Assessment of external and internal geogrid confinement of reinforced concrete columns

Abstract

Geogrid is a geosynthetic material commonly used for soil stability purposes in road embankments and reinforced earth walls due to its tensile reinforcing capability. Recent research has shown the efficiency of Geogrid as an internal reinforced concrete column confinement that increases significantly the ductility, but slightly decreases the axial compressive strength of the column. The study reported in this paper investigated the feasibility of using geogrids as external column confinement. It was important to compare external geogrid confinement with internal geogrid confinement on one hand and with bitumen coated E-glass textile sheets on the other. A total of 22 small-scale reinforced concrete (RC) column specimens were tested under uniaxial compression. Each specimen had a 240 mm diameter, 500 mm length, and was reinforced with four 10 mm longitudinal bars confined with three 6 mm ties spaced at 200 mm. The test variables were the confinement material (Geogrid, or Bitumen coated E-glass textile), type of geogrid (uniaxial or biaxial), number of confinement layers (one or two), and confinement location (internal or external). Assessment of the variables was done by analyzing the axial load-displacement behavior, the modes of failure, and the structural ductility measured by fracture energy and energy dissipation. Available analytical models for FRP confined specimens were modified to be applicable to the tested geogrid and bitumen textile confined specimens. A performance-to-cost analysis was also conducted. Results showed that external confinement of reinforced concrete columns using geogrid significantly enhanced the strength, ductility, and energy capacity of the tested specimens.

Keywords

• Reinforced concrete columns
• column confinement
• structural strengthening
• geogrid
• bitumen coated E-glass textile
• ductility enhancement