Influence of Clear Edge Distance and Spacing of Piles on Failure of Pile Cap
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RESEARCH PAPER
Influence of Clear Edge Distance and Spacing of Piles on Failure of Pile Cap Sushilkumar B. Magade1 · Ramakant K. Ingle1 Received: 7 February 2019 / Accepted: 12 June 2019 © Shiraz University 2019
Abstract The design and dimensioning of pile cap is a challenging task depending upon shape and thickness of cap, soil strata, pile dimension and their locations in plan. A pile cap is a reinforced concrete structural rigid slab, which distributes column forces to a group of individual piles as per rivet formula. The main assumption in rivet formula is that the pile cap should be rigid enough to distribute load uniformly. Most of the pile cap are designed by short-cut or thumb rule procedures for 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 cap is performed to capture the behavior of pile cap under axial load and moment. The focus of this study is to find adequacy of the clear edge distance for pile cap, as there are very few guidelines available. In case of minimum clear edge distance, a large amount of tensile stresses are developed at edge of pile cap, which may not acceptable. It is observed that providing 100 mm or 150 mm or 250 mm as clear edge distance suggested by most of the codes 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 depending upon the mathematical model of structure. Moreover, the proposed suggestions are well agreement with the experimental results. Keywords Pile cap · Clear edge distance · Finite element analysis · Allowable stresses
1 Introduction Engineers use approximate empirical procedures to design the reinforced concrete pile cap because worldwide codes do not state unified procedure to design the pile cap. Pile cap transfers the load from the structures to a pile group, then the load further get transferred to firm soil either through friction or end bearing or combination of both (Rao 2010). A pile cap has the function of spreading the load on a group of piles so that, the load is shared equally between the piles depending their stiffness (Reynolds et al. 2007). A group of ‘n’ piles connected by a rigid pile cap with the center of gravity of the load P and the piles are coincident; then, each pile will be equally loaded and will be subjected to a load P/n (Tomlinson and Woodward 2014). The reaction * Sushilkumar B. Magade [email protected] Ramakant K. Ingle [email protected] 1
Department of Applied Mechanics, VNIT Nagpur, Nagpur, India
from piles can also be taken to be distributed at 45° from the edge of the pile, up to the mid-depth of the pile cap (IS 2911 2010). The pile cap should be sufficiently reinforced and should have appropriate depth to resist the large amount of shear forces. The thickness of the pile cap must be sufficient to spread imposed load among the piles and usually determined by consideration of shear along a ve
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