4.1.8.21.Supplemental Energy Dissipation

(1) For the purposes of this Article and Article 4.1.8.22., the following terms shall have the meanings stated herein: (a) “supplemental energy dissipation device” is a dedicated structural element of the supplemental energy dissipation system that dissipates energy due to relative motion of each of its ends or by alternative means, and includes all pins, bolts, gusset plates, brace extensions and other components required to connect it to the other elements of the structure; a device may be classified as either displacement-dependent or velocity-dependent, or a combination thereof, and may be configured to act in either a linear or non-linear manner; and (b) “supplemental energy dissipation system” is a collection of energy dissipation devices installed in a structure that supplement the energy dissipation of the SFRS. (2) Every structure with a supplemental energy dissipation system and every portion thereof shall be designed and constructed in accordance with (a) this Article and Article 4.1.8.22., (b) other applicable requirements of this Subsection, and (c) appropriate engineering principles and current engineering practice. (See Note A-4.1.8.21.(2)) (3) Where supplemental energy dissipation devices are used across the isolation interface of a seismically isolated structure, displacements, velocities, and accelerations shall be determined in accordance with Article 4.1.8.20. (4) For the analysis and modeling of structures with supplemental energy dissipation devices, the following criteria shall apply: (a) a three-dimensional Non-linear Dynamic Analysis of the structure shall be performed in accordance with Article 4.1.8.12., (See Note A-4.1.8.21.(4)(a)) (b) for an SFRS with Rd > 1.0, the non-linear hysteretic behaviour of the SFRS shall be explicitly—with sufficient detail—accounted for in the modeling and analysis of the structure, (c) unless verified from rational analysis, the inherent equivalent viscous damping—excluding the damping provided by the supplemental energy dissipation devices—used in the analysis shall not be taken as more than 2.5% of the critical damping at the significant modes of vibration, (d) all supplemental energy dissipation devices shall be modeled with sufficient detail to account for their non-linear force deformation characteristics, including effects of the relevant loads, and with consideration of variations in their properties over the design life of the structure, and (e) except for the SFRS and elements of the supplemental energy dissipation system, other components of the structure shall be modeled using elastic material properties in accordance with Sentence 4.1.8.3.(8). (5) The ground motion time histories used in Sentence (4) shall be (a) appropriately selected and scaled following good engineering practice, (b) compatible with a 5%-damped response spectrum derived from the design spectral acceleration values, S(T), defined in Sentence 4.1.8.4.(6), and (c) amplitude-scaled in an appropriate manner over the period range of 0.2T 1 to 1.5T1, where T1 is the fundamental lateral period of the structure with the supplemental energy dissipation system. (See Note A-4.1.8.19.(4) and 4.1.8.21.(5))