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Structural Health Monitoring - SHM

Continuous monitoring of structures to address structural properties, durability and operational safety

Many buildings like bridges, tunnels and other infrastructure suffer from increasing age and increasing volume of traffic. Cumulative damage on the one hand and high maintenance costs on the other, make it necessary to subject these structures to permanent monitoring.

Monitoring strategies may aim to detect singular events - e.g. wire breaks in tensioned structures -  or to derive continuous information about the condition of a structure - e.g. strain in beams or elongation of trusses. Based on sensor readings engineers are able to take measures as necessary. Failure of elements or whole structures can be avoided, overall operational safety is increased and finally – with a properly scaled SHM design stakeholders will save money.

To achieve a high level of robustness and significance SHM systems should capture several measurands at different positions over time. A synopsis of all available data will help the skilled engineer to derive a detailed picture of the state of a structure.

Typical SHM systems in civil engineering may comprise sensors like displacement sensors, thermometers, strain gauges, accelerometers, seismometers, acoustic sensors for structural or airborne sound, fiber optic cables, magnetic field sensors (etc.).

As an example, prestressed concrete elements that may be prone to wire breaks (e.g. due to external loads or corrosion effects) can be monitored with acoustic emission (AE) sensors. With a proper sensor layout (i.e. total number and positions of individual sensors) wire breaks can be detected and even localized in real time. Thus, in contrast to sensors that derive localized information (like strain gauges) AE enables monitoring on a global scale, although sensors are placed at distinct locations.

Design and execution of building work concerning water-impermeable concrete structures has always been a challenging task. There are plenty of influencing factors which have to be considered, in order to reach the requested high engineering standards of new structures. Mistakes and defects even in latest projects validate the complexity and actuality of this topic and are one of the reasons why the state of the art is not always in demand. A significant factor in reaching the requested high standards is the coordinated cooperation and collaboration of all the professionals involved in the design and execution process. New technologies like fully bonded sheet membrane-systems can help to achieve a higher level of safety.

Our services include:

  • If necessary, comprehensive structural analysis with non-destructive (NDT) and destructive test methods (core removal, steel removal, etc.)
  • Expert valuation of the condition of a structure and analysis of damage scenarios
  • Design of a holistic monitoring strategy with inclusion of different measuring systems
  • Design of a holistic data evaluation to integrate data of all measuring systems in one evaluation tool
  • Design of alarm concepts and alarm systems, e.g. traffic management for immediate closures when alarm values ​​are exceeded
  • Installation and maintenance of measuring systems, monitoring of the installation of measuring systems of external companies
  • Deployment and expert valuation of comprehensive SHM systems taking into account all structure specific details.

The following measuring systems are often installed, operated and evaluated in combination:

  • Deformation measurements (geodetic, inductive, fiber optic)
  • Strain measurements on tendons (strain gauge)
  • Temperature measurements over the cross section with special sensor rods
  • Acoustic Emission (AE) for wire break detection and localization
  • Crack detection with fiber optic technology
  • Groundwater level measurements
  • Corrosion monitoring.
Strain gauges during installation on exposed tendons
Acoustic sensor to detect wire breaks
Results of rainflow-counting algorithm applied on long term strain measurements
Acoustic emission signals acquired during monitoring of a bridge structure. Top right: signal of a wire break