Skillnader vid horsiontallastberäkning mellan Eurokod och ”bygga med prefab”

Sammanfattning: The use of concrete in the construction industry goes back a long way, which in itself creates a huge amount of information that can be used to understand its properties and components. Through the many different calculation-methods that have been used over the years, new solutions have come and gone [1]. With many years of constructing different elements in concrete, a number of different standards have also been developed. Before the introduction of the Eurocode, there was a large number of documents that were applied for the same construction. One of these was ”betongelementföreningens handbok”. This book is based on several years of experience around a more specific niche in concrete, prefabricated industrialized building. As today's guideline means that the principles of the Eurocode are what today's standards should be built on, it is interesting to discuss which calculation method is best for prefabricated concrete elements. One of the corner stones of the Eurocode is that it should be versatile and suit the demand of all countries, while at the same time being sustainable and functional [2]. Differences in demand between the calculation methods mean that different things are taken into account. The purpose of the project is to provide Prefabmästarna AB with a basis for method change from the current dimensioning method to Eurocode. The aim of the report was to shed light on the calculation methods' difference in loads and moments that affect an example building. The frame consists of prefabricated concrete based on the company's requirements. The impact of the skew load differs between the calculation methods in that Eurocode uses reduction in connection with the building's number of stabilizing units and a reduction of the angle of incidence depending on the height of the building. According to "bygga med prefab", only a reduction factor is used that is affected by the number of stabilizing units in the building. The roof will have, for example, a skewload of 27,1 kn according to Eurokod and 56,6 kN according to ”bygga med prefab”. The moment of inertia was calculated in a similar way between the calculation methods, except that "building with prefab" takes into account the lateral stiffness that occurs in certain cross-sections. In this way, a fictitious reduction of the moment of inertia is applied, which depends on the height and width of the wall panel. The coordinates of the rotation center also differ. Eurokod had the same rotation center for all floors at the same time as the "bygga med prefab" rotation center separates the floor plans. The conclusion was that the total skew load and the calculation model of the moment of inertia differed between Eurocode and "building with prefab". This meant that the overturning load and torque that affected the building showed a difference in the resulting calculations. Eurocode calculations showed a reduction in loads and torque compared to "build with prefab" calculations. The load distribution of the calculation methods was equally designed where the percentage impact on each wall panel was the same. The calculations of loads and torques meant that a reduction in material use and oversizing was the basis for motivating the company to change the calculation method. The attachment was calculated on the basis of a model that corresponds to an arbitrary example of how the board is affected by the moment, but in addition to this, there are equivalent methods that lead to an even more favorable answer for the dimensioning.