The study moves from the current debate about the suitability of the unidirectional tests regulated in the standards, and aims at investigating the effect of the displacement trajectory on the evaluation of seismic isolators. A 3D finite element thermal-mechanical model of a Curved Surface Sliders is formulated, and numerical analyses are performed considering unidirectional and bidirectional displacement-controlled orbits. The temperature rise at the sliding surface is calculated from the software and used to adjust at each iteration step the coefficient of friction of the bearing. The results of the analyses examining different orbits are compared in terms of maximum shear force, dissipated energy and temperature rise on the surface of the thermoplastic pad. The conclusions point to the fact that the unidirectional tests provide a conservative evaluation of the bearing performance, but are not suitable for determining the bearing properties that are needed for accurate nonlinear response history analyses. Furthermore, unidirectional tests tend to underestimate the temperature rise induced from bidirectional trajectories.
