Numerical and experimental investigation on angle multiple slit bolted connections for precast wall panels

Flat Multiple Slit Devices (MSDs) have been introduced in steel constructions located in earthquake-prone areas as compact hysteretic dampers connected to braces, and were further proposed to be employed also in other structural typologies, including aligned precast concrete walls. Nevertheless, similar angle connections needed for horizontal joints of orthogonal walls are not tackled in literature. The shape of MSDs, obtained by selective weakening by removing part of the steel area of flat plates, may allow to attain a highly ductile and stable dissipative behaviour, given local plate buckling is avoided, protecting the bolted joints through capacity design. Laser cutting as an alternative to mechanical milling introduces the possibility to easily optimise the shape of the slits in order to attain better performance under laterally imposed cyclic load. This paper analyses the application of right-angle-bent MSDs for the horizontal connection between orthogonal precast walls typical of panel structures with rigid diaphragms. In particular, bolted angle plates with hourglass-shaped multiple slits obtained after laser cutting are investigated numerically via non-linear finite shell elements and experimentally with original cyclic tests. The effect of the aspect ratio of the plate and of the restraint condition, possibly affecting the performance under imposed shear deformation due to the presence of the bent corner, is investigated by parametric analysis. Finally, general design rules and recommendations are presented.