 My short-term scientific mission took place in the May of this year, at Ljubljana, at Slovenian National Institute. The name of my STSM is Application of Bridge Weight and Motion Measurements in Assessment of Existing Growth Bridges. So bridge weight and motion measurements are one method of structural part of structural health monitoring. And I will try to demonstrate to you how I have used it with my mentor and my host in order to assess the existing bridge on load carrying capacity. Some general information. It took place for only three weeks in May at Slovenian National Building and Civil Engineering Institute, known as ZEG. My host was Mr. Aleš Nidaric. Unfortunately, he's not here today. And let's eat about general information. Now I want to talk about purpose of my STSM because in order to go to the STSM, you have to write a really good and efficient work plan. And especially because it was only three weeks, we had to prepare everything in advance. So my main purpose was to study and analyze application of bridge weight and motion measurements. I will explain what weight and motion is in the second slide if somebody here is not familiar with it. It's a method of structural health monitoring and to application of measurements in load carrying capacity assessment of existing bridges. Long-term outcome, which we are hoping that will come in the next two years of my PhD, is to create a valuable link between a certain monitoring tool, so structural health monitoring tool, and structural performance of interest. In this case, it's existing bridge reliability, which is showed through bending moment capacity or shear force capacity. The main focus during three weeks, which I spent at the institute, was to relate bridge weight and motion data, which they have on real bridges, with theoretical bridge models developed in Sophistic software, which we are doing at our faculty, and to combine those two data in order to upgrade our models and obtain more realistic results. The main motivation was that at the moment, me and my mentor are working on development of multi-level assessment method for existing road bridges, mainly because a lot of existing bridges in Croatia, and now I'm talking about smaller, small and medium-sized bridges, are constructed in the 60s and 70s years of last century, and a lot of them doesn't have proper shear reinforcement, a lot of them is in bad condition, and if we want to assess them in load carrying capacity or reliability, if we use current European standards for design of new bridges, we don't get good results because of the conservative assumptions that are in current European standards in Eurocodes, which are good for designing of new bridges, but when assessing existing bridges, a lot of bridges turn out that they need reconstruction or even they need to be demolished and replaced. So, in this multi-level method that we are trying to develop, weight and motion measurements are one of our input parameters, and the opportunity to work with world leading expert in VIM technology in Ljubljana was too good to be passed, and along with that, along with theoretical knowledge, I had the opportunity to go with professional personnel on field measurements on existing bridges where they show me how they decide how many sensors would they put, where would they put the sensor, how long the measurement should take place, etc. And about the weight and motion measurements for you, if there's you who are not familiar with it, that's a method of measuring vehicles as they drive over measurement sites, so sensors, but the main advantage is that it measures vehicles at full speed, so they don't need to slow down or stop, and we have two types, we have weight and motion or VIM and bridge weight and motion or known as BVIM. Weight and motion on regular roads requires sensors like this, and you have to drive over them, and they are providing you with a lot of useful information like total weight of the vehicle, axle number and spacing of every vehicle, weight of every axle, speed and correct timestamps of the vehicle, but the problem with regular VIM is that you need to shut down traffic in order to put sensors, and these sensors are very sensitive because a lot of heavy traffic is going through them, so the idea that started in America approximately 30, 40 years ago is bridge weight and motion, you use simple and small bridges as instrumented scales, so you use the superstructure of the bridge as a scale and we put the sensors, strain gauges on the bottom side of the bridge, and with influence line method, we can provide with the same data without stopping traffic for a longer period, the only period when we need to stop traffic is when we put all the sensors, then we only need to do a calibration with a truck of familiar size and weight, so it's really minimum traffic interruption and sensors are placed really quickly, they are wireless, so they are working, they are measuring for a time period that you set, it's often or two weeks or a month, and also in Slovenia there is a couple of constant measurement sites which are measuring all the time, and along with these data we can also get realistic influence lines of the bridge which can tell us a lot about bridge structure, dynamic factor, and transverse load distribution, or load distribution if we have a girder bridge, then distribution in transverse direction, and that information is quite essential because it can tell us is there any cracks or hidden deteriorations in structure, so to start with my STSM we made a work plan in four steps, in order it's a multi-level assessment method, we choose a case study bridge in Slovenia, and we decided to do assessment in four steps in order to show quantification of this data provided by VIM measurements. First step is load carrying capacity assessment according to standard for design of new bridges and based only on theoretical model made in FEM software. Second step is that we'll modify the model with realistic influence line, third step is that we modify the model again with a real load distribution, and fourth step is that we will not use Eurocode traffic load models, but we will use site-specific load effects which are calculated from VIM measurements. Of course in practice it would be logical to take these three steps at time, not separately, but here we've done it separately so that results can show in every subsequent level how does this data is helping and quantifying the assessment of existing bridges. Only a short description of case study bridge, so this bridge is located in Slovenia, it's simply supported highway bridge, it has single span of 24.8 meters, its superstructure is consisted of five prefabricated girders with a concrete deck above, it is highway bridge so it has emergency lane, driving lane and overtaking lane. We chose this bridge because we have enough bridge-weighted motion data in order to develop a real traffic load model and we had original designs, plans from the archives, so we had reinforcement and pre-stressing designs and from them we can calculate resistance to bending moment and shear force. I developed a 3D model in Sophistic Software, it's based on grillage method in order to obtain the real load distribution from deck to each girder and I added, it's a simply supported bridge, but I added additional rotational springs on supports which in first step they are not used but they will be used later when we use realistic influence line because we will see that in reality bridge behavior is not 100% simply supported and we use permanent actions, permanent actions from dead load and traffic loads are taken into account. So we are not using horizontal forces, wind break forces, etc. First level, so we use a procedure from Eurocode for design of new bridges, we are using partial and safety factors from materials, theoretical influence line from this model and transverse load distribution also from the theoretical model. Permanent action are based on original plan, traffic load is according to Eurocode load model 1 and we did an analysis in Sophistic Software. I will show you the results from all four steps at the end of the diagram so you can see the quantification but this was the first initial level where everything is strictly theoretical based on Eurocodes. In second level, I calculated an influence line, theoretical influence line from my model and from VIM data we calculated a real measured influence line and as you can see them here, this one red is theoretical and it has a shape for a simply supported beam or bridge and the blue one is measured so we can see that there is a difference here and that our bridge is not 100% simply supported. So what we've done, we tried to modify our existing model with additional rotational stiffness on these springs in order to simulate it and try to achieve that our influence line in the model would be the same as the one that we measured. So we did that in several tryouts. We've done an influence line with a different rotational stiffness. This here is rotational stiffness, CM, Sophistic is calling it CM and we've done a multiple rotational stiffness in order to see which one fits best for the measured influence line. This is without rotational stiffness and this is this one with rotational stiffness on 10 on the power of 8. So we choose this one, 10 on the power of 6 and we did a modification to our model and with that we got reduced bending moments at the middle of the span which was already changed our results and we obtained smaller bending moments. So that is the second step. In the first step we done a comparison between measured and theoretical transverse load distribution which is very useful because it can discover any type of degradation even non-visual degradation and in our case we got results as expected because there was no visible signs of degradation. Bridge is in a very good condition and you can see this is load distribution to every girder. Measured is a blue one and from Sophistic is a red one. The only significant difference is on girder 5 but girder 5 is on the right side of the bridge in emergency lane and it's not loaded so much and other girders are in couple of percentages difference between Sophistic and measured load distribution and we can conclude that there are no significant degradations, cracks or anything on our girders and this method, this procedure can also not only show us degradation but can also show us construction flows. For example, if the connection between girder and the superstructure deck is not done correctly then we could see that we can notice that on this load distribution because it would be a big difference. So this is internal level and we didn't modify the model because it's almost the same so the results were the same as a level before. And in fourth level with statistical post-processing of weighted motion data we created convolution curves for traffic load effects. In this case it's bending moment in the middle of the span so it's basically done that every vehicle that goes across the bridge its load effect is calculated and saved and then all those vehicles are put into histograms for each lane and then we convolve the histograms. It's a bit of process, it's a method developed by Mr. Znidaric and his colleagues at the institute. It's very interesting but we don't have enough time for that but with extreme value theory we can extrapolate that data in order to get expected load effects for some time period. We choose here time period of 75 years and this is the convolution curve. For deterministic procedure we use the upper characteristic value 95% and for probabilistic because we've done a probabilistic check at the end we use the mean value and standard deviation. So with all that we can see the results now. These are girder 1 to 5. This is bending moment at the middle of the span in first initial level done by Eurocodes. This is the second and third level as they are the same. It's with modified influence line and the fourth step is with modified influence line and traffic load model developed from WIM data and we can see how bending moment in the middle of the span is decreasing which is of course good and here graphically we can see the ratio between bending resistance and bending moment in the middle of the span. It's increasing in every step of course for girder 5 it's the biggest because it's not loaded so much as it is on emergency line. So this graphic maybe shows the best the quantification of WIM data in bridge assessment. As we started for example this girder 2 it doesn't pass the initial test on step 1 because this is the bending resistance and this is the bending moment. So if we try to assess it with Eurocodes we would get that it needs rehabilitation or at least some strengthening and if we use our data from monitoring, from measurements we can see that its resistance is more than enough for a traffic load on that bridge. The same results are shown here because we also done a probabilistic check with the limit state equation and statistical parameters for each variable. These are the results shown as calculated reliability index beta. You can see them here in the first step, in the second and third step and in fourth step of assessment procedure. Targeted reliability level is 3.8 for design of new bridges according to Eurocode and for existing bridges there is a really good articles by these two authors and they have targeted reliability index for existing bridges and from their article for bridge of similar age target is 3.7 but even that is not enough for a girder 2 in first step. So again it would have to be reassessed or reconstructed or strengthened and in second, third and fourth step we can see that reliability is more than enough for traffic load on that particular bridge. And with conclusions we can see that the results clearly show the quantification of these measurements as a part of structural health monitoring for assessment of existing bridges and from economic aspect of course some cost benefit analysis is needed in order to make comparison between initial investments and measurements and reduction of bridge maintenance cost during the bridge lifetime. We haven't done anything like that but colleagues from the institute in Slovenia they done something for Slovenian road directorate and with very, very good results showing that baby measurements are absolutely effective. And also in bridge management this data and these measurements can be used for early discovery even of non-visible degradation as shown in step 3 with that low distribution. So it has multiple applications on our targeted goals and that's it for me. Thank you for your attention.