Introduction
Pile lateral support may be modeled using P-y curves. P-y curves, typically provided by the geotechnical engineer, describe the lateral soil resistance along the depth of a pile or drilled pier. For each layer of soil along the depth, the P-y curve represents a nonlinear relationship in which lateral pile displacement y mobilizes lateral soil reaction P per unit length.
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- Fully restrain the grounded end of each link, which is away from the pile, as shown in Figures 1 and 2:
Link definition
Define nonlinear link properties, available through Define > Section Properties > Link/Support Properties, as follows:
- Add a new link property of Multi-Linear Plastic type, then specify the nonlinear link stiffness for the axial (U1) DOF such that it matches the stiffness of the P-y curve, as described through the following process:
- Define the P-y curve as a force-deformation (F-D) relationship in which F is total force acting along the tributary length of a pile joint.
- Use the minimum number of points to characterize the P-y curve such that computation time may remain efficient.
For soil with non-gapping behavior, link definition should extend stiffness through both sides of the F-D relationship, and the hysteretic model should be selected as Kinematic, as shown in Figure 3:
For soil with gapping behavior, only compression should be specified. Tensile stiffness should be set to zero, and the hysteretic model should be selected as Takeda, as shown in Figure 4:
Link assignment
These link definitions should be assigned to link objects through Assign > Link/Support > Link/Support Properties.
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To demonstrate hysteretic behavior, an increasing cyclic-displacement load is applied to a pile joint during nonlinear displacement-based quasi-static time-history analysis. Hysteretic response for the Kinematic and Takeda models are shown in Figures 5 and 6:
Distributed springs
Rather than drawing links as discrete elements, line springs may expedite the modeling process when assigned as follows:
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