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Strengthening of Reinforced Concrete Columns for Earthquake Resistance.
Kahn, L. F.
National Science Foundation, Washington, DC. Engineering and Applied Science., June 1979, 97 p.
Several methods of strengthening reinforced concrete columns to improve their seismic resistance are described. Four identical 10-inch concrete columns were constructed using No. 7 bars and 6400 psi concrete. Their design included no special transverse reinforcement for earthquake resistance. Three of the columns were strengthened externally using various techniques in order to improve their shear resistance and ductility. All four columns were tested under static reversed cycle deflections of increasing magnitude and with a constant axial load of 80,000 pounds. The unstrengthened column collapsed when the lateral deflection was about twice the deflection causing yield of the tension steel. The three strengthened columns responded nearly identically and resisted three reversed cycles at four times the yield deflection with little deterioration. Based on the test results and the ease of construction, it was concluded that U-clamp and banding techniques showed great promise in providing low cost, easy-to-construct methods for greatly improving the ductibility and earthquake resistance of existing reinforced concrete columns. The report includes photographs showing column construction, reinforcement techniques, and results of testing.
Seismic design; Earthquake resistant structures; Axial stress; Reinforced concrete; Columns (Supports); Earthquake engineering; Axial strain; Cyclic loads; Concrete construction; Dynamic structural analysis