Cross Section Analyses - Main Span
Cross Section Analyses - Main Span |
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| The main span was analyzed using
UCFyber with the static axial load of 51 MN.
First, the section without the drop in precast panels was analyzed assuming the model shown above. The capacity orbit UCFyber analysis showed the section to have a strong axis bending capacity of 354 MN-m. The Weak axis capacities for top in compression and bottom in compression are 98 MN-m and 111 MN-m respectively. |
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Figure 1 - UCFyber capacity orbit the main span without the drop in precast wings. Click the graph to see a detailed UCFyber report. |
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| Running a moment curvature analysis
about the strong axis with nominal axial load shows very non-ductile
response with a curvature ductility of 6. The first yield moment is
at 278 MN-m.
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Figure 2 - Moment curvature and its equal area bilinearization for strong axis bending without the precast panels. Click the graph to see a detailed UCFyber report. |
| An analysis with the wings in
compression shows bending capacities quite a bit higher, a factor of 1.8,
but at the cost of half the curvature capacity.
Post peak moment capacity on the section with wings, analysis predicts a very rapid deterioration in strength.
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Figure 3 - Moment curvature and its equal area bilinearization for strong axis bending with the precast panels in compression. Click the graph to see a detailed UCFyber report. |
| Bending about the weak axis, top
in compression, showed a much more ductile response than bending about the
strong axis. The details of the web are such that enough concrete is
confined to ensure response in the nonlinear range.
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Figure 4 - Moment curvature and its equal area bilinearization for weak axis bending of the main span with the top in compression. Click the graph to see a detailed UCFyber report. |
| Bending about the weak axis with
the top in tension showed mildly ductile response.
Overall, the most favorable failure of the deck would be under weak axis bending on the main span with the top in compression. The Pylon/Main span design is a strong column weak beam. Thus, under large lateral displacements, failure about the main span weak axis is to be expected.
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Figure 5 - Moment curvature and its equal area bilinearization for weak axis bending of the main span with the top in tension. Click the graph to see a detailed UCFyber report. |
