D+ was the grade that the ASCE gave to America’s infrastructures in their 2013 Report Card.
This grade is assigned based on eight criteria: capacity, condition, funding, future need, operation and maintenance, public safety, resilience, and innovation. According to the grading scale used, the infrastructures are in “poor to fair condition and mostly below standard, with many elements approaching the end of their service life” . Although it is a slight improvement from the last Report Card, this grade shows that America’s aging infrastructures are failing to keep pace with the current needs of the country. This problem is particularly apparent in older cities, comprised of numerous masonry structures. As the bricks and mortar get older, they become susceptible to several kinds of deterioration that make the structure unsafe.
Reliable infrastructures are critical for the population’s safety and health but also for long-term economic growth, increasing GDP, and employment . In this regard, more attention needs to be given to the maintenance of existing infrastructures. Currently, most infrastructures have their condition evaluated via visual inspection. Unfortunately, this method remains very subjective and fails to be comprehensive. Masonry structure’s deterioration can be very apparent as shown in figure 1, but in some cases, it is not as easy to identify. Models based on the initial structure design produce a more objective evaluation; however, the numbers computed with these models have a significant lack of precision due to the changes that structures undergo over time. It is essential to develop a new condition assessment method that is more reliable and impartial.
This need led to the creation of a new specialization of Structural Engineering: Structural Health Monitoring (SHM). It aims to help engineers improve the safety and increase the longevity of critical structures through the use of advanced damage detection technology. SHM is becoming widespread in Civil Engineering and it was even used to monitor the performance of the 2008 Olympic venues in China . Several techniques can be used to carry out SHM; Structural Identification (St-Id) is one in which a great amount of research has been conducted lately. It is attractive because it makes it possible to reduce the gap between the constructed structural systems and their structural design models. The focus of this research is the application of Structural Identification (St-Id) to unreinforced masonry structures for SHM purposes.
The Structural Identification Paradigm
Structural Identification (St-Id) is a developing area of Structural Engineering that has the potential to resolve a number of the issues pertaining to the maintenance of existing structures. The paradigm was first introduced to Structural engineering researchers by Liu and Yao (1978)  and has been defined as: “the parametric correlation of structural response characteristics predicted by a...