Structural Engineering Health Monitoring: The Basics

Just as is standard and important to the health of a human body, a structural engineering expert knows that monitoring the health of building structures is critical to its health and longevity. Promoting the health of your building can increase efficiency, longevity, and prevent accidents, such as collapse, that could potentially be detrimental to the survival of your company


These are the most important components to monitor the health of a structure:

 

  1. Identifying damage when it occurs
  2. Type of Damage
  3. Location of Damage
  4. Severity of Damage

 

Data recording equipment is very important and is used within structures to monitor the physics of the building and identify damage when it presents itself. These instruments allow you to see any changes in natural frequency of the system, deflection surpassing the limits of the structure,  rotations that exceed at joints, and a variety of other structural engineering issues that may occur. The presence of any of these occurrences would mean that something is wrong with the structure. Most of these would describe a loss of stiffness in the structure which can ultimately lead to collapse if the issue is not promptly addressed.

 

Following natural disasters like earthquakes and tsunamis, it is especially important to immediately check the data provided by these monitoring devices. As these disasters can cause severe damage to buildings, they often cause a major loss of overall stiffness creating an increased hazard of collapse. These devices will allow you to observe how an impact traveled within a building, the primary point of damage, the sequence of damage, and the specific components that may have failed first.

 

Most are well aware of the fact that structural engineering has evolved based on historical failures and a lot of experience. But this history does not always inform us of things like whether a load actually is the upper limit of a building. Structural engineering health monitoring can help us in this case. Based on data collected by monitoring devices, we can find the load that was acting and reverse calculate so that we can ensure it is a controlled load.

Here are a few basic principles, or axioms, from Fundamental Axioms of Structural Health Monitoring by Charles R. Farrar that are important when it comes to structural engineering health monitoring:

 

  • Axiom I: All materials have inherent flaws or defects;
  • Axiom II: The assessment of damage requires a comparison between two system states;
  • Axiom III: Identifying the existence and location of damage can be done in an unsupervised learning mode, but identifying the type of damage present and the damage severity can generally only be done in a supervised learning mode;
  • Axiom IVa: Sensors cannot measure damage. Feature extraction through signal processing and statistical classification is necessary to convert sensor data into damage information;
  • Axiom IVb: Without intelligent feature extraction, the more sensitive a measurement is to damage, the more sensitive it is to changing operational and environmental conditions;
  • Axiom V: The length- and time-scales associated with damage initiation and evolution dictate the required properties of the SHM sensing system;
  • Axiom VI: There is a trade-off between the sensitivity to damage of an algorithm and its noise rejection capability;
  • Axiom VII: The size of damage that can be detected from changes in system dynamics is inversely proportional to the frequency range of excitation.

 

Consult a structural engineering expert witness today to evaluate the health of your building, and ensure the longevity of the structure!