Probabilistic Evaluation of the Uplift Capacity of Transmission Tower Foundations Using Reinforced Anchors

The present study pertains to the probabilistic assessment for analysis and design of uplift capacity of transmission tower foundation reinforced with horizontal anchor using the radial basis function (RBF)-based response surface method. The deterministic uplift capacities of horizontal anchors in both unreinforced and reinforced soils were obtained using a finite difference numerical scheme. For the case of reinforced soil, geogrid was used and placed on top of the anchor plate. The improvement in uplift capacity due to the inclusion of geogrid reinforcement is first discussed. Next, RBF-based response surface models were constructed using the observed uplift resistance from the deterministic numerical model. The reliability of the foundation subjected to uplift forces was assessed using the Monte Carlo simulation, considering uncertainties of the soil and geogrid properties. The influence of safety factors on the failure probability of the foundation for both unreinforced and reinforced cases was shown. Variation of the probability of failure with different coefficients of variation of input variables was also investigated. The reinforcement stiffness was the most influencing parameter, having a pronounced effect on the failure probability of the reinforced foundation. Significant improvement in the uplift capacity and reduction in failure probability of the foundation were observed when a reinforced anchor was used, showing the effectiveness of reinforcement on top of the anchor plate. The results indicated that for the same failure probability, the reinforced anchors require much lower depth compared to unreinforced anchors.