The influence of prestress force on the fundamental frequency and static deflection shape of an uncracked Prestressed Concrete (PC) bridge beam made in Taiwan was examined in this work. In literature, due to the conflicts among existing theories, the models for properly considering the dynamic and static response of these members is not straightforward. A set of experiments were conducted for a total period of approximately 2.5 months on a PC beam prototype composed of a high strength concrete made in Taiwan, subsequently and closely to the 28 days of concrete age. In specific, the simply supported PC specimen was short term subjected to free transverse vibration and three-point bending tests during its early-age. Subsequently, the experimental data were compared with a solution that represents the dynamics of PC girders as a combination of two substructures interconnected, i.e., a compressed Euler–Bernoulli beam and a tensioned parabolic cable. It was established that the fundamental frequency of uncracked PC bridge beams in Taiwan is sensitive to the variation of their initial elastic modulus in the early-age based on Model B4-TW. Moreover, the small variation in experimental frequency with time makes doubtful its use in inverse problem identifications. By contrast, the relationship between prestress force and static deflection shape is properly described by the magnification factor formula of the “compression-softening” theory by assuming the variation of the chord concrete elastic modulus with time. The obtained results are proper information for developing the patent of a nondestructive method for prestress loss prediction in PCI bridge beams in Taiwan based on static deflection measurements.
An investigation into the dynamic and static response of an uncracked prestressed concrete bridge member in Taiwan
Bonopera M.
Primo
;
2020
Abstract
The influence of prestress force on the fundamental frequency and static deflection shape of an uncracked Prestressed Concrete (PC) bridge beam made in Taiwan was examined in this work. In literature, due to the conflicts among existing theories, the models for properly considering the dynamic and static response of these members is not straightforward. A set of experiments were conducted for a total period of approximately 2.5 months on a PC beam prototype composed of a high strength concrete made in Taiwan, subsequently and closely to the 28 days of concrete age. In specific, the simply supported PC specimen was short term subjected to free transverse vibration and three-point bending tests during its early-age. Subsequently, the experimental data were compared with a solution that represents the dynamics of PC girders as a combination of two substructures interconnected, i.e., a compressed Euler–Bernoulli beam and a tensioned parabolic cable. It was established that the fundamental frequency of uncracked PC bridge beams in Taiwan is sensitive to the variation of their initial elastic modulus in the early-age based on Model B4-TW. Moreover, the small variation in experimental frequency with time makes doubtful its use in inverse problem identifications. By contrast, the relationship between prestress force and static deflection shape is properly described by the magnification factor formula of the “compression-softening” theory by assuming the variation of the chord concrete elastic modulus with time. The obtained results are proper information for developing the patent of a nondestructive method for prestress loss prediction in PCI bridge beams in Taiwan based on static deflection measurements.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
