A new device for stress monitoring of ancient masonry buildings: Pilot study and results

Abstract

Summary The need to obtain the mechanical characteristics for analysis and understanding of the mechanical behaviour of historic buildings is highlighted. Destructive tests and non‐destructive tests are widely used for this purpose; however, they only provide a value associated with a specific instant. Structural health monitoring contributes to the monitoring of specific processes before, during, or after an intervention. Nevertheless, among the available sensors, there is a lack of devices for continuous monitoring of stress variations undergone by masonry structures. In response to this need, a new stress‐measurement device for structural monitoring of masonry structures has been developed. It has the aim of determining the initial stress in masonry structural element and providing continuous control of the evolution of the stress variation. The article describes the design of the device, as well as its implementation in a historic building. Moreover, an assessment is performed of the stress variations registered in comparison with the displacements recorded in the monitored areas, as well as the influence of the thermic fluctuations on these. A good relation was confirmed between these measurements. The results demonstrate that the designed device proved to be a useful tool for monitoring structural strengthening interventions.

Device for continuous assessment of uniaxial stress of existing masonry structures: Laboratory validation

“…As for the stress variations, it should be said that once the SFJ test was over, a slightly decreasing slope was registered, considering stabilisation from the first of September 2017. Bearing in mind this behaviour, it is important to highlight that it is necessary to overpressurise the device to compensate for the possible relaxation over time of the material of the pressure pad and/or the readjustment of the surrounding masonry structure itself . However, in this experimental campaign, it was not necessary to perform this overpressurisation, given that the stress at the end of the SFJ test was sufficiently higher than the value of the cancelling pressure to take that effect into account (Figure ).…”

“…Bearing in mind this behaviour, it is important to highlight that it is necessary to overpressurise the device to compensate for the possible relaxation over time of the material FIGURE 10 Evolution of the deformations undergone for each pair of monitoring points for several stress levels of the pressure pad and/or the readjustment of the surrounding masonry structure itself. 24 However, in this experimental campaign, it was not necessary to perform this overpressurisation, given that the stress at the end of the SFJ test was sufficiently higher than the value of the cancelling pressure to take that effect into account (Figure 9).…”

An integrated structural health monitoring system for determining local/global responses of historic masonry buildings

“…Throughout the intervention process on the building, a detailed monitoring of the most relevant elements (arches, buttresses, domes, and walls) was done through the sensors implemented in the Subsystems 2–4. However, considering the mechanical characteristics of the materials and the magnitude of the intervention processes in the building, the article highlights the monitoring of the three most significant actuations: Execution of the passive reinforcement in the load‐bearing east wall consisting of a reinforced concrete frame (Figure a), partially closing some gaps opened in an intervention previous to the monitoring period, so enabling the communication between the east cloister to the church. The equipment utilized for the monitoring of this actuation was included in Subsystem 2. Removal of the propping system from the domes after reinforcing them (Figure b).…”

“…With respect to the initial behaviour of the sensors, it should be indicated that the difference between the initial stress taken as a reference during the continuous follow‐up and the service stress value determined corresponded to the tasks of over‐pressurization of the pressure pad . After this actuation, the behaviour observed in the devices in the first stages showed a slight downward slope associated with the readjustment of the system “pressure pad—masonry structure” under maintained pressure.…”

“…Throughout the intervention process on the building, a detailed monitoring of the most relevant elements (arches, buttresses, domes, and walls) was done through the sensors implemented in the Subsystems 2-4. However, considering the mechanical characteristics of the materials and the magnitude of the intervention processes in the building, the article highlights the monitoring of the three most significant actuations [32,33]…”