University of Alaska Building 7 Report

a. Floor 12

b. Floor 13

Figure 2.54 a. Floor 12, b. Floor 13 (NIST, 2008, NCSTAR 1-9, Vol. 2, Figures 10-36 to 10-39). The images at top represent the temperature distribution in the top layer of the concrete slab. The images at bottom represent the temperature distribution on the floor beams. 2.6.1 SAP2000 Thermal Deformation Analysis As stated above, the displacement of the floor system surrounding Column 79 was simulated based on the temperature distribution reported by NIST. The purpose of this analysis was to determine if NIST’s computed fire condition would cause the same response in our models. Note that the models in this analysis consist only of Floors 12 and 13 and note, these are 3-D models. Boundary conditions above and below the two floors were included so the model would be able to accurately assess the thermal response of these two floors. Prior to conducting our analysis, we studied the structural response due to changing boundary conditions and the sensitivities of the building to various types of loading conditions. The boundary conditions (i.e. columns above Floor 13 and below Floor 12) were simulated by determining axial, bending, and torsional stiffness (for each column framing into these floors). This approach enabled the research team to accurately simulate the interdependent response due to a fire.

University of Alaska Building 7 Report

Articles inside

REFERENCES

Figure 4.20 Velocity comparison between Chandler measurement (green plotted line) and UAF simulation (red plotted line). Bold green trend line illustrates free fall

Figure 4.17 (a) Comparison of simulated collapse to perspective 1; (b) comparison of simulated collapse to perspective 2

2.7 Summary and Conclusion

3.2.2 Girder A2001 Web Stiffeners Prevent Flange Failure and Girder Walk-off

Table 2.3 Comparison of UAF and NIST Modeling

4.6 Results of Core Column/Exterior Column Failure Analysis

2.6.2 ABAQUS Analysis

3.2.3 Lateral Support Beams Prevent Beam Buckling

2.6.1 SAP2000 Thermal Deformation Analysis

Figure 2.36 Modeling process for a beam to girder shear connector, “STC.”

Table 2.1 Column loading for the Floor 12 and 13 assembly

Figure 2.21 SAP2000 model of entire WTC 7 without roof

Figure 2.24 Column number layout of Floor 13 (NIST, 2008, NCSTAR 1A

Figure 2.26 Small section of typical floor slab of WTC 7 with finer meshing

Figure 2.29 Plan View: Model of floor slabs in strong direction (parallel to flutes

Figure 2.46 Seated moment connection of exterior girders to exterior columns ABAQUS model

2.2 Solid Works Modeling

2.1.3 Background Studies

1.5.3 Approach 3: Simulating the Collapse of WTC 7

Figure 2.5 Area of floor where connection failure was modeled by NIST

1.5.2 Approach 2: Evaluation of NIST’s Collapse Initiation Hypothesis

Figure 2.6 Progressive collapse separated into two parts

Figure 2.3 Approach used to model buckled beams in LS-DYNA model (NIST, 2008, NCSTAR 1-9, Vol. 2

1.4.3 Arup and Nordenson, April 2010

Figure E.3 Finite Element Model of WTC7 in SAP2000, as viewed from the south

Figure 1.6 WTC 7 was in free fall for approximately 2.25 seconds over a distance of approximately 8 stories or 32.0 meters (NIST, 2008, NCSTAR 1A

EXECUTIVE SUMMARY

2.2 Hypothetical Failure Mechanisms for West Penthouse and North Face Roofline

Figure 1.4 WTC 7 tenants on September 11, 2001 (FEMA, 2002

Figure 1.9 WTC 7 steel frame building geometry prior to its collapse (FEMA, 2002

Figure 1.5 The collapse of WTC 7 at 5:20 PM (source unknown

1.4.2 National Institute of Standards and Technology, November 2008