Case Study: Roof Truss Structure With Large Cut Out and Elliptic Glazing Surface

The article presents the technical solutions implemented during the design of the roof trusses and the elliptic skylight structure (Figure. 1) for the extension of the "Shopping City Sibiu" commercial centre in Romania. The area of the roof structure was approximately 1600 sqm (29x56 m). In the central region of the roof, a 27 m long and 10 m wide elliptic skylight was placed. The challenges of the project arouse from the relatively large span of the structure, being supported only on 13 non-symmetrically placed perimeter concrete columns. Thus, the structure had to be designed in such a way, that it would support the extra 20 tones coming from the skylight structure, while also bring inside the natural light unobstructed by any main structural elements. The relatively large deformations between the supporting points of the skylight under variable loads (especially snow loads) can also have adverse effects on the glazing surface during operational phase. Due to this, also the serviceability limit state checks had an important role in the engineering calculations. The structural configuration steps with performed analyses on the partial structural models and on the complex 3D model were especially useful for the identification of the sensitive zones, helping to create the surface shape and develop adequate structural details. The paper summarizes the structural engineering challenges during the design and execution process.