The diamond of innovation for UPWr

The St. Stanislaw, St. Dorothy and St. Vaclav Church in Wrocław has the largest gothic roof truss in Poland. The wooden structure of the church measuring nearly 24 metres – similar to an eight storey residential building – was constructed around 1400, underwent two major renovations at the beginning of the 19th and 21st centuries and was lucky not to suffer any damage in a fire or war. The truss was elevated above surrounding buildings which makes it greatly vulnerable to weather conditions, mainly wind. Thanks to its location it has been, for the last few years, a test station for scientists from the UPWr Institute of Building Engineering. The “imodos” group (Interactive Measurements of Deformation of Structures), i.e. Maciej Orzechowski and Radosław Tatko PhDs are researching deformations and complex movements of the truss construction. As it often happens, also in this case necessity was the mother of invention.

- We began by measuring deformations with draw-wire sensors placed in the plane of roof trusses. It quickly turned out that measuring deformations of such a large construction only in this plane, with one sensor for one measuring point, does not make sense. Construction displaces spatially rather than on a plane – says doctor Orzechowski. – We had an idea to connect three sensors into a group. Their indications will show us spatial displacement vector from the initial point to the point in a given displacement moment.

- Path sensors which we use in our research are commonly used in various areas of industry where they are supposed to control the displacement of some elements in relation to others – in magnetic resonance, airplane platforms or cranes. They always control the displacement of one point in relation to a point to which the sensor is attached on the direction linking these two points. It must be pointed out that in a structure like the roof of St. Dorothy’s Church there are many elements – beams and poles – which make the measurements harder – adds Radosław Tatko.

Draw Wire 3D is a system which allows displacement of any point to be measured in any direction in the 3D space. For the sake of lab tests a metal structure was made in the form of a cubic frame. The frame is stiffened with steel ropes connecting its corners. At the same time the ropes imitate obstacles which have to be overcome when measuring the displacement of a given construction element. Draw-wire sensors are installed on one of the frame poles, wires from the sensors go out in any different directions to intermediate points on the cube and only from there to a measuring point placed on a wooden element whose displacement is measured by Draw Wire 3D. Thanks to a simple mechanism using a Roman screw any displacement can be forced on a researched element. The measurements are registered with a tenth of a millimetre accuracy.

- Of course as scientists and practitioners we are thinking of implementing the system. We want our device to be used in industry. Thanks to our own definition of displacement coordinate system we are no longer limited by the wire direction and we can measure practically everything, for example displacement of a laptop on a desk if somebody wishes – explains doctor Orzechowski. The new application for sensors, their grouping and writing appropriate software were awarded with the Diamond of Innovation which the “imodos” group won at the IV International Building & Interiors Exhibition Warsaw Build 2016.

- When it comes to the research in the church, we are waiting for… the wind – laugh the scientists. – Constructions are built with regard to normative loads, e.g. wind load. Normative wind speed is 22 m/s. According to this norm wind would have to blow with such speed for ten minutes incessantly. The problem is that the probability of such a wind is only 63% in a period of 50 years. Since we established our test station at the St. Stanislaw’s, St. Dorothy’s and St Vaclav’s Church, wind has never blown with such a speed for more than a few seconds. Of course we don’t limit ourselves to examining the influence of wind on the construction but we still hope, we’ll be able to “catch” it. And, since we are frequently asked about it, our observation of the church construction does not mean there’s something wrong with it. On the contrary – it has just been renovated and it’s not threatened in any way. Our test station is purely for scientific research – sums up Tatko.

mj