Behavior of Continuous FRP Rectangular Spirals as Shear Reinforcement for Concrete Beams

The replacement of steel stirrups with FRP stirrups in concrete structures can significantly improve the durability under severe environmental conditions, increase the service life of the structure. In some cases where the application of traditional concrete structures is restricted, such as structures that require the environment without magnetic and electric interferences, the best way is to use nonmetallic materials. Considering the unique properties compared with traditional reinforcements, FRP reinforcements is very suitable in such cases. This paper discussed the behavior of FRP stirrups used as shear reinforcement for concrete structures, continuous FRP rectangular spirals, a type of FRP stirrups, was used in the experimental investigation. Inspired by the test method suggested by ACT Committee 440, L shape specimen and U shape specimen are designed to test the tensile strength of continuous FRP rectangular spirals. Through the analysis of test results, it is indicated that the strength of the bent portion of FRP spirals is significantly lower than that of the straight portion, and the strength of FRP spirals would increase as the concrete strength or the embedment length of the bent portion increased. The loading mechanism of continuous FRP rectangular spirals embedded in concrete beams can be better represented by U shape specimen compared with L shape specimens, it is suggested by the author that the U shape specimen can be use when the dimension of FRP stirrups or spirals does not meet the requirements of ACI Committee 440 test method.