Bursting and Spalling in Pretensioned U-Beams - Ferguson ...

particularly in the area of required end-region reinforcement. Detailed calculations forend-region reinforcement required by various codes of practice are presented inAppendix B.2.7.1 Texas U-BeamThe Texas U-beam was developed in the late 1980s and early 1990s, first by theHouston District of TxDOT as the trapezoidal box beam. The drive for the U-beam wasprimarily aesthetics: through provision of two webs, U-beams are able to be used atapproximately twice the spacing of I-beams (Figure 2.48).Figure 2.48 U-beam as replacement for two I-beams (Ralls, Ybanez & Panak, 1993)Beams are 40 or 54 in. deep, have 5 in. webs and can be used economically forspans of up to 120 ft. Section properties are given in Figure 2.49. Two sets of beams wereoriginally designed, the A-series, with two rows of 27 strands in the bottom flange; andthe B-series, with three rows (Figure 2.50). Presently, the three-strand-row beams arestandard. Strands may be placed in beam webs, but economics limit their use: themaximum economical span can be reached before the bottom flange is filled.83