Despite that tapered piles have a substantial advantage over straight-sided wall piles with regard to their load-carrying capacity in the downward frictional mode, tapered steel and concrete piles have not been routinely considered as a design option because of the lack of knowledge about their characteristics. A 5-m radius centrifuge facility located at C-CORE, Memorial University, Newfoundland, was used to test steel open-ended tapered and cylindrical piles with different slenderness ratios (14--26) and with different taper angles. A scale factor of 10 was used to resemble piles with different embedded depths ranging from 4.0m to 7.12m. This thesis presents research focusing on the axial performance of tapered piles under different loading conditions. The main focus of the chapters were to: (a) develop a simplified approach for calculating the shaft resistance of tapered piles; (b) experimentally characterize the load transfer mechanism for tapered piles; and (c) investigate the pile taper effect on the performance of tapered piles subjected to uplift or cyclic loading events. A procedure was developed to calculate the shaft resistance of tapered piles. This procedure is based on hole expansion theory and the experimental observations. The developed procedure was used to calculate the capacity of test piles. The calculated capacity using this procedure agreed well with the experimental results of the tapered piles. The results of this study confirmed that tapered piles are much more efficient than uniform cross-section ones in the compressive loading mode. The results also showed that the performance of tapered piles under uplift or axial cyclic loading is comparable or superior to that of uniform cross-section piles.
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