Multi-Criteria Assessment of Bridge Sites for Conducting PSTD/ISTD: Case Histories

Abstract

The Federal Highway Administration (FHWA) has recently developed the Portable Scour Testing Device (PSTD) to improve scour analysis around bridge piers in cohesive soils as part of the NextScour project. The PSTD is a compact field erosion testing device that, apart from a drill rig and larger water pump, has a lot of similarity with the In-situ Scour Testing Device (ISTD) in mechanism and data acquisition. The purpose of this paper is to provide recommendations on the suitability of using PSTD and ISTD at sites that have cohesive subsurface soils. An overview of the capabilities and limitations of the PSTD/ISTD in relation to hydraulic considerations, soil types, depth coverages, and erodibility potential is given. A multi-criteria assessment methodology to evaluate site suitability for conducting PSTD/ISTD is presented. The assessment methodology was utilized to detect suitable sites among 30 Illinois bridge sites using soil layer information, boring locations, groundwater level readings, in-situ testing results, geospatial analysis, site accessibility, and aerial photos.