The Use of Concrete-Enclosed Reinforcing Rods as Grounding Electrodes

Abstract

The findings of Ufer that concrete-encased metal objects were effective in providing improved grounding under adverse soil conditions suggests that the reinforcing framework of footings for the columns of structural steel buildings would provide effective grounding function and means. Ensuing tests in high, medium, and low resistivity soils indicate that the grounding capability of such reinforced foctings (per unit) is equivalent to that of conventional electrodes under low and medium soil resistivity conditions and superior to them under high soil resistivity conditions. In addition, the much larger number of column footings required for structural reasons does, when used, provide much more effective grounding under all soil conditions than previously used systems. The steel framework of such buildings, if electrically connected at each column base to an inherent grounding electrode, then functions as a very efficient grounding network for system, lightning, and static grounding. Fault grounding should always employ a return conductor following the routing of the faulted conductor. The use of new types of grounding electrodes is becoming obligatory due to the widening unsuitability of water pipe systems for grounding purposes. This unsuitability is due to the use of nonconducting joints in the water piping and to the use of nonconducting piping for the water system.