Joints and Cracking
“Areas in a hydraulic steel structure that may be susceptible to fracture may be determined by considering the combined effect of nominal tensile stress levels and complexity of connection details. Connection details interrupt or change the flow of stress, resulting in stress concentrations; therefore, a moderate level of nominal stress tension stress occurring at a complex detail (stress concentration) may be amplified to a significant level. To identify critical areas for fracture, determine locations of moderate to high nominal stress concentrations, and combine the effects of stress level and sensitive detail”.[1]
“Field inspection for cracking on welded or riveted structures can be accomplished by various non-destructive testing methods. The six non-destructive testing methods (NDT) commonly used in industry are visual testing (VT), penetrant testing (PT), magnetic-particle testing (MT), radiographic testing (RT), ultrasonic testing (UT), and eddy-current testing (ET). Selection of an NDT method for inspection depends on a number of variables, including the nature of the discontinuity, accessibility, joint type, and geometry, material type, detectability, and reliability of the inspection method, inspector qualifications, and economic considerations”.[1]
“The following are recommended steps for inspecting for cracks: (1) visual examination, particularly with the aid of a magnifying glass (5 x or higher), is the most efficient first step; (2) if cracks are suspected and the gate component is dry, PT inspection can be used to confirm the presence of a crack. For most cases, more sophisticated methods, such as UT and MT, can also be employed but may not be needed; (3) record the location, orientation, and length of the cracks. Record conditions of the gate when cracks are detected; (4) take photographs of all cracks showing their position relative to the components of the structure; (5) the inspector should complete a report following the actual inspection. The report should include the identification and location of inspected structures, date and time of inspection, type of inspection, inspection procedure, inspection equipment, inspector identity and qualifications, and a record of discontinuities detected that includes the location, size, orientation, and classification of each discontinuity”.[1]
Best Practices Resources
Instrumentation for Concrete Structures (EM 1110-2-4300) (U.S. Army Corps of Engineers)
Citations:
Revision ID: 3459
Revision Date: 09/16/2022