Bend Strength of Complete Closed-Type Carbon Fiber-Reinforced Polymer Stirrups with Rectangular Section

Complete closed-type carbon fiber-reinforced polymer stirrups with a rectangular section (CFRPRS) were developed and tested in the research reported in this paper. The use of a CFRPRS is intended to relieve stress concentrations and reduce the number of kinked fibers at the bent portion. A total of 16 B. 5 specimens were tested with consideration of the bend strength of the CFRPRS as well as carbon fiber-reinforced polymer (CFRP) stirrups with circular sections. Observations were made regarding the bend strength and failure modes. Three different types of CFRPRS were tested with different width-thickness ratios (34.4 for a sectional area of 27.9 mm(2) and 4.5 or 8.0 for 72 mm(2)) and three different ratios of the bend radius to the area-equivalent bar diameter (1.5, 3.0, and 4.5). The test results indicated that CFRPRSs exhibited improved bend strength as compared to its counterpart, the conventional CFRP stirrups with circular sections. CFRPRSs possessing a larger stirrup width-thickness ratio provided more strength for a given sectional area. The best correlation between the test results and predictions of the CFRPRS bend strength was observed when sections of the CFRPRS were modeled as a collection of transformed individual circular sections. (C) 2013 American Society of Civil Engineers.