Experimental and Theoretical Study on Strengthened Low Compressive Strength Deficient Columns

Relatively recent materials, such as fiber reinforced polymer (FRP), have been used to strengthen circular short columns. Six circular columns were cast with 200mm diameter and having length of 1300mm. The first group, was three unreinforced concrete columns. The second group, was three reinforced concrete columns with six bars having diameter of 12mm, however, stirrups with 8mm diameter and spacing 150mm. Low compressive strength concrete was used with 200kg/cm2 strength after twenty eight days. External glass fiber reinforced polymer (GFRP) sheet were used in the circumferential direction to confine circular columns by strips or jacket mode. Columns were tested under an axial load after twenty eight days. The study was conducted to compare GFRP strengthened columns (strips or jacket) with control specimens (columns). Theoretical study was incorporated to verify the experimental results and investigate the effect of strength reduction factors in ACI design equations on experimental results. Test results revealed that, the two techniques significantly enhanced the capability of the low compressive strength columns to carrying axial load for both reinforced and unreinforced columns. The achieved conclusions confirmed that, the studied techniques capable of increasing the vertical load capacity of deficient columns with significant values.