Metal Loss for Metallic Reinforcements and Implications for LRFD Design of MSE Walls

Abstract

Previous calibrations of resistance factors for load and resistance factored design (LRFD) of mechanically stabilized earth (MSE) retaining walls with galvanized metallic reinforcements have not considered cross-sectional area as a variable in the reliability analysis. The remaining cross section at the end of a 75-or 100-year design life is considered, however the metal loss from corrosion is estimated using recommended rates of metal loss that render conservative estimates of remaining cross section. This paper describes reliability-based calibration of resistance factors for the rupture limit state considering the variability of observed corrosion rates. Results are compared with resistance factors cited in the current American Association of State Highway and Transportation Officials (AASHTO) design specifications. The comparison identifies conditions for which the current AASHTO resistance factors achieve the targeted probability of failure inherent to the LRFD strategy.

Reliability-Based Design of Mechanically Stabilized Earth

“…In this procedure, the reliability-based calibration of resistance factors considers the yield limit state function, explicitly, at every reinforcement location, and a target reliability index (β T ) of 2.3, which corresponds to a probability of failure ( p f ) of 0.01, is adopted that considers the large redundancy inherent to the system (16). Loss of cross section affects the yield resistance of MSE reinforcements and is incorporated into the LRFD procedure in terms of the yield limit state equations (3,17 ). The yield limit state is reached when the reinforcement tension exceeds the yield resistance.…”

“…The Monte Carlo simulation technique was used to extrapolate the limit state equation and assess the probability of failure considering uncertainties in yield strength, metal loss, and remaining cross section. Detailed descriptions of the calibration of resistance factors described in this paper are included in other publications related to the study, including the final report (3,17 ). Table 1 presents a summary of the results from the calibration of resistance factors for the tensile strength limit state.…”