Modal and Seismic Response of a SMF with Living Roof Systems
Denise Steffen
School of Engineering
Faculty Supervisor: Jenna Wong
This research investigates the seismic performance and structural dynamics of a SMF structure incorporating living roof systems. While living roofs offer significant environmental benefits, the substantial mass of deep soil layers, often exceeding 12 inches, presents unique challenges for structural resilience in high-seismic regions like the San Francisco Bay Area.
Using finite element modeling in ETABS, this study compares the dynamic response of structures with varying roof assemblies, focusing on the shift from shallow to deep systems. The analysis specifically evaluates how the increased dead load and potential soil saturation affect the building’s fundamental period, inter-story drift, and mode shapes from applied ground motions. Results indicate that while the soil mass provides a degree of supplemental damping, the inertial forces generated during a seismic event significantly impact the lateral force-resisting system.
The findings emphasize the necessity of accounting for peak saturation weight in structural calculations to prevent overstressing members. This study provides a critical framework for engineers to balance sustainable urban design with rigorous structural safety standards, ensuring that intensive living roofs can be safely integrated into modern, resilient infrastructure.