Evaluation of prestress losses in high-strength concrete bulb-tee girders for the Rigolets Pass Bridge

Abstract

One span of the Rigolets Pass Bridge containing 4 131-ft-long (40 m), high-strength concrete bulb-tee girders was instrumented and monitored to obtain measured strain and temperature data. During fabrication of the 4 girders for span 43 of the Rigolets Pass Bridge, several vibrating-wire strain gauges were installed near the midspan. During construction of the high-performance concrete deck slab for span 43, additional instrumentation was installed to measure concrete strains and temperatures. Samples of the girder and deck slab concrete were obtained and used for material property studies. Throughout the bridge construction process, instrumentation readings were taken and recorded at selected time- or event-based intervals. After completion of the Rigolets Pass Bridge construction, the instrumentation installed in the girders and deck slab of span 43 was connected to an automated, on-site data acquisition system with remote-access capabilities. The on-site data acquisition system was used to record concrete temperature and strain data at hourly intervals for a period of 1 year after completion of construction. Measured girder prestress losses derived from concrete strains corrected for temperature and load effects were less than corresponding values calculated using AASHTO LRFD Bridge Design Specifications. Prestress losses calculated using both the approximate and refined estimates of time-dependent losses were evaluated relative to the measured losses.