Fatigue Behaviour of Bolted Connections Applied in Racking Structures. Experimental Perspective

Abstract

Racking systems, applied in logistics warehouses, are often built using zinc-coated thin steel plates that are joining by bolted connections. In fully automatic systems, these structures are loaded 7/7 days and 24/24 hours raising fatigue issues due to the cyclic nature of the resulting stresses. FASTCOLD project intends to provide fatigue design rules because until nowadays there is no reference about fatigue rules of bolted connections between thin-walled cold-formed steels, under diverse preloaded bolts, including snug tight condition. This work revealed differences between S-N curves suggested by Eurocode 3 and fatigue data obtained experimentally. In addition, preloaded bolts presented better fatigue resistance than snug tight bolts; the use of multiple bolted joints also improves the fatigue resistance due to the joint effect of bolts. Failed specimens showed that if the bolts preload and applied load level are respectively high and low enough, the specimen failures occurs along the gross cross-section, near the hole vicinity, instead of the typical net cross-section failure as occurred in single and multiple connections with snug tight bolts.