![]() highway transportation infrastructure began in 2006. First structural deployments began in the late 1990s. Initial material development research on UHPC began more than two decades ago. This class of concrete has been demonstrated to facilitate solutions that address specific problems in the U.S. The term Ultra-High Performance Concrete (UHPC) refers to a relatively new class of advanced cementitious composite materials whose mechanical and durability properties far surpass those of conventional concrete. strands may be a viable option – with additional study – in prestressing applications if their longer transfer and development lengths are acceptable for the member. This preliminary study indicates that 1-1/8 in. Some differential slip between outer wires and inner wires was noted during the NASP testing, though this was not noticed during large-scale flexural testing. diameter strands performed as expected though there was some evidence that higher strength concretes would benefit end-zone performance and bond performance. depending on transfer lengths observed) were much higher than those observed. Generally, the AASHTO predicted development lengths (between 161 in. diameter strand in 9500 psi class concrete indicated development length is between 66 in. Finally, large scale embedment length testing of 1-1/8 in. diameter strand in 8500 psi class concrete indicated development length is between 66 in. Large scale embedment length testing of 1-1/8 in. diameter strand in 6500 psi class concrete indicated development length is greater than 135 in. Half of the tests resulted in bond failure and the other half resulted in the section reaching its predicted strength. The beams were tested in flexure to evaluate their bond performance as related to their development length. The average transfer lengths were 60, 42, 32, and 29 inches for concrete strengths of 6.2, 8.3, 9.4 and 10.2 ksi, respectively, which were shorter than was predicted by the AASHTO LRFD equation (60db). Transfer lengths were monitored for various concrete strengths and found to be over predicted by the AASHTO LRFD provisions. diameter control strands.Įight total large-scale T-beams were pretensioned and tested in the lab. Bond behavior of the large diameter strands exhibited higher pullout values, due to their larger diameter with direct comparison to 0.5 in. Bond testing was performed using several standard and popular research methods for benchmarking purposes. diameter strands were procured and investigated for use in pretensioning applications in a largely preliminary study. Furthermore, it is unclear how a 19-wire strand will perform embedded in concrete and the applicability of current code expressions which are widely regarded as conservative, but based on 7-wire strands of diameters under 0.7 in. Larger diameter strands and higher wire count strands exist on the international market but have largely remained unstudied in the United States and elsewhere. diameter strands available in the United States. Common strand diameters in use today for bridge girder applications and range from 0.5 in. Large diameter prestressing strands have been investigated in recent years as potential options for increasing span lengths of prestresses members. diameter strands in the concretes tested. The beams were also employed to assess the strands’ development length, and it was determined that the current code might overestimate 1-1/8 in. The transfer length measurements were determined by analyzing the concrete surface strain readings and their corresponding strain profiles employing the 95% Average Maximum Strain (AMS) method. The other two full-scale beams were tested to assess multiple strands’ effect on the previously mentioned parameters. diameter strands exhibit good bonding quality to normal-weight concrete and mortar, though there is limited in-formation for comparison, and the testing presented is the only one of its kind for this strand size.Įight full-scale beams were tested to evaluate the development length, prestress losses, and large diameter strands’ flexural performance employing one strand only. Three different bond testing methodologies were employed to appraise the strands’ pullout force values in concrete and mortar, namely the Large Block Pullout Test (LBPT), the ASTM A1081 test, and the non-prestressed square concrete prisms. diameter grade 250 strands to concrete is presented in this dissertation. Experimental research addressing the bond performance, transfer, and development length of 1-1/8 in. ![]()
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