Shear Damage Behavior of RC Columns with Small Shear-to-span Ratios Under Lateral Impact and Static Load
To investigate the impact resistance and shear damage behavior of reinforced concrete(RC)columns with small shear-to-span ratios,lateral pendulum impact tests and horizontal static loading tests were conducted on six and eight RC columns,respectively.The tests examined the effects of the shear-to-span ratios,amount of longitudinal rebars and stirrups,and axial compression force on the shear performance of the specimens;and the shear and bending damage of the specimens under impact loads were classified.The test results showed that RC columns with small shear-to-span ratios were prone to shear failure under both dynamic and static loads.Stirrups significantly contributed to the deformation capacity and static shear capacity of the columns but did not affect the shear capacity of the specimens under impact loads significantly.With an increase in the impact energy,the angle between the first diagonal crack and horizontal direction became smaller,and the failure mode of the specimen under the second impact was strongly affected by the damage sustained after the first impact.In the static loading tests,the increase in the axial compression force delayed the bending and shear damage of the specimens in the early stages and enhanced their load-carrying capacity.However,it significantly reduced the ductility of the specimens with very small shear-to-span ratios(e.g.,equal to 1.4).Based on the tests,the ratio of the peak impact force to the shear capacity(dynamic or static)of the specimens was used as a damage index to evaluate the shear damage status of the specimens under impact loads.The analysis results show that the existing dynamic shear capacity calculation method fails to fully consider the difference in inertial effects caused by different shear-to-span ratios and column boundary conditions,and the static shear capacity obtained from the tests cannot effectively reflect the change rule of the dynamic shear capacity with the shear-to-span ratio.Therefore,it is difficult to adopt the ratio of the peak impact force to the shear capacity to assess the shear damage of RC columns with changes in shear-to-span ratios.
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