RECTANGULAR CONCRETE COLUMNS RETROFITTED BYEXTERNAL PRESTRESSING FOR SEISMIC SHEAR RESISTANCE

摘要

Experimental investigation was conducted to study the shear mode of failure in rectangular reinforcedconcrete bridge columns, built before the enactment of modern seismic codes, and to establish theeffectiveness of external prestressing as a seismic retrofit methodology. The retrofit technique involvesexternal prestressing of concrete columns in transverse direction to improve their seismic performance interms of strength and deformability. Typical rectangular columns with substandard shear design anddetails have been tested with and without seismic retrofitting. The test results indicate that the seismicretrofit technique can be highly effective in controlling diagonal tension cracks caused by shear, therebyimproving their shear resistance significantly. Premature shear failure of columns was prevented and themode of behaviour was changed from shear to flexure. External prestressing also improved theconfinement of compression concrete in flexural-compression and diagonal strut regions, therebyimproving deformability of concrete. The technique also resulted in substantial improvements in lateraldrift and energy dissipation capacities of columns. Column drift capacity was improved up toapproximately 4%. Test data is presented along with a design methodology for seismic retrofit of suchcolumns.