End Plate Moment Connections with Superelastic Shape Memory Fasteners

In the Northridge earthquake more than 150 structures experienced brittle fractures in their welded moment connections.  The brittle failure of welded connections was also noticed in the Kobe earthquake.  Ductility in the components of structural systems has been demonstrated to be very effective in dissipating vibrations induced due to seismic activities. Researchers have identified that the ductility of structural components and systems would truly enhance structural performance subjected to dynamic or earthquake loads.  Recently, shape memory alloy (SMA) materials, which have two characteristics known as shape memory and superelasticity effects, have been used for seismic applications in structural systems. This is due to SMA’s high energy dissipating capabilities and their ability to endure large strains without undergoing permanent deformation.
This study compares the energy dissipative characteristics of end plate bolted moment connections using steel and SMA fasteners. The initial phase of the study focused on the calibration of the finite element model of the SMA superelasticity effect with the existing experimental results of the SMA rod.  Then the end plate moment connection models were subjected to cyclic loadings. Using the steel and/or SMA bolts, hysteresis results from the finite element analyses were compared in order to determine the effectiveness of the superelasticity capabilities of the SMA in dissipating energy.