Current design practices recommend to comply with the capacity protection
principle, which pays special attention to ensuring an elastic response of the foundations under ground motion events. However, in cases such as elevated reinforced
concrete (RC) pile-cap foundation typologies, this design criterion may lead to conservative designs, with excessively high construction costs.
Reinforced concrete elevated pile-cap foundations is a system formed by a group of partially embedded piles connected through an aboveground stayed cap
and embedded in soil. In the cases when they are subjected to ground motions, the piles suffer large bending moments that make it difficult to maintain their
behavior within the elastic range of deformations.
Aiming to make an in-depth analysis of the nonlinear behavior of elevated
pile-cap foundations, a cyclic loading test was performed on a concrete 2x3 pile
configuration specimen of elevated pile-cap foundation. Two results of this test,
the failure mechanism and the ductile behavior, were used for the calibration of a
numerical model built in OpenSees framework, by using a pushover analysis.
The calibration of the numerical model enabled an in-depth study of the seismic
nonlinear response of this kind of foundations. A parametric analysis was carried
for this purpose, aiming to study how sensitive RC elevated pile-cap foundations
are, when subjected to variations in the diameter of piles, reinforcement ratios,
external loads, soil density or multilayer configurations. This analysis provided
a set of ductility factors that can be used as a reference for design practices and
which correspond to each of the cases analyzed.