RUST-EXPANSION-CRACK SERVICE LIFE PREDICTION OF EXISTING REINFORCED CONCRETE BRIDGE/VIADUCT USING TIME-DEPENDENT RELIABILITY ANALYSIS

摘要

It is necessary to develop a calculation method to help in the making of feasible, reliable, and serviceable predictions for the service lives of bridge or viaduct structures. This article presents the basis for doing rust-expansion-crack service life predictions for existing reinforced concrete (RC) bridges and viaducts in chloride-laden environments based on time-dependant reliability modeling due to the corrosion of steel in concrete. The corrosion process has three stages, the initiation (diffusion or carbonation) time (t_i = t_c), the depassivation time (t_p), and the propagation (corrosion) time (t_(corr)). The rust-expansion-crack service lives (t_(cr)) of existing RC bridges or viaducts can be expressed in terms of t_(cr) = t_c + t_p. Many mathematical models could be applied to calculate each value of t_c and t_p. The values of t_(cr) may be directly predicted from the relationship between reliability index and time. The existing Wann-fwu bridge and Chorng-ching viaduct in Taipei were provided as illustrative examples for the modeling approach and rust-expansion-crack service life prediction. The results of t_(cr) predicted from the relationship between reliability index and time were in good agreement with the results of t_(cr) calculated from the sum of t_c and t_p. The results of present study were offered as a decision making for repair, strengthening, and demolition of existing RC bridges or viaducts.