Nonstructural Component Seismic Spectral Accelerations in Two Existing Steel Buildings with Supplemental Damping

Lessons learned from previous earthquakes and the results from some analytical research studies have indicated that basic building code equations for seismic forces on nonstructural components may not return sufficiently accurate force values under certain circumstances. Floor accelerations and their effects on nonstructural components can be highly variable due to characteristics such as varying structure nonlinearity, building-specific dynamic characteristics, input ground motions, and geometric configurations. Ensuring that nonstructural components meet specified building code performance criteria is important for maintaining the safety of structures during and after a design-level seismic event. The seismic performance of nonstructural components may be of increased concern for high-importance facilities that must remain operational following an earthquake. As a result of lessons learned from recent earthquakes, more attention has also been paid to the seismic performance of nonstructural components in low-level seismic events that do not cause structural damage. The results of nonstructural seismic analyses of two west coast pre-Northridge steel moment frame buildings are presented. Nonstructural component spectral accelerations were calculated from the floor acceleration results of nonlinear response history analysis models. Nonstructural component accelerations were numerically calculated across a range of periods to develop response spectra. The analysis results obtained from the nonlinear response history analyses are compared against equations from ASCE 7-10 Minimum Design Loads for Buildings and Other Structures and ASCE 41-13 Seismic Evaluation and Retrofit of Existing Buildings. The implications of assumed nonstructural component damping are also discussed. The information presented highlights some questions for designers and academics to consider for use in practical design. In addition, the results highlight some challenges in conducting computationally intensive, detailed analysis on nonstructural components using current code provisions.