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.

17 Jan 2023

State-of-Practice on the Mechanical Properties of Metals for Armor-Plating

Abstract: This report presents a review of quasi-static and dynamic properties of various iron, titanium, nickel, cobalt, and aluminum metals. The physical and mechanical properties of these materials are crucial for developing composite armoring systems vital for protecting critical bridges from terrorist attacks. When the wide range of properties these materials encompass is considered, it is possible to exploit the optimal properties of metal alloys though proper placement within the armoring system, governed by desired protective mechanism and environmental exposure conditions.

1 Oct 2021

Acoustic Nondestructive Testing and Measurement of Tension for Steel Reinforcing Members

Abstract: Many concrete structures contain internal post-tensioned steel structural members that are subject to fracturing and corrosion. The major problem with conventional tension measurement techniques is that they use indirect and non-quantitative methods to determine whether there has been a loss of tension. We have developed an acoustics-based technology and method for making quantitative tension measurements of an embedded, tensioned steel member. The theory and model were verified in the laboratory using a variety of steel rods as test specimens. Field tests of the method were conducted at three Corps of Engineers dams, located in Oklahoma, Georgia, and Illinois. Measurements of the longitudinal and shear velocity were able to be made on rods up to 50 ft long. Not all rods of this length were able to be measured and the quality and consistency of the signal varied. There were fewer problems measuring the longitudinal velocity than shear velocity. While the tension predictions worked in the laboratory tests, the tension could not be accurately calculated for any of the field sites. This is because we were not able to obtain the longitudinal or shear velocities in an unstressed state or precise measurements of the longitudinal and shear velocities due to the lack of knowledge of the precise length of the rods in the tensioned state.

12 May 2021

Classical and Innovative Methods of Fatigue and Fracture Repairs in Navigation Steel Structures

Abstract: Most of the hydraulic steel structures (HSS) in the U.S. have reached or have past their design life, which leads to unsatisfactory performance. Welded connections with low fatigue resistance, poor weld quality, unanticipated structural behavior, or unexpected loading due to the deterioration of the design boundary conditions are the causes of fatigue cracking. The purpose of this report is to identify and evaluate the traditional and new methods used for fatigue and fracture repairs in navigation steel structures to restore their load carrying capacity and fatigue and fracture resistance. The final objective was to generate a guidance report comprising of recommended and more efficient repair methods for the different fatigue limit states observed in navigation steel structures.