JК
11 сентября 2001 :: Мейссан Тьерри
Страница: 264 из 286The extra vertical load on the perimeter columns would have distributed itself symmetrically around the perimeter frame (and would not have been concentrated on the adjacent columns). Preliminary structural analyses of similar damage to WTC 2 suggests that axial load demands on columns immediately adjacent to the destroyed columns may have increased by as much as a factor of 6 relative to the load state prior to aircraft impact. However, these exterior columns appear to have had substantial overstrength for gravity loads. Indeed, these exterior columns were designed to resist significant lateral loading and would have had more than sufficient capacity to resist this extra load.
Figure 2-14 Approximate zone of impact of aircraft on the north face of WTC 1.
Neglecting the potential loss of lateral support resulting from collapsed floor slabs and any loss of strength due to elevated temperatures from fires, the most heavily loaded columns were probably near, but not over, their ultimate capacities. Columns located further from the impact zone are thought to have remained substantially below their ultimate capacities. The preliminary analyses also indicate that loss of the columns resulted in some immediate tilting of the structure toward the impact area (extremely unlikely) subjecting the remaining columns and structure to additional stresses from P-delta effects. Also, in part, exterior columns above the zone of impact were converted from compression members to hanger-type tension members, so that, in effect, a portion of the floors' weight became suspended from the outrigger trusses (Figure 2-10) and were transferred back to the interior core columns. The outrigger trusses also would have been capable of transferring some of the load carried by damaged core columns to adjacent core columns. Figure 2-19 illustrates these various secondary load paths. Section 2.2.2.2 provides a more detailed description of these analyses and findings. The above paragraph is mainly nonsense. The building was in fact unlikely to have been stressed any more than it would have been in a hurricane force wind.
Figure 2-19 Redistribution of load after aircraft impact.
The resulting load distribution after the aircraft impact would have been almost identical to the load distribution incurred by strong wind from the back (i.e., from behind the plane of the page) as in the above graphic. Following the aircraft impact into the building, the structure was able to successfully redistribute the building weight to the remaining elements and to maintain a stable condition.
Figure 2-14 Approximate zone of impact of aircraft on the north face of WTC 1.
Neglecting the potential loss of lateral support resulting from collapsed floor slabs and any loss of strength due to elevated temperatures from fires, the most heavily loaded columns were probably near, but not over, their ultimate capacities. Columns located further from the impact zone are thought to have remained substantially below their ultimate capacities. The preliminary analyses also indicate that loss of the columns resulted in some immediate tilting of the structure toward the impact area (extremely unlikely) subjecting the remaining columns and structure to additional stresses from P-delta effects. Also, in part, exterior columns above the zone of impact were converted from compression members to hanger-type tension members, so that, in effect, a portion of the floors' weight became suspended from the outrigger trusses (Figure 2-10) and were transferred back to the interior core columns. The outrigger trusses also would have been capable of transferring some of the load carried by damaged core columns to adjacent core columns. Figure 2-19 illustrates these various secondary load paths. Section 2.2.2.2 provides a more detailed description of these analyses and findings. The above paragraph is mainly nonsense. The building was in fact unlikely to have been stressed any more than it would have been in a hurricane force wind.
Figure 2-19 Redistribution of load after aircraft impact.
The resulting load distribution after the aircraft impact would have been almost identical to the load distribution incurred by strong wind from the back (i.e., from behind the plane of the page) as in the above graphic. Following the aircraft impact into the building, the structure was able to successfully redistribute the building weight to the remaining elements and to maintain a stable condition.