This paper will demonstrate how the CHBDC new changes increase the cost of a typical MSE structure. Presently there are guidelines for Load and Resistance Factor Design (LRFD) approach which is more economical than ASD approach due to proper FS. This paper will compare the design of an inextensible reinforced MSE wall system using the latest edition of Canadian Highway Bridge Code (CHBDC, CAN/CSA-S6-14) to the AASHTO (2014) LRFD Bridge Design Specification. As RS walls being geotechnical structure, a lot of uncertainties are involved in geotechnical parameters and hence there is ample scope of an economical design of RS wall. The American Association of State Highway and Transportation Official (AASHTO) implemented the LRFD method to design MSE structures in 2002 and has established load and resistance factors through calibration to the ASD method, experience and collaboration with the MSE industry. Design of MSE structures has progressed from using the Allowable Stress Design(ASD) method to the Load and Resistance Factored Design (LRFD) method. The analyses adopt load models found in current North American LRFD specifications in combination with a coupled mechanical-corrosion model for the reinforcement tensile strength and pullout models found in design guidelines and in the research literature. This results in a retaining wall system that has a reduced carbon footprint when compared to other retaining wall systems such as Cast-in-Place wall systems. The Preliminary Design of a structure begins with the district submitting a Bridge Survey indicating their need for a structure, and ends with the completion of the Substructure Layout or TS&L submittal (type, size and location). The paper demonstrates load and resistance factor design (LRFD) calibration for tensile strength and pullout strength limit states for steel strip mechanically stabilized earth (MSE) walls using a reliability theory-based approach. MSE structures have become the solution of choice over traditional retaining wall systems due to their reduced material costs, ease of installation, and improved performance. Mechanically Stabilized Earth (MSE) structures have been used in their current form since the early 1970s.
Comparison between AASHTO and CHBDC Design Methods for MSE Retaining Wall and its Implications on Transportation Agencies