Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
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- Table B Factored loads. Limit State Moment Longitudinal (kip-ft) Moment Transverse (kip-ft)
- Figure B Pile group model (from GROUP program.
| (longitudinal) p-multiplier (transverse) 1 0.4 0.4 2 0.4 0.8 3 0.8 0.4 4 0.8 0.8 Step 4: Determine Factored Loads The determination of the factored loads is beyond the scope of this example. In this example, Strength, Service, and Extreme Limit States are provided by others as a result of structural design analyses. Table B presents the factored loads used in this example. All loads are applied at the bottom of the pile cap. Table B Factored loads. Limit State Moment Longitudinal (kip-ft) Moment Transverse (kip-ft) Moment Torsion (kip-ft) Shear Longitudinal (kip) Shear Transverse (kip) Axial (kip) Service 250 80 8 15 25 1200 Strength 400 110 10 40 65 1600 Extreme 800 1000 150 120 90 900 Step 4: Obtain Bending Moment, Shear, and Lateral Deformation Profiles The program GROUP was used to compute bending moment, shear and lateral deformation profiles. Figure B shows the pile group model. 246 Figure B Pile group model (from GROUP program. Note that the in accordance with LRFD guidelines, the pile lateral deflection is computed using the Service Loads, while bending moment and shear diagrams are evaluated using the Strength Limit State Loads and Extreme Loads. In summary Pile top maximum lateral deflection = 0.04 inch Bottom of pile cap displacement (longitudinal) = 0.01 inch Bottom of pile cap displacement (transverse) = 0.03 inch Maximum bending moment (STRENGTH) = 48 kip-ft Maximum shear (STRENGTH) = 19 kip Maximum bending moment (EXTREME) = 114 kip-ft Maximum shear (EXTREME) = 38 kip The values reported above are combined values in the longitudinal and transverse directions, and are used in the next step to assess the pile structural integrity. Step 5: Assess Pile Structural Integrity The structural capacity of the pile can be verified utilizing the same procedure presented above for the single pile example. Given that the piles are closed ended composite piles, the design should follow AISC and AASHTO 6.5. This example is also computed with spColumn v (by Structure Point, LLC), and shows both Strength and Extreme Load Cases. The results are shown in Figure B. The values reported are well within the PM interaction diagram (acceptable structural capacity. If desired, the section could be optimized by modifying the pile structural section and restarting from Step 2. This optimization process is not presented in this example. 247 Step 6: Final Design This step consists of the evaluation of the data collected in previous steps, and in the assessment of any potential design optimization. First, the results of the structural assessment (Step 6) should be used to determine whether a change in the pile structural section (diameter, wall thickness, etc) is needed. If any element affecting the pile lateral response is modified, the analyses should restart from Step 2 based on the new proposed structural design. If the structural assessment is considered adequate, and no modification to the pile structural section is needed, then a check on the pile length should be performed. This procedure is discussed in the previous example, and will not be repeated here. Download 6.03 Mb. Share with your friends:
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