The fifth set of systems covered in this synopsis is systems that combine fuses, rocking and self-centering. This includes structures with walls prestressed with partially unbonded tendons, hybrid systems for frames and shear walls, SCPT beam-column connections in steel frames, self-centering steel frames with rocking beams and base plates, rocking frames with metallic structural fuses, and structures with SC-SPSW and PT connections.

Azuhata et al. (2008) investigated self-centering systems composed of rocking structural members, in which part of the system was allowed to uplift during an earthquake. This system can prevent steel building structures from yielding and suffering from excessive residual drift after severe earthquakes by using the effect of building’s self-weight to self-center the structure. Force deformation relationships of the rocking structural members, the self-centering ability of the system and the energy dissipation mechanism were investigated by means of numerical models.

Simple rocking systems allowed the structure to uplift and can be applied to slender building structures. Rocking systems with footing dampers controlled the uplift response, and coupled rocking systems connected two rocking systems and improved energy-dissipating performance when compared to other methods.

Azuhata et al. (2008) investigated a steel frame system with a rocking mechanism composed of rocking structural members, coupled braced units with yielding base plates and one-side rocking beams. Dampers were used as connection devices between two narrow braced frames and were allowed to deform only vertically, as shown in Figure 8. Each braced unit was connected to the base of the structure by thin base plates. The structure could rock by means of wings at the base plates. This configuration allowed for replacement of vertical dampers after yielding.

Hajjar and Eatherton et al. (2009, 2010, and 2011) examined a steel braced frame with controlled rocking and energy-dissipating fuses. They investigated the behavior of the system and its components, validated the expected performance objectives, studied the limit states and recommended construction details (Ma et al. 2010 and Hajjar et al. 2010, 2011). A number of different types of fuses and different fuse configurations under varying ground motions were tested (Hajjar et al. 2009, 2010 and Ma et al. 2010). They demonstrated the viability of the controlled rocking system as a method of self-centering the entire building via use of hybrid simulation (Hajjar et al 2010); and the cyclic behavior of the components through large-scale testing (Hajjar et al 2011).

The structure is comprised of dual elastic steel frames allowed to rock about the column bases, vertical post tensioning strands for self-centering, and replaceable steel fuse plates to dissipate seismic energy through yielding. The purpose of this structure is to increase self-centering capabilities, dissipate seismic energy, assure high resilience of the system when subjected to large story drifts, and to use fuses that can easily be replaced after an earthquake.

In addition to analyzing the behavior of the controlling rocking system, several configurations of fuses were also examined (Hajjar et al 2009, 2010, and 2011). Fuses were located between two frames or concentrated at the central base of the frames. The work culminated with shake table tests to validate the dynamic response of the system at two-thirds scale (Ma et al. 2010).