Analysis of Load Capacity of Roof Trusses with Imperfections and the Issue of Equivalent Load Adoption

The internal forces and stresses were analyzed and utilization of the design resistance in selected members of the roof structure with local and global geometrical imperfections was evaluated. Values of these imperfections were based on the information given in the standards EN 1090-2 and EN 1993-1-1. Besides the basic reference model with imperfections, models without imperfections, with different equivalent load arrangements by the authors’ own concept and comparatively according to the standard EN 1993-1-1 were analyzed. The calculations were made using the 1^st and the 2^nd order analysis. Conclusion concerning accuracy of the internal forces estimation and limit states check by use the equivalent load system proposed in the standard EN 1993-1-1 are presented. Deficiencies in the provisions of this standard in terms of adopting equivalent loads in roof structures with imperfections, resulting in underestimation of the stresses in the bottom chords of the roof trusses, has been demonstrated.