A new hysteretic damper for seismic protection of highway bridges is presented. The Multidirectional Torsional Hysteretic Damper (MTHD) works based on torsional yielding of steel cylindrical cores. The device demonstrates a hyperbolic post-elastic stiffness as a result of its special working mechanism which produces this geometric hardening effect. The post-elastic stiffness was found to be effective in limiting the lateral displacement of the seismic-isolated bridge decks in near-fault. Results of nonlinear time history analyses revealed the adaptive behavior of the device which is a result of this gradual hardening feature, such that at lower displacements (DBE), force levels are close to a regular system while at highest levels of displacements (MCE), the device hardens to make the substructure yield and limit deck's displacement.