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The design of shallow foundations typically proceeds by using the load and resistance factor design (LRFD) methodology to avoid various limit states with some probability. This paper looks at the sliding limit state of shallow foundations, and the sliding resistance factors required for the LRFD approach are estimated using reliability analyses of surface strip foundations. Cohesive and frictional soils are separately studied under wind loading conditions. Monte Carlo simulations are used to estimate the sliding failure probability of foundation designs on cohesive soils, and an analytical method is developed for frictional soils. The results indicate the existence of a "worst case" correlation length for cohesive soils, and the sliding resistance factor required to achieve target maximum lifetime failure probabilities is around 0.4–0.65 for moderate soil variability. For frictional soils, the required sliding resistance factor is about 0.5–0.85 for νϕ′ = 0.15. Overall, the sliding resistance factors recommended here agree well with the resistance factors of ϕgu = 0.6 for cohesive soils and ϕgu = 0.8 for frictional soils stipulated by geotechnical LRFD code provisions in Canada. The analyses can be used to estimate the reliability of current designs and can also aid the calibration of geotechnical design codes. [ABSTRACT FROM AUTHOR]

Abstract: Highway geometric design in mountainous areas has been a typical challenge. The combination of short horizontal curves and restricted right-of-way is a common ground for contemplating design exception in British Columbia, Canada. In practice, collision modification factors (CMFs) are advocated as quantitative measures of changes in road features on safety. However, in many situations, there are no CMFs in the literature to predict the safety impact of changing particular road features. An important example of these road features is sight distance restriction on horizontal curves. A mechanism for risk measurement has been proposed in earlier work to assist designers in comparing the safety impact of different deviations from sight distance requirements. This paper attempts to answer the questions as to whether it is possible to reduce overall risk and achieve consistency in such reduction without demanding wider right-of-way. This problem was formulated in a multi-objective optimization framework. Following this methodology, it was possible to achieve an average reduction in risk of 25% on the nine critical cross-sections. This reduction in risk was achieved without demanding wider right-of-way and without creating measurable increase in expected collision frequency due to independent re-dimensioning of different geometric elements. On theoretical grounds, this paper represents another step into the direction of developing fully probabilistic geometric design standards. On practical grounds, this paper provides an important decision mechanism that enables the efficient use of available right-of-way for new highway construction. Case studies in this paper have been applied on a major highway development in British Columba, Canada. [Copyright &y& Elsevier]

In geotechnical engineering, the load and resistance factor design (LRFD) approach has been recommended as an alternative to the global factor of safety method. In this paper, the geotechnical resistance factors for the ultimate and serviceability limit states (ULS and SLS) of laterally loaded piles under wind loading are calibrated using a reliability-based method. Both cohesive and frictional soils are considered. Parametric studies are performed to investigate the effects of various parameters on the estimated failure probability, and the required resistance factors for ULS and SLS are provided. The results indicate that the effect of the limiting maximum pile head deflection on the required resistance factor is negligible and that the "worst case" correlation length depends on the pile length. In addition, the required resistance factor for ULS design is 0.55 to 0.78, suggesting that the value of ϕ g = 0.50 stipulated by geotechnical code provisions in Canada is relatively conservative. Considering the target lifetime failure probability of 0.01 for SLS, the required resistance factor is around 0.60 for both clay and sand, which is smaller than the recommendation of ϕ g = 0.80 by the design codes in Canada. [ABSTRACT FROM AUTHOR]