Online Monitoring of Steel Constructions Using Passive Methods

In the chapter the possibilities of development of distributed diagnostic system capable of online structural health monitoring of civil engineering structures are discussed. Instead of commonly used methods of determining the technical state of the construction that are usually focused on searching for cracks, material heterogeneities and assessing concrete or steel degradation, the methods proposed for the system are based on the comparative strain gauge, acceleration and passive magnetic measurements. All this measurement methods are used for stress assessment in critical fragments that are vital for stability and durability of the structure. Evolution of defects in the construction causes measurable changes of stress distribution in critical joints of the construction. Additionally, materials that could cause threat of the catastrophic accident caused by fatigue wear, exceeding stress limits or emerging of plastic deformations have magnetic properties that could affect the local magnetic field. Stress limits could be then constantly supervised taking into account the range of permanent and elastic deformation, which would allow for early detection of threats. SHM data analysis is taking into consideration a series of magneto-mechanical and other phenomena occurring during the construction/machine’s operation and also actual magnetization conditions of the object examined in exterior magnetic field (Earth’s or derived from adjacent elements).