Parametric Study of Seismic AASHTO Design Methods for Metallic Mechanically Stabilized Earth Walls

The use of the Load-Resistance Factor Design (LRFD) method found in the AASHTO Bridge Design Specifications for design of MSE walls has steadily replaced the Allowable Stress Design (ASD) method, as part of a FHWA mandate to state DOTs for a change over by 2010. Incorporated in the change of design methods has been the core practice for seismic analysis of MSE walls, which adopts a modified Mononabe-Okabe (M-O) pseudo static method together with a horizontal displacement-to-dynamic coefficient reduction developed from a simplified Newmark sliding block model. In this paper, the outcome of seismic design for MSE walls between the LRFD and ASD methods are discussed. Parametric studies are used to highlight the variations that occur in MSE reinforcement design. In addition, the results from dynamic constitutive models are provided for comparison to the M-O pseudo static approach with corresponding reduction basis found in AASHTO.