Experimentation with tension-only devices for use with seismic energy dissipation systems
Seismic damage-resistant structures, such as jointed precast connections and rocking wall structures, usually require supplementary energy dissipation devices to limit peak displacements. Yielding steel fuses or buckling restrained braces (BRBs) can provide energy dissipation but have a tendency to create residual compressive forces after joint closing that can resist the re-centring of the structure and fight the post-tensioning forces on subsequent cycles. A ratcheting, tension-only device has been developed to offer resistance to loading in tension, while offering negligible resistance to compressive motion, and can be used in conjunction with a range of energy dissipation mechanisms. This lack of compressive forces allows re-seating of a rocking connection to minimise residual structural displacements. Upon re-loading, fuse engagement will be more rapid due to the ratcheting mechanism, as the absence of residual compressive loads reduces the amount of elastic take-up before yielding occurs. A tension-only solution also removes the requirement for buckling restraint to be designed into the fuse element. Two prototype ratcheting mechanisms have been designed and experimentally tested in an MTS-810 test machine with fuses providing a yield force of 45 kN and an ultimate tensile force of 65 kN. Experimental proof-of-concept testing on fourteen fuse elements demonstrated the function of the ratcheting mechanisms and assessed the hysteretic behaviour of each system. The influence of tooth pitch is investigated experimentally, varying from 3-40 mm in the different prototypes.