Seismic actions induced by cladding panels to precast concrete frame structures

The strong earthquakes occurred in Southern Europe in the last decade pointed out a poor seismic performance of the connection system of the cladding of precast industrial structures. The cladding of these buildings usually consists of sandwich concrete panels of remarkable mass, connected to the frame structure with mechanical devices. The estimation of the out-of-plane seismic action on these connections is a key step for their correct proportioning. However, the formulation currently provided in the Eurocode 8 for the estimation of the seismic action on non-structural elements was calibrated with different objectives. Furthermore, given there is no in-plane structure-panel interaction, a quote of the panel mass is lumped in correspondence of their connection for a correct proportioning of the frame structure. The designers need to make assumptions on both aspects that often bring to remarkably different solutions. The paper presents a rigorous dynamic formulation of the problem of the vibration of rigid bodies connected with cantilever columns. The solution brings to analytical expressions to evaluate the exact out-of-plane action on the connections and the correct amount of panel mass to be lumped.