Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities

238 ab) c)
Figure B Pile top lateral deflection (a, bending moment (band shear diagrams (c.
0 5
10 15 20 25 30 35 40 45 50
-0.01 0
0.01 0.02 0.03 Depth below top of P
ile
(f t)
Displacement (in)
Pile Lateral Deflection (Service Loads 5
10 15 20 25 30 35 40 45 50
-200 0
200 400 600 Depth below top of P
ile
(f t)
Bending Moment (kip-ft)
Bending Moment Diagram (Strength Loads 5
10 15 20 25 30 35 40 45 50
-40
-30
-20
-10 0
10 Depth below top of P
ile
(f t)
Shear (kip)
Shear Force Diagram (Strength Loads)

239 Step 4: Obtain Bending Moment, Shear, and Lateral Deformation Profiles The program LPILE was used to compute bending moment, shear and lateral deformation profiles. Note that 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 Loads. In summary Pile top lateral deflection = 0.03 inch Maximum bending moment = 727 kip-ft Maximum shear = 35.5 kip The values reported above are computed using the appropriate factored loads, and are used in the next step to assess the pile structural integrity. Step 5: Assess Pile Structural Integrity The engineer must check the structural integrity of the selected section by constructing an interaction diagram for the effect of combining the Bending Moment (M) and Axial Load (P. The PM interaction diagram is based on an equilibrium and strain compatibility approach for biaxial flexure and compression. If the section is non-circular, under special circumstances, the AASHTO Article 5.7.4.5 allows designers to use an approximate method to evaluate biaxial bending combined with axial. In lieu of the simplified or rigorous analysis, designers could compute their PM interaction diagram using commonly available software such as spColumn (Structure Point, 2016) or WinYield (Caltrans b, keeping in mind the material of the section and the standards that govern the calculation. The single reinforced-concrete pile example was computed using spColumn v (by Structure Point,
LLC), following ACI 318-14 and AASHTO Articles 5.5.4.2.1 and 5.7.4.4. 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.

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