The project: Full-scale seismic retrofit, architectural, and MEP renovation of 651 Gateway, an existing 17-story, steel-framed office building into a life science laboratory.

The goals: Improve seismic performance while maintaining the building’s current square footage and flexibility of the floor plate and also provide a structural design that accommodates the architectural and MEP upgrades, stiffening the floor systems to accommodate laboratory space.

Project approach: The design team used performance-based design, nonlinear response-history analysis (NLRHA), and innovative engineering solutions and details to make the renovation and adaptive re-use efficient, affordable, and environmentally sustainable.

Challenge: Retrofit column splices in a way that the overall seismic performance for the building was improved, without the need for costly and invasive strengthening of the existing deep foundation system. Solution: The design team used a combination of conventional strengthening splice retrofits, and also developed an innovative sleeve retrofit. With this alternative detail, a built-up steel tube was installed around the column splice. The plates comprising the tube were welded to the column below the splice, and the section of column above the splice was left unattached but confined. The detail allowed columns to fracture if they experience large axial tension demands but restrain the column against horizontal movement so that it returns to its initial position.

The outcome: The structural solution of fluid viscous damper frames, coupled with thoughtful brace layout and detailing, and a state-of-the art NLRHA, led to a pronounced improvement in seismic performance. The building went from being collapse prone to meeting basic safety objectives with recoverable performance. In the retrofitted structure, story drift levels are well below new building standards, residual drift is minimized, and reduced lateral accelerations protect nonstructural systems and critical laboratory equipment. With the exception of upgrades to existing column splices, the damper solution eliminated the need to strengthen or retrofit nearly any other existing element, including moment frames, eccentrically braced frames, base plates, and foundations.