Destructive Testing of Dam Spillway Gates for Development and Validation of Structural Health Monitoring Methods

Abstract

Dams are used throughout the world to enable commercial traffic on rivers, provide hydropower and/or flood protection, as well as collect and store water for drinking and irrigation needs. Many dams have steel spillway gates that are used to release water or otherwise regulate flow through the dam. Failure of dam spillway gates can lead to uncontrolled release of water with significant risk to life safety and the economy. Structural Health Monitoring (SHM) of dam spillway gates is increasingly used to monitor these critical assets and provide information to enable proactive maintenance and prevention of catastrophic failures. Like most civil infrastructure, a key challenge to development of SHM systems is the acquisition of validation and/or training data of the structure in the damaged state. At Lock and Dam 22 on the Mississippi River, the spillway gates of the dam are being replaced, with the intention to scrap and recycle the old gates. This gate replacement provides a unique opportunity to perform destructive testing on the existing gates to deliberately induce damage and/or undesirable operational characteristics on the gates that would be valuable detection targets for an SHM system. This paper discusses the first sets of testing performed on the existing gates prior to their removal, where a sensor system was installed. Then, just prior to removal of the gate, a number of simulated cracks were flame-cut into. Additionally, extreme friction in the gate’s pivot points was induced using a novel procedure, and skewed lifting of the gate was induced with the use of a crane. In each case, the gate was operated, and data was collected. This paper presents the preliminary analysis and conclusions of the data collected including simple methods for detection of trunnion friction and a surprising method of using accelerometers on structural components to measure and monitor for uneven hoisting of the gate.