Limit States Design Calibration for Internal Stability of Multi-Anchor Walls

The paper describes the methodology and results of limit states design calibration for two limit states of Japanese multi-anchor wall (MAW) earth retaining systems: anchor plate pullout and anchor rod rupture due to soil self-weight loading. Bias statistics are computed from measured loads from instrumented MAW structures and in-situ anchor load tests. Two different load models and two different plate load capacity equations are used in the calibrations. A load factor of γQ=2.25 is recommended to meet a 3% load exceedance criterion using a new load model by the writers which increases to 3.00 if the current approach recommended by PWRC (2002) is used. A target probability of failure Pf=1% is used in calibrations and is judged to be a reasonable value for the highly load-redundant MAW systems. Resistance factors of 0.80 and 0.95 are recommended for anchor plate and anchor rod rupture limit states using the new load and resistance models proposed by the writers. While the paper is focused on one particular wall system, the reliability-based limit states design calibration approach described in the paper provides an instructive template for limit states calibration of other reinforced soil retaining wall systems in Japan.