Tests and analysis of variable cross section reinforced concrete columns for highway bridges

The results of a series of 21 full scale tests carried out on pin-ended reinforced concrete columns are reported. The columns tested had either rectangular or octagonal cross sections. The rectangular sections were uniform, tapered in one plane, or tapered in both planes of bending. All columns, except the last 8, were subjected to uniaxial eccentricities at one of the ends (the stronger end), and a nominally concentric load at the other. Six of the last 8 columns had biaxially eccentric loading applied at the stronger end. The remaining two columns were loaded with a mid-height shear as well as an axial load. For all tests, a complete set of measurements, covering the entire range of loading up to collapse, were recorded. The test results are compared with the analytical results produced by the program VARCOLS. Correlation between test and VARCOLS results has been found to be good in most cases, and excellent in some others. Using the program VARCOLS in a parametric study, a new method of design for slender reinforced concrete columns with tapered or uniform cross sections is developed and design charts for the extreme proportions of longitudinal steel are presented. The method is simple and easy to use, and when compared with test results, gives good agreement.