torsional moment unexpected in the structural design may additionally act.
The torsional moment causes the brittle fracture of the reinforced concrete member by overlapping the shear stress on the weak side of the member together with the combined load of the member''s bending and shear. Therefore, repair and enhanced reinforcement of the damaged structure is necessary.
Fiber sheet system, one of the methods for repair and reinforcement is a composite material with high material properties such as high strength, corrosion resistance, non-conductivity, etc., and has been spotlighted in high-tech industries such as aviation industry and automobile industry. When applied, the strength-improving effect and workability of the structure are superior to other reinforcement methods. However, the study on torsion is relatively insufficient compared to the flexural and shear design, and the design guideline or strength evaluation method of the fiber reinforced member is not described in the other design criteria except FIB(International Federation for Structural Concrete). Further study on the stress resistance mechanism of the fiber composites is necessary.
Therefore, this study conducted a torsional test of reinforced concrete beams full wrapped in GFRP(Glass Fiber Reinforced Polymer)sheets. To evaluate the difference in effective strain, torsional strength, and torsional behavior of fibers according to GFRP.

This study consists of five chapters, and the contents of each chapter are as follows:

■ Chapter Ⅰ : Introduction
■ Chapter Ⅱ : A Study on the Torsional Behavior
■ Chapter Ⅲ : Evaluation of Behavior of Reinforced Concrete Beams Subjected to Pure Torsion Strengthened with GFRP Sheet
■ Chapter Ⅳ : Experimental results and comparative analysis
■ Chapter Ⅴ : Conclusions