Performance evaluation and finite element analysis of fiber reinforced precast concrete underground structures.

摘要

This study aimed at evaluating the performance of BASF Synthetic and Steel fibers as alternative reinforcements in concrete pipes. A total of 93 synthetic fiber and 60 steel fiber reinforced pipes were produced and tested based on the ASTM C497 in order to have a benchmark for comparison with conventionally reinforced concrete pipes. Three production sites with different production equipment were used in different geographical locations in the United States. Standard ASTM C76 diameters of up to 36 in. with "Wall-B" and "Wall-C" were used in this study for both synthetic and steel fibers. Vertical and horizontal load-deformation plots for the majority of the pipes were obtained by instrumenting the test pipes with linear variable displacement transducer (LVDT). The load-deformation plots were recorded for up to 5% of the pipe diameter. The load-deformation plots for steel and synthetic fibers were compared with each other. During production, compressive cylinder and beam specimens from the same mix designs were produced and cured for ASTM C39 and ASTM C1609 tests, respectively. A total of 353 cylinders and 77 beams were produced and tested. The ASTM C1609 beam load deformation plots were compared for different fiber dosages and the area under this curve was calculated for each test specimen and modulus of toughness was calculated and documented. The patterns for material law (constitutive relationship) for low and high fiber dosages of both synthetic and steel fibers were identified. From the ASTM C39 and ASTM 1609 tests, a relationship between the tensile strength and square root of compressive strength was established on all the tests conducted.;This study showed that the use of BASF synthetic and steel fibers in concrete pipes as alternative reinforcement is feasible. This study recommends the use of synthetic fibers with adequate dosage for up to 21 in. concrete pipes with "B-Walls," and up to 36 in. concrete pipes with "C-Walls." BASF (Maccafferri) steel fiber pipes are recommended as alternative reinforcement with adequate fiber dosage for up to 24 in. concrete pipes with "B-Wall" and up to 36 in. concrete pipes with "C-Walls." It should be noted that proper fiber dosage is a trial and error process based on local aggregate and cementitious materials and the type of production equipment used, which is also the case for the production of the conventionally reinforced concrete pipes.