Episode 106 - Mast Frame: Rethinking Seismic Systems

In this episode, we take a deep dive into mast frames a hybrid seismic system that challenges the traditional boundaries between elastic and energy‑dissipating components. Using the Samuel Merritt University project as a case study, we unpack why the design team stepped away from conventional BRB‑only frames and moment‑frame/dual systems, and instead embraced a BRBM (Buckling‑Restrained Brace + Mast) approach.

We explore how mast frames redistribute stiffness, improve drift control, and preserve architectural openness in ways that standard systems struggle to match. From nonlinear response history analysis to capacity design of mast members, we walk through the technical decisions that shaped the system. We also get into the practical realities detailing strategies that allow the mast to rock, base connections that handle massive overturning forces, and the construction challenges of erecting a tall, stiff truss inside a transparent building.

Finally, we zoom out to discuss where mast frames fit in the future of seismic design. Will hybrid systems like BRBM become more common in dense urban environments? How might codes evolve to better capture their behavior? And what lessons should engineers carry forward before attempting a similar system on their own project?

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