The effectiveness of using a tuned mass damper (TMD) to improve a structures ability to dissipate earthquake input energy is investigated through the use of seismic fragility curves. Nonlinear material behavior of the structure is captured using the Force Analogy Method, the backbone for analytically quantifying the plastic energy dissipation in the structure. Numerical analysis was performed to study the global response and local energy dissipation of a six-story moment-resisting steel frame with and without a TMD installed for 100 simulated non-stationary Gaussian earthquake ground motions. The effectiveness of the TMD, based on reduction of seismic responses and enhancement of the seismic fragility, is considered at structural performance levels for Immediate Occupancy and Life Safety as identified in FEMA 440. An equivalent monotonic plastic strain approach a local measure of structural damage is used to correlate the seismic fragilities at different global performance levels based on story drift. Results illustrate that a TMD can enhance the structures ability to dissipate energy at low levels of earthquake shaking, while less effective during moderate to strong earthquakes, that can cause a significant period shift associated with major structural damage. This de-tuning effect suggests that an extremely sizable TMD is not effective in reducing damage of a structure.
Citation: The Structural Design of Tall and Special Buildings
Pub Type: Journals
Force analogy method, structural dynamics, energy dissipation, plastic energy, drift ratio, ductility, plastic strain, Gaussian process, response history analysis, fragility analysis