Strength of pile caps under eccentric loads: Experimental study and review of code provisions

Abstract

Pile caps are rigid reinforced concrete structures that transfer column loads, generally consisting of a combination of an axial load and bending moments in one or two directions, to the piles. The design formulations of pile caps for more than two piles were derived from the results of experimental tests under a centered load. The practice of checking both punching and shear failure modes is common as described in the literature review, even thoughdespite these formulations were developed for more slender elements.Currently, Codes ACI 318-14 and EC2 allow designing pile caps with strut-and-tie models or sectional approaches (shear, punching and flexural designs).In this study, 21 full-scale pile caps with different shear span-depth ratios and reinforcement layouts were studied to investigate the effect of eccentric loading on the strength and accuracy of the code formulations. The results show that in eccentrically loaded pile caps, the ultimate load is reduced but the maximum pile reaction increases and the secondary reinforcement proves effective to enhance the pile cap strength.Although the strut-and-tie models (STM) allow eccentric loads to be taken into consideration, they predict a much lower peak load than that observed at the experimental results and do not adequately reflect either the influence of slenderness or the failure mode.In general the sectional approach provided by Codes ACI-318-14, EC2 and MC-2010 (Level I of Approximation) lead to safe predictions of the peak load but do not always correctly predict the failure mode. The ultimate load predicted by EC-2 formulation comes closest to the experimental peak load, accurately reflects the influence of slenderness and the effect of secondary reinforcement, however, additional assumptions need to be made for its application. The ACI formulation complemented by the CRSI-Definición de estilo: Título 1

Strength-based material layout optimization of solid reinforced concrete

“…The cost of the original design from the paper by Miguel et al [43] was 226.5kg CO 2 e when using the unit prices as in this paper. This means for the combined load case when optimizing reinforcement only, a saving of 22.2kg CO 2 e and 3.7kg CO 2 e or 9.8% and 1.6% is obtained, for the free and material group optimization respectively.…”

“…Lastly, a 3D example of a pile cap with and without material groups is considered. The loading and geometry of the example are adapted from an experimental setup by Miguel-Tortola et al [43].…”

“…Now a three dimensional problem is considered in the shape of a pile cap with four piles. The model is based on a pile cap design from an experimental setup by Miguel-Tortola et al [43]. A sketch of the model with geometric properties as well as boundary condi-tions and loading can be seen in Fig.…”