P-Delta Effects on a Helical Pile

A. INTRODUCTION – MODEL DATA

In this document we will examine the influence of the P-Δ effect in helical piles. Analysis of piles in accordance with the assumption of small deformation is not always a valid one. For flexible piles where significant lateral deflection is expected, second-order effects could lead to an incorrect calculation of moments and subsequently design of the piles. Specifically, the additional moment contributed from the Axial load along the pile multiplied with the lateral pile deflection, is not considered in small deformation analysis (Fig. 1). As a result, for such scenarios the use of the P-Delta effect option within DeepFND is essential.

P-DELTA Effects on Flexible Piles

Figure 1: P-Delta Effect in Flexible Piles

B. DEEPFND SOFTWARE – SOIL PROPERTIES & STRATIGRAPHY – DM EDIT

Table 1: Soil Properties and Soil Layer Elevations

Soil Properties and Soil Layers

Soil Properties and Soil Layers in DeepFND Software

Figure 2: Soil Properties & Soil Layers in DeepFND

C. DEEPFND/HELIXPILE SOFTWARE – PILE SECTION PROPERTIES

Table 2: Pile Properties

Helical Pile Section Properties

Helical Pile Section Properties in DeepFND Software

Figure 3: DeepFND – Helical Pile Properties

D. DEEPFND/HELIXPILE SOFTWARE – ANALYSIS SETTINGS

1. Bearing Capacity Method: Meyerhoff/Hansen

Bearing Capacity Calculation Method in DeepFND Software

2. Installation Torque: AC358-2007 Torque Factor Profile

Selected Installation Torque Profile in DeepFND Software

3. P-DELTA: Check the model with and without the P-DELTA Effects

P-Delta Effects Selection in DeepFND Software

E. DEEPFND/HELIXPILE SOFTWARE – ANALYSIS RESULTS

Lateral Pile Analysis Displacement Results without P-Delta Effects

Figure 4: Pile Displacements without P-DELTA Effects with DeepFND i) 0.8 kips lateral load, ii) 2 kips lateral load

Lateral Pile Analysis Displacement Results with P-Delta Effects

Figure 5: Pile Displacements with P-DELTA Effects with DeepFND i) 0.8 kips lateral load, ii) 2 kips lateral load

Pile Displacement Results Comparison with and without P-Delta Effects

Figure 6: Pile Displacements Comparison with and without P-DELTA Effects in DeepFND

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