Introducing a framework for determining the financial value of Structural Health Monitoring on maintenance management of bridges; The case study of the effect of SHM on retrofitting of a bridge

The safety of bridges as the vital arteries of cities is of great importance. There are several factors that raise concerns about the safe performance of bridges, and resolving these concerns are dependent on the appropriate decision-making of urban managers throughout the service life of bridge. These factors can be divided into two major types. The first type are factors affecting the safety of a part or whole structure of bridge and producing concerns about the bridge collapse. For easing the danger of collapse, totally or partially, a proper decision should be made to improve the behavior of a specific part of bridge at a certain time during its service life. The second type are factors influencing the safety of one or more bridge elements and increasing the life cycle costs of bridge. To prevent the growth of bridge costs due to deterioration, an appropriate plan for repair and maintenance should be implemented in order to enhance the condition of one or several elements.  In order to make the right decision, it is necessary to obtain accurate information on the condition of bridges. One of the best ways to get this information is to use bridge health monitoring. Health monitoring is the process of information acquisition from structure by installing sensors on its components and analyzing the data obtained from implemented sensors. By bridge structural health monitoring and interpreting the gathered data, the access to accurate and timely information, which is consistent with the reality of the bridge structure, is provided. Having the correct information about the bridge, the managers can decide at a lower level of risk. However, choosing specific monitoring strategy among different health monitoring systems for a bridge is a challenge that should be solved. A Quantitative index is needed to find the best technically and economically monitoring system.  The value of information (VoI) analysis is used for determining the effectiveness of monitoring information in decision-making. VoI is a method which quantifies the price of information and specifies the cost-effectiveness of decisions made on the basis of monitoring. This analysis also makes it possible to choose the most economical monitoring strategy among several alternatives. In the VoI calculation, all the uncertainties involved in the performance of a Health monitoring and probabilities of any anticipated event are considered. Thus, the decision making based on VoI is risk-based and reliable especially for important structures like bridges. In this paper, after investigating the worries and solutions for eliminating worries about the bridges in detail and introducing the applications of structural health monitoring (SHM) systems for bridges, the equations governing the VoI analysis is presented and the procedures for determining the VoI is discussed, and as an example, the VoI analysis of a bridge is discussed. According to the results of this analysis, implementing a specific amount of strain gauges with specific accuracy can provide worthy information about the bridge safety for the manager. Moreover, by the VoI analysis, the best approach for sensing system of SHM in the bridge is determined.