Cross Section Analyses - End Piers
Cross Section Analyses - End Piers |
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| The P11 and P13 end piers (Figure 1) were a simple two column bent tied together with a cap beam. The main span of the bridge sat on two support points contained within a lateral shear key. The bridge was free to move longitudinal within the key but restrained laterally under static and moderate dynamic loading. Structural damage to the bent was in the form of diagonal shear cracking and mild cracking at the base of the column. The cracking at the base was, however, opposite from that predicted by flexural theory and is investigated further. Architectural damage was seen heavily in the end piers as the main span pounded on the architectural walls. |  |
Figure 1 - P11/P13 end pier |
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| The Pier Beam (Figure 2) at the P11/P13 has a longitudinal reinforcing ratio 1.6% and a transverse reinforcing ratio of 4%. The beam has an ACI estimated shear capacity of 16.9 MN when loading in the vertical direction. |  |
Figure 2 - Pier beam, cross section |
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| Moment curvature analyses were done using
UCFyber for the case
of the top in compression near the center span. Results are given in Table
1 and on the UCFyber analysis
report.
Zero axial load was assumed in this case as the section of interest is in the center of the span. The section had a curvature ductility of 31 but, the section behavior is controlled by shear failure given geometry and loading conditions. This is explored in more detail in the End Piers Investigation. |
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Table 1 - Pier beam, top in compression |
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| Analyses was also
done for the case of the bottom in compression for the section nearest the
pier column. This cross section at this location is different from
that of Figure 2. This section at this point is purely rectangular with outer dimensions
of 200X210 cm. The longitudinal and transverse reinforcing
reinforcing ratios are 1.19% and .55% respectively.
Analysis was done for the axial load cases of .1(AgF'c), .05(AgF`c), and zero. The Yield moment varied from 18.9 MN-m, 24.5 MN-m, and 29.61 MN-m respectively. Values provided in Table 2 are for the .05(AgF`c) case. The section had a curvature ductility of 20 for the 8 MN-m load case. More discussion on the beam behavior is available in the End Piers Investigation. |
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Table 2 - Pier beam, top in tension |
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| The Pier Columns (Figure 3) at the P11/P13 has a longitudinal reinforcing ratio 1.13% and a transverse reinforcing ratio of 1%. The column bending about the weak axis showed no cracking or damage at all. In the strong direction; however, tension were observed at the foundation level. |  |
Figure 3 - Pier beam, cross section |
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| Moment curvature analyses were done using
UCFyber for the case
of the bending about the strong axis. An analysis is available
for the case of .1(AgF'c). However, an Axial-Moment
Interaction analysis is more useful in this case for the section did not penetrate heavily into the nonlinear range.
Between zero axial and the balance point, the yield moment varies from 75 to 150 MN-m. The complete UCFyber report is also available. The pier is a strong column weak beam design. |
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Figure 4 - Axial Moment Interaction for column in strong bending |
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