Abstract:

Passive energy dissipation (PED) devices are useful to enhance structural performance by reducing seismically induced structural damage. Metallic dampers are one such PED. When they are designed such that all damage is concentrated on the PED devices, allowing the primary structure to remain elastic, they can be defined as structural fuses (SF). A comprehensive parametric study was conducted to investigate the SF concept, and to identify combinations of key parameters essential to ensure adequate seismic performance for SF systems. Non-linear time history analyses were conducted for several combinations of parameters, chosen to cover a range of feasible designs. Viable combinations of parameters are identified and used to provide guidelines to design and retrofit systems using Buckling-restrained Braces (BRBs), Triangular Added Damping and Stiffness (T-ADAS), and Shear Panels (SP) as examples of metallic dampers working as structural fuses. Studies focus on the application of the structural fuse concept to single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) systems. As part of this research, floor demands velocities and accelerations are also investigated, with the objective of assessing the applicability of the structural fuse concept to protect nonstructural components.

As a proof of concept to the developed design procedure, an experimental project was conducted on the shaking table at University at Buffalo, which consists of a three-story frame designed with BRBs. Two types of BRBs with different types of connections were used in this test: BRBs with moment-resisting connections, and BRBs with pin connections, manufactured by Nippon Steel Corporation (Japan) and Star Seismic (USA), respectively. This experimental project also assesses the replaceability of BRBs designed as sacrificeable and easy-to-repair members. These BRBs are connected to the frame by removable and eccentric gusset-plate, especially designed to prevent performance problems observed in other experimental research. Design and behavior of this type of connection is also investigated here. Another objective of this test is to examine the use of seismic isolation devices to protect nonstructural components from severe floor vibrations in buildings designed per the structural fuse concept. The seismic isolation device consists of a bearing with a spherical ball rolling in conical steel plates, a.k.a. Ball-in-Cone (BNC) system. (Abstract shortened by UMI.)