Restraint Performance of Stud Connection during Lateral-Torsional Buckling under Synchronized In-Plane Displacement and Out-of-Plane Rotation

Generally speaking, steel beams are mechanically assembled with a concrete slab and stud shear connectors. The concrete slab works as a restraint against buckling instability such as lateral and lateral—torsional buckling of a steel beam. During an earthquake, the concrete slab is subjected to fully reversed stress. Previous studies have shown that the concrete slab begins to crack under tensile stress and that the composite effect is considerably degraded more than under compressive stress. The restraint effect therefore possibly degrades under negative bending. Eventually, beams have less than their expected lateral and lateral—torsional buckling strength. To alleviate this concern, cyclic loading tests were conducted on a component model of a composite beam subjected to in-plane displacement and out-of-plane rotation. Furthermore, the formulae for evaluation of the ultimate rotation strength and stiffness were constructed considering the influence of the stud specification and loading protocol.