{"description":"Structural and geometric data for WTC Towers 1 and 2, for modeling one tower. All values extracted from primary sources; NIST preferred over FEMA where both exist.","heights":{"wtc1_roof_ft":{"value":1368,"note":"Height of WTC 1 at roof level above the Concourse Level","source":"NIST NCSTAR 1-1, p. 7; also NIST NCSTAR 1, p. 5"},"wtc2_roof_ft":{"value":1362,"note":"WTC 2 was 6 ft shorter than WTC 1","source":"NIST NCSTAR 1-1, p. 7 (\"1,368 ft ... 6 ft taller than WTC 2\")"},"wtc1_antenna_ft":{"value":360,"note":"Antenna mast atop WTC 1 for TV/radio transmission","source":"NIST NCSTAR 1-1, p. 7"}},"plan":{"stories_above_grade":{"value":110,"note":"Plus 6 stories below grade","source":"NIST NCSTAR 1-1, p. 9"},"plan_dimensions_ft":{"value":"207 ft 2 in. by 207 ft 2 in. (based on column reference lines)","note":"NCSTAR 1 main report rounds footprint to 'about 210 ft on a side' with interior floors 'about 206 ft on a side'","source":"NIST NCSTAR 1-1, p. 9; NIST NCSTAR 1, p. 5"},"corner_chamfer_ft":{"value":"6 ft 11 in.","note":"NIST NCSTAR 1 main report says corners beveled 9 ft 9 in. (p. 5); NCSTAR 1-1 (detailed design report) says chamfered 6 ft 11 in. Prefer NCSTAR 1-1.","source":"NIST NCSTAR 1-1, pp. 8-9; discrepancy: NIST NCSTAR 1, p. 5"},"typical_story_height_ft":{"value":12,"note":"Story heights of typically 12 ft","source":"NIST NCSTAR 1-1, p. 9"},"rentable_area_ft2":{"value":10000000,"note":"About 10 million sq ft of rentable floor area in the two towers","source":"NIST NCSTAR 1-1, p. xxxvi (Executive Summary)"}},"perimeter_wall":{"columns_per_face":{"value":59,"source":"NIST NCSTAR 1-1, p. 8; NIST NCSTAR 1, p. 6"},"total_perimeter_columns":{"value":236,"note":"236 narrow columns, 59 on each face from the 10th to the 107th floor; additional columns on alternate stories at beveled corners carried no gravity loads","source":"NIST NCSTAR 1, p. 6"},"column_cross_section_in":{"value":"14 in. square welded steel box columns","source":"NIST NCSTAR 1-1, p. 8"},"column_spacing_in":{"value":40,"note":"3 ft 4 in. on center","source":"NIST NCSTAR 1-1, p. 8"},"spandrel_depth_in":{"value":52,"note":"Deep spandrel plates, typically 52 in. deep, interconnecting adjacent columns at each floor level","source":"NIST NCSTAR 1-1, p. 8"},"prefab_panel":{"value":"36 ft high by 10 ft wide panels, each consisting of three columns and three spandrels (3 columns x 3 stories)","source":"NIST NCSTAR 1-1, p. 88"},"below_floor_7":{"value":"Between Elevation 363 ft and floor 7, single exterior wall columns spaced 10 ft on center transitioned ('tree' assemblies) to three columns spaced 3 ft 4 in. on center","source":"NIST NCSTAR 1-1, p. 10"},"plate_thickness_taper":{"top_in":{"value":0.25,"note":"Columns in upper stories typically fabricated of plates as thin as 0.25 in.; FEMA 403 confirms exterior wall plate generally 1/4 in. in upper stories","source":"NIST NCSTAR 1-1, p. 11; FEMA 403, Ch. 2, p. 2-3"},"base_in":{"value":4,"note":"At the base, column plates as thick as 4 in. were used (FEMA); NIST NCSTAR 1-1 notes lower-story perimeter column webs 'often more than 2 in. thick'","source":"FEMA 403, Ch. 2, p. 2-3; NIST NCSTAR 1-1, p. 11"}},"gravity_load_share_percent":{"value":50,"note":"Exterior columns resisted total lateral (wind) loads and about 50 percent of gravity loads","source":"NIST NCSTAR 1-1, p. xxxvi (Executive Summary)"}},"core":{"plan_dimensions_ft":{"value":"approximately 135 ft by 87 ft","source":"NIST NCSTAR 1-1, p. 9"},"orientation":{"value":"Long axis of core oriented east-west in WTC 1, north-south in WTC 2","source":"NIST NCSTAR 1, p. 8"},"core_columns_count":{"value":47,"note":"47 core columns, fabricated primarily of 36 ksi and 42 ksi steels, decreasing in size at higher stories; four corner columns bore nearly one-fifth of total core gravity load","source":"NIST NCSTAR 1, p. 8"},"column_types":{"value":"Welded box columns at lower floors; rolled wide-flange shapes at upper floors; core box columns 36 or 42 ksi; core WF columns one of four grades 36-50 ksi, ~90 percent 36 or 42 ksi","source":"NIST NCSTAR 1-1, p. xxxvii (Executive Summary) and p. 11"},"layout":{"value":"All elevators and three egress stairs located within the core; 99 elevators per tower including seven freight elevators; skylobbies on 44th and 78th floors","source":"NIST NCSTAR 1-1, pp. 8-9"}},"floor_system":{"truss_spacing":{"value":"6 ft 8 in. on center (paired trusses supported at every other exterior column)","source":"NIST NCSTAR 1-1, p. 12"},"truss_spans_ft":{"value":"about 35 ft in short-span zone, 60 ft in long-span zone; three zones: long-span, short-span, two-way","source":"NIST NCSTAR 1-1, p. 12"},"truss_depth_in":{"value":29,"note":"29 in. out-to-out of the double-angle top and bottom chords; round bar webs","source":"NIST NCSTAR 1-2A, p. 48; NIST NCSTAR 1-1, p. xxxvii"},"slab":{"value":"4 in. thick lightweight concrete slab cast on 1.5 in., 22-gauge fluted metal deck; composite action via truss diagonals (knuckles) extended into slab","source":"NIST NCSTAR 1-1, p. xxxvii (Executive Summary)"},"prefab_floor_panels":{"value":"Floor trusses pre-assembled into panels typically 20 ft wide, two sets of double trusses in interior and a single truss along each edge","source":"NIST NCSTAR 1-1, p. 12"},"viscoelastic_dampers":{"value":"Approximately 10,000 per building, connecting floor truss bottom chords to perimeter spandrels/gusset plates; first use of the technology in a high-rise; purpose was limiting wind-induced building oscillations","source":"FEMA 403, Ch. 2, p. 2-4; NIST NCSTAR 1-1, p. 12"}},"hat_truss":{"location":{"value":"From floor 107 to the roof (floors 107-110 region), an assembly of hat trusses interconnected the core columns and the exterior wall panels","source":"NIST NCSTAR 1-1, p. 12; p. xxxv (Executive Summary)"},"function":{"value":"Resisted downward movement of damaged walls/core after impact and redistributed loads between core and perimeter","source":"NIST NCSTAR 1, pp. 150-151"}},"steel_grades":{"specified":{"value":"14 grades specified in structural plans, yield strengths 36 ksi to 100 ksi; 12 actually used (100 ksi substituted for 85/90 ksi)","source":"NIST NCSTAR 1, p. 67"},"perimeter":{"value":"Perimeter column and spandrel plates used yield strengths between 42 ksi and 100 ksi","source":"FEMA 403, Ch. 2, p. 2-3"},"trusses":{"value":"Both 36 ksi and 50 ksi steels specified for different parts of the floor trusses","source":"NIST NCSTAR 1-1, p. 12"}}}