Experimental study on structural performance of 7A04-T6 high-strength aluminium alloy shear connections in and after fire

Abstract

The present study addresses the structural behaviour and design of 7A04-T6 high-strength aluminium alloy double shear connections under elevated temperatures and post-fire conditions with air cooling. A total of thirty-three connection specimens, featuring different fastener types and geometric characteristics, including end distances and edge distances, were tested under varying temperature histories, ranging from 20 to 400 ℃. An electric furnace was employed to heat the connection specimens, while digital image correlation (DIC) technology was employed to record displacements of the specimens during testing. Three distinct failure modes were observed in the tested specimens, namely the bearing, shear-out, and net section tension failures. The experimental results obtained from this study were compared to the predictions generated by the current design methods outlined in the American specification (AA), European standard EN 1999–1-1 (EC9) and Chinese code GB 50429 (GB). The comparisons revealed that the design rules often exhibit conservatism in predicting the ultimate resistances of 7A04-T6 high-strength aluminium alloy shear connections under elevated temperatures and post-fire conditions. Notably, EC9 emerged as providing the most accurate predictions for both resistances and failure modes of the investigated shear connections.