Abstract：Most unfavorable shear behavior of concrete frame columns subjected to velocity pulse-like excitations is studied. First floor columns of reinforced concrete frame structures is used to investigate the effects of vertical and horizontal velocity pulse-like acceleration on shear behavior of concrete columns. Three equivalent velocity pulse sine excitations are employed to execute nonlinear dynamic time history analysis. Combined effects of vertical-to-horizontal peak acceleration ratio, arrival time interval of peak acceleration between vertical and horizontal excitations, shear span ratio, as well as fundamental period on shear-resistant demand and shear-resistant capacity is concerned with the assessment of the effect of velocity pulse action. The results demonstrate that shear-resistant demand of concrete columns increase with increasing intensity of velocity pulse, and shear-resistant capacity decrease with increasing vertical-to-horizontal peak acceleration ratio. Arrival time interval between vertical and horizontal excitations has an important influence on the most unfavorable shear behavior of concrete frame columns. At higher values of shear span ratio, the influence of velocity pulse excitations is significant. Nonlinear regression analysis of analytical data of the present study is carried out, and empirical approach considering different effect of these factors is proposed.
2011, Vol. 30 
