Strategic slab-column joint details for improved transmission of HSC column loads

Abstract

In typical construction, the slab is made of normal-strength concrete (NSC) and is cast in a continuous fashion through the slab-column joint. For the case of high-strength concrete (HSC) columns, this results in a layer of lower-strength concrete between the upper and lower columns at the floor levels. Since this lower-strength concrete layer can limit the capacity of the column, it is necessary to provide alternative design or construction strategies for the transmission of column loads through slab-column connections. The current paper presents the structural characteristics of slab-column connections by using full-scale tests and non-linear three-dimensional finite-element analyses. Finite-element analyses considering material non-linearity were performed to investigate the axial load plotted against average column strain responses, the type of failure, the principal stress distribution and the reinforcement yielding conditions for various slab-column members. The puddled HSC in the joint, the HSC core, the use of high-strength steel for the column longitudinal reinforcement, and the additional vertical compression reinforcement through the joint were investigated. The alternative reinforcement methods in the slab-column joints significantly improved the performance of the joints-that is, higher axial compressive strength, greater loading stiffness and higher ductility.