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EARLY MOVEMENT · reconstructed transitions
Calculated impact interior
Exterior: observed damage. Interior: selected NIST calculation. Inspection opens this same case.0 inObserved maximum visible bow
0°Reported early orientation
8° southSequence endpoint
Historical overview
INSPECT THE SAME STRUCTURE
Southeast viewpoint · NIST face names
Evidence navigation · no physical playback time.
Evidence and reconstruction choices
Floor calculations. NCSTAR 1-6D, Fig. 5-4, p. 316, reproduces Bᵢ full-floor subsystem results at 100 model minutes. These are slab-inclusive contours, not observed floor positions or exact truss-node data. The four sampled south-office fields have about ±10 ft plan-registration uncertainty. Applying them to our impact geometry is a reconstructed overlay. Floor 99 has no quantitative sag field here.
Connection calculations. Fig. 5-5 shows subsystem support-loss regions on floors 97–98. They do not establish observed fracture times or a final global attachment map. The sequence’s coupling and gradual releases are reconstructed.
Wall observation. NCSTAR 1-3, §6.2.6, p. 59 and Figs. 6-14/15: maximum visible inward bow 55 ± 6 in near south column 316 / floor 97. The continuous displayed wall shape is interpolated; concealed parts are not measured. The final global calculation’s approximately 43 in result is distinct from this observed 55 in anchor.
Early movement and stopping point. NIST reports at least 8° southward tilt near floor 98. The model reaches a representative 8° south / 80 ft downward pose. Its downward placement is a conditional archive-image estimate using uncertain camera and Floor 98 ejection-band calibration; it is not a NIST distance or a pose synchronized to the reported angle. NIST’s north and west image sequences show why the mast can appear to sink as the upper structure tilts. Reference cuts, nominal pivot, intermediate motion and timing are display choices.
One continuous explanation. Sagging, bowing and early tilt share the existing structure and one playback control. The whole context remains visible. Source states lets you inspect the calculations and observations separately. Playback does not imply a physical timeline.
The custom impact panels, fragments, openings and retained framing remain intact in all views. NIST’s initiation explanation involves interacting floors and weakened columns; it does not establish floors first detaching in a pancake sequence.
Source controls and audit · NIST’s explanationEvidence and reconstruction choices
Floor calculations. Final NCSTAR 1-6D, Fig. 5-9, p. 323, shows floors 79–83 at the same Dᵢ 40 model minutes. These are slab-inclusive subsystem calculations, separate from final global Case D. The five east-office fields use 234 signed contour samples with about ±10 ft plan-registration uncertainty. They are not scaled to the whole-model maximum. In particular, floor 79’s whole-model maximum lies outside the sampled east-office region.
Moving the existing floors. The retained office slabs and trusses transition toward one total contour displacement, accounting for their existing impact bends and preserving their section depth. Recorded members keep their floor assignment even where they are already bent downward. Registration between these separately reconstructed states is approximate; local upward adjustments are not evidence of physical recovery. Core framing and building-side supports receive no office-floor sag. Sharing the contour state between member types and tapering outside the sampled office area are display assumptions. This does not solve support forces or introduce new fractures.
Connections. Horizontal gusset or bolt failure does not always remove vertical bearing. The Dᵢ calculation, later global-model connection inputs and observed hanging floor-edge material are distinct evidence. Shared horizontal motion between the displayed floors and wall is reconstructed, without an asserted per-seat failure sequence.
East-wall observation. NCSTAR 1-3, Fig. 6-18, p. 66: photographs from 9:52:54–9:53:04 supply 176 readable controls across labeled floors 77–83. The maximum is 20 in at the floor-80 window / column 321. The map prints ±1 in uncertainty; §6.2.7 estimates 1–2 in. Values belong to upper-left window corners, registered here to the nominal opening top 38.5 in below the next slab; the exact window-frame offset is unresolved. Unknown cells are interpolated; chosen zero tails at window rows 75/85 and near the face ends close the displayed field. Blank regions are not measured zero. Final global Case D’s approximately 62 in calculated bow is a different result.
First movement. NIST reports approximately 7–8° east and 3–4° south, followed by eastward rotation to 20–25° before obscuration. The model passes 7° east / 3° south and continues to a selected 20° east, holding 3° south. Downward placement is an illustrative geometric convention that keeps the bounding reference cut from rising; it is not a measured fall distance or solved support response. The reference cut near floor 82, intermediate poses and timing remain display choices.
The custom impact panels, fragments, openings and retained framing stay in the model. Sagging floors and weakened columns interact in NIST’s initiation explanation; it does not establish floors first detaching in a pancake sequence. Source states keeps the interior in its impact-context position while the original figures can be inspected.
South source controls and audit · Final NIST reportVisible model layers
