Abstract

This paper will present field verified methods for corrosion engineers and/or technicians to accurately inspect and log structure configuration, field conditions and perform field tests to verify electrical continuity prior to concrete operations (prepour testing). Additional topics will include troubleshooting as it pertains to prepour testing and also if a structure has already been poured (postpour) whether it was previously tested or not. The concluding topic addresses the utilization of project documents such as structural and shop drawings to extract relevant reinforcing steel information used in the creation of theoretical resistance and when to use either a standard mathematical analysis or Simulation Program with Integrated Circuit Emphasis (SPICE) software to develop said theoretical resistance as a computer model.

Introduction

Population growth in city centers has spurred the expansion and new construction of direct current (DC) powered transit systems throughout the world1. Despite stringent design criteria, quality assurance and quality control (QA/QC) monitored construction practices and ongoing track maintenance, it is a fact that DC stray current will eventually occur and negatively impact buried and/or submerged metallic structures immediately adjacent and within the transit right-of-way (ROW)2. In combination with other methods to reduce stray current such as high track-to-earth (TTE) resistance values and shorter distances between substations, transit agencies are specifying the welding of reinforced steel structures within their purview such as retaining walls and footings, approach slabs, aerial inverts, and bridge abutments to prevent stray current from reducing the design life of surrounding metallic structures. The information presented in this paper is intended to share safe and efficient methods developed and refined in the field at multiple transit projects. However, these methods can be applied to projects exposed to transit as well as alternate sources of DC stray current. Consider nuclear power plants with facilities adjacent to high voltage direct current (HVDC) transmission lines and reinforced concrete buildings within the influence of impressed current cathodic protection (ICCP) systems set at levels to protect a multitude of underground metallic piping networks. The ultimate goal is that corrosion engineers and/or technicians successfully document visual inspections, develop efficient prepour and postpour continuity test methodologies, and construct accurate computer simulation models for data analysis.

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