IWSHM 2017: Quantifying the benefit of structural health monitoring: what if the manager is not the owner?

Abstract

Only very recently our community has acknowledged that the benefit of Structural Health Monitoring (SHM) can be properly quantified using the concept of Value of Information (VoI). The VoI is the difference between the utilities of operating the structure with and without the monitoring system. Typically, it is assumed that there is one decision maker for all decisions, i.e. deciding on both the investment on the monitoring system as well as the operation of the structure. The aim of this work is to formalize a rational method for quantifying the Value of Information when two different actors are involved in the decision chain: the manager, who makes decisions regarding the structure, based on monitoring data; and the owner, who chooses whether to install the monitoring system or not, before having access to these data. The two decision makers, even if both rational and exposed to the same background information, may still act differently because of their different appetites for risk. To illustrate how this framework works, we evaluate a hypothetical VoI for the Streicker Bridge, a pedestrian bridge in Princeton University campus equipped with a fiber optic sensing system, assuming that two fictional characters, Malcolm and Ophelia, are involved: Malcolm is the manager who decides whether to keep the bridge open or close it following to an incident; Ophelia is the owner who decides whether to invest on a monitoring system to help Malcolm making the right decision. We demonstrate that when manager and owner are two different individual, the benefit of monitoring could be greater or smaller than when all the decisions are made by the same individual. Under appropriate conditions, the monitoring VoI could even be negative, meaning that the owner is willing to pay to prevent the manager to use the monitoring system.

Quantifying the benefit of SHM: can the VoI be negative?

“…In this chapter, we review the concepts of the VoI, presented in detail in (Bolognani, et al, 2018). In the classical formulation, which we will refer as unconditional, i.e.…”

“…We propose now, a new formulation for the quantification of the VoI, which we will refer as conditional, for the specific case of two separate individuals involved in the decision chain (Bolognani, et al, 2018). We use the indices (M) and (O) to indicate that a quantity is intended respectively from the manager's and owner's perspective.…”

“…The bridge and its monitoring system are illustrated in much detail in a number of publications (Glisic & Adriaenssens, 2010) (Glisic & Inaudi, 2012). The SHM-based decision problem, the assumptions and the individuals involved, are the same as in (Bolognani, et al, 2018). The bridge is managed by two fictitious agents with distinct roles: Ophelia (O) the owner responsible for Princeton's estate, who decides on whether or not to install the monitoring system; Malcom (M) the manager responsible for the bridge operation and maintenance, who has to take decisions on the state of the bridge based on monitoring data.…”

“…Consider now the monitoring system installed. Ophelia's and Malcolm's pre-posterior expected utilities of doing nothing, respectively (O) u * DN(ε) and (M) u * DN(ε), depend on the posterior probability of having the bridge damaged p(D|ε), which in turn depends on the monitoring observations ε, as reported in (Bolognani, et al, 2018). As rational agents, Ophelia and Malcolm will always take the decision related to the minimum loss.…”

“…In the classical literature of the VoI, the main assumption is that all decisions concerning system installation and operation are taken by the same rational agent. However, we must recognize that in the real world SHM-based decision processes are typically more complex, with more individuals involved in the decision chain (Bolognani, et al, 2018). Indeed, even oversimplifying, we always have at least two different decision stages.…”