Development of a Guided-Wave Technology Capable of the Detection of Open Cracks and Microcracks in Embedded Trunnion Anchor Rods

Abstract

BACKGROUND: Catastrophic failure of post-tension trunnion anchor rods at dams is an ongoing problem caused by propagating orthogonal stress corrosion cracks described in CHETN-IX-32 (Evans et al. 2013). This condition is shown in Figure 1 which presents a cracked rod that was removed from Robert F. Henry Lock and Dam, which has 376 trunnion rods supporting the tainter gates. In the broken rod image, a blue arrow indicates the fracture origin, and white arrows indicate the crack propagating direction. The green ellipse encircles an area that contains a pre-existing crack. This older crack area is more heavily oxidized than the rest of the fracture surface. This crack over time resulted in the complete failure of the rod. The right side of Figure 1 shows the tainter gate trunnion rods located on a dam pier. These rods serve to prestress the concrete to prevent excessive tensile loading on the concrete during gate operation.