Detecting Pile Length of Sign Structures and High Mast Poles

Several hundred high mast light towers (HMLTs) throughout the state of Minnesota have foundation systems, that are typically concrete-filled steel pipe piles or steel H-piles, with no construction documentation (e.g. pile lengths) and soil stratigraphy information. Reviews of designs within current standards suggest that many of these foundations may have insufficient uplift capacity in the event of peak wind loads. Without knowledge of the in situ pile length, an expensive retrofit or replacement program would need to be conducted. Thus, providing a screening tool to determine in situ pile length - as compared to a bulk retrofit of all towers with unknown foundations - would provide significant cost savings. The goal of the project is to establish a non-destructive field testing technique, including data analysis algorithm, for determining in-place pile lengths by way of seismic waves. A unique feature of the proposed work is the use of computational modeling to account for the effects of soil profile and ground conditions (e.g. moisture) on the sensitivity of the method. The length of each pile supporting an HMLT will be identified through a systematic sensing approach that includes (i) collection and classification of the pertinent foundation designs and soil conditions; (ii) three-dimensional (3D) simulation of dynamic soil-foundation interaction; (iii) parametric studies of the 3D pile vibration problem; (iv) field testing; and (v) analysis-driven data interpretation.