Challenges:NYA encountered an extraordinary web of complexities that required innovative solutions to preserve the historic architectural finishes of the building while increasing the seismic ductility and safety of the building. With rising construction costs, the efficiency of the structural solution was critical in making the project feasible. One of the most challenging features that impacted the structural system of Metro 417, was accommodating the existing occupancy and the architectural requirements of retail space at street level and parking flow while preserving the historic elements.
"Because of all the elements involved – the abandoned subway tunnel underneath the building, the two-story podium and the five independent wings of the building – this project was such a unique challenge.”
- Nabih Youssef, president of NYA
Solution:New punched shear walls interlaced with existing masonry struts and Unreinforced Masonry (URM) testing was used to help complete this project. NYA utilized the inherent stiffness and strength of the URM infill, rather than ignoring its seismic contribution, as would be required in a new structure. To do so, an in-situ testing program using a hydraulic flat-jack test apparatus was created to obtain and utilize the stiffness and strength of the existing masonry. Using the obtained parameters, a non-linear finite element analysis was performed for each URM panel, confined by a single steel beam-column bay. The force-displacement relationship of the URM was obtained, with the cracked section iterated at each non-linear step, and then modeled as an equivalent steel strut in the global three-dimensional
Due to the knowledge collected and techniques employed in the subway terminal building, the project was contributed as a case study for the City of Los Angeles' adaption of ordinance and cost modeling of adaptive reuse buildings, further protecting many of the city's historic 20th century buildings, and making it feasible to reuse much of the existing office space throughout the historic corridor.