Perimeter Column Data
Chapter 2 of the NIST document NIST NCSTAR 1-3: Mechanical and Metallurgical Analysis of Structural Steel indicates that the perimeter columns were 14 in (35.56 cm) in width and 13.5 in (34.29 cm) in depth for all of the columns from the 9th to the 107th floor. This data is shown in the following figure from the NIST document.
Regarding the thickness of the steel used inthe perimeter columns, the NIST document makes the following statements:
Perimeter columns in the upper stories were typically fabricated of lighter gauge steel, most commonly 0.25 in (6.35 mm) ...
In contrast to the upper stories, in the lower stories, the perimeter column flanges were as thick as 3 in. (76 mm) and typically made of lower strength steels.
Fourteen grades of steel were used in the construction of the perimeter columns with minimum yield strengths of 36, 42, 45, 46, 50, 55, 60, 65, 70, 75, 80, 85, 90, and 100 ksi. No further information is given on the transition points in the columns from one thickness to another and one grade of steel to another.