Accelerated Bridge Construction Applications In California PDF Download

A relatively new type of beam falling under the accelerated bridge construction (ABC) umbrella, the Northeast Extreme Tee (NEXT) D beam, was designed by the PCI Northeast Bridge Technical Committee, with connection details that substitute traditional welded ties joining butted-beam systems, such as bulb-tee girders and double-tee beams. Grout has traditionally been used in joints between prefabricated bridge elements and systems (PBES). This material, however, has resulted in issues with shear key cracking reported by the Federal Highway Administration. An alternative cementitious material, ultra-high performance concrete (UHPC), has been used as a great solution for connections between PBES in ABC. This material exhibits superior properties such as compressive, tensile, and bond strength, durability, and long-term stability when compared to conventional connection materials. Three main studies are presented herein. The first study presents a tensile strength evaluation of 54 UHPC specimens by comparing the direct tension (DT), four-point bending, and double-edge wedge-splitting (DEWS) test methods. No statistically significant difference was found between the peak tensile strengths obtained from DT and DEWS specimens. DEWS specimens are tested using a compression-testing machine, and can be cored and finished from existing UHPC members. The second study evaluates the bond-slip behavior of UHPC and untensioned prestressing strands. The variables studied in the 54 tested pull-out specimens include clear cover, embedment length, and strand diameter (dPT). It was observed that specimens that experienced strand failure had an embedment length of at least 24×dPT or clear cover distance of 2.17×dPT. The third study investigates the behavior of NEXT D beams under fatigue loading. Four double-tee and four slab specimens were subjected to 1 million cycles under AASHTO standard wheel truck loads. Moreover, finite element analyses (FEAs) were performed, effectively simulating the tested specimens, and a 60-ft. long bridge model was created to simulate a constructed bridge in Mobile County, Alabama. It was observed that an 8-in. (203-mm) wide UHPC joint with a single reinforcement layer containing straight #5 bars, an 8-in. (203-mm) embedment length, and spaced every 6 in. (152 mm) had satisfactory performance according to results from experimental testing and FEAs.