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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. 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. Resistance factors for prescribed load factors and different load and resistance model combinations are compiled in tables. The limitations of the LRFD approach to generate resistance factors that are judged to be acceptable based on current practice are demonstrated. The challenges to generate consistent design outcomes with the same margin of safety expressed probabilistically are identified, and the link to reliability-based design is described. Example designs are provided to show the impact on steel reinforcement quantities and length when using different models in combination with proposed and current specified load and resistance factors. The calibration outcomes will be of value to code writers in Canada and the US for MSE wall design sections in the next editions of national geotechnical foundation LRFD codes. [ABSTRACT FROM AUTHOR]

6.Databaseofloaddata Miyata and Bathurst (2019) developed a database of 113 measured steel grid loads (T max) from 11 instrumented steel grid walls constructed with cohesive-frictional soils and purely frictional soils. Reliability-based design and analysis for internal limit states of steel grid-reinforced mechanically stabilized earth walls. Thegeneralapproachdescribedin thispaperisanimportantcontributiontonext-generationanalysis and design using modern concepts of RBD for internal stability design of both steel and polymeric soil-reinforced MSE walls and is thus in alignment with the international movement towards RBD for geotechnical structures (e.g., Low and Phoon 2015;Phoon2017;PhoonandChing2015;ISSMGE2017). Allen et al. (2001, 2004) quantified the level of accuracy of the Simplified Method for steel MSE walls using bias statistics deduced from a large number of instrumented walls. 1.Introduction This paper is focused on reliability-based design (RBD) and analysis for tensile strength and pullout limit states of steel grid-reinforced mechanically stabilized earth (MSE) walls constructed with frictional soils and subjected to typical operational conditions. [Extracted from the article]

Mechanically stabilized earth (MSE) walls must be designed with adequate margins of safety against internal stability failure described by tensile strength and pullout limit states. Probabilities of failure (or reliability index) will vary strongly with the accuracy of the underlying models that appear in limit state performance functions. In this paper, prior work by the authors and co-workers on this topic is reviewed. Relative performance is explored in the context of the reliability (or probability of failure) of steel and polymeric reinforcing elements in MSE walls using limit state performance functions with load and resistance models having different accuracy. [ABSTRACT FROM AUTHOR]

• Buried steel grids used in mechanically stabilized earth (MSE) walls can corrode. • Probability of failure is computed for limit states of galvanized steel grids. • Three-stage corrosion model is coupled with reinforcement load and resistance models. • Probability of steel grid tensile and pullout failure with time is computed. • Pullout failure of coated steel members due to corrosion is shown to be unlikely. Design for internal limit states of steel grid reinforcement in mechanically stabilized earth (MSE) walls must provide for loss of steel thickness due to corrosion. The paper combines key features of zinc and steel corrosion models used in North American practice with corrosion rate statistics reported in the literature for the zinc coating on buried galvanized steel strips and for steel rebar. Examples of loss of strength and pullout capacity of steel grid elements constructed with different member diameters and up to 120 years after construction are presented in probabilistic terms. Results of reliability-based analysis for the tensile strength and pullout limit state at design lives of 75 and 120 years are demonstrated for a typical wall under operational conditions using tensile load and resistance models in combination with non-aggressive soils recommended in North American design codes. The results of calculations show that for the wall example the influence of different zinc cover thickness on probability of tensile failure of longitudinal members is detectable at the end of design life. However, the typical minimum specified zinc thickness of 0.086 mm recommended in North American practice is likely sufficient to keep probabilities of failure to 1% or less (i.e., reliability index of 2.33 or greater). The influence of a range of initial zinc thickness reported in the literature on probability of pullout failure of the same steel grid elements was found to be negligible. [ABSTRACT FROM AUTHOR]

Model checking, evaluation and comparison are critical steps in Bayesian data analysis but not routinely considered in statistical analysis of geotechnical data. This paper presents an overview of model checking and comparison concepts and techniques employed in modern Bayesian data analysis that are useful for analysis of geotechnical engineering data. These methods are applied to statistical analysis of load and pullout model bias data for steel strip mechanically stabilized earth walls. It is shown how model checking can result in statistical models with better fits. The practical implications of using improved statistical models are discussed in the context of reliability-based design and load and resistance factor design calibration of the internal stability pullout limit state. Finally, statistical model uncertainty and Bayesian model averaging are discussed and explored using an example of reliability-based design for the same limit state. [ABSTRACT FROM AUTHOR]

A rigorous probabilistic-based approach for load and resistance factor design (LRFD) calibration of internal stability tensile rupture and pullout limit states for geogrid reinforced mechanically stabilized earth (MSE) walls is presented. Load and resistance factors are provided for different combinations of the load model with pullout model and the tensile strength model used in current practice. The load models are the AASHTO Simplified Method and the Simplified Stiffness Method. Resistance factors are tabulated for use in LRFD foundation practice in Canada which rewards designers with larger resistance factors for greater project level of understanding. Resistance factors are also provided that are amenable to US practice where the notion of level of understanding is not explicitly considered in LRFD practice. The paper demonstrates the application of the load and resistance factors for tensile rupture and pullout internal stability limit states using a design example and shows the reduction in required reinforcement strength using the Simplified Stiffness Method. The paper is of value to practitioners and LRFD code writers in the United States and Canada for future revisions of design specifications in their jurisdictions. [ABSTRACT FROM AUTHOR]