Behavior of Composite Piles Subjected to Combined Loads: Numerical Analysis

Abstract

Piles are one-dimensional (1D) beam–column elements designed to support axial loads from superstructures. However, in tall buildings, ports, bridges, and both onshore and offshore structures, they are subjected to combined loads that include axial forces, lateral loads, and bending moments. The study of pile behavior under such loading remains limited, particularly in the numerical evaluation of the combined effects of composite geometry and soil stratification. At the same time, analysis and design are based primarily on Timoshenko (TB) and Euler–Bernoulli (EBB) beam theories. The objective of this research was to numerically assess the behavior of composite piles under combined loads. Three cases were considered: i) a homogeneous soil layer, ii) stratifiedtwo-layer soils, and iii) composite sections, to analyze the influence of such loads on structural response and soil–structure interaction. The methodology included incremental static analyzes under axial and lateral loads using SAP2000 finite element software. Three numerical examples were developed to evaluate the performance of embedded Concrete-Filled Steel Tubular Piles (CFSTP) with circular and square cross sections. The results revealed two trends depending on the axial load: 0 < P ≤ 5 MN and P > 5 MN. Regardless of the soil stiffness ratio (ks1/ks2 = 0.5–1.5), the lateral performance was dominated by geometry, the square–square pile (SSP) being the most efficient, followed by the circular–circular pile (CCP) and the solid pile (SP). The maximum bending moments were slightly higher in the stiffer sections, particularly in SSP and CCP. Finally, it is concluded that the axial load induces a dual effect: it amplifies lateral deflections while reducing the variation in bending moment, demonstrating that cross-sectional geometry is the dominant parameter in pile performance.