Also required are external stability analyses to assess whether the coherent reinforced soil mass resistance to direct sliding, its eccentricity, and its bearing capacity, are all satisfied.

Both require assessment of internal stability analyses to assess whether the long-term strength of the reinforcement, the geosynthetic-block connection, and the resistive pullout length, are all satisfied. The same basic mechanics (i.e., statics) are utilized by ASD and LRFD. The difference between ASD and LRFD is how the “larger” supply versus demand is defined. Actually, design ensures that the supply is larger than the demand. For example, the geosynthetic long-term strength needs to equal the applied load. That is, the capacity of a system can safely sustain the applied loading. The essence of limit state design is to insure that the supply (e.g., system resistance) matches the demand.

As the LRFD is mandated by FHWA, the following legitimate question is asked: “Considering the wide and successful use of ASD, why is LRFD needed for the design of MSE walls?” While clearly discussed herein, no clear answer is provided in this article. This article illustrates common elements between ASD and LRFD. Since procedures in AASHTO are usually accepted as the prevailing design in the public sector, it will be quite difficult for designers to avoid LRFD. Yet, as of October 2007, the Federal Highway Administration (FHWA) mandates design of MSE walls using LRFD as currently presented in AASHTO 2004 with updates to appear in 2006. While all wall designers in the United States are familiar with the ASD process (though some may not be aware of the name), only a few are familiar with, or even aware of, the LRFD concept. Program MSEW(3.0)=Version 3.0 of software analyzing Mechanically Stabilized Earth Walls including reinforced SRW.ĭetails of MSEW(3.0) are posted at Abbreviated names are just names, not substance however, such names do imply design procedures with serious outcomes.SRW=Segmental Retaining Walls reinforced with geosynthetics (e.g., reinforced block walls).LRFD=Load Resistance Factor Design (e.g., AASHTO 2004).ASD=Allowable Stress Design (e.g., AASHTO 1998, 2002 or NCMA in the private sector).

Msew 3.0 Crack