Why do we see what we see? Structural diagnostics is the process of synthesizing a comprehensive list of potential failure mechanisms, data obtained from the field, and thorough physics-based analyses to determine the root cause of an observed structural performance issue.
The term "structural failure" conjures up dramatic mental images of a collapsed building or bridge. In reality, much more common examples of structural performance failures are a crack in a concrete or fiberglass structural member, a deformed steel beam, noticeable deflection of a floor, or an annoying level of vibration to name just a few.
The challenge in many failure investigations is to sort through an over-abundance of meaningless data and an absence of essential data to arrive at the most likely root cause(s) of a known failure from a seemingly endless list of possible failure mechanisms. This is where a fault tree comes in handy. We develop a fault tree at the outset of each failure investigation. The fault tree starts with the most basic observation; e.g., a steel beam is bent, and then each of the potential causes for the observed failure are listed below the top level (e.g., the beam was bent when it arrived at the site, the beam was bent during erection, the applied forces are too large, etc.). Then the potential causes for each of those causes are added to the next level in the tree. Each box in the tree may suggest another underlying root cause/causes or an analysis, measurement, or record check that can confirm or eliminate that item as a potential root cause. A thorough and systematic approach is the key to a successful failure investigation.