Ayres Knowledge Center Scour Evaluation: Bridges with Unknown Foundations | Page 37

Pile Lateral Load Evaluation
The stability analysis was performed using the computer program FB-MULTIPIER. The FB-MULTIPIER program
considers both axial and lateral pile-soil interaction. The soil is characterized by user-defined parameters. Group
effects are considered through P-Y multipliers that are assigned for each row within the pile group. The
recommended FB-MULTIPIER soil parameters are shown in Attachment C.
4.0 STRUCTURAL ASSESSMENT
The foundation stability of Bascule Pier No. 17 at the 100-year scour elevation was evaluated in accordance with
the Department's directives. The remaining pile embedment and unsupported length for the intermediate bents
were determined at the existing conditions (using the 2011 Bridge Survey and the 6/14/2011 Field Visit Channel
Profiles) and at the calculated 100-year scour event. Bascule Pier No. 17 (1-W per plans) was chosen for the
analysis because its piles have the least amount of remaining embedment and the longest unsupported length. At
the 100-year scour event, the piles at Bascule Pier No. 17 would have scour up to 18.6 ft. and have 69.7 ft. of
reamining embedment. A stability analysis, using FB-MULTIPIER, showed Bascule Pier No. 17 to be unstable for
the modified Group 1 loads at the calculated 100-year scour elevation, however, it is stable at its existing
conditions. The bridge is therefore rated scour critical.
The vertical and lateral loads for Bascule Pier No. 17 were estimated in accordance with the 17th edition of the
"Standard Specifications for Highway Bridges" (AASHTO). The Load Factor Design method was used to evaluate
the foundation stability. The Department directive states that load factors (gamma and beta) of 1.0 are to be used
for Group 1 loading combination as specified in Table 3.22.1A of AASHTO. Serviceability requirements were not
considered. Construction tolerances were also not included in this analysis. The stream pressure was calculated
in accordance with Article 3.18.1 of AASHTO and applied only to the exposed pile surfaces. Debris accumulation
and ship impact were not considered.
The axial forces in all the piles were lower than the soil's ultimate (theoretical) compression capacity. The applied
moments were insignificant. Pile axial and lateral displacements are within tolerable limits. These results indicate
that Bascule Pier No. 17 is stable under the applied loads at the 100-year scour elevation, and the bridge was
therefore rated low risk.
For further information, refer to Attachment D. See Page 1 of 3 for recommendations.
5.0 MATERIALS AND DOCUMENTATION
· 1957 Bridge Design Plans
· 2004 Bridge Rehabilitation Plans
· 2010 Bridge Inspection Report
· Scour Evaluation Report, Phase 1, Phase 2, Phase 3, & Phase 4 (Ayres Associates, Inc.)
· Attachments
A. FDOT Memorandums regarding Phase 3 Scour Evaluation Criteria
B. Nondestructive Parallel Seismic Testing Evaluation Report
C. Geotechnical Evaluation
D. Structural Evaluation
4/25/2013
FINAL
Supplementary Report
Page 4 of 12
62-0144.00
BRIDGE NO 794004
Page SR-34