In the thesis, we design and analyze a prestressed concrete "V" beam which is part of the roof structure of a reinforced prefabricated concrete hall. The beam is 28.08 m in length and 1.0 m in height. The beam is prestressed with 22 flat tendons and a part of them are neutralized on both ends. The calculation is made in accordance with the requirements of Standard SIST EN 1992-1-1:2005. In the first part of the thesis, we checked the stress and strain state of the beam for serviceability and ultimate limit state. In calculating its serviceability limit state we checked the stress, the width of cracks and deflection of the beam. In calculating its ultimate limit state we checked shear and the bending resistance of the beam. In our calculations, we took into account the loss of prestressing force, the effect of heat treatment on loss of prestressing force, and the mechanical characteristics of the actual installed materials. The analysis of stress and strain state of the cross-section was made using Microsoft Excel software. In the second part of the thesis, we present the results of the tests carried out by the Italian company Pre System S.p.A.. The test consisted of computer-calculated as well as measured deflection of a load test according to a characteristic combination of loads. In the third part of the thesis, we calculated the beam by using non-linear calculation methods with NFIRA computer software. We found that the results from all three parts of the thesis correspond well.