Experimental and numerical investigations of reinforced concrete columns confined internally with biaxial geogrids

Abstract

Geogrids are geosynthetic materials that have been proven effective for stabilization and strengthening applications in infrastructure, such as: reinforcement and stabilization of pavement layers, reinforcement of embankments and soil walls, in addition to soil improvement. The main aim of this study is to investigate the feasibility of using biaxial geogrids as a replacement of ordinary transverse steel reinforcement in columns. Using geogrids as confining material in reinforced concrete columns offers advantages over steel stirrups in that they are less laborious to install and are more durable. The study presents results of experimental and analytical investigations of the behavior of small-scale reinforced concrete columns of 500 mm height subjected to monotonic uniaxial compressive loading. The main test variables include confining material (steel stirrups or geogrids), number of geogrids layers, and the aspect ratio (height to diameter) of the column. Strain gauges were installed on the geogrids to determine the displacement fields of the geogrid elements. Axial displacement and axial load were measured to assess the overall load-displacement behavior, stiffness, ultimate strength, and ductility of the confined column specimens. Analysis of the results revealed that the ductility and energy absorption capacity of concrete column specimens are substantially enhanced without any significant effect on the ultimate load capacity when internally confined by biaxial geogrids. Two distinct analytical models were developed to predict the load-displacement behavior, one for unconfined plain concrete specimens, and the other for columns with transverse reinforcement using biaxial geogrids. The models provided satisfactory predictions of the stress–strain response when the analytical and experimental results were compared.