Investigation of the Buckling Capacity of Concrete Encased Steel H-Piles on Highway Bridge Structures

Concrete encasements are usually utilized to protect bridge above-ground piles from corrosion. These concrete encasements are usually square or round shapes reinforced by longitudinal rebars. However, the contributions of concrete encasements are not considered in traditional pile design procedures. On the other hand, rating engineers need to have realistic evaluations of the piles to estimate the capacity of the foundation for scour-critical bridges. Underestimation and overestimation of pile capacity can result in either potential bridge failure or uneconomical assessment. The objective of this paper is to investigate the effect of concrete encasement on pile buckling behavior subject to concentric load. To achieve this objective, four full-scale concrete encased pile specimens with various pile and concrete encasement lengths were fabricated and tested with concentric axial loading to measure the specimen ultimate capacity. In addition, the finite-element (FE) approach was utilized to simulate the buckling behavior and predict the ultimate capacities of the lab-tested specimens. The developed FE models were validated against the laboratory test data. Finally, the validated FE models were utilized in the parametric study to investigate the effect of the length and shape of the concrete encasement on the ultimate capacities of the steel H-piles. The results indicated that the concrete encasement could increase the buckling load of the pile, and ignoring the effect of the concrete encasement, as with the use of the equations suggested by the AISC, could result in a significantly underestimated prediction. It was also found that the concrete encasement increases the initial axial stiffness of the pile before the buckling load is achieved.