Testing and Development of Pre-Stressed CFRP Retrofit Strategies for Controlling Fatigue Cracking in Steel Waterway Lock Gate Structures

Steel waterway lock gates across the national inland waterway transportation network are reaching and exceeding their intended service life, often experiencing component failures that lead to service interruptions. Unscheduled maintenance and repair of lock gates can be expensive and cause economic ripples throughout the entire inland waterway network. These lock gate component failures are often caused by fatigue cracking from repeated loading during operation. This thesis develops and tests a prestressed carbon fiber reinforced polymer (CFRP) fatigue retrofit for controlling fatigue demands within lock gate components. The study expands upon a recent analytical work by Lozano (2017) by experimentally investigating prestressing strategies, bonding mechanisms, prestress creep/relaxation performance, and large-scale experimental fatigue testing. A total of seven large-scale cyclic tests were conducted on lock gate components (with and without applied retrofits) to gauge the effectiveness of the developed prestressing strategies. All gate specimens tested were artificially notched to create a local stress concentration and worsened fatigue condition. Results indicate that the addition of the prestressed CFRP retrofit increases the fatigue life of the retrofitted gate component despite the prestress loss due to epoxy adhesive debonding following rapid cyclic loading. The retrofitted specimen experienced a fatigue life increase of nearly 3 times over the un-retrofitted specimen. Additionally, load shedding into the CFRP, even without significant prestress applied, contributes to a reduction in the component notch stress. The applied CFRP clamping force is able to provide enough force transfer to the CFRP to reduce the notch local stresses

Fatigue Analysis of the Greenup Lock Gate on the Ohio River

This thesis analyzes damage due to fatigue of a typical lock gate on the United States waterway transportation system. Functioning lock gates are essential for this mode of transportation because they control water levels and provide access through dams for ships. Fatigue cracking is caused by cyclic loading and corrosion. Cyclic loading on a lock gate was imitated using a finite element model. This model was used to calculate stress ranges for a cycle so that the number of cycles to failure could be calculated. The proportion of cycles to cycles to failure is known as the fatigue capacity. A linear fatigue damage accumulation rule (Miner’s Rule) helped determine the fatigue critical regions within the gate. Twenty-seven sections of high stress were identified and analyzed. A section at the base of the lock gate sustained the most damage and was determined to be the most fatigue susceptible location. Further analysis and experimentation will validate these results so that retrofits become a possibility in preventing damage due to fatigue caused by cyclic loading

Analytical and Experimental Investigation into Pre-Stressed Carbon Fiber Reinforced Polymer (CFRP) Fatigue Retrofits for Steel Waterway Lock-Gate Structures

Lock gates are an important part of the transportation infrastructure within the United States (US). Unfortunately, many existing lock gates have reached or exceeded their initial design lives and require frequent repairs to remain in service. Unscheduled repairs often increase as gates age, having a local economic impact on freight transport, which can create economic ripples throughout the nation. Metal fatigue is a key cause of unscheduled service interruptions, degrading lock gate components over time. Additionally, because lock gates are submerged during operation, crack detection prior to component failure can be difficult, and repair costs can be high. This paper presents an analytical and experimental investigation into fatigue damage within common lock gate geometries, as well as fatigue mitigation strategies with a focus on extending gate service lives. Detailed finite element analyses are combined with fatigue and fracture mechanics theories to predict critical fatigue regions within common gate details and develop retrofit strategies for mitigating fatigue cracking. Full-scale experimental fatigue testing of a critical lock gate component is conducted to provide a baseline for the evaluation of retrofit strategies. Retrofit strategies and issues in using carbon fiber reinforced polymer (CFRP) plates having optimized pre-stress levels are discussed