Assessing Corrosion Damage and Corrosion Progression in Multistrand Anchor Systems in Use at Corps Projects.

摘要

Stressed steel tendons have been used to strengthen hydraulic structures and to improve their serviceability and stability. Over the past three decades, the US Army Corps of Engineers has worked to upgrade its projects by installing high-capacity, post-tensioned foundation anchors. The goal has been to achieve structural stability for Corps hydraulic concrete structures and/or to remediate cracked concrete monoliths. Substantial improvements to protect multistrand anchor systems from corrosion have been made since they were first used at Corps projects more the 50 years ago. Corrosion of older multistrand units is of concern. Researchers at the US Army Engineer Research and Development Center (ERDC) are looking to develop engineering procedures to estimate the current state of load-carrying capacity of the ground anchorage, to estimate remaining life of the tendon, and to establish the deterioration of anchorage capacity (with time) so costly replacement of ground anchorage can be delayed until absolutely needed. Analytical, laboratory, and field-testing efforts will be used to develop a methodology and analytical models. Probabilistic procedures will be used to quantify uncertainties for the primary variables and will be carried into the analytical model. Procedures to extend the life of deteriorating multistrand tendons also will be investigated. A review of Corps projects using multistrand anchors and a literature review of corrosion of the anchors are summarized in this report. Also included are the history and performance of the multistrand anchors at the John Day Navigation Lock (Columbia River, Portland District), along with post-installation lift-off test results. A summary of a review of nondestructive testing (NDT) to identify defects in the anchors is part of this report, too.