The Apex Hosiery Company factory building was designed by the Architect Frederick Muhlenberg in 1924 and remained in operation until 1954. The structure was constructed as a reinforced, cast-in-place concrete flat slab supported by round and rectangular concrete columns, with column capitals and slab drop panels. In 1967 the School District of Philadelphia (SDP) purchased the building and converted the facility for use as the Pennsylvania Advancement Middle School, which was later renamed the Roberto Clemente Middle School. After a new middle school was constructed to replace the building, it was closed in 2007. In 2013 a local developer began the process of purchasing the building from the SDP for conversion into an affordable housing development to be named the Roberto Clemente Homes. The development involved the partial demolition of the upper floors of the six-story building to a three-story building so that the height of the structure would reflect the height of the existing surrounding residential neighborhood of three story row homes.
Due to the collapse of an existing mercantile loft building in Philadelphia on June 5, 2013 onto a neighboring Salvation Army Thrift Store, six people were killed, and fourteen others were injured. As a result, the City of Philadelphia enacted an Ordinance requiring structures that exceeded three stories or 40-feet in height that were to be demolished to comply with the requirements of the new Ordinance. Provisions of the Ordinance that required the involvement of a qualified structural engineer included the development of a Site Safety Demolition Plan (SSDP) for permitting and Structural Special Inspection during the actual demolition phase. The primary aspects of the SSDP that involve structural engineering include determining that the existing structure can safely support the intended demolition equipment and debris, and that the method and sequencing of the demolition of the structure proposed by the contractor maintained the structural integrity of the remaining structure.
Pennoni was retained by the developer of the Roberto Clement Homes to peer review the SSDP submitted by the demolition contractor, perform a pre-demolition structural assessment of the existing structure, provide Special Inspections during the demolition operation and perform a post-demolition structural assessment of the remaining structure. As a part of the pre-demolition assessment it was determined that the building had been constructed using two different methods of construction; conventional two-way orthogonal reinforcing and the SMI system of reinforcing that involves the use of smooth, round concentric bars of reinforcing. As a result, Pennoni modeled both the two-way and SMI slab to confirm their ability to support the proposed demolition equipment and debris. In addition, recommendations concerning the sequence of demolition of the SMI slab were also provided to the demolition contractor.
The contractor had difficulty following the method of demolition recommended for the SMI, and as a result Pennoni also reviewed and provided input concerning the repairs developed by another engineer for the damaged areas of the SMI slab. Pennoni’s involvement with this projected helped to ensure the safe demolition and subsequent adaptive reuse of the structure.