 all three presentations and then we'll have a discussion. So with this I would like to invite the first speaker from the University of Migno, Maria Giovanna Maciota, who will present the value of structural health monitoring for the structural behavior of masonry structures under varying environmental effects. Have you heard? This is just a brief outline of the main points I'm going to talk about during my presentation. First of all I will start with a focus and scope of my study. Then I will show you the general framework underlying my work. I will go through the case study describing the structure we analyzed, key performance indicators we identified and tracked over time, and then I will talk about the warning levels and threshold value condition we define. And I will finally go to the conclusion. Well since we are here I guess we all know why structural monitoring is important so I'm not going to spend too many words about that. But one comparison I always like to make when I talk about structural monitoring is the fact that we engineers act on structures the same way doctors act on human bodies. So basically we start with an amnesis of the structures, we collect all past information about the structure, we gather all possible data and we do a condition serving, then we move to a diagnosis phase. So we study the symptoms of the structures and from there we go back to the building pathology and then from there we move to, we address a certain therapy so we choose remedial measures rather than other kind of certain remedial measure other than other kind of intervention and then we control over time the efficiency of the remedial measure we adopted. So stated that going back to the scope of my short term scientific mission, basically I tried to find a link between structural monitoring and performance assessment or rather I tried to show how to use the old information that we can collect through monitoring campaigns to assess, better assess the performance of our building of historical buildings in this case and how to integrate this information within a strategy for structural management proposals. This is the framework, underline my work, actually it's a general framework that can be adapted to any kind of structures, so not only to historical building as in my case. The first thing that I wanted to do before starting my work was having a systematic, setting a systematic approach in order to follow a step-by-step procedure and to reach my goal. This framework is in fact a step-by-step approach in which each step is kind of a piece of a puzzle that contributes to create the final picture. So once we know the structure we are going to deal with, we do this one inspection, we acquire all possible data and then we, in case of historical building, of course, with one historical investigation because it's very important to know the building phases of the structures and we collect as many information as possible to select the best key performance indicators that we can track over time in order to have a complete, sorry, diagnosis of the system and also to have the definition of treasure value condition and warning levels and to finally use all this information to effectively understand better the structural performance, to understand whether the structure is still meeting our life safety requirements or it's deviating from the target behavior. And then we can use all this background, all this information for structural management purposes. This is the case study structures I've been analyzing. It's the church of Santa Ricardo that is located in the Omonimos village, close by the Morfem cities of the Maras in Portugal. It's an historical church which construction started in 1825 and stretched over two centuries involving the work of three different architects. This is an hybrid cell temple because it's a mix of different styles, gaudy, classical and renaissance styles. This is the geometric survey of the church. As you can see, the church has a Latin cross longitudinal plan with a central nave heading into an abse that is oriented towards the north and a transept. The facade, each limb as you can see there from the picture is covered with a bare bolt and the crossing between the limbs is capped with a dome. The facade of the building is a gable facade with a central rose window and a tin pan here on the top and it's framed symmetrically framed by two spire towers which reach a total eight of about 58 meters. This is the damage survey of the church. The church was severely damaged because it presented here these big cracking patterns with cracks reaching over 50 millimeters here at the top. The major cracks was even crossing the whole thickness of the facade. Besides these big cracking patterns, there were several vertical cracks along the weakest link of the side walls of the church. Because of this severe damage in 1980-1998, the University of Munich organized a wide experimental campaign which included a condition survey, damage survey, visual inspection and also the installation of simple monitoring system to monitor the crack and the use of optical teodolite and so on, topographic survey, geotechnical survey to understand which was the building pathology. Basically, with the geotechnical investigation, was found out that the main cause triggering the big cracking pattern and also separation movement of the towers. It was the differential soil settlement in the street beneath towers and facade because basically the church is built on a slope which was leveled by a landfill bank. In the part, the bedrock layer is very close to the foundation of the system in the abscess and transit area, but it goes deeper and deeper while proceeding towards the front of the temple. Basically, this is causing an increase or worsening of the damage going towards the facade of the church. This is also causing a separation movement and tilting of the towers. This, of course, the situation can lead in a long-term perspective to the failure of the system. The experimental campaign allowed to understand that the most active part of the church was exactly the facade where there was this severed damage. Basically, both crack width and opening rate as well as the tilting of the towers were judged the critical factors reflecting the structural performance of the church. That's why they were identified as key performance indicators. Together with these key performance indicators, we decided also to take into account another indicator that is the correlation with ambient parameters. This is an important parameter to take into account in case of historical buildings because we all know that historical buildings are almost always built with messery. Messery is a porous material, so due to that, historical building can be extremely prone and sensitive to change of environmental condition, especially to change of temperature and moisture content because they can also close the opening and closing of the cracks. I'm talking about key performance indicators. Of course, we all know what they are, but in simple word, what are key performance indicators? Why are they important and how they can be tracked? Well, key performance indicators can be simply defined as key specific quantifiable measurements that help to establish baseline information on the current state of the system health, can help to set performance standards, can help to optimize the control of the structural integrity of the system over the operational lives and can help to quantify changes in the system response. How can we track them? It depends on the key performance indicators we select. In our case, since we are dealing with cracked-width tower stillting, we used a static monitoring system consisting of 40 meters, two per inch tower, one inch direction, two cracked meters, one for the crack on the outer side of the facade, another one for the crack on the inner side of the facade, two surface temperature sensors and one combined sensor for temperature and relative air humidity. This is the temporal evolution of both cracks opening rate and tower stillting over five years monitoring because the system is working since April 2009. If we look, for example, at the evolution of the crack opening rate over time, we can see that there is a linear increasing trend with reading an opening rate of 0.1 millimeter per year, which is higher in case of the external crack, which is alerted in red here. Regarding the tower stillting, we can see that both towers present a common trend, have this in-phase cyclical oscillation in both east-west direction and north-south direction, but the oscillation amplitudes are higher here for the western towers. In fact, also, if we look, they both have a common trend in leaning towards which south direction, but this is, of course, greater in case of the western towers here, where we reach also a tilting values of almost one millimeter per meter. This is the track of the Senghi performance indicators, but comparing also with the temperature on the top and with the relative humidity on the bottom. As we can see, with respect to the cracks, if we read at the coefficient of correlation here, at the bottom of the charts, with respect to the outer crack, there is a certain correlation even although it's rather weak. By the way, it's common like when the temperature increases, the crack with actually decreases and vice versa. This basically for the outer crack, because it's the one that is more exposed to the environmental conditions. Looking instead at the correlation with respect to the towers tilting and temperature and humidity, the coefficient and correlation are very high, especially with the temperature. In fact, the cyclic oscillations of the towers actually reflect the seasonal fluctuation of the temperature. With this inverse proportion in the sense, it depends on the orientation actually of the starting monitoring system. When the temperature increases, the towers are actually leaning towards south-west. When the temperature decreases, the towers are leaning towards north-east. Opposite is with the humidity because, of course, temperature and humidity have an inverse relationship between them. As I've shown before, the main cause triggering the big cracking pattern in the facade of the building as well as the separation movement of the towers is the differential soil settlement in the strata beneath towers and the facade. Since the progressive increase of tilting can lead over in a long-term perspective to a decrease of the tower stability, we decided to define some warning levels according to certain criteria so as to evaluate the current state of the structures and also to support the future decision on structural management. We defined three levels. We're corresponding action in a general way than probably in the future more specifically. In case of deviation from the target behavior, of course, the relevant warning level is issued. Each warning level is separated, of course, by respect to the other one, by a borderline. To set this borderline, we computed the traditional value condition by a stability analysis of the western towers. We took into account the western towers because it was, as I showed before, it was the one showing greater oscillation amplitudes and higher tilting values. For the stability analysis, we adopted a few assumptions. We considered the tower as a rigid body, so undergoing rotation movements about a fixed axis at the bottom of the foundation. The equilibrium condition is guaranteed if the resultant of the compressive forces, of course, is within the, not the section in this case, but specifically within the central co-inertia because we adopted the assumption of limit analysis to avoid tension because we use no tension material with infinite compressive strength and no sliding between units. That's why we consider as equilibrium condition the fact that the resultant of the compressive forces is within the central co-inertia, not only within a section. To solve, to find our treasure value condition, so we solved the basically an equilibrium equation, and we considered both the plan, so the east-west direction, which is the one parallel to the facade of the building and the north-south direction that is perpendicular to the facade of the building. And of course, we considered the whole system, composite by the tower, and the foundation. So the solution of the equation gave us the treasure value condition in terms of maximum tilt angles and maximum top displacement in both the direction, so we obtained the tilting angles with a pretty, I mean, the structure is safe, so 8 degrees and 18 and almost 4 degrees for the perpendicular direction, north-south direction, and these values correspond to the limit condition in which the resultant of the compressive force, compressive forces, it's tangent to the central co-inertia. So we compared this value, of course, with the current values of the structures, which are based not only on the tilt meters, but also on the survey obtained from the laser scanning, because the tilt meters, of course, are relative values. We tried to have absolute value from the laser scanning, and we compared and we could, of course, state that so far the structure is behaving within a target, within a normal range, so it's still in level 0, whereas, of course, to reach the alarm level, the structure, the variation of the tilt trend should change consistently, so far we are in a completely safe condition, but, of course, until now we worked, if we look at this chart on the vertical axis, what about the temporal axis, what about the time, or we are going to work on that too, so in order to do that we need to develop predictive model, and we are working on that, we are going to forecast the structure response into the future in order to estimate future inspection periods also, and to support, of course, a future decision on structure management, but before doing that we need to update our key performance indicators, because actually the structure last year underwent a strengthening intervention that was basically devoted to the elimination of the differential soil settlement, as well as the reduction of the tilting of the towers, so we monitored actually the structure throughout the intervention, we are going now to install a new monitoring system, dynamic monitoring system, so we will let not only crack with an opening rate and tower tilting as key performance indicators to track, but we will also monitor the natural frequencies and more shape of the structures, and also we will study, we will keep on studying the environmental variability of the system. Just a few remarks, of course, the assumption that I adopted for the limit analysis are simplification of the real, complex behavior of the matter in material, we should also take into account the solid structure interaction, because the rotational stiffness of the soil is important, because it can vary the outcome of the equilibrium analysis, and also we should always control the admissibility of the compression tensile stress in the structures, because high stress levels, of course, can cause, can lead the system to fail before the defined the threshold conditions, but what I wanted to show with my work, and it was that the information collected through monitoring campaign can be effectively and efficiently used within a strategy for the preservation of the historical buildings, and well-designed key performance indicators, as well as social value condition and warning levels are fundamental for structural management purposes. Thank you very much. Okay, thank you very much, Maria, for a very interesting contribution. So, from the...