Comparison between AASHTO and CHBDC Design Methods for MSE Retaining Wall and its Implications on Transportation Agencies

Mechanically Stabilized Earth (MSE) structures have been used in their current form since the
early 1970s. 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.
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. Design of MSE structures has
progressed from using the Allowable Stress Design(ASD) method to the Load and Resistance
Factored Design (LRFD) method. 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. 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. This paper will demonstrate how the CHBDC new changes increase the cost of a
typical MSE structure. Indirectly, it will demonstrate the present sustainability issues being faced
with the current CHBDC design method including, an increase in the steel reinforcement
required to be manufacture and the additional select MSE fill that will be required to be
processed and shipped to site, resulting in an increase in the carbon footprint for the structure.
Keyword: Mechanically Stabilized Earth, Retaining Wall, sustainability, design, code, CHBDC,


Essery, D.
Taylor, T.
El-Sharnouby, M.

Session title



Structures Standing Committee


Structural Design & Management







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