Parametrical analysis of partially encased composite columns with fiber reinforced concrete subjected to uniaxial and biaxial non-constant bending moments

Partially encased composite (PEC) columns are efficient structural elements that offer ease and agility for prefabrication, requiring no molds for casting concrete. The manufacture of these elements involves anchoring the reinforcement to the metallic profile, which is a laborious process. Thus, alternative solutions capable of maintaining the column performance can propel PEC columns, providing more practical construction technics. One of these alternatives is substituting steel rebar with Fiber Reinforced Concrete (FRC), saving time. The benefits of such solutions were already proven with laboratory experiments. Therefore, this study aims to numerically analyze the structural behavior of PEC columns under different load conditions from available experiments based on a calibrated numerical model. The performance of the models was compared using two reinforcement configurations: conventional reinforcement and steel fiber reinforced concrete. Several cases of eccentric axial loads were evaluated, presenting the influence of the eccentricity and the skew angle relative to the major axis of inertia. Finally, simulations were carried out on columns subjected to non-uniform moments along with their height. The models showed a more abrupt rupture when bending around the minor axis of inertia when subjected to a constant moment on the length. Regarding non-uniform moments, the critical situation in all cases investigated occurs when the moment is constant along with the height. Results were favorable to FRC use because the two reinforcement configurations evaluated showed similar behavior in all the conducted analyses; the model of FRC showed higher ductility than the model with conventional reinforcement, mainly due to the confinement provided by fibers. Nevertheless, columns with FRC presented more significant lateral displacements, resulting in slightly lower maximum loads than those shown by columns with conventional reinforcement.