Metodbeskrivning och tillämpning i Strut-and-Tie metoden vid höga balkar

Sammanfattning: Deep beams have traditionally been calculated through experiments and estimations. The purpose of the Strut-and-Tie method is to design a truss with struts, ties and nodes and to calculate these. The method is by Eurocode 2 recommended to use for deep beams and the result will always be on the safer side because the actual capacity will always be equal to or greater than the truss.   The purpose of the study is to create a step by step method description on how to use the method and then apply it in a deep beam for a five-story building.   The study includes an FE-analysis of the sheet and of the truss. After that hand calculations will be made to control the strength and to dimension the reinforcement.  The wall sheet have three supports and the length is 12 m, 3 m high and 0.2 m thick. The result shows that the area reinforcement FS9150 will be needed along with 4 layers of 2Ø16 in the bottom of the deep beam and 5 layers of 2Ø12 in the top of the deep beam. It is also necessary to extend the middle support by 400 mm for the node to have enough capacity.   One difficulty with the method was to develop an optimal truss model. It was difficult to produce models that matched the direction of the forces in the sheet while getting the right angle between the struts and ties. In addition to that, there is also a recommendation to have as few struts and ties as possible. Making a model where all of these are taken into account is a difficult task. It is likely that the method gives a better result, the more experience the structural engineer has with the method.