A Preloaded Spring Damper (PSD) is a unit designed to dissipate seismic energy on structures such as bridges. The PSD reduces longitudinal and transverse displacement of the deck.  Jarret Structures can provide two types of PSD: working in tension/compression, or acting only in compression.  Jarret Structures can install the PSD compression type longitudinally between the deck and the abutment, or install a PSD tension/compression unit in transverse between the deck and the pier structure.  The PSD acts as a shear key which has the possibility to regenerate itself automatically after a dynamic event.  The seismic energy is dissipated in the PSD unit instead of being dissipated in a steel or concrete structure.  Jarret Structures can accommodate transverse and longitudinal displacement such as creep shrinkage and thermal expansion or contraction.