Experimental testing of a bolted connection system for precast concrete load-bearing panel structures

The paper presents the result of an experimental programme carried out at Politecnico di Milano to characterize the local mechanical behaviour of a connection system for precast concrete load-bearing wall panels recently patented based on the combination of vertical bolted and horizontal headed connections. The vertical connection consists in a threaded bar, protruding from the bottom panel, bolted to a cast-in steel plate, anchored in the top panel above by means of rebars through a circular slotted washer allowing for large production/assemblage tolerances. The horizontal connection consists in a milled pipe steel element located in an upper recess of the panels which hosts headed studs protruding from each panel (up to a maximum of four elements). An upper square ring is finally installed to provide lateral confinement to the joint. This process eases the correct positioning of the wall panels, minimizing the use of external diagonal props for their positioning. Quasi-static monotonic tests, employing up to four jacks acting simultaneously, were carried out to evaluate the bearing capacity of the joints under the individual and contemporary action of shear and axial load. Both mortar filled and bare conditions simulating transitory assemblage phases were tested.