Seismic response of a braceless seismic restraint system for suspended nonstructural elements

Nonstructural elements present a high seismic vulnerability due to their susceptibility to exhibit damage under low seismic intensities. Even though a supporting structure remains unaffected by seismic actions, nonstructural damage can generate large economic losses, loss of functionality, and loss of operability. Similar to structural systems, nonstructural elements can be equipped with seismic protection systems to either reduce their seismic demand or improve their seismic performance. This study explores numerically the implementation of a braceless seismic restraint for suspended nonstructural elements. The proposed system is composed of a vertical hanger connected to a rotational hysteretic damper that provides supplemental damping in the direction of interest to control the seismic response of the suspended nonstructural element without the need for sway braces. A three-dimensional suspended piping system, located on the top floor of a nine-story steel moment-resisting framed building, is considered as case study, including pipes running in both transverse and longitudinal directions. Nonlinear time-history analyses were conducted using the equivalent floor motions obtained from the FEMA P-695 far-field ground motion set. The peak displacements and residual displacements were used to compare the seismic response of the proposed braceless seismic restraint with that of a conventional braced channel trapeze restraint installation. The numerical results indicate that the proposed braceless seismic restraint exhibited smaller median peak displacements compared to those of the conventional braced channel trapeze. Additionally, due to the concentration of the inelastic response in the rotational hysteretic damper, the proposed braceless seismic restraint exhibited comparable residual deformations and smaller, if any, induced damage compared to the conventional braced channel trapeze