Title: Effect of Clear Edge Distance on Failure of Pile Cap
Author(s): Sushilkumar B. Magade and Ramakant K. Ingle
Publication: Structural Journal
Appears on pages(s): 131-140
Keywords: allowable stresses; clear edge distance; finite element analysis; pile cap
Depending upon shape and thickness of cap, soil strata, pile dimension, and locations of piles in pile cap, design and dimensioning of pile cap is a challenging task. A pile cap is a reinforced concrete structural rigid slab and, as per rivet formula, it distributes column load to a group of individual piles uniformly. This means the pile cap should be rigid enough to do so. Most pile caps are designed by empirical or thumb rule procedures irrespective of spacing of piles, thickness of pile cap, and minimum edge distance of pile cap from pile center or edge. In the present paper, finite element analysis of pile caps is carried out with axial load and moment. The objective of this study is to find adequacy of the clear edge distance for pile cap. High tensile stresses are developed at the edge of pile caps for minimum clear edge distance, which may not be acceptable. It is observed that providing 100, 150, or 250 mm as clear edge distance—as suggested by codes such as ACI 318, IBC, and ASCE—is inappropriate. However, it should be at least half of the diameter of pile used to accommodate the stresses developed at the edge, as proposed in this paper.