Tests and Design of Welded-bar Angle Connections of Precast Floor Elements

Welded floor-to-floor connections are widely employed in dry-assembled precast concrete decks with the main aims to stiffen the diaphragmatic action under horizontal loads and increase robustness of the construction. Bars or slugs are often preferred to plates for their smaller room, better allowance, and cost-effectiveness. Despite welded bar connections are mentioned in many official design codes, their design rules are not therein specified, which was only recently done in ISO Standard 20987:2019 on simplified design guidelines for mechanical connections between precast concrete structural elements in buildings. This standard is the result of EU's Safecast Research Projects FP7-SME-2007-2 and GA 218417:2009, in the framework of which many structural connections of precast structures were tested and investigated at different scale levels, although specific local testing of welded bar connections was not carried out. Thus, the quoted ISO formulation lacked from direct experimental check. This paper aims at filling this gap by presenting the results of shear tests on floor-to-floor connections made by bars welded to rebar-anchored inclined angles. The tests were carried out considering anchorage rebars having different shape and diameter. Moreover, the validity of the currently available ISO design rule is commented, highlighting a disproportioned degree of conservativeness referring to concrete spalling failure. An updated formulation is proposed based on a novel mechanical behaviour model matching the experimental observations and results.