Steel, defined by Merriam-Webster, is a “commercial iron that contains carbon in any amount up to about 1.7 percent as an essential alloying constituent.” It is strong and used to build structures. However, when used underwater for navigation and waterway structures, the steel hydraulic structures (SHS) are exposed to corrosive environments and susceptible to fatigue and cracking. In most cases, damage cannot be detected without dewatering and structures often surpass their service life. When identified, traditional repair methods to SHS have mirrored bridge repairs, such as gouging and rewelding, and adding welded cover plates. Despite this, the ongoing corrosive damage continues underwater, and the repairs are often short-lived. Finding an alternative that is easy to implement would be ideal. Could fiber-reinforced polymer, long used for general strengthening and repair of structural components on dry land, work underwater?
Researchers Guillermo Riveros, Emad M. Hassan, Lauren Hudak, and Hussam Mahmoud explore the applicability of FRP repairs for fatigue and the need to maximize adhesion in underwater environments. Basalt FRP is a relatively new civil engineering application. While there are no studies on its use in repairing steel components, it does not cause galvanic corrosion, which may improve bonding and extend fatigue life. Their paper, “Basalt Fibers for Underwater Fatigue Repair of Steel Panels” in the Journal of Structural Engineering, fills a gap in the literature specific to the effectiveness of basalt fibers in underwater fatigue repair of cracked steel structures. Learn more about how engineers can apply this work in underwater environments at https://doi.org/10.1061/(ASCE)ST.1943-541X.0003489. The abstract is below.
Fatigue damage is a major threat to the safety and integrity of many steel structures. Steel hydraulic structures (SHS), in particular, experience fatigue loading during operation and are exposed to harsh environmental conditions that can further reduce fatigue life through mechanisms. The traditional inspection and repair process for SHS is time-consuming and leads to economic losses. Studies investigating the behavior and advantages of using bonded carbon fiber-reinforced polymer (CFRP) to repair fatigue cracks in SHS are lacking. The main objectives of this study are to increase the bonding of CFRP, investigate the effectiveness of different fiber-reinforced polymers, and test different retrofitting configurations for SHS. In this study, eight large-scale center-cracked panels were tested under constant amplitude mode I fatigue loading that utilized different surrounding environments, repair materials, and retrofitting configurations. Results indicated that the use of both CFRP and basalt fiber-reinforced polymer (BFRP) are both effective at extending fatigue life. Steel retrofitted with full patches of BFRP that cover the crack can have infinite fatigue life. The extent of fatigue life extension was still controlled by the quality of the fiber-reinforced polymers bond to steel; however, bond behavior was significantly improved in comparison to previous underwater applications.
Read the paper in full in the ASCE Library: https://doi.org/10.1061/(ASCE)ST.1943-541X.0003489.