NIST documents, as well as the FEMA/ASCE Building Performance Study report, frequently cite a paper by John Salvarinas entitled “Seven World Trade Center, New York, Fabrication and Construction Aspects”. He presented the paper at the 1986 Canadian Structural Engineering Conference. Salvarinas was project manager for Frankel Steel Limited on construction of 7 World Trade Center.

The paper details challenges faced by structural engineers in designing the building, due to the presence of the Con Edison substation that was built in 1967. The substation and caissons built into the foundation were designed to support a building atop it at a later time, but one that would have been ~25 stories tall, with a footprint the same size as the substation. Instead, 7 World Trade Center was a 47 story building, with a much larger building footprint. Design modification had to be made, including installing additional caissons and incorporating a system of gravity column transfer trusses and girders was located between floors 5 and 7 to transfer loads to the smaller foundation. There were some other unusual features from the seventh floor down to the ground level. Salvarinas also details the construction process and gives information about steel used in construction of the building.

The paper is difficult to find, but recently NIST sent me a copy of the paper. As a service to readers, to save you the trouble of finding it, the paper is posted here:

* Seven World Trade Center, New York, Fabrication and Construction Aspects - by John J. Salvarinas (3.7 MB PDF)