Flange local buckling strength of hot-rolled steel W-shape solar array piers partially braced by soil

The local buckling strength of W-shaped hot-rolled steel piles braced by soil is approximated in this study. W-shaped piles are common foundations in solar array supports. For wind loadings, the piles experience flexural stresses below grade. The pier design typically calls for some of the lightest W-sections available, and with corrosion section loss assumed over the foundation design life, the W-shape cross-sections end up being non-compact or slender. There is not much available information on how soil interacting with the pile underground might benefit local buckling strength with some engineers choosing to consider the pile fully braced against local buckling in their designs. To explore this soil-structure interaction, finite strip elastic buckling analysis is used to approximate the critical elastic flange buckling stress of W-shaped piers in soil. The cross-section elastic buckling analysis includes linear springs that simulate the soil bracing on the cross-section, where the spring constant is related to common geotechnical parameters: soil subgrade modulus and the number of blows in a Standard Penetration Test. A parameter study is performed to calculate W-shape pier flange local buckling stress as a function of soil subgrade modulus, and this flange local buckling stress is used to calculate the local buckling strength in accordance with AISC 360-16. It is observed that the largest strength benefit from soil interaction occurs in the most locally slender W-shapes, although the maximum strength increase observed was still less than 10 percent.

Learning Objectives:
Calculate hot-rolled steel W-shape local buckling strength including partial soil bracing.

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