 Good afternoon. My name is Tomasz Owiacki and I represent team from Krakow University of Technology, Poland. Thank you for my previous speaker, Antonio, for very nice presentation and good introduction because I also want to say a few words about application of distributed optical fiber sensor technology for strain monitoring in concrete. And I'll put my attention on researchers, which are researchers which were carried out in our laboratory in Krakow and on challenges which still remains to deal with. Today most of structural health monitoring systems are based on spot measurements and they have their advantages but also limitations. I think that future of structural health monitoring system is to perform measurements of physical values along structural member and this is possible by using optical fiber strands. For example, black ratings or fabric perot interferometers allow us for quasi-continuous measurements but what is the most interesting from engineering point of view, we are able to use relay, Raman or Brilliance scattering to monitor, for example, strains or temperature continuously along the strand. In all researchers, which I'll be talking about, we have used optical fibers with relay scattering. Some exemplary tests which were carried out before, for example, they have created rainforest concrete beams which were tested in four point bending test. Local fiber strands were embedded into these elements and also glued to the surface and they obtained trapezoidal distribution of strains and they were able to localize the crack location but they were difficult to estimate the width of this crack. And the second point is that the shape of the strain distribution was unchanged during the following load stages so it seems that we are able to predict the localization of crack even in early stage when we are not able to see it with naked eye. Okay, now few words about one of our tests. We have prepared a concrete sample of 300 millimeters height and 150 millimeters of diameter. The individual optical fibers strand was glued to the surface of this sample in that way that we have created five measurement sections. Three, longitudinal, which corresponds to compressive stress and to circumferential which corresponds to tensile stress. Sensor base along this optical fiber was five millimeter. We have also external extensors meters to verify the whole process. And researchers were divided into stages. Firstly, we have compressed this sample until 40 megapascals and later until destruction. Here you can see the photos from the test and the sample after destruction. And this is the most important plot I want to show you today. And few northward remarks. Firstly, we have individual optical fiber strands so we have obtained only one plot but on this plot we are able to select five measurement sections. One remark that with theoretical analysis in LSTC range and assumption of homogeneous concrete, this plot should be constant. And that information we would obtain from traditional spot measurements because such kind of sensors average strains on some measuring base. So using optical fibers we are able to recognize reality in much more comprehensive way than in traditional ways. And next point is that this longitudinal strains which corresponds to compressive stresses are much more smoother and we do not observe such local extremes like in this circumferential strains which corresponds to tensile stresses. This local extremes of course corresponds to localization of cracks. And the last point that the shape of our strain distributions in following load stages is unchangeable. So we are able to predict the place of crack before it will be visible with naked eyes. And in the early stage these cracks do not affect behavior of structural member. Because we analyze data in two domains, time and length, we are able to create 3D plots. Here we have measuring length and time of loading for circumferential strains so tensile stresses. And here we can see exactly these local extremes but in the longitudinal strains this plot is much more smoother and this has its own. So mathematical justification for example variation of coefficient for longitudinal strains it is 36 percent for circumferential 45. Some problems which still remain to do but I always said that engineers do not have a problem but he has a challenge to deal with. We should create computational algorithms for crack with estimation because it strongly depends on material, on the way of mounting. We should estimate accuracy and usable range for compressed strains as well as tensile strains. We should estimate the best way to mount these optical fibers depending on material. We can analyze transmission length so the length on which the strains are fully transferred for the strand from structural member. We try to do measurements in remote and automatic way. We can analyze correlation between longitudinal and transverse strains which is quite important when we are talking about effort of structural member. Okay and possible advantages of such kind of technology, early warning about abnormalities, damage detection in early stage of loading, crack monitoring in reinforced concrete structures which also is important in context of durability, monitoring of engineering structures, pipelines, dimes, distributed strain and temperature measurements, reducing cost in SHM systems. That's the question you asked before and I think that this acquisition systems which is now quite expensive in next few years will be much and much cheaper so we'll see. And of course development of science and I want to conclude with words of one of some famous Polish professors who said that the only true model of Elasticity is this body so especially in engineering science, theory is not enough and we have to search some devices, improved devices which will help us verify theory in practice. Thank you for your attention.