Seismic Response of an Irregular Pile-Supported Building on Liquefiable Sand: 2D Effective-Stress Analysis and Failure-Mode Assessment

The soil–pile–structure interaction (SPSI) has an important effect on the design of earthquake-resistant structures and becomes more complicated for irregular structures constructed on liquefiable soils. Using pile foundations is an efficient method for improving structure stability because they enhance bearing capacity and reduce structural settlement. To assess the effects of SPSI, a 10-story irregular reinforced concrete structure supported by a group of five piles was modeled in PLAXIS2D. To examine the effect of input shaking amplitude on system response, four sinusoidal ground motions with different amplitudes and a real earthquake record were used. The results were assessed, considering the superstructure’s inter-story drift, rotation, and basement settlement. Furthermore, the distributions of curvature and internal forces along the piles were compared in various scenarios. Several failure modes were investigated, including bending, buckling, bending–buckling interaction, shear, and slenderness instability. The results show that internal forces and curvature development in piles are strongly influenced by the shaking amplitude, pile diameter, superstructure load magnitude, and presence of a liquefied layer. These factors also determine the failure mode that is experienced.