Effect of column and pile configuration and dimension on shear performance of reinforced concrete pile caps

Despite extensive research on reinforced concrete (RC) pile caps, the influence of column and pile configuration and dimensions on their shear performance remains unexplored. This study investigates the structural behavior of RC pile caps through experimental and numerical analyses, focusing on how variations in column and pile geometry affect shear capacity. Two pile cap specimens (700 mm long × 300 mm wide) with heights of 250 mm (SB1) and 350 mm (SB2) were tested under shear-dominated conditions. Both were supported by two square piles (200 × 200 mm) and loaded centrally via a square column (200 × 200 mm). The study reports crack patterns, ultimate shear load, load-displacement behavior, elastic stiffness, and energy absorption capacity. A validated 3D finite element model was developed to parametrically analyze rectangular/circular columns and piles with dimensions ranging from 0.2d to d (where d = pile cap width). The findings indicate that failure modes were consistently shear-dominated and remained unaffected by variations in column or pile configuration and size. Increasing the rectangular column length from 0.2d to d enhanced the ultimate load capacity by 108% and energy absorption by 100%. Similarly, increasing the circular column diameter from 0.2d to d improved these metrics by 348% and 373%, respectively. Widening the rectangular pile from 0.2d to d resulted in a 34% increase in ultimate load capacity. Overall, the study demonstrates that larger column and pile dimensions significantly enhance shear performance, with circular configurations yielding superior improvements. These insights offer practical guidance for optimizing pile cap design.