Three benefits of “Caution (Yellow Tag)” in SHM‐driven condition assessment of buildings: Eight years experience with market‐based SHM

In Japan, structural health monitoring (SHM) for building structures has received increased attention since the 2011 Tohoku earthquake, particularly regarding business continuity and functional recovery. Most applications are market‐driven, and building owners deploy an SHM system at their own expense so that they can promptly assess the condition of their buildings as one of the tags denoted “Green,”“Yellow,” or “Red.” In 2015, the authors’ group began installing such an SHM system, and as of December 2023, 553 privately owned buildings have been equipped with this SHM system. This opinion paper presents the authors’ experiences to date on monitoring, utility of data, and interaction with building owners. It conveys three opinions that the authors believe to be most interesting, particularly in the context of the benefits of the “Caution (Yellow)” tag. The article briefly introduces SHM, followed by the specific system in question and the data accumulated over the years in Japan. The first opinion is that the damage criteria, that is, the boundaries among the three tags, should not be considered permanent but subject to updates based on experience and newly acquired data. The second opinion is that SHM is one of the best means to characterize the damage (and fragility) of major nonstructural elements, while “Caution (Yellow)” has inherent relevance to the nonstructural damage, particularly for initial damage states. The third opinion is that “Caution (Yellow)” is a good message for building owners and managers with a solid contingency plan that includes readily available building maintenance workers and engineers. On the contrary, it tends to frighten building owners and managers when such a contingency plan is absent, discouraging them from installing SHM. Overall, it presents some valuable insights of interest to those wishing to further such SHM systems on a broader scale.