The Wilkie D. Ferguson Jr US Federal Courthouse in Miami. Norman McGrath Photographers, Inc.
Protective Design, which became a Thornton Tomasetti practice in September 2015, provided blast analysis and design services for construction of the 557,000-square-foot federal courthouse located on a two-block site in downtown Miami. The building consists of two 14-story towers joined by a curving glass prism that encloses the public circulation and waiting spaces. The facility houses tenants such as the U.S. District Court, General Services Administration, U.S. Attorney’s offices, U.S. Probation offices, U.S. Marshal’s offices and Federal Public Defender offices.
Built to Protect
To comply with GSA Security Criteria, the project included perimeter site security features such as bollards, planters and benches to guarantee standoff distance from the adjacent public streets, a blast analysis and design of the building structure, façade hardening and mitigation against progressive collapse. Unique design features included hardening of the exposed two-story columns at the ground floor level that support the two 14-story towers and special detailing that was required to allow for deep post-tensioned beams spanning in two directions supporting a mild steel reinforced slab.
Multi-Hazard Design Approach
The building façade, including the glass curtainwall, punched windows and precast panels, had to satisfy both the Southern Florida Building Code requirements for high winds and projectiles and the GSA Security Criteria blast design criteria. This proved to be particularly challenging for the ground floor storefront glazing system, which was subject to the large-missile debris impact hurricane requirements, per the building code. The robust glass assemblies required for debris impact resistance acted as load collectors for the design blast pressures. This had a considerable effect on the design of the storefront framing members and connections, since the GSA Security Criteria required the capacity of these elements to be balanced with the selected glass assemblies. Through careful detailing of the glass bite enclosure, Protective Design was able to limit the loads transferred to the framing members, satisfy both the building code and blast design requirements and maintain the overall architectural design intent for the storefront system.
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