Field Monitoring of Rebar Debonding in Concrete Bridge Decks under Traffic-Induced Vibrations

Concrete deck resurfacing is conducted through staged construction under active traffic conditions in lanes adjacent to the newly poured concrete. Many engineers are concerned about the potential of cracking and rebar debonding and other factors, such as shrinkage, thermal expansion and contraction, and live loads. There is a need to evaluate these detrimental effects with techniques that are reliable under field conditions. In this paper, results are presented from a field study that measured peak rebar velocities during concrete pours. The peak velocities were then compared with experimentally established limits for the cracking potential of the concrete surrounding the rebar. However, it is often more feasible to process accelerometer measurements to obtain velocity indirectly from common processing techniques, such as direct integration. A numerical approach was developed to mitigate the various sources of error in the integration and produce accurate estimates of velocities and displacements from raw accelerometer data. The comprehensive field testing of a rehabilitated bridge span was conducted to capture the dynamic response of the bridge girders, stringers, and deck reinforcement. The bridge was monitored during the pour of a simple span and for several hours after the initial concrete placement. The response predicted by the numerical analysis compared well with the field results: the time histories of velocity and displacement were accurately reconstructed. A comparison with the established limits of peak particle velocity suggested that vibrations induced by typical truck traffic during the initial concrete setting period should not pose any significant risk of debonding.