Non-residential single-story older steel buildings: Effects of design options and envelope panels on seismic fragility.

The paper describes a study that is part of an Italian research project (named RINTC), which is addressed to assess the seismic reliability of existing structures made of RC, masonry or steel. Within the project, among the case studies nonresidential single-story steel buildings were selected and analyzed by the authors of this paper. First, the design of the steel buildings was simulated according to structural codes and standards of practice used in Italy in the 1980s-1990s. Different structural systems were generated starting from the same structural layout, consisting of five trussed portals in the transverse direction and concentric braces in the longitudinal direction. The main differences between the case studies were in (i) column base and (ii) truss-to-column connections for the portal frames in the transverse direction, (iii) brace cross section and (iv) brace connections for the longitudinal direction. 3D non-linear finite element models were built in OpenSees. Analyses were carried out including or excluding envelope panels from the structural model. This paper describes first results, comparing the structural response for different types of connections in the portal frame direction. Furthermore, the paper presents relevant collapse fragility curves, emphasizing the effect of envelope panels.