Development of Socketed Foundations for S3x5.7 Posts
Scott K. Rosenbaugh, Tyler L Schmidt, Ronald K. Faller, John D. Reid · Lincoln (University of Nebraska) · 2015
The objective of this study was to develop a socketed foundation for use with the S3x5.7 (S76x8.5) weak post. The design focused on cylindrical, reinforced concrete foundations with a steel tube placed in the center for use as the socket. The foundation was to prevent both damage and displacements exceeding 1 in. (25 mm), as measured at groundline, during an impact event. To evaluate various foundation designs, ten dynamic bogie tests were conducted over three separate rounds of testing. Round 1 was conducted in a weak, sandy soil; Round 2 was conducted in a strong, stiff soil; and Round 3 was conducted within a 4-in. (102-mm) thick asphalt pad. The results of the bogie testing led to the development of three socketed foundation design options. Option 1 consisted of a 12-in. (305-mm) diameter foundation; Option 2 was a 15-in. (381-mm) diameter foundation; and Option 3 was a foundation installed within an asphalt mow strip. Option 1 carried a risk of concrete damage during severe impacts, but it was included for those agencies wishing to be more aggressive and accept the risks of damage. Each design option had a unique reinforcement configuration and minimum embedment depth. Further, the recommended minimum embedment depths were also a function of the surrounding soil conditions and the frost line depth of the installation site.