Seismic Behavior Of RC Short Columns Under Bilateral Loading

The damage of rectangular reinforced concrete (RC) columns under bilateral horizontal loads is very complicated, which is far from fully understood. From previous experiences of earthquakes, the RC columns whose shear-span ratio are less than 2.5 were damaged severely in the way of brittle shear failure. In the meantime, e deformation capacity of such columns was insufficient. In recent years, research on seismic behavior of such short RC columns is drawing much more attention.In this study, the test setup of BRI was used, and twelve specimens under bilateral shear are tested with reversed cyclic loading. The following research was carried out:①Five specimens were tested in an effort to investigate effect of different loading angle (0°,30°,45°,60°,90°)on seismic behavior of short RC columns.②Four specimens were tested to investigate effect of different stirrup ratio (0.84%,1.1%,1.5%,3%) on seismic behavior of short RC columns.③Three specimens were tested to investigate effect of different longitudinal reinforcements ratio (1%,1.88%,3%) on seismic behavior of short RC columns.④Three specimens were tested to investigate effect of different axial compression ratio (0.3,0.2,0.1) on seismic behavior of short RC columns.Based on these testing rusult, the following conclusions are obtained:①For the short rectangular RC columns under bilateral shear loading, the relationship of strength and loading angle agrees with the elliptical curve; if tit is less than 1.5%,increasing the stirrup ratio can increase the shear strength, it is not true if the stirrup ratio is greater than 1.5%. The shear strength increases if the axial compression ratio is not high. Increasing the longitudinal reinforcement ratio can also improve the shear strength.②The increase of the loading angle can increase the short rectangular section RC columns'plastic deformation capacity. The increase of stirrup ratio can also increase plastic deformation capacity significantly. If the longitudinal reinforcement ratio is decreased, flexural failure may happen and deformation capacity increases significantly. The increase of axial compression ratio decreases deformation capacity.③When the short rectangular RC columns are in elastic range, the capacity of energy dissipation are not significant; And with the increase of plastic deformation, their capacity of energy dissipation begins to increase gradually until columns lost their bearing capacity. For example, increasing both the loading angle and the stirrup ratio, and decreasing the axial compression, both the specimen's deformation capacity and their capacity of energy dissipation increase. The specimens failed in flexure can dissipate more energy than those failed due to shear.④For specimens with shear failure under bilateral horizontal loads, the longitudinal reinforcement at outer layer yield when the specimens are near to reach their ultimate capacity, but this point can not be taken as yield point of the specimens. Yield displacement can be obtained from equivalent energy method, but displacement ductility obtained from that method can not reflect the characteristics of plastic deformation.