Investigating out-of-plane strength & stiffness of a nailed glulam connection

During March 2020 a large-span arena, Tarfalahallen, collapsed. The main load-bearing girders with a 54 m span were high and slender glulam trussed beams, supported from below by a cable system via vertical struts. Investigations concluded that the failure was initiated by out-of-plane buckling of the struts and slender beam, in spite of lateral stabilization by steel roof sheeting at the top edge of the beam and by glulam rods at the lower end of the strut where the cable system was attached. The nailed connection between strut and main glulam beam was not stiff enough to prevent buckling. In this study a nailed connection similar to that used in the arena, though on a smaller scale, was tested under combined bending and axial loading. The biaxial testing simulates vertical loading in the strut combined with out-of-plane loading created by second order effects. It was found that the out-of-plane stiffness is reduced when vertical loading is at high levels.