When a static load is applied to a connection that has fatigue cracks, the cracks will grow slightly, causing the emission of stress waves. Perhaps the inspection with AE can be performed during routine maintenance cycles for light replacements, thereby simplifying traffic control. The illustration below shows the sensors located on a test pole. Such inspections are routinely used for other systems such as pressure vessels and utility truck booms. Collaboration with the various NDTs, fatigue crack growth observations, field performance, and modeling all play an important and integrated role in the assessment of the behavior, design of improved systems, and the development of test methods for improve inspection.
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Eliminating the Problem Retrofit Retrofitting poles that may, or may not, have exhibited cracking is a possible solution. The authors suggest that strengthening retrofits would be ill advised for system where cracks have initiated. It is unlikely that modifications can be substantial enough to redirect stresses away from the cracks thereby slowing crack growth. As an alternative to strengthening, extensive research is currently in progress to increase the damping of the system. Attach a strut between the mast arm and the post with an automobile shock absorber inline with the strut.