52 APRIL 20 0 3 / Concrete international BY NABIL F. GRACE, GEORGE ABDEL-SAYED, FREDERICK C. NAVARRE, RICHARD B. NACEY, WAYNE BONUS, AND LORIS COLLAVINO C urrently, advanced fiber-reinforced polymer (FRP) materials find worldwide application in the construction of small and large structures, 1-5 such as beams and bridges. However, there are few prestressed concrete bridges constructed using carbon fiber-reinforced polymer (CFRP) tendons as the only flexural reinforce- ment. 1-6 FRP is a linearly elastic material, which may not provide a ductile failure mode if substituted directly for steel. Results of early research investigations 6-10 con- ducted at the Structural Testing Center of Lawrence Technological University, Southfield, MI, have shown that internally bonded CFRP tendons, in combination with externally draped unbonded CFRP tendons, can lead to reasonably ductile systems for simply sup- ported 6,7 and continuous 8,10 prestressed concrete bridges. We based both the design of the Bridge Street Bridge 11 (located in the city of Southfield, MI) and the double-tee (DT) test beam 14 used in this study on these results. The Bridge Street Bridge is the most recent CFRP prestressed concrete bridge in the U.S., and the first to use CFRP Leadline * tendons, carbon fiber composite cable (CFCC) † strands, and CFRP NEFMAC ‡ sheets. Due to the lack of existing design standards for FRP prestressed concrete bridges, the Bridge Street Bridge design and research team decided to validate the design and construction approach they had developed by testing a full-scale DT beam 14 to failure prior to proceeding with the manufacture of the 12 DT beams to be used in the bridge itself. This article presents the experimental investigation of the DT test beam (identical to those used in the Bridge Street Bridge 11) to evaluate the design and Full-Scale Test of Prestressed Double-Tee Beam Carbon fiber-reinforced polymer provides reinforcement for new bridge design construction procedures used, along with critical major structural parameters such as concrete strains, deflec- tions, forces in the post-tensioning strands at the service load, cracking load, ultimate load, and the type and pattern of failure experienced at the ultimate load. FABRICATION AND INSTRUMENTATION Figure 1 shows the cross section of the DT test beam. Reinforcement for each web of the DT beam consisted of 10 rows of 10-mm-diameter bonded prestressed CFRP tendons and six rows of 12.5 mm nonprestressed CFCC strands. The cross section of the DT beam contains four externally draped, 40-mm- diameter post-tensioned CFCC strands between the webs and 19 10-mm-diameter nonprestressed CFRP rods in the flange. In addition, the flange also contains two layers of transverse, 10-mm-diameter CFRP rods. A CFRP sheet located in the composite concrete topping provides reinforcement to control temperature and shrinkage cracks. Table 1 gives the mechanical charac- teristics of the CFRP tendons/rods and the CFCC strands, while Table 2 and 3 present the characteristics of the CFRP sheets and the concrete, respectively. 12, 13 * Trademark name of CFRP Leadline tendons provided by Mitsubishi Chemical Corp., Japan † Trademark name of CFCC strands provided by Tokyo Rope Mfg. Co., Ltd., Japan ‡ Trademark name of CFRP grids provided by Autocon Composites Inc., Canada