Finite Element Analysis of Structural Test Pedestals under Different Loading Combinations

Abstract

Structural test pedestals form part of the reaction system used in large-scale structural testing, and their response may vary with loading-point arrangement and loading direction. This study compares two displacement-controlled loading combinations for an existing reinforced-concrete test pedestal using a three-dimensional finite element model comprising top and bottom slabs, columns, cross-shaped columns, loading pads, and reinforcement cages. Concrete is represented using a damage-plasticity formulation, while steel members and reinforcement are modelled as elastoplastic materials. Tie constraints are applied between concrete components and between the loading pads and top slab, with reinforcement embedded in the concrete. Both loading cases use a target displacement of 6 mm. Case 1 applies downward displacement through two pads, whereas Case 2 applies upward displacement at the middle pad and downward displacement at two side pads. The numerical response shows that Case 2 develops the higher reaction up to approximately 4.5 mm displacement, after which Case 1 becomes higher. At 6 mm, approximate reactions read from the source curve are 15 MN for Case 1 and 13 MN for Case 2. Equivalent-stress contours indicate stress concentrations around the pad load-transfer zones and adjacent connections. The comparison demonstrates that loading arrangement and direction influence the global reaction response and local load-transfer pattern.