Softactivity Activity Monitor [UPD] Crack
Abstract:Cracks in concrete structures can be indicators of important damage and may significantly affect durability. Their timely identification can be used to ensure structural safety and guide on-time maintenance operations. Structural health monitoring solutions, such as strain gauges and fiber optics systems, have been proposed for the automatic monitoring of such cracks. However, these solutions become economically difficult to deploy when the surface under investigation is very large. This paper proposes to leverage a novel sensing skin for monitoring cracks in concrete structures. This sensing skin is constituted of a flexible electronic termed soft elastomeric capacitor, which detects a change in strain through changes in measured capacitance. The SEC is a low-cost, durable, and robust sensing technology that has previously been studied for the monitoring of fatigue cracks in steel components. In this study, the sensing skin is introduced and preliminary validation results on a small-scale reinforced concrete beam are presented. The technology is verified on a full-scale post-tensioned concrete beam. Results show that the sensing skin is capable of detecting, localizing, and quantifying cracks that formed in both the reinforced and post-tensioned concrete specimens.Keywords: crack; strain; distributed dense sensor network; structural health monitoring
Softactivity Activity Monitor Crack
Near-neutral pH SCC also occurs on external pipe surfaces under areas of coating disbondment but where CP is fully shielded. As for high pH SCC, the surface cracks generally form colonies in the axial direction of the pipe. Near-neutral pH SCC cracking typically occurs in association with pits and general corrosion, as it occurs under freely corroding conditions, i.e. under no CP polarization. In contrast to high pH SCC, the crack propagation through pipe wall thickness is of a transgranular nature. The cracks tend to be wider, with corroded crack walls and filled with corrosion products. It is thought to be most prevalent in high latitudes where there is a marked seasonal change in the carbon dioxide content of the soil. Some investigations have also associated anaerobic microbial activity with the initiation of near-neutral pH SCC; overall, however, the mechanism remains unclear and debated. It is nevertheless accepted that some level of stress cycling is required for initiation and growth.