Experimental analysis of new moment resisting steel connections

In the recent past, the authors proposed a new steel device devoted to representing an innovative moment resisting connection for steel frame elements called LRPD (Limited Resistance Plastic Device). It is a steel element characterized by symmetry with respect to three orthogonal barycentric planes and constituted by a sequence of three portions with abrupt cross section changes, each of one identifies a steel element of suitably designed geometry. LRPD possesses the following characterizing features: any elastic flexural stiffness variation with respect to the original selected member must be avoided; the bending moment resistance must be an appropriate reduced percentage of the original beam bending resistance; any local instability phenomenon must be avoided ensuring a full plastic deformation field. In previous papers the deep description of the geometrical and mechanical features of the device and the optimal design formulation are reported. In the present paper a first stage of experimental campaign on the mechanical behaviour of LRPD is presented. Specifically, the pure bending behaviour of LRPD is investigated by performing the four-point bending test. The test is performed monotonically until the selected ultimate plastic bending moment acts on the specimen. The mechanical response of LRPD, both in terms of deflections as well as of axial strains is evaluated by means of suitably positioned displacement and strain gauges. The experimental test is performed on LRPD designed for HEB240 cross section beams. The obtained results confirm the expected performance of LRPD constituting a fundamental step for the subsequent experimental steps mainly constituted by cyclic tests.