29 Aug 2024

Experimental Evaluation of Steel Beams with Mechanical Section Reduction Retrofitted with Fiber Polymers

Abstract: Steel elements working in a harsh environment can be exposed to corrosion that degrades their performance and threatens the integrity of the whole structure. Recent studies propose using carbon (CFRP) and basalt (BFRP) fiber–reinforced polymers to repair corroded steel cross sections; however, most of these studies have not explored many of the structural characteristics, including ductility. In this study, we conduct a series of full-scale experimental tests to investigate the impact of corrosion, represented as mechanical section reduction, on steel beams as well as the impact of repairing the beams using CFRP and BFRP in enhancing the beams’ structural performance. Mechanical section reduction, introduced to the flange and web elements, is used to establish a baseline dataset that captures the impact of repairs in the absence of corrosion. Four-point bending loading conditions are utilized for all tested beams. The results show that the reduction of the flange and web section lowers the beams’ yielding load by 10% and 8%, respectively, compared with a beam with a full cross section. Utilizing CFRP and BFRP patches can partially restore the corroded beams’ ductility; however, the BFRP is outperforming the CFRP in improving their ultimate strength by 10% and enhancing their ductility by 10%.

9 Aug 2023

Repair of Corroded Steel Girders of Hydraulic Steel Structures (HSS) Using Fiber-Reinforced Polymers (FRP)

Abstract: Although steel hydraulic structures have a protective system to prevent corrosion, this type of deterioration will eventually occur due to the constant exposure to harsh environmental conditions. There are several techniques that can be implemented to repair corroded steel structural elements. This report presents a numerical study to evaluate the mechanical behavior of corroded steel girders used in hydraulic steel structures and to evaluate several carbon fiber–reinforced polymers (CFRP) layups to repair them. The girders were modeled as simply supported with four-point loading boundary conditions. The corrosion deterioration was modeled as loss in section as 10%, 25%, and 40%. The effectiveness of the deterioration was established based on the level of stresses at the steel compared with the undamaged condition after it is strengthened with CFRP. It was found that CFRP repair is more practical for reducing the stresses at the steel in the shear dominated zone if deterioration is below 25%. At the tensile dominated zone, CFRP is effective for reducing the stresses for deterioration below 40%.

23 Mar 2023

Experimental Fatigue Evaluation of Underwater Steel Panels Retrofitted with Fiber Polymers

Abstract: Many steel structures are susceptible to fatigue loading and damage that potentially threaten their integrity. Steel hydraulic structures (SHS) experience fatigue loading during operation and exposure to harsh environmental conditions that can further reduce fatigue life through stress corrosion cracking and corrosion fatigue, for example. Dewatering to complete inspections or repairs to SHS is time consuming and leads to economic losses, and current repair methods, such as rewelding, often cause new cracks to form after relatively few cycles, requiring repeated inspection and repair. The use of bonded carbon fiber–reinforced polymer (CFRP) to repair fatigue cracks in metallic structures has been successful in other industries; recent work suggests that this method offers a more reliable repair method for SHS. Studies regarding CFRP retrofits of SHS indicate that early bond failure often controls the degree of fatigue life extension provided by the repair. This study aims to extend previous studies and increase the fatigue life of repaired steel components by employing methods to improve CFRP bonding. Additionally, using basalt reinforced polymer (BFRP) instead of CFRP is proposed. BFRP is attractive for SHS because it does not react galvanically and has excellent resistance to chemically active environments.