Tests on ductile short-length splice connections for precast concrete load-bearing elements

The use of mechanical connections for the main load-bearing elements (columns and walls) in the precast construction sector is recently increased worldwide mainly thanks to the advantages of reduced crane time, avoidance of external diagonal props, stability in temporary phases, and replacement of in-situ pouring of a large volume of concrete with a small volume of mortar. This paper presents the experimental outcome of a novel structural connection system recently patented by DLC Consulting S.r.l. providing splicing of the vertical reinforcement through two typologies of bolted connections installed on flat surface elements: one based on a mechanical device to be employed in the minimum number required by verticality regulation and temporary bearing capacity and one based on traditional splicing. Both systems employ nutted high-strength threaded bars which, in combination with proper local reinforcement, allow to dramatically reduce the standard splicing length in the range of 12-15 times the diameter of the bar. The results of quasi-static monotonic tensile tests carried out at the LPMSC Laboratory of Politecnico di Milano, encompassing different embedment length, bar diameter and local reinforcement detailing, show the possible over-strength and ductility of the proposed connection systems.